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  • 1. Beckman, John
    et al.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Piñol, Núria
    Toonen, Silvia
    Hernandez, Olivier
    Carignan, Claude
    The Tremaine-Weinberg method for pattern speeds using H-alpha emission from ionized gas2008In: Formation and Evolution of Galaxy Disks, Astronomical Society of the Pacific , 2008, p. 353-Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The Fabry-Perot interferometer FaNTOmM was used at the 3.6m Canada France Hawaii Telescope and the 1.6m Mont Megantic Telescope to obtain data cubes in H-alpha of 9 nearby spiral galaxies from which maps in integrated intensity, velocity, and velocity dispersion were derived. We then applied the Tremaine-Weinberg method, in which the pattern speed can be deduced from its velocity field, by finding the integrated value of the mean velocity along a slit parallel to the major axis weighted by the intensity and divided by the weighted mean distance of the velocity points from the tangent point measured along the slit. The measured variables can be used either to make separate calculations of the pattern speed and derive a mean, or in a plot of one against the other for all the points on all slits, from which a best fit value can be derived. Linear fits were found for all the galaxies in the sample. For two galaxies a clearly separate inner pattern speed with a higher value, was also identified and measured.

  • 2.
    Blasco Herrera, Javier
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, J.
    Instituto de Astrofísica de Canarias.
    Gutiérrez, L.
    Instituto de Astrofísica de Canarias.
    Lundgren, A.
    APEX telescope, ESO.
    Font, J.
    Instituto de Astrofísica de Canarias.
    Hernandez, O.
    Université de Montréal.
    Carignan, C.
    Université de Montréal.
    HII Regions Feeding the Interstellar Medium in M 832010In: Galaxies in Isolation: Exploring Nature Versus Nurture / [ed] Lourdes Verdes-Montenegro, Ascencíon del Olmo, and Jack Sulentic, San Francisco: Astronomical Society of the Pacific , 2010, p. 244-Conference paper (Other academic)
  • 3.
    Blasco-Herrera, J.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Font, J.
    Beckman, J. E.
    H alpha kinematics of 11 starburst galaxies selected from the Sloan Digital Sky Survey2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 435, no 3, p. 1958-1983Article in journal (Refereed)
    Abstract [en]

    We present analysis of Fabry-Perot interferometric observations for a sample of 11 starburst galaxies with redshift z less than or similar to 0.03 selected from the Sloan Digital Sky Survey. We have targeted the H alpha lambda 6562.78 emission line at spatial sampling of 0.2arcsec-0.4 arcsec and at spectral resolution of R similar to 16 000. Studying two-dimensional maps for the velocity, velocity dispersion, line emission and continuum deliver new insights into the nature of starburst and postburst galaxies. The velocity fields are fitted to an exponential disc model, providing scalelengths and masses, to be compared with the photometric scalelength and the mass estimated from the velocity dispersions. From the line emission, the star formation rates are also calculated and compared with values in the literature. We have found that between 55 and 64 per cent of our sample show large-scale dominating rotation, while 27 per cent show local rotation typically restricted to the central part of each system. The morphology and line profiles in the centre of eight objects are consistent with a recent merger, while another two seem to be involved in a accretion process which, for the moment, has not disrupted their kinematics.

  • 4.
    Blasco-Herrera, Javier
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Physics, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Beckman, J.
    Gutierrez, L.
    Lundgren, A.
    Epinat, B.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Physics, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Font, J.
    Hernandez, O.
    de Denus-Baillargeon, M. -M
    Carignan, C.
    An improved method for statistical studies of the internal kinematics of H ii regions: the case of M832010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 407, no 4, p. 2519-2529Article in journal (Refereed)
    Abstract [en]

    We present the integrated H alpha emission line profile for 157 H ii regions in the central 3.4 x 3.4 arcmin2 of the galaxy M83 (NGC 5236). Using the Fabry-Perot interferometer GH alpha FaS, on the 4.2-m William Herschel Telescope on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity-velocity dispersion relation is also studied, and in the log(L)-log(Sigma) plane we do not find a linear relation, but an upper envelope with equation log(L-H alpha) = 0.9 log(Sigma) + 38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L = 1038.5 erg s-1, in full agreement with previous studies of other galaxies, reinforcing the idea of using H ii regions as standard candles.

