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  • 1. Biver, N. ...
    et al.
    Floren, H.G. ...
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aa. et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Odin observations of water emission variation in comet 103P/Hartley 22010In: Central Bureau Electronic Telegrams (CBET), Vol. CBET, no 2524Article in journal (Other academic)
  • 2. Biver, N.
    et al.
    Lellouch, E.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Florén, H.G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Observation of Saturn and the Enceladus water torus at 557 GHz with Odin2011In: EPSC Abstracts, 2011, p. 912-1-2Conference paper (Refereed)
  • 3. Biver, N.,....
    et al.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Floren, H.-G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Molecular composition and outgassing variability of 103P/Hartley 2 from mm and submm observations2011In: EPSC Abstracts, EPSC , 2011, p. 938-1-2Conference paper (Refereed)
  • 4. Biver, Nicolas
    et al.
    Bockelée-Morvan, Dominique
    Moreno, Raphaël
    Crovisier, Jacques
    Colom, Pierre
    Lis, Dariusz C.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Boissier, Jérémie
    Despois, Didier
    Milam, Stefanie N.
    Ethyl alcohol and sugar in comet C/2014 Q2 (Lovejoy)2015In: Science Advances, ISSN 2375-2548, Vol. 1, no 9, p. 1-5, article id e1500863Article in journal (Refereed)
    Abstract [en]

    The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.

  • 5. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Radio observations of Comet 9P/Tempel 1 before and after Deep Impact2007In: Icarus, Vol. 187, no 1, p. 253-271Article in journal (Refereed)
  • 6. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Radio observations of Comet 9P/Tempel 1 before and after Deep Impact2007In: Icarus (Supplement), Vol. 191, no 2, p. 494-512Article in journal (Refereed)
  • 7. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Submillimetre observations of comets with Odin: 2001 20052007In: Planetary and Space Science, Vol. 55, no 9, p. 1058-1068Article in journal (Refereed)
    Abstract [en]

    The Odin satellite, launched in February 2001, is equipped with a 1.1-m submillimetre telescope. Odin was used to observe the 557 GHz line of water with high spectral resolution in 12 comets between 2001 and 2005. Line shapes and spatial mapping provide information on the anisotropy of the outgassing and constraints on water excitation, enabling accurate measurements of the water production rate. Five comets were regularly observed over periods of more than one month to monitor the variation of their water outgassing rate with heliocentric distance. Observing campaigns have been generally coordinated with ground-based observations of molecular lines at Nançay, CSO or IRAM 30-m telescopes to obtain molecular abundances relative to water. Thanks to Odin's frequency coverage, it was also possible to detect the H218O 548 GHz line, first in comet 153P/Ikeya Zhang in April 2002 [Lecacheux, A., Biver, N., Crovisier, J. et al., 2003, Observations of water in comets with Odin. Astron. Astrophys. 402, L55 L58.] and then in comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). The 16O/18O isotopic ratio (≈450) is consistent with the terrestrial value. Ammonia has been searched for in three comets through its J=1 0 line at 572 GHz and was tentatively detected in C/2001 Q4 and C/2002 T7. The derived abundances of NH3 relative to water are 0.5% and 0.3%, respectively, similar to values obtained in other comets with different techniques.

  • 8. Cavalie, T.
    et al.
    Biver, N.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Odin space telescope monitoring of water vapor in the stratosphere of Jupiter2012In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 61, no 1, p. 3-14Article in journal (Refereed)
    Abstract [en]

    The Odin space telescope has monitored the H2O (110–101) line in Jupiter's stratosphere over the 2003–2009 period. When comparing these data with previous spectra obtained with SWAS and Odin over the 1999–2002 period, we see no significant variations in the line-to-continuum ratio of the H2O line over the whole period. We have however tentatively identified a decrease by ∼15% of the line-to-continuum ratio between 2002 and 2007–2009, indicating that there was less H2O in the stratosphere of Jupiter in 2007–2009 than anticipated. We have tested the IDP (interplanetary dust particles) and SL9 (Shoemaker-Levy 9) 1D time-dependent models presented in Cavalié et al. [2008, Observation of water vapor in the stratosphere 613 of Jupiter with the Odin space telescope. Planetary and Space Science 56, 1573–1584]. We present a series of scenarios that lead to satisfactory fits of the whole data set (1999–2002 and 2003–2009 periods) based on IDP and SL9 models. The evolution of Jupiter's stratospheric H2O that we have tentatively observed has however to be confirmed by Herschel/HIFI observations. If the decrease of the line-to-continuum ratio is confirmed by future observations, it would be a direct evidence that Jupiter's H2O comes from SL9. In addition, this study shows that new constraints on Jupiter's eddy diffusion coefficient profile could be obtained (in the pressure ranges that are probed) from the monitoring of SL9 species in its stratosphere.

