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  • 1. Benz, A. O.
    et al.
    Bruderer, S.
    van Dishoeck, E. F.
    Stäuber, P.
    Wampfler, S. F.
    Melchior, M.
    Dedes, C.
    Wyrowski, F.
    Doty, S. D.
    van der Tak, F.
    Bächtold, W.
    Csillaghy, A.
    Megej, A.
    Monstein, C.
    Soldati, M.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bergin, E.
    Bjerkeli, P.
    Blake, G. A.
    Bontemps, S.
    Braine, J.
    Caselli, P.
    Cernicharo, J.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Dieleman, P.
    Dominik, C.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herczeg, G. J.
    Herpin, F.
    Hogerheijde, M. R.
    Jacq, T.
    Jellema, W.
    Johnstone, D.
    Jørgensen, J. K.
    Kristensen, L. E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    Marseille, M.
    McCoey, C.
    Melnick, G.
    Neufeld, D.
    Nisini, B.
    Olberg, M.
    Ossenkopf, V.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Santiago-García, J.
    Saraceno, P.
    Schieder, R.
    Shipman, R.
    Stutzki, J.
    Tafalla, M.
    Tielens, A. G. G. M.
    van Kempen, T. A.
    Visser, R.
    Yıldız, U. A.
    Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L35-Article in journal (Refereed)
    Abstract [en]

    Context. Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (≃2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J = 1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation. Herschel is an ESA space observatory with science instruments provided by a European-led Principal Investigator consortia and with important participation from NASA.Appendix (page 5) is only available in electronic form at http://www.aanda.org

  • 2. Bergin, E. A.
    et al.
    Hogerheijde, M. R.
    Brinch, C.
    Fogel, J.
    Yildiz, U. A.
    Kristensen, L. E.
    van Dishoeck, E. F.
    Bell, T. A.
    Blake, G. A.
    Cernicharo, J.
    Dominik, C.
    Lis, D.
    Melnick, G.
    Neufeld, D.
    Panic, O.
    Pearson, J. C.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Benz, A. O.
    Bjerkeli, P.
    Bontemps, S.
    Braine, J.
    Bruderer, S.
    Caselli, P.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Doty, S. D.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th
    Helmich, F.
    Herczeg, G. J.
    Herpin, F.
    Jacq, T.
    Johnstone, D.
    Jorgensen, J. K.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Marseille, M.
    Mc Coey, C.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Plume, R.
    Risacher, C.
    Santiago-Garcia, J.
    Saraceno, P.
    Shipman, R.
    Tafalla, M.
    van Kempen, T. A.
    Visser, R.
    Wampfler, S. F.
    Wyrowski, F.
    van der Tak, F.
    Jellema, W.
    Tielens, A. G. G. M.
    Hartogh, P.
    Stuetzki, J.
    Szczerba, R.
    Sensitive limits on the abundance of cold water vapor in the DM Tauri protoplanetary disk2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L33-Article in journal (Refereed)
    Abstract [en]

    We performed a sensitive search for the ground-state emission lines of ortho-and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3 sigma levels in 0.5 km s(-1) channels of 4.2 mK for the 1(10)-1(01) line and 12.6 mK for the 1(11)-0(00) line. We report a very tentative detection, however, of the 1(10)-1(01) line in the wide band spectrometer, with a strength of T-mb = 2.7 mK, a width of 5.6 km s(-1) and an integrated intensity of 16.0 mK km s(-1). The latter constitutes a 6 sigma detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane.

  • 3. Bergman, P.
    et al.
    Parise, B.
    Liseau, R.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Deuterated formaldehyde in rho Ophiuchi A2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 527, p. A39-Article in journal (Refereed)
    Abstract [en]

    Context. Formaldehyde is an organic molecule that is abundant in the interstellar medium. High deuterium fractionation is a common feature in low-mass star-forming regions. Observing several isotopologues of molecules is an excellent tool for understanding the formation paths of the molecules. Aims. We seek an understanding of how the various deuterated isotopologues of formaldehyde are formed in the dense regions of low-mass star formation. More specifically, we adress the question of how the very high deuteration levels (several orders of magnitude above the cosmic D/H ratio) can occur using H(2)CO data of the nearby rho Oph A molecular cloud. Methods. From mapping observations of H(2)CO, HDCO, and D(2)CO, we have determined how the degree of deuterium fractionation changes over the central 3' x 3' region of rho Oph A. The multi-transition data of the various H(2)CO isotopologues, as well as from other molecules (e. g., CH(3)OH and N(2)D(+)) present in the observed bands, were analysed using both the standard type rotation diagram analysis and, in selected cases, a more elaborate method of solving the radiative transfer for optically thick emission. In addition to molecular column densities, the analysis also estimates the kinetic temperature and H(2) density. Results. Toward the SM1 core in rho Oph A, the H(2)CO deuterium fractionation is very high. In fact, the observed D(2)CO/HDCO ratio is 1.34 +/- 0.19, while the HDCO/H(2)CO ratio is 0.107 +/- 0.015. This is the first time, to our knowledge, that the D(2)CO/HDCO abundance ratio is observed to be greater than 1. The kinetic temperature is in the range 20-30 K in the cores of rho Oph A, and the H(2) density is (6-10) x 10(5) cm(-3). We estimate that the total H(2) column density toward the deuterium peak is (1-4) x 10(23) cm(-2). As depleted gas-phase chemistry is not adequate, we suggest that grain chemistry, possibly due to abstraction and exchange reactions along the reaction chain H(2)CO --> HDCO --> D(2)CO, is at work to produce the very high deuterium levels observed.

  • 4. Bergman, P.
    et al.
    Parise, B.
    Liseau, R.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, H.
    Menten, K. M.
    Guesten, R.
    Detection of interstellar hydrogen peroxide2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 531, p. L8-Article in journal (Refereed)
    Abstract [en]

    Context. The molecular species hydrogen peroxide, HOOH, is likely to be a key ingredient in the oxygen and water chemistry in the interstellar medium. Aims. Our aim with this investigation is to determine how abundant HOOH is in the cloud core rho Oph A. Methods. By observing several transitions of HOOH in the (sub)millimeter regime we seek to identify the molecule and also to determine the excitation conditions through a multilevel excitation analysis. Results. We have detected three spectral lines toward the SM1 position of rho Oph A at velocity-corrected frequencies that coincide very closely with those measured from laboratory spectroscopy of HOOH. A fourth line was detected at the 4 sigma level. We also found through mapping observations that the HOOH emission extends (about 0.05 pc) over the densest part of the rho Oph A cloud core. We derive an abundance of HOOH relative to that of H(2) in the SM1 core of about 1 x 10(-10). Conclusions. To our knowledge, this is the first reported detection of HOOH in the interstellar medium.

  • 5. Bjerkeli, P.
    et al.
    Liseau, R.
    Brinch, C.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Santangelo, G.
    Cabrit, S.
    Benedettini, M.
    Black, J. H.
    Herczeg, G.
    Justtanont, K.
    Kristensen, L. E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Nisini, B.
    Tafalla, M.
    Resolving the shocked gas in HH54 with Herschel CO line mapping at high spatial and spectral resolution2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 571, article id A90Article in journal (Refereed)
    Abstract [en]

    Context. The HH 54 shock is a Herbig-Haro object, located in the nearby Chamaeleon II cloud. Observed CO line profiles are due to a complex distribution in density, temperature, velocity, and geometry. Aims. Resolving the HH 54 shock wave in the far-infrared (FIR) cooling lines of CO constrain the kinematics, morphology, and physical conditions of the shocked region. Methods. We used the PACS and SPIRE instruments on board the Herschel space observatory to map the full FIR spectrum in a region covering the HH 54 shock wave. Complementary Herschel-HIFI, APEX, and Spitzer data are used in the analysis as well. The observed features in the line profiles are reproduced using a 3D radiative transfer model of a bow-shock, constructed with the Line Modeling Engine code (LIME). Results. The FIR emission is confined to the HH 54 region and a coherent displacement of the location of the emission maximum of CO with increasing J is observed. The peak positions of the high-J CO lines are shifted upstream from the lower J CO lines and coincide with the position of the spectral feature identified previously in CO(10-9) profiles with HIFI. This indicates a hotter molecular component in the upstream gas with distinct dynamics. The coherent displacement with increasing J for CO is consistent with a scenario where IRAS12500 - 7658 is the exciting source of the flow, and the 180 K bow-shock is accompanied by a hot (800 K) molecular component located upstream from the apex of the shock and blueshifted by -7 km s(-1). The spatial proximity of this knot to the peaks of the atomic fine-structure emission lines observed with Spitzer and PACS ([O I]63, 145 mu m) suggests that it may be associated with the dissociative shock as the jet impacts slower moving gas in the HH 54 bow-shock.

  • 6. Bjerkeli, P.
    et al.
    Liseau, R.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Rydbeck, G.
    Nisini, B.
    Tafalla, M.
    Antoniucci, S.
    Benedettini, M.
    Bergman, P.
    Cabrit, S.
    Giannini, T.
    Melnick, G.
    Neufeld, D.
    Santangelo, G.
    van Dishoeck, E. F.
    H2O line mapping at high spatial and spectral resolution Herschel observations of the VLA 1623 outflow2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 546, p. A29-Article in journal (Refereed)
    Abstract [en]

    Context. Apart from being an important coolant, water is known to be a tracer of high-velocity molecular gas. Recent models predict relatively high abundances behind interstellar shockwaves. The dynamical and physical conditions of the water emitting gas, however, are not fully understood yet. Using the Herschel Space Observatory, it is now possible to observe water emission from supersonic molecular outflows at high spectral and spatial resolution. Several molecular outflows from young stars are currently being observed as part of the WISH (Water In Star-forming regions with Herschel) key program. Aims. We aim to determine the abundance and distribution of water, its kinematics, and the physical conditions of the gas responsible for the water emission. The observed line profile shapes help us understand the dynamics in molecular outflows. Methods. We mapped the VLA1623 outflow, in the ground-state transitions of o-H2O, with the HIFI and PACS instruments. We also present observations of higher energy transitions of o-H2O and p-H2O obtained with HIFI and PACS towards selected outflow positions. From comparison with non-LTE radiative transfer calculations, we estimate the physical parameters of the water emitting regions. Results. The observed water emission line profiles vary over the mapped area. Spectral features and components, tracing gas in different excitation conditions, allow us to constrain the density and temperature of the gas. The water emission originates in a region where temperatures are comparable to that of the warm H-2 gas (T greater than or similar to 200 K). Thus, the water emission traces a gas component significantly warmer than the gas responsible for the low-J CO emission. The water column densities at the CO peak positions are low, i.e. N(H2O) similar or equal to (0.03-10) x 10(14) cm(-2). Conclusions. The water abundance with respect to H-2 in the extended outflow is estimated at X(H2O) < 1 x 10(-6), significantly lower than what would be expected from most recent shock models. The H2O emission traces a gas component moving at relatively high velocity compared to the low-J CO emitting gas. However, other dynamical quantities such as the momentum rate, energy, and mechanical luminosity are estimated to be the same, independent of the molecular tracer used, CO or H2O.