  • 5.
    Blasco-Herrera, Javier
    et al.
    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).
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Font, J.
    Instituto de Astrof´ısica de Canarias, Tenerife, Spain.
    Beckman, J .E.
    Instituto de Astrof´ısica de Canarias, Tenerife, Spain.
    Halpha kinematics of 11 starburst galaxies selected from the Sloan Digital Sky Survey2012Manuscript (preprint) (Other academic)
    Abstract [en]

    We present analysis of Fabry-Perot interferometric observations for a sample of 11starburst galaxies with redshift z . 0.03 selected from the Sloan Digital Sky Survey.We have targeted the H 6562.78 emission line at spatial sampling of 0.002−0.004 andat spectral resolution of R 16000, and studying two-dimensional velocity, velocitydispersion, line emission and continuum maps deliver new insights into the nature ofstarburst and postburst galaxies. The velocity fields are fitted to an exponential discmodel, providing scale lengths and masses, to be compared with the photometric scalelength and the mass estimated from the velocity dispersions. From the line emissionthe star formation rates are also calculated and compared with values in the literature.We have found that between 55% and 64% of our sample show large scale dominatingrotation, while 27% show local rotation typically restricted to the central part of eachsystem. The morphology and line profiles in the centre of eight objects are consistentwith a recent merger, while another two seem to be involved in a accretion processwhich has not disrupted their kin

  • 6.
    Blasco-Herrera, Javier
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bergvall, N.
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Marquart, T.
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Structural parameters of starburst and postburst galaxies2012Manuscript (preprint) (Other academic)
    Abstract [en]

    We present two samples of 1173 starbursts and 145 postburst in the redshift range0.01 < z < 0.083, selected from Sloan Digital Sky Survey Data Release 7. We charac-terize both samples using 2D Sersic profiles and measure their asymmetry. The Sersicindex, n, and the effective radii show that starburst galaxies are more concentratedthan the postburst sample, with median n 1.85 for starbursts and 2.85 for post-bursts. There is a large fraction of disky (n < 2) postbursts, a fraction larger thanreported by previous studies. Part of the excess comes from low luminosity (Mr > −19)objects, vastly dominated by discs. We estimate the mass from the velocity dispersionof the H emission line, both for the starbursts and those postbursts with residualemission, finding that Lr / Mb, with b = 1.35 for starbursts and b = 1.5 for post-bursts. The typical values of the mass-to-light ratio range between 0 and 10. This,now, is surprising for starburst galaxies, for which mass-to-light ratios 1 have beenpreviously found.

  • 7. Carignan, Claude
    et al.
    Hernandez, Olivier
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    GHaFaS: Galaxy H alpha Fabry-Perot Spectrometer for the WHT2008In: Pathways Through an Eclectic Universe / [ed] Johan Knapen, Terry Mahoney and Alexandre Vazdekis, 2008, p. 168-Conference paper (Other academic)
    Abstract [en]

    A new scanning Fabry-Perot system will soon be available at the Nasmyth focus of the 4.2 m William Herschel Telescope. It has been designed by the Laboratoire d'Astrophysique Expérimentale in Montréal and is being built in collaboration with astronomers at the Instituto de Astrofísica de Canarias. The instrument will see first light at the beginning of July 2007.

  • 8. Carignan, Claude
    et al.
    Hernandez, Olivier
    Gach, Jean-Luc
    Balard, Philippe
    De Denus-Baillargeon, Marie-Maude
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    GHαFaS: galaxy Hα Fabry-Perot system for the WHT2008In: SPIE--The International Society for Optical Engineering, Vol. 7014, no 188Article, review/survey (Other (popular science, discussion, etc.))
    Abstract [en]

    GHαFaS is a new Fabry-Perot system available at the William Herschel Telescope. It was mounted, for the first time, at the Nasmyth focus of the 4.2 m WHT in La Palma in 2007 July. With a spectral resolution of the order R~15000 and a seeing limited spatial resolution, GHαFaS provides a new look at the Hα-emitting gas over a 4 arcminutes circular field in the nearby universe. Many types of objects can be observed with a scanning Fabry-Perot system on a 4.2 m class telescope such as galaxies, HII regions, planetary nebulae, supernova remnants outflows from stars and the diffuse interstellar medium. Astronomers from the Laboratoire d'Astrophysique Experimentale (LAE) in Montreal, the Laboratoire d'Astrophysique de Marseille (LAM), and the Instituto de Astrofisica de Canarias (IAC), have inaugurated GHαFaS by studying in detail the dynamics of nearby spiral galaxies. A robust set of tools for reducing and analyzing the data cubes obtained with GHαFaS has also been developed.