  • 9. Cavalie, T.
    et al.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Contribution of the Odin Space Telescope to the Understanding of the Origin of Water Vapor in the Atmosphere of Jupiter2007In: Societe Francaise d'Astronomie et d'Astrophysique, Vol. SF2A, p. 1-5Article, review/survey (Other (popular science, discussion, etc.))
  • 10. 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.

  • 11. 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

  • 12. 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.

  • 13. Hjalmarson, Åke
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    On the progress in Odin’s hunt for molecules2007In: Advances in Space Research, Vol. 40, no 5, p. 630-638Article in journal (Refereed)
  • 14.
    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.

  • 15.
    Karlsson, Roland
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Martin, Sergio
    The OH-streamer in Sagittarius A revisited: Analysis of hydroxyl absorption within 10 pc from the Galactic centre2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, article id A118Article in journal (Refereed)
    Abstract [en]

    Aims. We study the structure and kinematics of the OH-streamer and the +80 km s(-1) cloud and their interactions with the circumnu-clear disk (CND) and with other molecular clouds in the vicinity of the Galactic centre (GC), and we map OH absorption at about 6 '' resolution at R <= 10 pc from the GC, with about 9 km s(-1) of velocity resolution. Methods. The VLA was used to map OH line absorption at the 1665 and 1667 MHz lambda doublet main lines of the (2)Pi(3/2) state towards the Sagittarius A complex. Results. Strong OH absorption was found in the OH-streamer, the southern streamer (SS), the +20, +50, and +80 km s(-1) molecular clouds, the molecular belt, the CND, the expanding molecular ring (EMR), and the high negative velocity gas (HNVG). The OH-streamer was found to comprise three parts, head, mid, and tail, and to interact with the SS/+20, +80 km s(-1) clouds and the CND. Optical depths and column densities divided by excitation temperatures have been calculated for the OH-streamer and the +80 km s(-1) cloud. Conclusions. The OH-streamer, the SS, the +20 and +80 km s(-1) clouds, and the CND are intimately related in position and velocity space. The OH-streamer was found to be a clumpy object stretching in projection from the inner radius of the CND at about 1.8 pc from Sgr A*towards and partly engulfing Sgr A*. As a side result of our data, a possible link between the near side of the EMR and the CND's southwest lobe was found. Additionally, we found OH absorption against all four of the previously known compact H II regions A-D, located east of Sgr A East, indicating their close association with the +50 km s(-1) cloud.

  • 16.
    Karlsson, Roland
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Martin, Sergio
    VizieR Online Data Catalog: OH-streamer in SgrA at 1665 and 1667MHz (Karlsson+, 2015)2015Other (Other academic)
    Abstract [en]

    The VLA was used to map OH line absorption at the 1665 and 1667MHz lambda doublet main lines of the 2{Pi}3/2 state towards the Sagittarius A complex. Strong OH absorption was found in the OH-streamer, the southern streamer (SS), the +20, +50, and +80km/s molecular clouds, the molecular belt, the CND, the expanding molecular ring (EMR), and the high negative velocity gas (HNVG).

    Data cubes of VLA observations of the Sgr A complex at 1667- and 1665MHz OH-absorption at 7"x5" angular and 8.8km/s velocity resolution in 63 spectral channels centered at -38km/s (LSR). OH-absorption is defined as "continuum flux minus line flux". The continuum is taken as the average of 1665 and 1667 MHz maps of line free channels. Observations with the VLA in BnA and DnC arrays have been concatenated with AIPS, and data were calibrated and CLEANed with NRAO AIPS standard procedures.

    (2 data files).