  • 7. Bjerkeli, P.
    et al.
    Liseau, R.
    Nisini, B.
    Tafalla, M.
    Benedettini, M.
    Bergman, P.
    Dionatos, O.
    Giannini, T.
    Herczeg, G.
    Justtanont, K.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    McCoey, C.
    Olberg, M.
    Olofsson, A. O. H.
    Herschel observations of the Herbig-Haro objects HH52-542011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 533Article in journal (Refereed)
    Abstract [en]

    Context. The emission from Herbig-Haro objects and supersonic molecular outflows is understood as cooling radiation behind shocks, which are initiated by a (proto-)stellar wind or jet. Within a given object, one often observes both dissociative (J-type) and non-dissociative (C-type) shocks, owing to the collective effects of internally varying shock velocities. Aims. We aim at the observational estimation of the relative contribution to the cooling by CO and H(2)O, as this provides decisive information for understanding the oxygen chemistry behind interstellar shock waves. Methods. The high sensitivity of HIFI, in combination with its high spectral resolution capability, allowed us to trace the H(2)O outflow wings at an unprecedented signal-to-noise ratio. From the observation of spectrally resolved H(2)O and CO lines in the HH52-54 system, both from space and from the ground, we arrived at the spatial and velocity distribution of the molecular outflow gas. Solving the statistical equilibrium and non-LTE radiative transfer equations provides us with estimates of the physical parameters of this gas, including the cooling rate ratios of the species. The radiative transfer is based on an accelerated lambda iteration code, where we use the fact that variable shock strengths, distributed along the front, are naturally implied by a curved surface. Results. Based on observations of CO and H(2)O spectral lines, we conclude that the emission is confined to the HH54 region. The quantitative analysis of our observations favours a ratio of the CO-to-H(2)O-cooling-rate >> 1. Formally, we derived the ratio A(CO)/A(o-H(2)O) = 10, which is in good agreement with earlier determination of 7 based on ISO-LWS observations. From the best-fit model to the CO emission, we arrive at an H(2)O abundance close to 1 x 10(-5). The line profiles exhibit two components, one that is triangular and another that is a superposed, additional feature. This additional feature is likely to find its origin in a region that is smaller than the beam where the ortho-water abundance is smaller than in the quiescent gas. Conclusions. Comparison with recent shock models indicate that a planar shock cannot easily explain the observed line strengths and triangular line profiles. We conclude that the geometry can play an important role. Although abundances support a scenario where J-type shocks are present, higher cooling rate ratios are derived than predicted by these types of shocks.

  • 8. Bruderer, S.
    et al.
    Benz, A. O.
    van Dishoeck, E. F.
    Melchior, M.
    Doty, S. D.
    van der Tak, F.
    Stäuber, P.
    Wampfler, S. F.
    Dedes, C.
    Yıldız, U. A.
    Pagani, L.
    Giannini, T.
    de Graauw, Th.
    Whyborn, N.
    Teyssier, D.
    Jellema, W.
    Shipman, R.
    Schieder, R.
    Honingh, N.
    Caux, E.
    Bächtold, W.
    Csillaghy, A.
    Monstein, C.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bergin, E.
    Bjerkeli, P.
    Blake, G. A.
    Bontemps, S.
    Braine, J.
    Caselli, P.
    Cernicharo, J.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Dominik, C.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Goicoechea, J. R.
    Helmich, F.
    Herczeg, G. J.
    Herpin, F.
    Hogerheijde, M. R.
    Jacq, T.
    Johnstone, D.
    Jørgensen, J. K.
    Kristensen, L. E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    Marseille, M.
    McCoey, C.
    Melnick, G.
    Neufeld, D.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Santiago-García, J.
    Saraceno, P.
    Shipman, R.
    Tafalla, M.
    van Kempen, T. A.
    Visser, R.
    Wyrowski, F.
    Herschel/HIFI detections of hydrides towards AFGL 2591. Envelope emission versus tenuous cloud absorption2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L44-Article in journal (Refereed)
    Abstract [en]

    The Heterodyne Instrument for the Far Infrared (HIFI) onboard the Herschel Space Observatory allows the first observations of light diatomic molecules at high spectral resolution and in multiple transitions. Here, we report deep integrations using HIFI in different lines of hydrides towards the high-mass star forming region AFGL 2591. Detected are CH, CH+, NH, OH+, H2O+, while NH+ and SH+ have not been detected. All molecules except for CH and CH+ are seen in absorption with low excitation temperatures and at velocities different from the systemic velocity of the protostellar envelope. Surprisingly, the CH(JF,P = 3/22,- - 1/21,+ ) and CH+(J = 1-0, J = 2-1) lines are detected in emission at the systemic velocity. We can assign the absorption features to a foreground cloud and an outflow lobe, while the CH and CH+ emission stems from the envelope. The observed abundance and excitation of CH and CH+ can be explained in the scenario of FUV irradiated outflow walls, where a cavity etched out by the outflow allows protostellar FUV photons to irradiate and heat the envelope at larger distances driving the chemical reactions that produce these molecules. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Apppendices and Table 1 (pages 6 to 7) are only available in electronic form at http://www.aanda.org

  • 9. Caselli, P.
    et al.
    Keto, E.
    Pagani, L.
    Aikawa, Y.
    Yıldız, U. A.
    van der Tak, F. F. S.
    Tafalla, M.
    Bergin, E. A.
    Nisini, B.
    Codella, C.
    van Dishoeck, E. F.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Benz, A. O.
    Bjerkeli, P.
    Blake, G. A.
    Bontemps, S.
    Braine, J.
    Bruderer, S.
    Cernicharo, J.
    Daniel, F.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Gaier, T.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herczeg, G. J.
    Herpin, F.
    Hogerheijde, M. R.
    Jackson, B.
    Jacq, T.
    Javadi, H.
    Johnstone, D.
    Jørgensen, J. K.
    Kester, D.
    Kristensen, L. E.
    Laauwen, W.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, René
    Luinge, W.
    Marseille, M.
    McCoey, C.
    Megej, A.
    Melnick, G.
    Neufeld, D.
    Olberg, M.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Santiago-García, J.
    Saraceno, P.
    Shipman, R.
    Siegel, P.
    van Kempen, T. A.
    Visser, R.
    Wampfler, S. F.
    Wyrowski, F.
    Water vapor toward starless cores: The Herschel view2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L29-Article in journal (Refereed)
    Abstract [en]

    Aims: Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H2O) < 7 × 10-9). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation. Methods: High spectral resolution observations of the fundamental ortho water (o-H2O) transition (557 GHz) were carried out with the Heterodyne Instrument for the Far Infrared onboard Herschel toward two starless cores: Barnard 68 (hereafter B68), a Bok globule, and LDN 1544 (L1544), a prestellar core embedded in the Taurus molecular cloud complex. Detailed radiative transfer and chemical codes were used to analyze the data. Results: The RMS in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s-1. The continuum level is 3.5 ± 0.2 mK in B68 and 11.4 ± 0.4 mK in L1544. No significant feature is detected in B68 and the 3σ upper limit is consistent with a column density of o-H2O N(o-H2O) < 2.5 × 1013 cm-2, or a fractional abundance x(o-H2O) < 1.3 × 10-9, more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5σ level from which we obtain the first value of the o-H2O column density ever measured in dark clouds: N(o-H2O) = (8 ± 4) × 1012 cm-2. The corresponding fractional abundance is x(o-H2O) ≃ 5 × 10-9 at radii >7000 AU and ≃2 × 10-10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H2O) profile peaking at ≃10-8, 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible. Conclusions: Herschel has provided the first measurement of water vapor in dark regions. Column densities of o-H2O are low, but prestellar cores such as L1544 (with their high central densities, strong continuum, and large envelopes) appear to be very promising tools to finally shed light on the solid/vapor balance of water in molecular clouds and oxygen chemistry in the earliest stages of star formation. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  • 10.
    Cataldi, Gianni
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Blommaert, J.
    Fridlund, M.
    Ivison, R.
    Pantin, E.
    Sibthorpe, B.
    Vandenbussche, B.
    Wu, Y.
    Herschel/HIFI observations of ionised carbon in the beta Pictoris debris disk2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 563, article id A66Article in journal (Refereed)
    Abstract [en]

    Context. The dusty debris disk around the similar to 20 Myr old main-sequence A-star beta Pictoris is known to contain gas. Evidence points towards a secondary origin of the gas as opposed to being a direct remnant from the initial protoplanetary disk, although the dominant gas production mechanism is so far not identified. The origin of the observed overabundance of C and O compared with solar abundances of metallic elements such as Na and Fe is also unclear. Aims. Our goal is to constrain the spatial distribution of C in the disk, and thereby the gas origin and its abundance pattern. Methods. We used the HIFI instrument on board the Herschel Space Observatory to observe and spectrally resolve C II emission at 158 mu m from the beta Pic debris disk. Assuming a disk in Keplerian rotation and a model for the line emission from the disk, we used the spectrally resolved line profile to constrain the spatial distribution of the gas. Results. We detect the C II 158 mu m emission. Modelling the shape of the emission line shows that most of the gas is located at about similar to 100 AU or beyond. We estimate a total C gas mass of 1.3(-0.5)(+1.3) x 10(2) M-circle plus (central 90% confidence interval). The data suggest that more gas is located on the south-west side of the disk than on the north-east side. The shape of the emission line is consistent with the hypothesis of a well mixed gas (constant C/Fe ratio throughout the disk). Assuming instead a spatial profile expected from a simplified accretion disk model, we found it to give a significantly poorer fit to the observations. Conclusions. Since the bulk of the gas is found outside 30 AU, we argue that the cometary objects known as falling evaporating bodies are probably not the dominant source of gas; production from grain-grain collisions or photodesorption seems more likely. The incompatibility of the observations with a simplified accretion disk model might favour a preferential depletion explanation for the overabundance of C and O, although it is unclear how much this conclusion is affected by the simplifications made. More stringent constraints on the spatial distribution will be available from ALMA observations of C I emission at 609 mu m.

  • 11. Chavarria, L.
    et al.
    Herpin, F.
    Jacq, T.
    Braine, J.
    Bontemps, S.
    Baudry, A.
    Marseille, M.
    van der Tak, F.
    Pietropaoli, B.
    Wyrowski, F.
    Shipman, R.
    Frieswijk, W.
    van Dishoeck, E. F.
    Cernicharo, J.
    Bachiller, R.
    Benedettini, M.
    Benz, A. O.
    Bergin, E.
    Bjerkeli, P.
    Blake, G. A.
    Bruderer, S.
    Caselli, P.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Hartogh, P.
    Helmich, F.
    Herczeg, G. J.
    Hogerheijde, M. R.
    Johnstone, D.
    Jorgensen, J. K.
    Kristensen, L. E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    McCoey, C.
    Melnick, G.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Santiago-Garcia, J.
    Saraceno, P.
    Stutzki, J.
    Szczerba, R.
    Tafalla, M.
    Tielens, A.
    van Kempen, T. A.
    Visser, R.
    Wampfler, S. F.
    Willem, J.
    Yildiz, U. A.
    Water in massive star-forming regions: HIFI observations of W3 IRS52010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L37-Article in journal (Refereed)
    Abstract [en]

    We present Herschel observations of the water molecule in the massive star-forming region W3 IRS5. The o-(H2O)-O-17 1(10)-1(01), p-(H2O)-O-18 1(11)-0(00), p-H2O 2(02)-1(11), p-H2O 1(11)-0(00), o-H2O 2(21)-2(12), and o-H2O 2(12)-1(01) lines, covering a frequency range from 552 up to 1669 GHz, have been detected at high spectral resolution with HIFI. The water lines in W3 IRS5 show well-defined high-velocity wings that indicate a clear contribution by outflows. Moreover, the systematically blue-shifted absorption in the H2O lines suggests expansion, presumably driven by the outflow. No infall signatures are detected. The p-H2O 1(11)-0(00) and o-H2O 2(12)-1(01) lines show absorption from the cold material (T similar to 10 K) in which the high-mass protostellar envelope is embedded. One-dimensional radiative transfer models are used to estimate water abundances and to further study the kinematics of the region. We show that the emission in the rare isotopologues comes directly from the inner parts of the envelope (T greater than or similar to 100 K) where water ices in the dust mantles evaporate and the gas-phase abundance increases. The resulting jump in the water abundance (with a constant inner abundance of 10(-4)) is needed to reproduce the o-(H2O)-O-17 1(10)-1(01) and p-(H2O)-O-18 1(11)-0(00) spectra in our models. We estimate water abundances of 10(-8) to 10(-9) in the outer parts of the envelope (T less than or similar to 100 K). The possibility of two protostellar objects contributing to the emission is discussed.