  • 9.
    Cumming, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stellar dynamics of blue compact galaxies. II. Further indications of a merger in ESO 338-IG042007Report (Other academic)
    Abstract [en]

    Luminous blue compact galaxies, common at z~1 but now relatively rare, show disturbed kinematics in emission lines. As part of a programme to understand their formation and evolution, we have investigated the stellar dynamics of a number of nearby objects in this class. We obtained long-slit spectra with VLT/FORS2 in the spectral region covering the near-infrared calcium triplet. In this paper we focus on the well-known luminous blue compact galaxy ESO 338-IG04 (Tololo 1924-416). A previous investigation, using Fabry-Perot interferometry, showed that this galaxy has a chaotic H-alpha velocity field, indicating that either the galaxy is not in dynamical equilibrium or that H-alpha does not trace the gravitational potential due to feedback from star formation. Along the apparent major axis, the stellar and ionised gas velocities for the most part follow each other. The chaotic velocity field must therefore be a sign that the young stellar population in ESO 338-IG04 is not in dynamical equilibrium. The most likely explanation, which is also supported by its morphology, is that the galaxy has experienced a merger and that this has triggered the current starburst. Summarising the results of our programme so far, we note that emission-line velocity fields are not always reliable tracers of stellar motions, and go on to assess the implications for kinematic studies of similar galaxies at intermediate redshift.

  • 10.
    Cumming, Robert J.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Bergvall, Nils
    Adamo, Angela
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stellar kinematics in blue compact galaxies2009Other (Other (popular science, discussion, etc.))
    Abstract [en]

    In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.

  • 11.
    Cumming, Robert James
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Masegosa, Josefa
    Bergvall, Nils
    Amram, Philippe
    Stellar dynamics of blue compact galaxies.: II. Further indications of a merger in ESO 338-IG042008In: Astronomy & Astrophysics, Vol. 479, no 3Article in journal (Refereed)
    Abstract [en]

    Context: Luminous blue compact galaxies, common at z ~ 1 but now relatively rare, show disturbed kinematics in emission lines. Aims: As part of a programme to understand their formation and evolution, we have investigated the stellar dynamics of a number of nearby objects in this class. Methods: We obtained long-slit spectra with VLT/FORS2 in the spectral region covering the near-infrared calcium triplet. In this paper we focus on the well-known luminous blue compact galaxy ESO 338-IG04 (Tololo 1924-416). A previous investigation, using Fabry-Perot interferometry, showed that this galaxy has a chaotic Hα velocity field, indicating that either the galaxy is not in dynamical equilibrium or that Hα does not trace the gravitational potential due to feedback from star formation. Results: Along the apparent major axis, the stellar and ionised gas velocities for the most part follow each other. The chaotic velocity field must therefore be a sign that the young stellar population in ESO 338-IG04 is not in dynamical equilibrium. The most likely explanation, which is also supported by its morphology, is that the galaxy has experienced a merger and that this has triggered the current starburst. Summarising the results of our programme so far, we note that emission-line velocity fields are not always reliable tracers of stellar motions, and go on to assess the implications for kinematic studies of similar galaxies at intermediate redshift.

  • 12.
    Cumming, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergvall, Nils
    Adamo, Angela
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stellar kinematics in blue compact galaxies2009Report (Other academic)
    Abstract [en]

    In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.

  • 13. Dicaire, I
    et al.
    Andra, 8
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Annan, Annan
    Hα kinematics of the Spitzer Infrared Nearby Galaxies Survey - II2008In: Monthly Notices of the Royal Astronomical Society, Vol. 385, no 2, p. 553-605Article in journal (Refereed)
    Abstract [en]

    This is the second part of an Hα kinematics follow-up survey of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this paper is to shed new light on the role of baryons and their kinematics and on the dark/luminous matter relation in the star-forming regions of galaxies, in relation with studies at other wavelengths. The data for 37 galaxies are presented. The observations were made using Fabry-Perot interferometry with the photon-counting camera FaNTOmM on four different telescopes, namely the Canada-France-Hawaii 3.6-m, the ESO La Silla 3.6-m, the William Herschel 4.2-m and the Observatoire du mont Mégantic 1.6-m telescopes. The velocity fields are computed using custom IDL routines designed for an optimal use of the data. The kinematical parameters and rotation curves are derived using the GIPSY software. It is shown that non-circular motions associated with galactic bars affect the kinematical parameters fitting and the velocity gradient of the rotation curves. This leads to incorrect determinations of the baryonic and dark matter distributions in the mass models derived from those rotation curves.

  • 14. Dicaire, Isabel
    et al.
    Carignan, Claude
    Amram, Philippe
    Hernandez, Olivier
    Chamin, Laurent
    Daigle, Olivier
    de Denus-Baillargeon, Marie-Maude
    Balkowski, Chantal
    Boselli, Alessandro
    Fathi, Kambiz
    Stockholm University.
    Kennicutt, Rob
    Hα kinematics of the Spitzer Infrared Nearby Galaxies Survey2008In: Monthley Notices of Royal Astronomical Society (MNRAS), Vol. 385, p. 52-Article in journal (Refereed)
    Abstract [sv]

    This is the second part of an Hα kinematics follow-up survey of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this paper is to shed new light on the role of baryons and their kinematics and on the dark/luminous matter relation in the star-forming regions of galaxies, in relation with studies at other wavelengths. The data for 37 galaxies are presented. The observations were made using Fabry-Perot interferometry with the photon-counting camera FaNTOmM on four different telescopes, namely the Canada-France-Hawaii 3.6-m, the ESO La Silla 3.6-m, the William Herschel 4.2-m and the Observatoire du mont Mégantic 1.6-m telescopes. The velocity fields are computed using custom IDL routines designed for an optimal use of the data. The kinematical parameters and rotation curves are derived using the GIPSY software. It is shown that non-circular motions associated with galactic bars affect the kinematical parameters fitting and the velocity gradient of the rotation curves. This leads to incorrect determinations of the baryonic and dark matter distributions in the mass models derived from those rotation curves.