  • 17.
    Karlsson, Roland
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hjalmarson, A.
    Winnberg, A.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Olberg, M.
    Hydroxyl, water, ammonia, carbon monoxide, and neutral carbon towards the Sagittarius A complex VLA, Odin, and SEST observations2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 554, article id A141Article in journal (Refereed)
    Abstract [en]

    Aims. The Sagittarius A complex in the Galactic centre comprises an ensemble of molecular clouds of different species with a variety of geometrical and kinematic properties. This work aims to study molecular abundances, morphology, and kinematics by comparing hydroxyl, water, carbon monoxide, ammonia, and atomic carbon and some of their isotopologues, in the +50 km s(-1) cloud, the circumnuclear disk (CND), the +20 km s(-1) cloud, the expanding molecular ring and the line-of-sight spiral arm features, including the Local/Sgr arm, the -30 km s(-1) arm, and the 3-kpc arm. Methods. We observed the +50 km s(-1) cloud, the CND and the +20 km s(-1) cloud, and other selected positions at the Galactic centre with the VLA, and the Odin satellite. The VLA was used to map the 1665 and 1667 MHz OH lambda doublet main lines of the (H-2(3/2)) state, and the Odin satellite was used to map the 557 GHz H2O (1(10)-1(01)) line as well as to observe the 548 GHz (H2O)-O-18 (1(10)-1(01)) line, the 572 GHz NH3 (1(0)-0(0)) line, the 576 GHz CO J = 5-4 line and the 492 GHz C-I (P-3(1)-P-3(0)) line. Furthermore, the SEST was used to map a 4'.5 x 6' region of the SgrAcomplex in the 220 GHz (CO)-O-18 J = 2-1 line. Results. Strong OH absorption, H2O emission and absorption lines were seen at all observed positions, and the (H2O)-O-18 line was detected in absorption towards the +50 km s(-1) cloud, the CND, the +20 km s(-1)cloud, the expanding molecular ring, and the 3-kpc arm. Strong CO J = 5-4, (CO)-O-18 J = 2-1, and neutral carbon C-I emissions were seen towards the +50 and +20 km s(-1) clouds. NH3 was only detected in weak absorption originating in the line-of-sight spiral arm features. The abundances of OH and H2O in the +50 and +20 km s(-1) clouds reflect the different physical environments in the clouds, where shocks and star formation prevail in the +50 km s(-1) cloud and giving rise to a higher rate of H2O production there than in the +20 km s(-1) cloud. In the CND, cloud collisions and shocks are frequent, and the CND is also subject to intense UV-radiation emanating from the supermassive black hole and the central star cluster. The CND is rich in (HO)-O-2 and OH, and these abundances are considerably higher than in the +50 and +20 km s(-1) clouds. We compare our estimated abundances of OH, H2O, and NH3 with similar and differing results for some other sources available in the literature. As compared to the quiescent cloud values of a few x 10(-9), or lower, the H2O abundance is markedly enhanced in the front sides of the Sgr A molecular cloud cores, (2-7) x 10(-8), as observed in absorption, and highest in the CND. A similar abundance enhancement is seen in OH. The likely explanation is PDR chemistry including grain surface reactions, and perhaps also the influence of shocks. In the redward high-velocity line wings of the +50 and +20 km s(-1) clouds and the CND, the H2O abundances are estimated to be (1-6) x 10(-6) or higher, i.e., similar to the water abundances in outflows of the Orion KL and DR21 molecular clouds, which are said to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry.

  • 18.
    Karlsson, Roland
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sjouwerman, Lorant O.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Whiteoak, John B.
    18-cm VLA observations of OH towards the Galactic Centre: Absorption and emission in the four ground-state OH lines2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 403, p. 1011-1021Article in journal (Refereed)
    Abstract [en]

    The OH distribution in the Sgr A Complex has been observed in the 1612-, 1665-, 1667- and 1720-MHz OH transitions with the Very Large Array (VLA) in BnA configuration. Maps are presented with a channel velocity resolution of about 9 km s -1 and with angular resolutions of  . Some clear results are highlighted here, such as absorption from the Circumnuclear Disk (CND) and the OH-Streamer inside the CND near Sgr , strong absorption towards most of the eastern and western parts of the Sgr A East shell, lack of absorption towards both Sgr A West and the compact H II-regions to the east of Sgr A East, and double-lobed structure of the High Negative Velocity Gas (HNVG) oriented northeast and southwest of Sgr , and finally compact, point-like maser emission in all four transitions, in particular a 1720-MHz maser at -132 km s -1 in the CND as counterpart to a 1720-MHz maser at +132 km s -1 in the CND.