  • 12. Codella, C.
    et al.
    Lefloch, B.
    Ceccarelli, C.
    Cernicharo, J.
    Caux, E.
    Lorenzani, A.
    Viti, S.
    Hily-Blant, P.
    Parise, B.
    Maret, S.
    Nisini, B.
    Caselli, P.
    Cabrit, S.
    Pagani, L.
    Benedettini, M.
    Boogert, A.
    Gueth, F.
    Melnick, G.
    Neufeld, D.
    Pacheco, S.
    Salez, M.
    Schuster, K.
    Bacmann, A.
    Baudry, A.
    Bell, T.
    Bergin, E. A.
    Blake, G.
    Bottinelli, S.
    Castets, A.
    Comito, C.
    Coutens, A.
    Crimier, N.
    Dominik, C.
    Demyk, K.
    Encrenaz, P.
    Falgarone, E.
    Fuente, A.
    Gerin, M.
    Goldsmith, P.
    Helmich, F.
    Hennebelle, P.
    Henning, Th.
    Herbst, E.
    Jacq, T.
    Kahane, C.
    Kama, M.
    Klotz, A.
    Langer, W.
    Lis, D.
    Lord, S.
    Pearson, J.
    Phillips, T.
    Saraceno, P.
    Schilke, P.
    Tielens, X.
    van der Tak, F.
    van der Wiel, M.
    Vastel, C.
    Wakelam, V.
    Walters, A.
    Wyrowski, F.
    Yorke, H.
    Borys, C.
    Delorme, Y.
    Kramer, C.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mehdi, I.
    Ossenkopf, V.
    Stutzki, J.
    The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1. I. Shock chemical complexity2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, p. L112-Article in journal (Refereed)
    Abstract [en]

    We present the first results of the unbiased survey of the L1157-B1 bow shock, obtained with HIFI in the framework of the key program Chemical HErschel Survey of Star forming regions (CHESS). The L1157 outflow is driven by a low-mass Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The bright blue-shifted bow shock B1 is the ideal laboratory for studying the link between the hot (~1000-2000 K) component traced by H2 IR-emission and the cold (~10-20 K) swept-up material. The main aim is to trace the warm gas chemically enriched by the passage of a shock and to infer the excitation conditions in L1157-B1. A total of 27 lines are identified in the 555-636 GHz region, down to an average 3σ level of 30 mK. The emission is dominated by CO(5-4) and H2O(110-101) transitions, as discussed by Lefloch et al. in this volume. Here we report on the identification of lines from NH3, H2CO, CH3OH, CS, HCN, and HCO+. The comparison between the profiles produced by molecules released from dust mantles (NH3, H2CO, CH3OH) and that of H2O is consistent with a scenario in which water is also formed in the gas-phase in high-temperature regions where sputtering or grain-grain collisions are not efficient. The high excitation range of the observed tracers allows us to infer, for the first time for these species, the existence of a warm (≥200 K) gas component coexisting in the B1 bow structure with the cold and hot gas detected from ground. Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA.Table 1 is only available in electronic form at http://www.aanda.org

  • 13. Comito, C.
    et al.
    Schilke, P.
    Rolffs, R.
    Lis, D. C.
    Belloche, A.
    Bergin, E. A.
    Phillips, T. G.
    Bell, T. A.
    Crockett, N. R.
    Wang, S.
    Blake, G. A.
    Caux, E.
    Ceccarelli, C.
    Cernicharo, J.
    Daniel, F.
    Dubernet, M. -L
    Emprechtinger, M.
    Encrenaz, P.
    Gerin, M.
    Giesen, T. F.
    Goicoechea, J. R.
    Goldsmith, P. F.
    Gupta, H.
    Herbst, E.
    Joblin, C.
    Johnstone, D.
    Langer, W. D.
    Latter, W. D.
    Lord, S. D.
    Maret, S.
    Martin, P. G.
    Melnick, G. J.
    Menten, K. M.
    Morris, P.
    Mueller, H. S. P.
    Murphy, J. A.
    Neufeld, D. A.
    Ossenkopf, V.
    Pearson, J. C.
    Perault, M.
    Plume, R.
    Qin, S. -L
    Schlemmer, S.
    Stutzki, J.
    Trappe, N.
    van der Tak, F. F. S.
    Vastel, C.
    Yorke, H. W.
    Yu, S.
    Olberg, M.
    Szczerba, R.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Lin, R. H.
    Samoska, L. A.
    Schlecht, E.
    Herschel observations of deuterated water towards Sgr B2(M)2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L38-Article in journal (Refereed)
    Abstract [en]

    Observations of HDO are an important complement for studies of water, because they give strong constraints on the formation processes - grain surfaces versus energetic process in the gas phase, e. g. in shocks. The HIFI observations of multiple transitions of HDO in Sgr B2(M) presented here allow the determination of the HDO abundance throughout the envelope, which has not been possible before with ground-based observations only. The abundance structure has been modeled with the spherical Monte Carlo radiative transfer code RATRAN, which also takes radiative pumping by continuum emission from dust into account. The modeling reveals that the abundance of HDO rises steeply with temperature from a low abundance (2.5 x 10(-11)) in the outer envelope at temperatures below 100 K through a medium abundance (1.5 x 10(-9)) in the inner envelope/outer core at temperatures between 100 and 200 K, and finally a high abundance (3.5 x 10(-9)) at temperatures above 200 K in the hot core.

  • 14. de Graauw, Thijs
    et al.
    Andra, 38
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Andra, 35
    The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI): instrument and pre-launch testing2008In: Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 2008, p. 701004-701004Conference paper (Other academic)
  • 15. Fich, M.
    et al.
    Johnstone, D.
    van Kempen, T. A.
    McCoey, C.
    Fuente, A.
    Caselli, P.
    Kristensen, L. E.
    Plume, R.
    Cernicharo, J.
    Herczeg, G. J.
    van Dishoeck, E. F.
    Wampfler, S.
    Gaufre, P.
    Gill, J. J.
    Javadi, H.
    Justen, M.
    Laauwen, W.
    Luinge, W.
    Ossenkopf, V.
    Pearson, J.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bergin, E.
    Benz, A. O.
    Bjerkeli, P.
    Blake, G.
    Bontemps, S.
    Braine, J.
    Bruderer, S.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Encrenaz, P.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herpin, F.
    Hogerheijde, M. R.
    Jacq, T.
    Jørgensen, J. K.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    Marseille, M.
    Melnick, G.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Risacher, C.
    Santiago, J.
    Saraceno, P.
    Shipman, R.
    Tafalla, M.
    van der Tak, F.
    Visser, R.
    Wyrowski, F.
    Yıldız, U. A.
    Herschel-PACS spectroscopy of the intermediate mass protostar NGC 7129 FIRS 22010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, p. L86-Article in journal (Refereed)
    Abstract [en]

    Aims: We present preliminary results of the first Herschel spectroscopic observations of NGC 7129 FIRS2, an intermediate mass star-forming region. We attempt to interpret the observations in the framework of an in-falling spherical envelope. Methods: The PACS instrument was used in line spectroscopy mode (R = 1000-5000) with 15 spectral bands between 63 and 185 μm. This provided good detections of 26 spectral lines seen in emission, including lines of H2O, CO, OH, O I, and C II. Results: Most of the detected lines, particularly those of H2O and CO, are substantially stronger than predicted by the spherical envelope models, typically by several orders of magnitude. In this paper we focus on what can be learned from the detected CO emission lines. Conclusions: It is unlikely that the much stronger than expected line emission arises in the (spherical) envelope of the YSO. The region hot enough to produce such high excitation lines within such an envelope is too small to produce the amount of emission observed. Virtually all of this high excitation emission must arise in structures such as as along the walls of the outflow cavity with the emission produced by a combination of UV photon heating and/or non-dissociative shocks. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Figure 3 is only available in electronic form at http://www.aanda.org

  • 16. Goldsmith, Paul F.
    et al.
    Liseau, Rene
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    HERSCHEL Measurements of Molecular Oxygen in Orion2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 737, no 2, p. 96-Article in journal (Refereed)
    Abstract [en]

    We report observations of three rotational transitions of molecular oxygen (O2) in emission from the H2 Peak 1 position of vibrationally excited molecular hydrogen in Orion. We observed the 487 GHz, 774 GHz, and 1121 GHz lines using the Heterodyne Instrument for the Far Infrared on the Herschel Space Observatory, having velocities of 11 km s–1 to 12 km s–1 and widths of 3 km s–1. The beam-averaged column density is N(O2) = 6.5 × 1016 cm–2, and assuming that the source has an equal beam-filling factor for all transitions (beam widths 44, 28, and 19''), the relative line intensities imply a kinetic temperature between 65 K and 120 K. The fractional abundance of O2 relative to H2 is (0.3-7.3) × 10–6. The unusual velocity suggests an association with a ~5'' diameter source, denoted Peak A, the Western Clump, or MF4. The mass of this source is ~10 M and the dust temperature is ≥150 K. Our preferred explanation of the enhanced O2 abundance is that dust grains in this region are sufficiently warm (T ≥ 100 K) to desorb water ice and thus keep a significant fraction of elemental oxygen in the gas phase, with a significant fraction as O2. For this small source, the line ratios require a temperature ≥180 K. The inferred O2 column density 5 × 1018 cm–2 can be produced in Peak A, having N(H2) 4 × 1024 cm–2. An alternative mechanism is a low-velocity (10-15 km s–1) C-shock, which can produce N(O2) up to 1017 cm–2.

  • 17. Gupta, H.
    et al.
    Rimmer, P.
    Pearson, J. C.
    Yu, S.
    Herbst, E.
    Harada, N.
    Bergin, E. A.
    Neufeld, D. A.
    Melnick, G. J.
    Bachiller, R.
    Baechtold, W.
    Bell, T. A.
    Blake, G. A.
    Caux, E.
    Ceccarelli, C.
    Cernicharo, J.
    Chattopadhyay, G.
    Comito, C.
    Cabrit, S.
    Crockett, N. R.
    Daniel, F.
    Falgarone, E.
    Diez-Gonzalez, M. C.
    Dubernet, M.-L.
    Erickson, N.
    Emprechtinger, M.
    Encrenaz, P.
    Gerin, M.
    Gill, J. J.
    Giesen, T. F.
    Goicoechea, J. R.
    Goldsmith, P. F.
    Joblin, C.
    Johnstone, D.
    Langer, W. D.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Latter, W. B.
    Lin, R. H.
    Lis, D. C.
    Liseau, R.
    Lord, S. D.
    Maiwald, F. W.
    Maret, S.
    Martin, P. G.
    Martin-Pintado, J.
    Menten, K. M.
    Morris, P.
    Müller, H. S. P.
    Murphy, J. A.
    Nordh, L. H.
    Olberg, M.
    Ossenkopf, V.
    Pagani, L.
    Pérault, M.
    Phillips, T. G.
    Plume, R.
    Qin, S.-L.
    Salez, M.
    Samoska, L. A.
    Schilke, P.
    Schlecht, E.
    Schlemmer, S.
    Szczerba, R.
    Stutzki, J.
    Trappe, N.
    van der Tak, F. F. S.
    Vastel, C.
    Wang, S.
    Yorke, H. W.
    Zmuidzinas, J.
    Boogert, A.
    Güsten, R.
    Hartogh, P.
    Honingh, N.
    Karpov, A.
    Kooi, J.
    Krieg, J.-M.
    Schieder, R.
    Zaal, P.
    Detection of OH+ and H2O+ towards Orion KL2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L47-Article in journal (Refereed)
    Abstract [en]

    We report observations of the reactive molecular ions OH+, H2O+, and H3O+ towards Orion KL with Herschel/HIFI. All three N = 1-0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111-000 transition at 1115 and 1139 GHz were detected; an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blueshifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 × 1012 cm-2 and 7 ± 2 × 1012 cm-2, and those in the outflow of 1.9 ± 0.7 × 1013 cm-2 and 1.0 ± 0.3 × 1013 cm-2. Upper limits of 2.4 × 1012 cm-2 and 8.7 × 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.