  • 15. Falcón-Barroso, Jesús
    et al.
    Bacon, Roland
    Bureau, Martin
    Davies, Roger
    de Zeeuw, Tim
    Emsellem, Eric
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Krajnovic, Davor
    Kuntschner, Harald
    McDermid, Richard
    Peletier, Reynier
    Sarzi, Marc
    A Sauron Study of Stars and Gas in SA Bulges2007In: Island Universes, 2007Conference paper (Other academic)
    Abstract [en]

    We present results from our ongoing effort to understand the morphological and kinematical properties of early-type galaxies using the integral-field spectrograph SAURON. We discuss the relation between the stellar and gas morphology and kinematics in our sub-sample of 24 representative Sa spiral bulges. We focus on the frequency of kinematically decoupled components and on the presence of star formation in circumnuclear rings.

  • 16.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    REVISITING THE SCALE LENGTH-mu(0) PLANE AND THE FREEMAN LAW IN THE LOCAL UNIVERSE2010In: Astrophysical Journal letters, ISSN 2041-8205, Vol. 722, no 1, p. L120-L125Article in journal (Refereed)
    Abstract [en]

    We have used Virtual Observatory technology to analyze the disk scale length r(d) and central surface brightness mu(0) for a sample of 29,955 bright disk galaxies from the Sloan Digital Sky Survey. We use the results in the r band and revisit the relation between these parameters and the galaxy morphology, and find the average value = 20.2 +/- 0.7 mag arcsec(-2). We confirm that late-type spirals populate the lower left corner of the r(d)-mu(0) plane and that the early and intermediate spirals are mixed in this diagram, with disky ellipticals at the top left corner. We further investigate the Freeman Law and confirm that it indeed defines an upper limit for mu(0) in bright disk galaxies with r(mag) < 17.0, and that disks in late-type spirals ( T >= 6) have fainter central surface brightness. Our results are based on a volume-corrected sample of galaxies in the local universe (z < 0.3) that is two orders of magnitudes larger than any sample previously studied and deliver statistically significant implications that provide a comprehensive test bed for future theoretical studies and numerical simulations of galaxy formation and evolution.

  • 17.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Allen, M.
    Gonzalez-Solares, E.
    Hatziminaoglou, E.
    Peletier, R.
    Scale Length of Disk Galaxies2009Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    As a part of a Euro-VO research initiative, we have undertaken a programme aimed at studying the scale length of 54909 Sa-Sd spiral galaxies from the SDSS DR6 catalogue. We have retrieved u, g, r, i, z-band images for all galaxies in order to derive the light profiles. We also calculate asymmetry parameters to select non-disturbed disks for which we will derive exponential disk scale lengths. As images in different bands probe different optical depths and stellar populations, it is likely that a derived scale length value should depend on waveband, and our goal is to use the scale length variations with band pass, inclination, galaxy type, redshift, and surface brightness, in order to better understand the nature of spiral galaxies.

  • 18.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Allen, Mark
    Boch, Thomas
    Hatziminaoglou, Evanthia
    Peletier, Reynier F.
    Scalelength of disc galaxies2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 406, no 3, p. 1595-1608Article in journal (Refereed)
    Abstract [en]

    We have derived disc scalelengths for 30 374 non-interacting disc galaxies in all five Sloan Digital Sky Survey (SDSS) bands. Virtual Observatory methods and tools were used to define, retrieve and analyse the images for this unprecedentedly large sample classified as disc/spiral galaxies in the LEDA catalogue. Cross-correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scalelengths for different types of disc/spiral galaxies. We further investigate asymmetry, concentration and central velocity dispersion as indicators of morphological type, and are able to assess how the scalelength varies with respect to galaxy type. We note, however, that the concentration and asymmetry parameters have to be used with caution when investigating type dependence of structural parameters in galaxies. Here, we present the scalelength derivation method and numerous tests that we have carried out to investigate the reliability of our results. The average r-band disc scalelength is 3.79 kpc, with an rms dispersion of 2.05 kpc, and this is a typical value irrespective of passband and galaxy morphology, concentration and asymmetry. The derived scalelengths presented here are representative for a typical galaxy mass of 1010.8 +/- 0.54 M-circle dot, and the rms dispersion is larger for more massive galaxies. Separating the derived scalelengths for different galaxy masses, the r-band scalelength is 1.52 +/- 0.65 kpc for galaxies with total stellar mass 109-1010 M-circle dot and 5.73 +/- 1.94 kpc for galaxies with total stellar mass between 1011 and 1012 M-circle dot. Distributions and typical trends of scalelengths have also been derived in all the other SDSS bands with linear relations that indicate the relation that connect scalelengths in one passband to another. Such transformations could be used to test the results of forthcoming cosmological simulations of galaxy formation and evolution of the Hubble sequence.