  • 19.
    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.

  • 20.
    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

  • 21. 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.

  • 22.
    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.

  • 23.
    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.

  • 24. Meech, K.J.
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 734, no L1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.

  • 25. Neufeld, David A.
    et al.
    Roueff, Evelyne
    Snell, Ronald L.
    Lis, Dariusz
    Benz, Arnold O.
    Bruderer, Simon
    Black, John H.
    De Luca, Massimo
    Gerin, Maryvonne
    Goldsmith, Paul F.
    Gupta, Harshal
    Indriolo, Nick
    Le Bourlot, Jacques
    Le Petit, Franck
    Larsson, Bengt
    Melnick, Gary J.
    Menten, Karl M.
    Monje, Raquel
    Nagy, Zsofia
    Phillips, Thomas G.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sonnentrucker, Paule
    van der Tak, Floris
    Wolfire, Mark G.
    HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 748, no 1, p. 37-Article in journal (Refereed)
    Abstract [en]

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed parachloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s(-1) cloud) and W31C. Both the para-(H2Cl+)-Cl-35 and para-(H2Cl+)-Cl-37 isotopologues were detected, through observations of their 1(11)-0(00) transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio (OPR) of 3, the observed optical depths imply that chloronium accounts for similar to 4%-12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed OPR of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of similar to 2 x 10(13) cm(-2) and similar to 1.2 x 10(13) cm(-2), respectively, for chloronium in these two sources. We obtained upper limits on the para-(H2Cl+)-Cl-35 line strengths toward H-2 Peak 1 in the Orion Molecular cloud and toward the massive young star AFGL 2591. The chloronium abundances inferred in this study are typically at least a factor similar to 10 larger than the predictions of steady-state theoretical models for the chemistry of interstellar molecules containing chlorine. Several explanations for this discrepancy were investigated, but none has proven satisfactory, and thus the large observed abundances of chloronium remain puzzling.

  • 26. 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.

  • 27. 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.

  • 28. 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)
  • 29. 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.

  • 30.
    Persson, C. M. ...
    et al.
    Onsala Space Observatory.
    Sandqvist, Aa.; et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    The first spectral line surveys searching for signals from the dark ages2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 515, p. A72 1-18Article in journal (Refereed)
    Abstract [en]

    Aims. Our aim is to observationally investigate the cosmic Dark Ages in order to constrain star and structure formation models, as well as the chemical evolution in the early Universe.

    Methods. Spectral lines from atoms and molecules in primordial perturbations at high redshifts can give information about the conditions in the early universe before and during the formation of the first stars in addition to the epoch of reionisation. The lines may arise from moving primordial perturbations before the formation of the first stars (resonant scattering lines), or could be thermal absorption or emission lines at lower redshifts. The difficulties in these searches are that the source redshift and evolutionary state, as well as molecular species and transition are unknown, which implies that an observed line can fall within a wide range of frequencies. The lines are also expected to be very weak. Observations from space have the advantages of stability and the lack of atmospheric features which is important in such observations. We have therefore, as a first step in our searches, used the Odin (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 Centre National d'Etudes Spatiales (CNES). The Swedish Space Corporation was the prime contractor and also is responsible for the satellite operation.) satellite to perform two sets of spectral line surveys towards several positions. The first survey covered the band 547–578 GHz towards two positions, and the second one covered the bands 542.0–547.5 GHz and 486.5–492.0 GHz towards six positions selected to test different sizes of the primordial clouds. Two deep searches centred at 543.250 and 543.100 GHz with 1 GHz bandwidth were also performed towards one position. The two lowest rotational transitions of H2 will be redshifted to these frequencies from z ~ 20–30, which is the predicted epoch of the first star formation.

    Results. No lines are detected at an rms level of 14–90 and 5–35 mK for the two surveys, respectively, and 2–7 mK in the deep searches with a channel spacing of 1–16 MHz. The broad bandwidth covered allows a wide range of redshifts to be explored for a number of atomic and molecular species and transitions. From the theoretical side, our sensitivity analysis show that the largest possible amplitudes of the resonant lines are about 1 mK at frequencies 200 GHz, and a few μK around 500–600 GHz, assuming optically thick lines and no beam-dilution. However, if existing, thermal absorption lines have the potential to be orders of magnitude stronger than the resonant lines. We make a simple estimation of the sizes and masses of the primordial perturbations at their turn-around epochs, which previously has been identified as the most favourable epoch for a detection. This work may be considered as an important pilot study for our forthcoming observations with the Herschel Space Observatory

  • 31. 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)
  • 32.
    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.