  • 18. Hjalmarson, Å.
    et al.
    Frisk, U.
    Olberg, M.
    Bergman, P.
    Bernath, P.
    Biver, N.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Crovisier, J.
    Curry, C. L.
    Dahlgren, M.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P. A.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fredrixon, M.
    Gerin, M.
    Gregersen, E. M.
    Hagström, M.
    Harju, J.
    Hasegawa, T.
    Horellou, C.
    Johansson, L. E. B.
    Kyrölä, E.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Llewellyn, E. J.
    Mattila, K.
    Mégie, G.
    Mitchell, G. F.
    Murtagh, D.
    Nyman, L.-Å.
    Nordh, H. L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, A. O. H.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Persson, G.
    Plume, R.
    Rickman, H.
    Ristorcelli, I.
    Rydbeck, G.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Schéele, F.
    Serra, G.
    Torchinsky, S.
    Tothill, N. F.
    Volk, K.
    Wiklind, T.
    Wilson, C. D.
    Winnberg, A.
    Witt, G.
    Highlights from the first year of Odin observations2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L39-L46Article in journal (Refereed)
    Abstract [en]

    Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H218O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR21, S140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; H218O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in~Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 have resulted in very low abundance limits, which are difficult to accomodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'études Spatiales (CNES, France). The Swedish Space Corporation (SSC) has been the prime industrial contractor, and is also responsible for the satellite operation from its Odin Mission Control Centre at SSC in Solna and its Odin Control Centre at ESRANGE near Kiruna in northern Sweden. See also the SNSB Odin web page: http://www.snsb.se/eng_odin_intro.shtml

  • 19. Hjalmarson, Åke
    et al.
    Bergman, Per
    Biver, Nicolas
    Florén, H.-G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, Urban
    Hasegawa, Tatsuhiko
    Justtanont, Kay
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lundin, Stefan
    Olberg, Michael
    Olofsson, Henrik
    Persson, Glenn
    Rydbeck, Gustaf
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    The Odin Team,
    Recent astronomy highlights from the Odin satellite2005In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 36, p. 1031-1047Article in journal (Refereed)
    Abstract [en]

    Astronomy highlights, mainly from the third year of Odin observations time shared 50/50% with aeronomy are presented: the very low O2 abundance limits achieved, the highly pressure broadened absorption lines of H2O, H218O, and CO (5 → 4) in the atmosphere of Mars, the high precision H2O and H218O observations of comets, the detections of NH3 and H2O around the C-rich star IRC+10216 (CW Leo) and of H2O around the O-rich star W Hya, NH3 and H2O observations of infall/outflow interactions, observations of H2O, H218O, H217O as well as NH3 and 15NH3 in multiple absorptions towards Sgr B2, and in emission towards Orion KL, the H2O detection of several new outflows in the DR21 W75S region. We also discuss the results of deconvolution of high S/N H2O, CO and 13CO (5 → 4) maps of the Orion KL region to 40″ resolution (the beam size of the Herschel telescope) and the first results from our ongoing “spectral scan” of Orion KL in bands around 555 and 570 GHz. Finally, a search for primordial molecules is presented.

  • 20. Johnstone, D.
    et al.
    Fich, M.
    McCoey, C.
    van Kempen, T. A.
    Fuente, A.
    Kristensen, L. E.
    Cernicharo, J.
    Caselli, P.
    Visser, R.
    Plume, R.
    Herczeg, G. J.
    van Dishoeck, E. F.
    Wampfler, S.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bergin, E.
    Benz, A. O.
    Bjerkeli, P.
    Blake, G.
    Bontemps, S.
    Braine, J.
    Bruderer, S.
    Codella, C.
    Daniel, F.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Encrenaz, P.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herpin, F.
    Hogerheijde, M. R.
    Jacq, T.
    Jorgensen, J. K.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    Marseille, M.
    Melnick, G.
    Neufeld, D.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Pearson, J.
    Risacher, C.
    Santiago-Garcia, J.
    Saraceno, P.
    Shipman, R.
    Tafalla, M.
    van der Tak, F.
    Wyrowski, F.
    Yildiz, U. A.
    Caux, E.
    Honingh, N.
    Jellema, W.
    Schieder, R.
    Teyssier, D.
    Whyborn, N.
    Herschel/HIFI spectroscopy of the intermediate mass protostar NGC7129 FIRS 22010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L41-Article in journal (Refereed)
    Abstract [en]

    Herschel/HIFI observations of water from the intermediate mass protostar NGC 7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four (H2O)-O-16 and two (H2O)-O-18 lines, were observed and all but one (H2O)-O-18 line were detected. The four (H2O)-O-16 lines discussed here share a similar morphology: a narrower, approximate to 6kms(-1), component centered slightly redward of the systemic velocity of NGC7129 FIRS 2 and a much broader, approximate to 25 km s(-1) component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H2O is constrained to approximate to 10(-7) for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H2O/CO relative abundance is found to be approximate to 0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.

  • 21.
    Justtanont, K.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Onsala Space Observatory.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schöier, F. L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Hasegawa, T.
    Hjalmarson, Å.
    Kwok, S.
    Olberg, M.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Volk, K.
    Elitzur, M.
    W Hya through the eye of Odin. Satellite observations of circumstellar submillimetre H2O line emission2005In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 439, p. 627-633Article in journal (Refereed)
    Abstract [en]

    We present Odin observations of the AGB star W Hya in the ground-state transition of ortho-H{2}O, 1{10}-101, at 557 GHz. The line is clearly of circumstellar origin. Radiative transfer modelling of the water lines observed by Odin and ISO results in a mass-loss rate of (2.5±0.5)×10-7 Mȯ yr-1, and a circumstellar H{2}O abundance of (2.0±1.0)×10-3. The inferred mass-loss rate is consistent with that obtained from modelling the circumstellar CO radio line emission, and also with that obtained from the dust emission modelling combined with a dynamical model for the outflow. The very high water abundance, higher than the cosmic oxygen abundance, can be explained by invoking an injection of excess water from evaporating icy bodies in the system. The required extra mass of water is quite small, on the order of 0.1 Moplus.

  • 22. Justtanont, Kay
    et al.
    Liseau, Rene
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Mapping the PAHs and H2 in ρ Oph A2008In: Organic Matter in Space: Proceedings of the International Astronomical Union, IAU Symposium, Volume 251,, 2008, p. 227-228Conference paper (Other academic)
    Abstract [en]

    We present an ISOCAM-CVF map of the ρ Oph A region, covering 3′ × 3′. For each 6 arcsec2 pixel, we extract the spectrum from 5–15 μm. We determine the fluxes of the main PAH features by fitting Lorentzian profiles to the spectrum. The peaks of the various PAH components correspond well with the known positions of the PDRs in this vicinity. The spectrum in several pixels exhibits strong rotational lines of molecular hydrogen which can be used to derive the physical properties of the cloud. The H2 emission traces the hot gas of the bipolar CO outflow from VLA1623.

  • 23. Kristensen, L. E.
    et al.
    Visser, R.
    van Dishoeck, E. F.
    Yıldız, U. A.
    Doty, S. D.
    Herczeg, G. J.
    Liu, F.-C.
    Parise, B.
    Jørgensen, J. K.
    van Kempen, T. A.
    Brinch, C.
    Wampfler, S. F.
    Bruderer, S.
    Benz, A. O.
    Hogerheijde, M. R.
    Deul, E.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bergin, E. A.
    Bjerkeli, P.
    Blake, G. A.
    Bontemps, S.
    Braine, J.
    Caselli, P.
    Cernicharo, J.
    Codella, C.
    Daniel, F.
    de Graauw, Th.
    di Giorgio, A. M.
    Dominik, C.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Giannini, T.
    Goicoechea, J. R.
    Helmich, F.
    Herpin, F.
    Jacq, T.
    Johnstone, D.
    Kaufman, M. J.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Liseau, R.
    Marseille, M.
    McCoey, C.
    Melnick, G.
    Neufeld, D.
    Nisini, B.
    Olberg, M.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Santiago-García, J.
    Saraceno, P.
    Shipman, R.
    Tafalla, M.
    Tielens, A. G. G. M.
    van der Tak, F.
    Wyrowski, F.
    Beintema, D.
    de Jonge, A.
    Dieleman, P.
    Ossenkopf, V.
    Roelfsema, P.
    Stutzki, J.
    Whyborn, N.
    Water in low-mass star-forming regions with Herschel . HIFI spectroscopy of NGC 13332010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L30-Article in journal (Refereed)
    Abstract [en]

    “Water In Star-forming regions with Herschel” (WISH) is a key programme dedicated to studying the role of water and related species during the star-formation process and constraining the physical and chemical properties of young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory observed three deeply embedded protostars in the low-mass star-forming region NGC 1333 in several H_216O, H_218O, and CO transitions. Line profiles are resolved for five H_216O transitions in each source, revealing them to be surprisingly complex. The line profiles are decomposed into broad (>20 km s-1), medium-broad (~5-10 km s-1), and narrow (<5 km s-1) components. The H_218O emission is only detected in broad 110-101 lines (>20 km s-1), indicating that its physical origin is the same as for the broad H_216O component. In one of the sources, IRAS4A, an inverse P Cygni profile is observed, a clear sign of infall in the envelope. From the line profiles alone, it is clear that the bulk of emission arises from shocks, both on small (⪉1000 AU) and large scales along the outflow cavity walls (~10 000 AU). The H2O line profiles are compared to CO line profiles to constrain the H2O abundance as a function of velocity within these shocked regions. The H2O/CO abundance ratios are measured to be in the range of ~0.1-1, corresponding to H2O abundances of ~10-5-10-4 with respect to H2. Approximately 5-10% of the gas is hot enough for all oxygen to be driven into water in warm post-shock gas, mostly at high velocities. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Tables 2 and 3 (page 6) are only available in electronic form at http://www.aanda.org

  • 24.
    Larsson, B.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Curry, C. L.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Johansson, L. E. B.
    Kwok, S.
    Lecacheux, A.
    Liljeström, T.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L. H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schéele, F. v.
    Tothill, N. F. H.
    Volk, K.
    Wilson, C. D.
    Hjalmarson, Å.
    First NH3 detection of the Orion Bar2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L69-L72Article in journal (Refereed)
    Abstract [en]

    Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (\cite{wilson01}). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5x 10-9. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor.

  • 25.
    Larsson, B.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Men'shchikov, A. B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    The ISO-LWS map of the Serpens cloud core. II. The line spectra2002In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 386, p. 1055-1073Article in journal (Refereed)
    Abstract [en]

    We present spectrophotometric ISO imaging with the LWS and the CAM-CVF of the Serpens molecular cloud core. The LWS map is centred on the far infrared and submillimetre source FIRS 1/SMM 1 and its size is 8',x 8'. The fine structure line emission in [O I] 63 mu m and [C II] 157 mu m is extended on the arcminute scale and can be successfully modelled to originate in a PDR with G0 = 15 +/- 10 and n(H2) in the range of (104-105) cm-3. Extended emission might also be observed in the rotational line emission of H2O and high-J CO. However, lack of sufficient angular resolution prevents us from excluding the possibility that the emssion regions of these lines are point like, which could be linked to the embedded objects SMM 9/S 68 and SMM 4. Toward the Class 0 source SMM 1, the LWS observations reveal, in addition to fine structure line emission, a rich spectrum of molecular lines, superposed onto a strong, optically thick dust continuum (Larsson et al. \cite{Lar00}). The sub-thermally excited and optically thick CO, H2O and OH lines are tracing an about 103 AU source with temperatures higher than 300 K and densities above 106 cm-3 (M=0.01 Msun). The molecular abundances, X=N(mol)/N(H2), are X=(1, 0.1, 0.02, ge 0.025) x 10-4 for CO, H2O, OH and 13CO, respectively. Our data are consistent with an ortho-to-para ratio of 3 for H2O. OH appears highly overabundant, which we tentatively ascribe to an enhanced (X-ray) ionisation rate in the Serpens cloud core (zeta >> 10-18 s-1). We show that geometry is of concern for the correct interpretation of the data and based on 2D-radiative transfer modelling of the disk/torus around SMM 1, which successfully reproduces the entire observed SED and the observed line profiles of low-to-mid-J CO isotopomers, we can exclude the disk to be the source of the LWS-molecular line emission. The same conclusion applies to models of dynamical collapse (``inside-out'' infall). The 6{' '} pixel resolution of the CAM-CVF permits us to see that the region of rotational H2 emission is offset from SMM 1 by 30{' '}, at position angle 340deg, which is along the known jet flow from the Class 0 object. This H2 gas is extinguished by AV = 4.5 mag and at a temperature of 10310 K, which suggests that the heating of the gas is achieved through relatively slow shocks. Although we are not able to establish any firm conclusion regarding the detailed nature of the shock waves, our observations of the molecular line emission from SMM 1 are to a limited extent explainable in terms of an admixture of J-shocks and of C-shocks, the latter with speeds of about (15-20) km s-1, whereas dynamical infall is not directly revealed by our data. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.