  • 19.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Axon, David J.
    Storchi-Bergmann, Thaisa
    Kharb, Preeti
    Robinson, Andrew
    Marconi, Alessandro
    Maciejewski, Witold
    Capetti, Alessandro
    AN H alpha NUCLEAR SPIRAL STRUCTURE IN THE E0 ACTIVE GALAXY Arp 102B2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 736, no 2, p. 77-Article in journal (Refereed)
    Abstract [en]

    We report the discovery of a two-armed mini-spiral structure within the inner kiloparsec of the E0 LINER/Seyfert 1 galaxy Arp 102B. The arms are observed in H alpha emission and located east and west of the nucleus, extending up to approximate to 1 kpc from it. We use narrow-band imaging from the Hubble Space Telescope Advanced Camera for Surveys, in combination with archival Very Large Array radio images at 3.6 and 6 cm to investigate the origin of the nuclear spiral. From the H alpha luminosity of the spiral, we obtain an ionized gas mass of the order of 10(6) solar masses. One possibility is that the nuclear spiral represents a gas inflow triggered by a recent accretion event which has replenished the accretion disk, giving rise to the double-peaked emission-line profiles characteristic of Arp 102B. However, the radio images show a one-sided curved jet which correlates with the eastern spiral arm observed in the H alpha image. A published milliarcsecond radio image also shows a one-sided structure at position angle approximate to 40 degrees, approximately aligned with the inner part of the eastern spiral arm. The absence of a radio counterpart to the western spiral arm is tentatively interpreted as indicating that the jet is relativistic, with an estimated speed of 0.45c. Estimates of the jet kinetic energy and the ionizing luminosity of the active nucleus indicate that both are capable of ionizing the gas along the spiral arms. We conclude that, although the gas in the nuclear region may have originated in an accretion event, the mini spiral is most likely the result of a jet-cloud interaction rather than an inflowing stream.

  • 20.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, J. E.
    Piñol-Ferrer, Nuria
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hernandez, O.
    Martínez-Valpuesta, I.
    Carignan, C.
    Pattern Speeds of Bars and Spiral Arms from Hα Velocity Fields2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 704, p. 1657-1675Article in journal (Refereed)
    Abstract [en]

    We have applied the Tremaine-Weinberg method to 10 late-type barred spiral galaxies using data cubes, in Hα emission, from the FaNTOmM and GHAFAS Fabry-Perot spectrometers. We have combined the derived bar (and/or spiral) pattern speeds with angular frequency plots to measure the corotation radii for the bars in these galaxies. We base our results on a combination of this method with a morphological analysis designed to estimate the corotation radius to bar-length ratio using two independent techniques on archival near-infrared images, and although we are aware of the limitation of the application of the Tremaine-Weinberg method using Hα observations, we find consistently excellent agreement between bar and spiral arm parameters derived using different methods. In general, the corotation radius, measured using the Tremaine-Weinberg method, is closely related to the bar length, measured independently from photometry and consistent with previous studies. Our corotation/bar-length ratios and pattern speed values are in good agreement with general results from numerical simulations of bars. In systems with identified secondary bars, we measure higher Hα velocity dispersion in the circumnuclear regions, whereas in all the other galaxies, we detect flat velocity dispersion profiles. In the galaxies where the bar is almost purely stellar, Hα measurements are missing, and the Tremaine-Weinberg method yields the pattern speeds of the spiral arms. The excellent agreement between the Tremaine-Weinberg method results and the morphological analysis and bar parameters in numerical simulations suggests that although the Hα emitting gas does not obey the continuity equation, it can be used to derive the bar pattern speed. In addition, we have analyzed the Hα velocity dispersion maps to investigate signatures of secular evolution of the bars in these galaxies. The increased central velocity dispersion in the galaxies with secondary bars suggests that the formation of inner bars or disks may be a necessary step in the formation of bulges in late-type spiral galaxies.