  • 33.
    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.

  • 34.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    COSMONOVA och Odin, en personlig återblick2007In: Den Svenska Almanackan 2008, 2007Chapter in book (Other (popular science, discussion, etc.))
  • 35.
    Sandqvist, Aage
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hjalmarson, A.
    Frisk, U.
    Lundin, S.
    Nordh, L.
    Stockholm Univ, AlbaNova Univ Ctr, Stockholm Observ, S-10691 Stockholm, Sweden.
    Olberg, M.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Odin observations of ammonia in the SgrA+50 km s(-1) cloud and circumnuclear disk2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 599, article id A135Article in journal (Refereed)
    Abstract [en]

    Context. The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A complex in the centre of the Milky Way.

    Aims. To study the presence of NH3 in the Galactic centre and spiral arms.

    Methods. Recently, Odin has made complementary observations of the 572 GHz NH3 line towards the SgrA + 50 km s(-1) cloud and circumnuclear disk (CND).

    Results. Significant NH3 emission has been observed in both the + 50 km s(-1) cloud and the CND. Clear NH3 absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy.

    Conclusions. The very large velocity width (80 km s 1) of the NH3 emission associated with the shock region in the southwestern part of the CND may suggest a formation / desorption scenario similar to that of gas-phase H2O in shocks / outflows.

  • 36.
    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).

  • 37. Wilson, C. D.
    et al.
    Mason, A.
    Gregersen, E.
    Olofsson, A. O. H.
    Bergman, P.
    Booth, R.
    Boudet, N.
    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.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Juvela, M.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljestrom, T.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    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.
    Serra, G.
    Tothill, N.
    Volk, K.
    von Scheele, F.
    Submillimeter emission from water in the W3 region2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L59-L62Article in journal (Refereed)
    Abstract [en]

    Using the Odin satellite, we have mapped the submillimeter emission from the 110-101 transition of ortho-water in the W3 star-forming region. A 5arcminx 5arcmin map of the W3 IRS4 and W3 IRS5 region reveals strong water lines at half the positions in the map. The relative strength of the Odin lines compared to previous observations by SWAS suggests that we are seeing water emission from an extended region. Across much of the map the lines are double-peaked, with an absorption feature at -39 km s-1; however, some positions in the map show a single strong line at -43 km s-1. We interpret the double-peaked lines as arising from optically thick, self-absorbed water emission near the W3 IRS5, while the narrower blue-shifted lines originate in emission near W3 IRS4. In this model, the unusual appearance of the spectral lines across the map results from a coincidental agreement in velocity between the emission near W3 IRS4 and the blue peak of the more complex lines near W3 IRS5. The strength of the water lines near W3 IRS4 suggests we may be seeing water emission enhanced in a photon-dominated region. 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.

  • 38. Wilson, Christine
    et al.
    Booth, Roy
    Olofsson, A
    Olberg, Michael
    Persson, C
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Upper limits to the water abundance in starburst galaxies2007In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 469, p. 121-124Article in journal (Refereed)
    Abstract [en]

    Aims.We have searched for emission from the 557 GHz ortho-water line in the interstellar medium of six nearby starburst galaxies. Methods: We used the Odin satellite to observe the 110{-}101 transition of o-H2O in the galaxies NGC 253, IC 342, M 82, NGC 4258, CenA, and M 51. None of the galaxies in our sample was detected. Results: We derive three sigma upper limits to the H2O abundance relative to H2 ranging from 2×10-9 to 1×10-8. The best of these upper limits are comparable to the measured abundance of H2O in the Galactic star forming region W3. However, if only 10% of the molecular gas is in very dense cores, then the water abundance limits in the cores themselves would be larger by a factor of 10 i.e. 2×10-8 to 1×10-7. Conclusions: These observations suggest that detections of H2O emission in galaxies with the upcoming Herschel Space Observatory are likely to require on-source integration times of an hour or more except in the very brightest extragalactic targets such as M 82 and NGC 253.

1 - 38 of 38
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