  • 26.
    Larsson, B.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Men'shchikov, A. B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Caux, E.
    Ceccarelli, C.
    Lorenzetti, D.
    Molinari, S.
    Nisini, B.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Saraceno, P.
    Sibille, F.
    Spinoglio, L.
    White, G. J.
    Stockholm University, Faculty of Science, Department of Astronomy.
    The ISO-LWS map of the Serpens cloud core. I. The SEDs of the IR/SMM sources2000In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 363, p. 253-268Article in journal (Refereed)
    Abstract [en]

    Iso-Lws mapping observations of the Serpens molecular cloud core are presented. The spectral range is 50 - 200 μ m and the map size is 8',x 8'. These observations suffer from severe source confusion at Fir wavelengths and we employ a Maximum Likelihood Method for the spectro-spatial deconvolution. The strong and fairly isolated source SMM 1/FIRS 1 presented a test case, whose modelled spectral energy distribution (SED), within observational errors, is identical to the observed one. The model results for the other infrared and submillimetre sources are therefore likely to represent their correct SEDs. Simulations demonstrating the reliability and potential of the developed method support this view. It is found that some sources do not exhibit significant Fir emission and others are most likely not pointlike at long wavelengths. In contrast, the SEDs of a number of SMMs are well fit by modified single-temperature blackbodies over the entire accessible spectral range. For the majority of sources the peak of the SEDs is found within the spectral range of the Lws and derived temperatures are generally higher (>= 30 K) than have been found by earlier deconvolution attempts using Iras data. SMM sizes are found to be only a few arcsec in diameter. In addition, the SMMs are generally optically thick even at Lws wavelengths, i.e. estimated lambda (TAu=1) are in the range 160-270 μ m. The Rayleigh-Jeans tails are less steep than expected for optically thin dust emission. This indicates that the SMMs are optically thick out to longer wavelengths than previously assumed, an assertion confirmed by self-consistent radiative transfer calculations. Models were calculated for five sources, for which sufficient data were available, viz. SMM 1, 2, 3, 4 and 9. These models are optically thick out to millimetre wavelengths (wavelength of unit optical depth 900 to 1 400 μ m). Envelope masses for these SMMs are in the range 2-6 Msun, which is of course considerably more massive than estimates based on the optically thin assumption. The luminosities are in the range 10-70 Lsun, suggesting the formation of low-mass to intermediate mass stars, so that the existence of such massive envelopes argues for extreme youth of the SMMs in the Serpens cloud core. Finally, we present, for the first time, the full infrared SEDs for the outburst source DEOS, both at high and low intensity states. Based on observations with Iso, an Esa project with instruments funded by Esa Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of Isas and Nasa.

  • 27.
    Larsson, Bengt
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Gas and dust in the star-forming region rho Oph A II. The gas in the PDR and in the dense cores2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 608, article id A133Article in journal (Refereed)
    Abstract [en]

    Context. The evolution of interstellar clouds of gas and dust establishes the prerequisites for star formation. The pathway to the formation of stars can be studied in regions that have formed stars, but which at the same time also display the earliest phases of stellar evolution, i.e. pre-collapse/collapsing cores (Class-1), protostars (Class 0), and young stellar objects (Class I, II, III).

    Aims. We investigate to what degree local physical and chemical conditions are related to the evolutionary status of various objects in star-forming media.

    Methods. rho OphA displays the entire sequence of low-mass star formation in a small volume of space. Using spectrophotometric line maps of H-2, H2O, NH3, N2H+, O-2, OI, CO, and CS, we examine the distribution of the atomic and molecular gas in this dense molecular core. The physical parameters of these species are derived, as are their relative abundances in rho Oph A. Using radiative transfer models, we examine the infall status of the cold dense cores from their resolved line profiles of the ground state lines of H2O and NH3, where for the latter no contamination from the VLA 1623 outflow is observed and line overlap of the hyperfine components is explicitly taken into account.

    Results. The stratified structure of this photon dominated region (PDR), seen edge-on, is clearly displayed. Polycyclic aromatic hydrocarbons (PAHs) and OI are seen throughout the region around the exciting star S 1. At the interface to the molecular core 0.05 pc away, atomic hydrogen is rapidly converted into H-2, whereas OI protrudes further into the molecular core. This provides oxygen atoms for the gas-phase formation of O-2 in the core SM1, where X(O-2) similar to 5 x 10(-8). There, the ratio of the O-2 to H2O abundance [X(H2O) similar to 5 x 10(-9)] is significantly higher than unity. Away from the core, O-2 experiences a dramatic decrease due to increasing H2O formation. Outside the molecular core rho Oph A, on the far side as seen from S 1, the intense radiation from the 0.5 pc distant early B-type star HD147889 destroys the molecules.

    Conclusions. Towards the dark core SM1, the observed abundance ratio X(O-2)/X(H2O) > 1, which suggests that this object is extremely young, which would explain why O-2 is such an elusive molecule outside the solar system.

  • 28.
    Larsson, Bengt
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, Rene
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, Laurent
    Bergman, Per
    Bernath, Peter
    Biver, Nicolas
    Black, John
    Booth, Roy
    Buat, Veronique
    Crovisier, Jacques
    Curry, Charles
    Dahlgren, Magnus
    Encrenaz, Pierre
    Falgarone, Edith
    Feldman, Paul
    Fish, Michel
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fredrixon,
    Frisk, Urban
    Gahm, Gösta
    Stockholm University, Faculty of Science, Department of Astronomy.
    Gerin, Maryvonne
    Hagström, Magne
    Harju, Jorma
    Hasegawa, Tatsuhiko
    Hjalmarsson, Åke
    Johansson, Lars
    Justtanout, Kay
    Stockholm University, Faculty of Science, Department of Astronomy.
    Klotz, Alain
    Kytölä, Erikii
    Kwok, Sun
    Lecacheux, Alain
    Liljeström, Tarja
    Llewellyn, Edward
    Lundin, Stefan
    Mégie, Gérard
    Mitchell, Gary
    Murtagh, Donal
    Nordh, Lennart
    Nyman, Lars-Åke
    Olberg, Michael
    Olofsson, Henrik
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, Hans
    Stockholm University, Faculty of Science, Department of Astronomy.
    Persson, Glen
    Plume, Rene
    Rickman, Hans
    Ristorcelli, Isabelle
    Rydbeck, Gustaf
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Scheele, Fredrik
    Serra, Guy
    Torchinsky, Steve
    Tothill, Nick
    Volk, Kevin
    Wiklind, Tommy
    Wilson, Christine
    Winnberg, Anders
    Witt, George
    Department of Meteorology.
    Molecular oxygen in the rho Ophiuchi cloud2007In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 466, no 3, p. 5-Article in journal (Refereed)
    Abstract [en]

    Context: Molecular oxygen, O2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O2 emission.

    Aims: The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium. Methods: The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core ρ Oph A was observed with Odin for 34 days during several observing runs.

    Results: We detect a spectral line at v_LSR =+3.5 km s-1 with Δ v_FWHM=1.5 km s-1, parameters which are also common to other species associated with ρ Oph A. This feature is identified as the O2 (NJ = 11 - 1_0) transition at 118 750.343 MHz.

    Conclusions: The abundance of molecular oxygen, relative to H{2} , is 5 × 10-8 averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.

    Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Étude Spatiale (CNES). The Swedish Space Corporation has been the industrial prime contractor and also is operating the satellite. Appendix A is only available in electronic form at http://www.aanda.org

  • 29. Lefloch, B.
    et al.
    Cabrit, S.
    Codella, C.
    Melnick, G.
    Cernicharo, J.
    Caux, E.
    Benedettini, M.
    Boogert, A.
    Caselli, P.
    Ceccarelli, C.
    Gueth, F.
    Hily-Blant, P.
    Lorenzani, A.
    Neufeld, D.
    Nisini, B.
    Pacheco, S.
    Pagani, L.
    Pardo, J. R.
    Parise, B.
    Salez, M.
    Schuster, K.
    Viti, S.
    Bacmann, A.
    Baudry, A.
    Bell, T.
    Bergin, E. A.
    Blake, G.
    Bottinelli, S.
    Castets, A.
    Comito, C.
    Coutens, A.
    Crimier, N.
    Dominik, C.
    Demyk, K.
    Encrenaz, P.
    Falgarone, E.
    Fuente, A.
    Gerin, M.
    Goldsmith, P.
    Helmich, F.
    Hennebelle, P.
    Henning, T.
    Herbst, E.
    Jacq, T.
    Kahane, C.
    Kama, M.
    Klotz, A.
    Langer, W.
    Lis, D.
    Lord, S.
    Maret, S.
    Pearson, J.
    Phillips, T.
    Saraceno, P.
    Schilke, P.
    Tielens, X.
    van der Tak, F.
    van der Wiel, M.
    Vastel, C.
    Wakelam, V.
    Walters, A.
    Wyrowski, F.
    Yorke, H.
    Bachiller, R.
    Borys, C.
    de Lange, G.
    Delorme, Y.
    Kramer, C.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lai, R.
    Maiwald, F. W.
    Martin-Pintado, J.
    Mehdi, I.
    Ossenkopf, V.
    Siegel, P.
    Stutzki, J.
    Wunsch, J. H.
    The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1. II. Shock dynamics2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, p. L113-Article in journal (Refereed)
    Abstract [en]

    Context. The outflow driven by the low-mass class 0 protostar L1157 is the prototype of the so-called chemically active outflows. The bright bowshock B1 in the southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD) shock models, for which dynamical and chemical processes are strongly interdependent. Aims: We present the first results of the unbiased spectral survey of the L1157-B1 bowshock, obtained in the framework of the key program “Chemical HErschel Surveys of star forming regions” (CHESS). The main aim is to trace the warm and chemically enriched gas and to infer the excitation conditions in the shock region. Methods: The CO 5-4 and o-H2O 110-101 lines have been detected at high-spectral resolution in the unbiased spectral survey of the HIFI-band 1b spectral window (555-636 GHz), presented by Codella et al. in this volume. Complementary ground-based observations in the submm window help establish the origin of the emission detected in the main-beam of HIFI and the physical conditions in the shock. Results: Both lines exhibit broad wings, which extend to velocities much higher than reported up to now. We find that the molecular emission arises from two regions with distinct physical conditions : an extended, warm (100 K), dense (3 × 105 cm-3) component at low-velocity, which dominates the water line flux in Band 1; a secondary component in a small region of B1 (a few arcsec) associated with high-velocity, hot (>400 K) gas of moderate density ((1.0-3.0) × 104 cm-3), which appears to dominate the flux of the water line at 179μm observed with PACS. The water abundance is enhanced by two orders of magnitude between the low- and the high-velocity component, from 8 × 10-7 up to 8 × 10-5. The properties of the high-velocity component agree well with the predictions of steady-state C-shock models. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  • 30. Lis, D. C.
    et al.
    Pearson, J. C.
    Neufeld, D. A.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Herschel/HIFI discovery of interstellar chloronium (H2Cl+)2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, no L9Article in journal (Refereed)
    Abstract [en]

    We report the first detection of chloronium, H2Cl+, in the interstellar medium, using the HIFI instrument aboard the Herschel Space Observatory. The 212–101 lines of ortho-HCl+ and ortho-HCl+ are detected in absorption towards NGC 6334I, and the 111–000 transition of para-HCl+ is detected in absorption towards NGC 6334I and Sgr B2(S). The H2Cl+ column densities are compared to those of the chemically-related species HCl. The derived HCl/H2Cl+ column density ratios, ~1–10, are within the range predicted by models of diffuse and dense photon dominated regions (PDRs). However, the observed H2Cl+ column densities, in excess of 1013 cm-2, are significantly higher than the model predictions. Our observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.