  • 21.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    Carignan, Claude
    Hernandez, Olivier
    Fabry-Perot Interferometry and Spiral Galaxy Dynamics2008In: Pathways Through an Eclectic Universe: Proceedings of a conference held at Santiago del Teide, Tenerife, Spain, 23-27 April 2007 to celebrate John Beckman's 40 years in astrophysics, 2008, p. 182-Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    We present two-dimensional Fabry-Perot observations of the emission-line distribution and kinematics in nearby spiral galaxies. We have developed and demonstrated the utility of a number of analysis tools which have general applicability, but which we have, so far, applied to only one galaxy (M74, Fathi et al. 2007). In this galaxy, we have found kinematic signatures of radial motions caused by an m=2 perturbation. Such a perturbation may well be responsible for the inflow of material forming the nuclear ring and the inner rapidly rotating disk-like structure. The latter, in turn, could help build a pseudo-bulge. In the second paper in this series, we will apply the kinematic analysis tools to a sample of nine late-type spiral galaxies observed with the FaNTOmM Fabry-Perot spectrometer at the Canada-France-Hawaii Telescope.

  • 22.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    Lundgren, Andreas
    Carignan, Claude
    Hernandez, Olivier
    Amram, Philippe
    Balard, Philippe
    Gach, Jean-Luc
    Boulesteix, Jacques
    Knapen, Johan
    Spiral Inflow Feeding the Nuclear Starburst in M83: Observed in Hα Emission with the GHαFaS Fabry-Perot Interferometer2008In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 675, no 1, p. L17-L20Article in journal (Refereed)
    Abstract [en]

    We present observations of the nearby barred starburst galaxy M83 (NGC 5236), with the new Fabry-Perot interferometer GHαFaS mounted on the 4.2 m William Herschel Telescope on La Palma. The unprecedented high-resolution observations, of 16 pc FWHM-1, of the Hα-emitting gas cover the central 2 kpc of the galaxy. The velocity field displays the dominant disk rotation with signatures of gas inflow from kpc scales down to the nuclear regions. At the inner inner Lindblad resonance radius of the main bar and centered at the dynamical center of the main galaxy disk, a nuclear (5.5 +/- 0.9) × 108 Msolar rapidly rotating disk with scale length of 60+/-20 pc has formed. The nuclear starburst is found in the vicinity as well as inside this nuclear disk, and our observations confirm that gas spirals in from the outer parts to feed the nuclear starburst, giving rise to several star formation events at different epochs, within the central 100 pc radius of M83.

  • 23.
    fathi, kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    Zurita, Almudena
    Relano, Monica
    Knapen, Johan
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Carignan, Claude
    Structure and evolution of star-forming gas in late-type spiral galaxies2007In: Stellar Populations as Building Blocks of Galaxies, Proceedings: AU Symposium #241, 2007Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    We study two dimensional Fabry-Perot interferometric observations of the nearby face-on late-type spiral galaxy, NGC 628. We investigate the role of the individual HII regions together with the large-scale gravitational mechanisms which govern star formation and overall evolution in spiral galaxies. Our kinematical analysis (reinforced by literature maps in HI and CO at lower angular resolution) enables us to verify the presence of an inner rapidly rotating inner disk-like component which we attribute to long term secular evolution of the large-scale spiral arms and oval structure. We find that gas is falling in from the outer parts towards the bluer central regions. This could be an early phase in the formation of a pseudo-bulge. We find signatures of radial motions caused by an m=2 perturbation, which are likely to be responsible for the inflow of material forming the circumnuclear ring and the rapidly rotating inner structure.

  • 24.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Beckman, John
    Zurita, Almudena
    Relaño, Monica
    Knapen, Johan
    Daigle, Olivier
    Hernandez, Olivier
    Carignan, Claude
    Evolution of structure in late-type spiral galaxies. I: Ionized gas kinematics in NGC 6282007In: Astronomy and Astrophysics, Vol. 466, no 905Article in journal (Refereed)
    Abstract [en]

    Aims.We study two dimensional Fabry-Perot interferometric observations of the nearby face-on late-type spiral galaxy, NGC 628, in order to analyse the ionized gas component of the interstellar medium. Covering the galaxy out to a radius larger than 12 kpc, and with a spatial sampling of 1.6'', we aim to investigate the large-scale dynamics as well as feedback from individual H ii regions into their surrounding medium. Methods: The observed Hα emission distribution and kinematics are compared with auxiliary data from molecular and atomic gas observations, which display many similarities. We decompose the observed line-of-sight velocities into rotational and higher-order harmonic components, and study the role of gravitational perturbations along with that of external triggers which can disturb the kinematics and morphology of NGC 628. We calculate radial profiles of the emission-line velocity dispersion which we use to study the role of feedback from individual H ii regions. Results: We verify the presence of an inner rapidly rotating disc-like component in NGC 628, which we interpret as caused by slow secular evolution of the large-scale spiral arms and oval structure. In combination with auxiliary data, we find indication for that gas is falling in from the outer parts towards the central regions, where a nuclear ring has formed at the location of the inner Lindblad resonance radius of an an m=2 perturbation. Complementary continuum subtracted narrow band images in Hα have been used to identify 376 H ii regions with calibrated luminosities. The mean velocity dispersion for the ionized gas (even when excluding pixels belonging to H ii regions) is almost constant out to 12 kpc, although it varies from 14 to 20 km s-1, with a steady decline in the outer parts. Conclusions: We have found kinematic signatures of radial motions caused by an m=2 perturbation. Such a perturbation may well be responsible for the inflow of material forming the nuclear ring and the inner rapidly rotating disc-like structure. The latter, in turn, could help build a pseudo-bulge in NGC 628. The current paper demonstrates a number of tools that we have developed for building a solid frame work for studying the evolution of structure in spiral galaxies using two dimensional kinematic observations.

  • 25.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hatziminaoglou, E.
    Epinat, B.
    Disc scalelengths out to redshift 5.82012In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 423, no 1, p. l112-L116Article in journal (Refereed)
    Abstract [en]

    We compute the exponential disc scalelength for 686 disc galaxies with spectroscopic redshifts out to redshift 5.8 based on Hubble Space Telescope archival data. We compare the results with our previous measurements based on 30 000 nearby galaxies from the Sloan Digital Sky Survey. Our results confirm the presence of a dominating exponential component in galaxies out to this redshift. At the highest redshifts, the disc scalelength for the brightest galaxies with absolute magnitude between -24 and -22 is up to a factor of 8 smaller compared to that in the local Universe. This observed scalelength decrease is significantly greater than the value predicted by a cosmological picture in which baryonic disc scalelength scales with the virial radius of the dark matter halo.

  • 26.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Izumi, Takuma
    Romeo, Alessandro B.
    Martin, Sergio
    Imanishi, Masatoshi
    Hatziminaoglou, Evanthia
    Aalto, Susanne
    Espada, Daniel
    Kohno, Kotaro
    Krips, Melanie
    Matsushita, Satoki
    Meier, David S.
    Nakai, Naomasa
    Terashima, Yuichi
    LOCAL INSTABILITY SIGNATURES IN ALMA OBSERVATIONS OF DENSE GAS IN NGC 74692015In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 806, no 2, article id L34Article in journal (Refereed)
    Abstract [en]

    We present an unprecedented measurement of the disk stability and local instability scales in the luminous infrared Seyfert 1 host, NGC 7469, based on ALMA observations of dense gas tracers and with a synthesized beam of 165 x 132 pc. While we confirm that non-circular motions are not significant in redistributing the dense interstellar gas in this galaxy, we find compelling evidence that the dense gas is a suitable tracer for studying the origin of its intensely high-mass star-forming ringlike structure. Our derived disk stability parameter Q accounts for a thick disk structure, and its value falls below unity at the radii in which intense star formation is found. Furthermore, we derive the characteristic instability scale lambda(c) and find a striking agreement between our measured scale of similar to 180 pc and the typical sizes of individual complexes of young and massive star clusters seen in high-resolution images.

  • 27.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundgren, Andreas A.
    Kohno, Kotaro
    Piñol-Ferrer, Nuria
    Stockholm University, Faculty of Science, Department of Astronomy.
    Martin, Sergio
    Espada, Daniel
    Hatziminaoglou, Evanthia
    Imanishi, Masatoshi
    Izumi, Takuma
    Krips, Melanie
    Matsushita, Satoki
    Meier, David S.
    Nakai, Naomasa
    Sheth, Kartik
    Turner, Jean
    van de Ven, Glenn
    Wiklind, Tommy
    ALMA FOLLOWS STREAMING OF DENSE GAS DOWN TO 40 PC FROM THE SUPERMASSIVE BLACKHOLE IN NGC 10972013In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 770, no 2, p. L27-Article in journal (Refereed)
    Abstract [en]

    We present a kinematic analysis of the dense gas in the central 200 parsecs of thenearby galaxy NGC1097, based on Cycle 0 observations with the Atacama LargeMillimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas (nH2 ~ 10^8 cm-3), and quantify its kinematics by means of Fourier decomposition. We find a striking similarity between the ALMA kinematic data and the analytic spiral in ow model that we have previously constructed based onionized gas velocity fields on larger scales. We are able to follow dense gas streamingdown to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulll marginal stability, we deduce that the dense gas is conned to a very thin disc, with 6.0+2.2-2.7 10^6 Msun dynamical mass inside a radius of 40 pc. Finally, we derive a dense gas in ow rate of 0.09Msun yr-1 at 40 pc radius. Combined with previous valuesfrom the H and CO gas, we calculate a combined molecular and ionized gas in ow rateof 0.2Msun yr-1 at 40 pc distance from the central supermassive black hole of NGC1097.