  • 31. Liseau, R.
    et al.
    Goldsmith, P. F.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Bergman, P.
    Le Bourlot, J.
    Bell, T. A.
    Benz, A. O.
    Bergin, E. A.
    Bjerkeli, P.
    Black, J. H.
    Bruderer, S.
    Caselli, P.
    Caux, E.
    Chen, J. -H
    de Luca, M.
    Encrenaz, P.
    Falgarone, E.
    Gerin, M.
    Goicoechea, J. R.
    Hjalmarson, A.
    Hollenbach, D. J.
    Justtanont, K.
    Kaufman, M. J.
    Le Petit, F.
    Li, D.
    Lis, D. C.
    Melnick, G. J.
    Nagy, Z.
    Olofsson, A. O. H.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Roueff, E.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Snell, R. L.
    van der Tak, F. F. S.
    van Dishoeck, E. F.
    Vastel, C.
    Viti, S.
    Yildiz, U. A.
    Multi-line detection of O-2 toward rho Ophiuchi A2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 541, p. A73-Article in journal (Refereed)
    Abstract [en]

    Context. Models of pure gas-phase chemistry in well-shielded regions of molecular clouds predict relatively high levels of molecular oxygen, O-2, and water, H2O. These high abundances imply high cooling rates, leading to relatively short timescales for the evolution of gravitationally unstable dense cores, forming stars and planets. Contrary to expectations, the dedicated space missions SWAS and Odin typically found only very small amounts of water vapour and essentially no O-2 in the dense star-forming interstellar medium. Aims. Only toward rho OphA did Odin detect a very weak line of O-2 at 119 GHz in a beam of size 10 arcmin. The line emission of related molecules changes on angular scales of the order of some tens of arcseconds, requiring a larger telescope aperture such as that of the Herschel Space Observatory to resolve the O-2 emission and pinpoint its origin. Methods. We use the Heterodyne Instrument for the Far Infrared (HIFI) aboard Herschel to obtain high resolution O-2 spectra toward selected positions in the rho Oph A core. These data are analysed using standard techniques for O2 excitation and compared to recent PDR-like chemical cloud models. Results. The N-J = 3(3)-1(2) line at 487.2 GHz is clearly detected toward all three observed positions in the rho Oph A core. In addition, an oversampled map of the 5(4)-3(4) transition at 773.8 GHz reveals the detection of the line in only half of the observed area. On the basis of their ratios, the temperature of the O-2 emitting gas appears to vary quite substantially, with warm gas (greater than or similar to 50 K) being adjacent to a much colder region, of temperatures lower than 30 K. Conclusions. The exploited models predict that the O-2 column densities are sensitive to the prevailing dust temperatures, but rather insensitive to the temperatures of the gas. In agreement with these models, the observationally determined O-2 column densities do not seem to depend strongly on the derived gas temperatures, but fall into the range N(O-2) = 3 to greater than or similar to 6 x 10(15) cm(-2). Beam-averaged O-2 abundances are about 5 x 10(-8) relative to H-2. Combining the HIFI data with earlier Odin observations yields a source size at 119 GHz in the range of 4 to 5 arcmin, encompassing the entire rho Oph A core. We speculate that one of the reasons for the generally very low detection rate of O-2 is the short period of time during which O-2 molecules are reasonably abundant in molecular clouds.

  • 32.
    Liseau, R.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandeker, A.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R.
    Buat, V.
    Curry, C.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L.
    Kwok, S.
    Lecacheux, A.
    Liljeström, T.
    Mattila, K.
    Mitchell, G.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schéele, F. v.
    Serra, G.
    Tothill, N.
    Volk, K.
    Wilson, C.
    First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L73-L76Article in journal (Refereed)
    Abstract [en]

    Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 x 10-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 x 10-10. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor. and based on observations collected with the Swedish ESO Submillimeter Telescope, SEST, in La Silla, Chile.

  • 33. Liseau, R.
    et al.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Search for HOOH in Orion2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, article id A53Article in journal (Refereed)
    Abstract [en]

    Context: The abundance of key molecules determines the level of cooling that is necessary for the formation of stars and planetary systems. In this context, one needs to understand the details of the time dependent oxygen chemistry, leading to the formation of O-2 and H2O.

    Aims: We aim to determine the degree of correlation between the occurrence of O-2 and HOOH (hydrogen peroxide) in star-forming molecular clouds. We first detected O-2 and HOOH in rho Oph A, we now search for HOOH in Orion OMCA, where O-2 has also been detected.

    Methods: We mapped a 3' x 3' region around Orion H-2-Peak 1 with the Atacama Pathfinder Experiment (APEX). In addition to several maps in two transitions of HOOH, viz. 219.17 GHz and 251.91 GHz, we obtained single-point spectra for another three transitions towards the position of maximum emission.

    Results: Line emission at the appropriate LSR-velocity (Local Standard of Rest) and at the level of >= 4 sigma was found for two transitions, with lower signal-to-noise ratio (2.8-3.5 sigma) for another two transitions, whereas for the remaining transition, only an upper limit was obtained. The emitting region, offset 18 '' south of H2-Peak 1, appeared point-like in our observations with APEX.

    Conclusions: The extremely high spectral line density in Orion makes the identification of HOOH much more difficult than in rho Oph A. As a result of having to consider the possible contamination by other molecules, we left the current detection status undecided.

  • 34. Liseau, R.
    et al.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Pagani, L.
    Black, J. H.
    Hjalmarson, A.
    Justtanont, K.
    (OO)-O-18 and (CO)-O-18 observations of rho Ophiuchi A2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 510, p. A98-Article in journal (Refereed)
    Abstract [en]

    Context. Contrary to theoretical expectation, surprisingly low concentrations of molecular oxygen, O-2, have been found in the interstellar medium. Telluric absorption makes ground based O-2 observations essentially impossible and observations had to be done from space. Millimetre-wave telescopes on space platforms were necessarily small, which resulted in large, several arcminutes wide, beam patterns. Observations of the (N-J = 1(1)-1(0)) ground state transition of O-2 with the Odin satellite resulted in a greater than or similar to 5 sigma detection toward the dense core rho OphA. At the frequency of the line, 119 GHz, the Odin telescope has a beam width of 10', larger than the size of the dense core. Aims. The precise nature of the emitting source and its exact location and extent are therefore unknown. The current investigation is intended to remedy this. Methods. Although the Earth's atmosphere is entirely opaque to low-lying O-2 transitions, it allows ground based observations of the much rarer (OO)-O-16-O-18 in favourable conditions and at much higher angular resolution with larger telescopes. In addition, rho OphA exhibits both multiple radial velocity systems and considerable velocity gradients. Extensive mapping of the region in the proxy (CO)-O-18 (J = 3-2) line can be expected to help identify the O-2 source on the basis of its line shape and Doppler velocity. Line opacities were determined from observations of optically thin (CO)-C-13-O-18 (J = 3-2). During several observing periods, two C18O intensity maxima in rho OphA were searched for (OO)-O-18 in the (2(1)-0(1)) line at 234 GHz with the 12m APEX telescope. These positions are associated also with peaks in the mm-continuum emission from dust. Results. Our observations resulted in an upper limit on the integrated O18O intensity of integral T-A* dv < 0.01 K kms(-1) (3 sigma) into the 26.""5 beam. Together with the (CO)-O-18 data, this leads to a ratio of N((CO)-O-18)/N((OO)-O-18) > 16. Combining Odin's O-2 with the present (OO)-O-18 observations we infer an O-2 abundance 5 x 10(-7) < X(O-2) less than or similar to 2.5 x 10(-6). Conclusions. Examining the evidence, which is based primarily on observations in lines of O18O and C18O, leads us to conclude that the source of observed O-2 emission is most likely confined to the central regions of the rho OphA core. In this limited area, implied O-2 abundances could thus be higher than inferred on the basis of Odin observations (5 x 10(-8)) by up to two orders of magnitude.

  • 35. Liseau, R.
    et al.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lunttila, T.
    Olberg, M.
    Rydbeck, G.
    Bergman, P.
    Justtanont, K.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    de Vries, Bernard L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Gas and dust in the star-forming region rho Oph A The dust opacity exponent beta and the gas-to-dust mass ratio g2d2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 578, article id A131Article in journal (Refereed)
    Abstract [en]

    Aims. We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent beta for spatial and/or temporal variations. Methods. Using mapping observations of the very dense rho Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimetre (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N2H+, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N2H+ (J = 3-2) and (J = 6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H-2), hence the surface density distribution of the gas. Results. The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM 1. The global average, = 88, is not far from the canonical value of 100, however. In rho Oph A, the exponent beta of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class -1 sources to low values close to 0 for the disk-dominated emission in Class III objects. beta assumes intermediate values for evolutionary classes in between. Conclusions. Since beta is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like (CO)-O-18, also N2H+ is frozen onto the grains.

  • 36.
    Liseau, René
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fridlund, C. V. Malcolm
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Physics of Outflows: The Binary Protostar L1551 IRS 5 and its Jets2005In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 619, p. 959-967Article in journal (Refereed)
    Abstract [en]

    Recent observations of the deeply embedded L1551 IRS 5 system permit the detailed examination of the properties of both the stellar binary and the binary jet. For the individual components of the stellar binary, we determine their masses, mass accretion rates, effective temperatures, and luminosities. For the atomic wind/jet flow, we determine the mass-loss rate, yielding observationally determined values of the ratio of the mass loss to the mass accretion rate f. For the X-ray-emitting region in the northern jet, we have obtained the jet velocity and derive the extinction and the densities on different spatial scales. Examining the observational evidence within the framework of the X-wind theory leads us to conclude that these models are indeed potentially able to account for the observational data for this deeply embedded source.

  • 37.
    Maercker, Matthias
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schöier, F.L.
    Olofsson, Hans
    Stockholm University, Faculty of Science, Department of Astronomy. Onsala Space Observatory, Sweden.
    Bergman, P.
    Frisk, U.
    Hjalmarson, Å.
    Justannont, K.
    Kwok, S.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Circumstellar water vapour in M-type AGB stars: constraints from H2O(1,10-1,01) lines obtained with odin2009In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 494, p. 243-252Article in journal (Refereed)
    Abstract [en]

    Context. A detailed radiative transfer code has been previously used to model circumstellar ortho-H2O line emission towards six M-type asymptotic giant branch stars using Infrared Space Observatory Long Wavelength Spectrometer data. Collisional and radiative excitation, including the v(2) = 1 state, was considered. Aims. Spectrally resolved circumstellar H2O(1(10)-1(01)) lines have been obtained towards three M-type AGB stars using the Odin satellite. This provides additional strong constraints on the properties of circumstellar H2O, in particular on the chemistry in the stellar atmosphere, and the photodissociation in the outer envelope. Methods. Infrared Space Observatory and Odin satellite H2O line data are used as constraints for radiative transfer models. Special consideration is taken to the spectrally resolved Odin line profiles, and the effect of excitation to the first excited vibrational states of the stretching modes (v(1) = 1 and v(3) = 1) on the derived abundances is estimated. A non-local, radiative transfer code based on the accelerated lambda iteration formalism is used. A statistical analysis is performed to determine the best-fit models. Results. The H2O abundance estimates are in agreement with previous estimates. The inclusion of the Odin data sets stronger constraints on the size of the H2O envelope. The H2O(1(10)-1(01)) line profiles require a significant reduction in expansion velocity compared to the terminal gas expansion velocity determined in models of CO radio line emission, indicating that the H2O emission lines probe a region where the wind is still being accelerated. Including the v(3) = 1 state significantly lowers the estimated abundances for the low-mass-loss-rate objects. This shows the importance of detailed modelling, in particular the details of the infrared spectrum in the range 3 to 6 mu m, to estimate accurate circumstellar H2O abundances. Conclusions. Spectrally resolved circumstellar H2O emission lines are important probes of the physics and chemistry in the inner regions of circumstellar envelopes around asymptotic giant branch stars. Predictions for H2O emission lines in the spectral range of the upcoming Herschel/HIFI mission indicate that these observations will be very important in this context.

  • 38. Marseille, M. G.
    et al.
    van der Tak, F. F. S.
    Herpin, F.
    Wyrowski, F.
    Chavarría, L.
    Pietropaoli, B.
    Baudry, A.
    Bontemps, S.
    Cernicharo, J.
    Jacq, T.
    Frieswijk, W.
    Shipman, R.
    van Dishoeck, E. F.
    Bachiller, R.
    Benedettini, M.
    Benz, A. O.
    Bergin, E.
    Bjerkeli, P.
    Blake, G. A.
    Braine, J.
    Bruderer, S.
    Caselli, P.
    Caux, E.
    Codella, C.
    Daniel, F.
    Dieleman, P.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Encrenaz, P.
    Fich, M.
    Fuente, A.
    Gaier, T.
    Giannini, T.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herczeg, G. J.
    Hogerheijde, M. R.
    Jackson, B.
    Javadi, H.
    Jellema, W.
    Johnstone, D.
    Jørgensen, J. K.
    Kester, D.
    Kristensen, L. E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Laauwen, W.
    Lis, D.
    Liseau, R.
    Luinge, W.
    McCoey, C.
    Megej, A.
    Melnick, G.
    Neufeld, D.
    Nisini, B.
    Olberg, M.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Roelfsema, P.
    Santiago-García, J.
    Saraceno, P.
    Siegel, P.
    Stutzki, J.
    Tafalla, M.
    van Kempen, T. A.
    Visser, R.
    Wampfler, S. F.
    Yıldız, U. A.
    Water abundances in high-mass protostellar envelopes: Herschel observations with HIFI2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, p. L32-Article in journal (Refereed)
    Abstract [en]

    Aims: We derive the dense core structure and the water abundance in four massive star-forming regions in the hope of understanding the earliest stages of massive star formation. Methods: We present Herschel/HIFI observations of the para-H2O 111-000 and 202-111 and the para-H_218O 111-000 transitions. The envelope contribution to the line profiles is separated from contributions by outflows and foreground clouds. The envelope contribution is modeled with Monte-Carlo radiative transfer codes for dust and molecular lines (MC3D and RATRAN), and the water abundance and the turbulent velocity width as free parameters. Results: While the outflows are mostly seen in emission in high-J lines, envelopes are seen in absorption in ground-state lines, which are almost saturated. The derived water abundances range from 5×10-10 to 4×10-8 in the outer envelopes. We detect cold clouds surrounding the protostar envelope, thanks to the very high quality of the Herschel/HIFI data and the unique ability of water to probe them. Several foreground clouds are also detected along the line of sight. Conclusions: The low H2O abundances in massive dense cores are in accordance with the expectation that high densities and low temperatures lead to freeze-out of water on dust grains. The spread in abundance values is not clearly linked to physical properties of the sources. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation of NASA.Appendix (pages 6 to 7) is only available in electronic form at http://www.aanda.org

  • 39. Nisini, B.
    et al.
    Benedettini, M.
    Codella, C.
    Giannini, T.
    Liseau, R.
    Neufeld, D.
    Tafalla, M.
    van Dishoeck, E. F.
    Bachiller, R.
    Baudry, A.
    Benz, A. O.
    Bergin, E.
    Bjerkeli, P.
    Blake, G.
    Bontemps, S.
    Braine, J.
    Bruderer, S.
    Caselli, P.
    Cernicharo, J.
    Daniel, F.
    Encrenaz, P.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S.
    Fich, M.
    Fuente, A.
    Goicoechea, J. R.
    de Graauw, Th.
    Helmich, F.
    Herczeg, G.
    Herpin, F.
    Hogerheijde, M.
    Jacq, T.
    Johnstone, D.
    Jørgensen, J.
    Kaufman, M.
    Kristensen, L.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lis, D.
    Marseille, M.
    McCoey, C.
    Melnick, G.
    Olberg, M.
    Parise, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pearson, J.
    Plume, R.
    Risacher, C.
    Santiago, J.
    Saraceno, P.
    Shipman, R.
    van Kempen, T. A.
    Visser, R.
    Viti, S.
    Wampfler, S.
    Wyrowski, F.
    van der Tak, F.
    Yıldız, U. A.
    Delforge, B.
    Desbat, J.
    Hatch, W. A.
    Péron, I.
    Schieder, R.
    Stern, J. A.
    Teyssier, D.
    Whyborn, N.
    Water cooling of shocks in protostellar outflows. Herschel-PACS map of L11572010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 518, p. L120-Article in journal (Refereed)
    Abstract [en]

    Context. The far-IR/sub-mm spectral mapping facility provided by the Herschel-PACS and HIFI instruments has made it possible to obtain, for the first time, images of H2O emission with a spatial resolution comparable to ground based mm/sub-mm observations. Aims: In the framework of the Water In Star-forming regions with Herschel (WISH) key program, maps in water lines of several outflows from young stars are being obtained, to study the water production in shocks and its role in the outflow cooling. This paper reports the first results of this program, presenting a PACS map of the o-H2O 179 μm transition obtained toward the young outflow L1157. Methods: The 179 μm map is compared with those of other important shock tracers, and with previous single-pointing ISO, SWAS, and Odin water observations of the same source that allow us to constrain the H2O abundance and total cooling. Results: Strong H2O peaks are localized on both shocked emission knots and the central source position. The H2O 179 μm emission is spatially correlated with emission from H2 rotational lines, excited in shocks leading to a significant enhancement of the water abundance. Water emission peaks along the outflow also correlate with peaks of other shock-produced molecular species, such as SiO and NH3. A strong H2O peak is also observed at the location of the proto-star, where none of the other molecules have significant emission. The absolute 179 μm intensity and its intensity ratio to the H2O 557 GHz line previously observed with Odin/SWAS indicate that the water emission originates in warm compact clumps, spatially unresolved by PACS, having a H2O abundance of the order of 10-4. This testifies that the clumps have been heated for a time long enough to allow the conversion of almost all the available gas-phase oxygen into water. The total H2O cooling is ~10-1 L_ȯ, about 40% of the cooling due to H2 and 23% of the total energy released in shocks along the L1157 outflow. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important partecipation from NASA.

  • 40. Olberg, M.
    et al.
    Frisk, U.
    Lecacheux, A.
    Olofsson, A. O. H.
    Baron, P.
    Bergman, P.
    Florin, G.
    Hjalmarson, Å..
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Murtagh, D.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Teyssier, D.
    Torchinsky, S. A.
    Volk, K.
    The Odin satellite. II. Radiometer data processing and calibration2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L35-L38Article in journal (Refereed)
    Abstract [en]

    The radiometer on-board the Odin satellite comprises four different sub-mm receivers covering the 486-581 GHz frequency range and one fixed frequency 119 GHz receiver. Two auto-correlators and one acousto-optical spectrometer serve as backends. This article gives an overview over the processing of the data delivered by these instruments and discusses calibration issues. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and the Centre National d'Études Spatiales (CNES, France). Odin is operated by the Swedish Space Corporation (SSC), the project's prime industrial contractor.

  • 41. Olofsson, A. O. H.
    et al.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hjalmarson, Å.
    Bergman, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Curry, C. L.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, H. L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Rydbeck, G.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Schéele, F.
    Serra, G.
    Tothill, N. F.
    Volk, K.
    Wilson, C. D.
    Odin water mapping in the Orion KL region2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L47-L54Article in journal (Refereed)
    Abstract [en]

    New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60\arcsec-110\arcsec. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or ``blue'') part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.

  • 42. Olofsson, henrik
    et al.
    Persson, Carina
    Koning, N
    Bergman, Per
    Bernath, Peter
    black, John
    Frisk, Urban
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Hasegawa, T
    Hjalmarsson, Åke
    Kwok, Sun
    Larsson, Bengt
    Department of Astronomy.
    Nummelin, albert
    Olberg, Mikael
    Sandqvist, Aage
    Department of Astronomy.
    Wirsröm, Eva
    A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite.: I. The observational data2007In: Astronomy and Astrophysics, Vol. 476, no 2Article in journal (Refereed)
  • 43. Pagani, L.
    et al.
    Olofsson, A. O. H.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Crovisier, J.
    Curry, C. L.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P. A.
    Fich, M.
    Floren, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L. H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Scheele, F.
    Serra, G.
    Tothill, N. F.
    Volk, K.
    Wiklind, T.
    Wilson, C. D.
    Low upper limits on the O2 abundance from the Odin satellite2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L77-L81Article in journal (Refereed)
    Abstract [en]

    For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsys(SSB) = 600 K), Odin has reached unprecedented upper limits on the abundance of O2, especially in cold dark clouds where the excited state levels involved in the 487 GHz transition are not expected to be significantly populated. Here we report upper limits for a dozen sources. In cold dark clouds we improve upon the published SWAS upper limits by more than an order of magnitude, reaching N(O2)/N(H2) <= 10-7 in half of the sources. While standard chemical models are definitively ruled out by these new limits, our results are compatible with several recent studies that derive lower O2 abundances. Goldsmith et al. (\cite{SWAS2002}) recently reported a SWAS tentative detection of the 487 GHz transition of O2 in an outflow wing towards rho Oph A in a combination of 7 beams covering approximately 10arcmin x 14arcmin . In a brief (1.3 hour integration time) and partial covering of the SWAS region (~65% if we exclude their central position), we did not detect the corresponding 119 GHz line. Our 3 sigma upper limit on the O2 column density is 7.3x 1015 cm-2. We presently cannot exclude the possibility that the SWAS signal lies mostly outside of the 9\arcmin Odin beam and has escaped our sensitive detector. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is operating Odin.

  • 44. Persson, Carina
    et al.
    Olofsson, Henrik
    Koning, N
    Bergman, Per
    Bernath, Peter
    black, John
    Frisk, Urban
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Hasegawa, T
    Hjalmarsson, Åke
    Kwok, Sam
    Larsson, Bengt
    Department of Astronomy.
    Lecacheux, A
    Olberg, Mikael
    Sandqvist, Aage
    Department of Astronomy.
    Wirsröm, Eva
    A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite.: II. Data analysis2007In: Astronomy and Astrophysics, Vol. 476, no 2Article in journal (Refereed)
  • 45. Ristorcelli, I.
    et al.
    Falgarone, E.
    Schöier, F.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Cabrit, S.
    Gerin, M.
    Baron, Ph.
    Frisk, U.
    Harju, J.
    Hjalmarson, Å.
    Klotz, A.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Odin observation of water in the IRAS 16293-2422 low-mass star forming region2005In: Astrochemistry: Recent Successes and Current Challenges: Proceedings of the 231st Symposium of the International Astronomical Union held in Pacific Grove, California, USA, August 29-September 2, 2005, 2005, Vol. 235, p. 227P-Conference paper (Other academic)
    Abstract [en]

    We present the Odin satellite submillimeter measurement of the ground state transition of ortho-water at 557 GHz around the low-mass protostar IRAS16293-2422. The three following regions have been probed: the on-source position, and the two regions of interaction between the molecular outflows and the dense ambient cloud, i .e. on the SiO peak E1, and near the deuterated peak (cf Lis et al.(2002)). The three spectra reveal broad emission, with a narrow and deep absorption feature at the velocity of the quiescent gas. The water line profiles and intensities have been compared and combined with the CO(3- 2) and HCO+ lines from Lis et al.(2002) after convolution over the Odin beam. The contribution from the central envelope on the water line emission has been estimated with the infall model of Shoier et al. 2002. We show that the water emission is dominated by the outflows, particularly in the red wing of the lines. Using a c-shock modelling (Cabrit et al. 2005), we derive an abundance of X(H2O) 1 - 3 × 10-5 of H2, and shock velocities of 12 - 15 km/s. We also show that the absorption feature is due to the cold outer halo and corresponds to a lower limit of a few 10-9 on the H2O abundance.

  • 46. Roelfsema, P. R.
    et al.
    Helmich, F. P.
    Teyssier, D.
    Ossenkopf, V.
    Morris, P.
    Olberg, M.
    Shipman, R.
    Risacher, C.
    Akyilmaz, M.
    Assendorp, R.
    Avruch, I. M.
    Beintema, D.
    Biver, N.
    Boogert, A.
    Borys, C.
    Braine, J.
    Caris, M.
    Caux, E.
    Cernicharo, J.
    Coeur-Joly, O.
    Comito, C.
    de Lange, G.
    Delforge, B.
    Dieleman, P.
    Dubbeldam, L.
    de Graauw, T.
    Edwards, K.
    Fich, M.
    Flederus, F.
    Gal, C.
    di Giorgio, A.
    Herpin, F.
    Higgins, D. R.
    Hoac, A.
    Huisman, R.
    Jarchow, C.
    Jellema, W.
    de Jonge, A.
    Kester, D.
    Klein, T.
    Kooi, J.
    Kramer, C.
    Laauwen, W.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Leinz, C.
    Lord, S.
    Lorenzani, A.
    Luinge, W.
    Marston, A.
    Martín-Pintado, J.
    McCoey, C.
    Melchior, M.
    Michalska, M.
    Moreno, R.
    Müller, H.
    Nowosielski, W.
    Okada, Y.
    Orlea´nski, P.
    Phillips, T. G.
    Pearson, J.
    Rabois, D.
    Ravera, L.
    Rector, J.
    Rengel, M.
    Sagawa, H.
    Salomons, W.
    Sánchez-Suárez, E.
    Schieder, R.
    Schlöder, F.
    Schmülling, F.
    Soldati, M.
    Stutzki, J.
    Thomas, B.
    Tielens, A. G. G. M.
    Vastel, C.
    Wildeman, K.
    Xie, Q.
    Xilouris, M.
    Wafelbakker, C.
    Whyborn, N.
    Zaal, P.
    Bell, T.
    Bjerkeli, P.
    De Beck, E.
    Cavalié, T.
    Crockett, N. R.
    Hily-Blant, P.
    Kama, M.
    Kaminski, T.
    Leflóch, B.
    Lombaert, R.
    de Luca, M.
    Makai, Z.
    Marseille, M.
    Nagy, Z.
    Pacheco, S.
    van der Wiel, M. H. D.
    Wang, S.
    Y\ild\iz, U.
    In-orbit performance of Herschel-HIFI2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 537, p. A17-Article in journal (Refereed)
    Abstract [en]

    <BR /> Aims: In this paper the calibration and in-orbit performance of the Heterodyne Instrument for the Far-Infrared (HIFI) is described. <BR /> Methods: The calibration of HIFI is based on a combination of ground and in-flight tests. Dedicated ground tests to determine those instrument parameters that can only be measured accurately using controlled laboratory stimuli were carried out in the instrument level test (ILT) campaign. Special in-flight tests during the commissioning phase (CoP) and performance verification (PV) allowed the determination of the remaining instrument parameters. The various instrument observing modes, as specified in astronomical observation templates (AOTs), were validated in parallel during PV by observing selected celestial sources. <BR /> Results: The initial calibration and in-orbit performance of HIFI has been established. A first estimate of the calibration budget is given. The overall in-flight instrument performance agrees with the original specification. Issues remain at only a few frequencies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  • 47. Roelfsema, P. R.
    et al.
    Shibai, H.
    Armus, L.
    Arrazola, D.
    Audard, M.
    Audley, M. D.
    Bradford, C. M.
    Charles, I
    Dieleman, P.
    Doi, Y.
    Duband, L.
    Eggens, M.
    Evers, J.
    Funaki, I
    Gao, J. R.
    Giard, M.
    di Giorgio, A.
    Gonzalez Fernandez, L. M.
    Griffin, M.
    Helmich, F. P.
    Hijmering, R.
    Huisman, R.
    Ishihara, D.
    Isobe, N.
    Jackson, B.
    Jacobs, H.
    Jellema, W.
    Kamp, I
    Kaneda, H.
    Kawada, M.
    Kemper, F.
    Kerschbaum, F.
    Khosropanah, P.
    Kohno, K.
    Kooijman, P. P.
    Krause, O.
    van der Kuur, J.
    Kwon, J.
    Laauwen, W. M.
    de Lange, G.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    van Loon, D.
    Madden, S. C.
    Matsuhara, H.
    Najarro, F.
    Nakagawa, T.
    Naylor, D.
    Ogawa, H.
    Onaka, T.
    Oyabu, S.
    Poglitsch, A.
    Reveret, V
    Rodriguez, L.
    Spinoglio, L.
    Sakon, I
    Sato, Y.
    Shinozaki, K.
    Shipman, R.
    Sugita, H.
    Suzuki, T.
    van der Tak, F. F. S.
    Torres Redondo, J.
    Wada, T.
    Wang, S. Y.
    Wafelbakker, C. K.
    van Weers, H.
    Withington, S.
    Vandenbussche, B.
    Yamada, T.
    Yamamura, I
    SPICA-A Large Cryogenic Infrared Space Telescope: Unveiling the Obscured Universe2018In: Publications Astronomical Society of Australia, ISSN 1323-3580, E-ISSN 1448-6083, Vol. 35, article id e030Article in journal (Refereed)
    Abstract [en]

    Measurements in the infrared wavelength domain allow direct assessment of the physical state and energy balance of cool matter in space, enabling the detailed study of the processes that govern the formation and evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions revealed a great deal about the obscured Universe, but were hampered by limited sensitivity. SPICA takes the next step in infrared observational capability by combining a large 2.5-meter diameter telescope. cooled to below 8 K, with instruments employing ultra-sensitive detectors. A combination of passive cooling and mechanical coolers will be used to cool both the telescope and the instruments. With mechanical coolers the mission lifetime is not limited by the supply of cryogen. With the combination of low telescope background and instruments with state-of-the-art detectors SPICA provides a huge advance on the capabilities of previous missions. SPICA instruments offer spectral resolving power ranging from R similar to 50 through 11 000 in the 17-230 mu m domain and R similar to 28.000 spectroscopy between 12 and 18 mu m.SPICA will provide efficient 30-37 mu m broad band mapping, and small field spectroscopic and polarimetric imaging at 100, 200 and 350 mu m. SPICA will provide infrared spectroscopy with an unprecedented sensitivity of similar to 5 x 10(-20) W m (-2) (5 sigma/1 h)-over two orders of magnitude improvement over what earlier missions. This exceptional performance leap, will open entirely new domains in infrared astronomy; galaxy evolution and metal production over cosmic time, dust formation and evolution from very early epochs onwards, the formation history of planetary systems.

  • 48.
    Sandqvist, Aa
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Bernath, P.
    Frisk, U.
    Hjalmarson, Å.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lindqvist, M.
    Olberg, M.
    Olofsson, A. O. H.
    Pagani, L.
    Odin spectral line observations of Sgr A and Sgr B2 at submm wavelengths and in the 118-GHz band2006In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 54, p. 72-76Article in journal (Refereed)
    Abstract [en]

    Since its launch in 2001, the Odin satellite has been observing the Galactic Centre Sgr A Complex (CND, +20 and +50 km s-1 Clouds) as well as the nearby star formation region, Sgr B2, a number of times. Observations have been made in the 118-119 GHz and 486-581 GHz bands. A limited mapping of the Sgr A Complex in the H162O line has been performed and new observations of the H182O line took place in 2006. In the 118-119 GHz band, a strong line of HC3N (J = 13 - 12) has been detected at a number of positions - sensitive upper limits have been obtained for the O2 (11 - 10) and the SiC (3Π2, J = 3 - 2) lines. Towards Sgr B2, submm observations have yielded absorption profles of H162O, H182O, H172O, NH3, and 15NH3.

  • 49.
    Sandqvist, Aa.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Black, J. H.
    Booth, R.
    Buat, V.
    Curry, C. L.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Floren, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, A. O. H.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Schéele, F. v.
    Serra, G.
    Tothill, N. F. H.
    Volk, K.
    Wilson, C. D.
    Winnberg, A.
    Odin observations of H2O in the Galactic Centre2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L63-L67Article in journal (Refereed)
    Abstract [en]

    The Odin satellite has been used to detect emission and absorption in the 557-GHz H216O line in the Galactic Centre towards the Sgr Astar Circumnuclear Disk (CND), and the Sgr A +20 km s-1 and +50 km s-1 molecular clouds. Strong broad H2O emission lines have been detected in all three objects. Narrow H2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km s-1 Spiral Arm and the Local Sgr Spiral Arm. Broad H2O absorption lines near -130 km s-1 are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity Gas'' - HPVG) has been identified in the positive velocity range of ~+120 to +220 km s-1, seen definitely in absorption against the stronger dust continuum emission from the +20 km s-1 and +50 km s-1 clouds and possibly in emission towards the position of Sgr Astar CND. The 548-GHz H218O isotope line towards the CND is not detected at the 0.02 K (rms) level. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is also responsible for the satellite operation.

  • 50.
    Sandqvist, Aage
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hjalmarson, Å.
    Encrenaz, P.
    Gerin, M.
    Goldsmith, P. F.
    Lis, D. C.
    Liseau, R.
    Pagani, L.
    Roueff, E.
    Viti, S.
    Herschel HIFI observations of the Sgr A+50 km s(-1) Cloud Deep searches for O-2 in emission and foreground absorption2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 584, article id A118Article in journal (Refereed)
    Abstract [en]

    Context: The Herschel Oxygen Project (HOP) is an open time key program, awarded 140 h of observing time to search for molecular oxygen (O-2) in a number of interstellar sources. To date O-2 has definitely been detected in only two sources, namely rho Oph A and Orion, reflecting the extremely low abundance of O-2 in the interstellar medium.

    Aims: One of the sources in the HOP program is the + 50 km s(-1) Cloud in the Sgr A Complex in the centre of the Milky Way. Its environment is unique in the Galaxy and this property is investigated to see if it is conducive to the presence of O-2. Methods. The Herschel Heterodyne Instrument for the Far Infrared (HIFI) is used to search for the 487 and 774 GHz emission lines of O-2.

    Results: No O-2 emission is detected towards the Sgr A + 50 km s(-1) Cloud, but a number of strong emission lines of methanol (CH3OH) and absorption lines of chloronium (H2Cl+) are observed.

    Conclusions: A 3 sigma upper limit for the fractional abundance ratio of [O-2]/[H-2] in the Sgr A + 50 km s(-1) Cloud is found to be X(O-2) <= 5x 10(-8). However, since we can find no other realistic molecular candidate than O-2 itself, we very tentatively suggest that two weak absorption lines at 487.261 and 487.302 GHz may be caused by the 487 GHz line of O-2 in two foreground spiral arm clouds. By considering that the absorption may only be apparent, the estimated upper limit to the O-2 abundance of <=(10-20) x 10(-6) in these foreground clouds is very high, as opposed to the upper limit in the Sgr A + 50 km s(-1) Cloud itself, but similar to what has been reached in recent chemical shock models for Orion. This abundance limit was determined also using Odin non-detection limits, and assumes that O-2 fills the beam. If the absorption is due to a differential Herschel OFF-ON emission, the O-2 fractional abundance may be of the order of approximate to(5-10) x 10 (6). With the assumption of pure absorption by foreground clouds, the unreasonably high abundance of (1.4-2.8) x 10(-4) was obtained. The rotation temperatures for CH3OH-A and CH3OH-E lines in the + 50 km s(-1) Cloud are found to be approximate to 64 and 79 K, respectively, and the fractional abundance of CH3OH is approximately 5 x 10(-7).

12 1 - 50 of 58
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