  • 28.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Storchi-Bergmann, Thaisa
    Riffel, Rogemar
    Winge, Claudia
    Axon, David
    Robinson, Andrew
    Capetti, Alessandro
    Marconi, Alessandro
    Streaming Motions toward the Supermassive Black Hole in NGC 10972006In: AstrophysicalJournal Letters, Vol. 641, no L25Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    We have used GMOS-IFU and high-resolution HST-ACS observations to map, in unprecedented detail, the gas velocity field and structure within the 0.7 kpc circumnuclear ring of the SBb LINER/Seyfert 1 galaxy NGC 1097. We find clear evidence of radial streaming motions associated with spiral structures leading to the unresolved (<3.5 pc) nucleus, which we interpret as part of the fueling chain by which gas is transported to the nuclear starburst and supermassive black hole.

  • 29.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Toonen, Silvia
    Falcón-Barroso, Jesús
    Beckman, John
    Hernandez, Olivier
    Daigle, Olivier
    Carignan, Claude
    de Zeeuw, Tim
    Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics2007In: Astrophysical Journal Letters, Vol. 667, no 137Article in journal (Refereed)
    Abstract [en]

    We study the two-dimensional kinematics of the Hα-emitting gas in the nearby barred Scd galaxy NGC 6946, in order to determine the pattern speed of the primary m=2 perturbation mode. The pattern speed is a crucial parameter for constraining the internal dynamics, estimating the impact velocities of the gravitational perturbation at the resonance radii, and setting up an evolutionary scenario for NGC 6946. Our data allow us to derive the best-fitting kinematic position angle and the geometry of the underlying gaseous disk, which we use to derive the pattern speed using the Tremaine-Weinberg method. We find a main pattern speed ΩPp=22+4-1 km s-1 kpc-1, but our data clearly reveal the presence of an additional pattern speed ΩSp=47+3-2 km s-1 kpc-1 in a zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we deduce the location of the resonance radii and confirm that inside the outer inner Lindblad resonance radius of the main oval, a primary bar has formed rotating at more than twice the outer pattern speed. We further confirm that a nuclear bar has formed inside the inner Lindblad resonance radius of the primary bar, coinciding with the inner inner Lindblad resonance radius of the large-scale m=2 mode oval.

  • 30.
    Fathi, Kambiz
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    van de Ven, Glenn
    Peletier, Reynier
    Falcón–Barroso, Jesús
    Cappellari, Michele
    de Zeeuw, Tim
    Two-Dimensional Kinematics of a Bar and Central Disk in NGC54482007Conference paper (Other academic)
    Abstract [en]

    We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa) barred spiral galaxy NGC 5448. The observed morphology and kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more regular, and displays a small inner disk-like system embedded in a large-scale rotating structure. We focus on the [O iii] gas, and use a harmonic decomposition formalism to analyse the gas velocity field. The higher-order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model, which is derived using linear theory. Our study illustrates how the harmonic decomposition formalism can be used as a powerful tool to quantify non-circular motions in observed gas velocity fields.

  • 31. Font, Joan
    et al.
    Beckman, John E.
    Epinat, Benoit
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gutierrez, Leonel
    Hernandez, Olivier
    RESONANT STRUCTURE IN THE DISKS OF SPIRAL GALAXIES, USING PHASE REVERSALS IN STREAMING MOTIONS FROM TWO-DIMENSIONAL H alpha FABRY-PEROT SPECTROSCOPY2011In: The Astrophysical Journal Letters, ISSN 2041-8205, Vol. 741, no 1, p. L14-Article in journal (Refereed)
    Abstract [en]

    In this Letter, we introduce a technique for finding resonance radii in a disk galaxy. We use a two-dimensional velocity field in H alpha emission obtained with Fabry-Perot interferometry, derive the classical rotation curve, and subtract it off, leaving a residual velocity map. As the streaming motions should reverse sign at corotation, we detect these reversals and plot them in a histogram against galactocentric radius, excluding points where the amplitude of the reversal is smaller than the measurement uncertainty. The histograms show well-defined peaks which we assume to occur at resonance radii, identifying corotations as the most prominent peaks corresponding to the relevant morphological features of the galaxy (notably bars and spiral arm systems). We compare our results with published measurements on the same galaxies using other methods and different types of data.

  • 32. Font, Joan
    et al.
    Beckman, John E.
    Rosado, Margarita
    Epinat, Benoit
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hernandez, Olivier
    Carignan, Claude
    Gutierrez, Leonel
    Relano, Monica
    Blasco-Herrera, Javier
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fuentes-Carrera, Isaura
    DETECTION OF INFALLING HYDROGEN IN TRANSFER BETWEEN THE INTERACTING GALAXIES NGC 5426 AND NGC 54272011In: The Astrophysical Journal. Letters, ISSN 2041-8205, Vol. 740, no 1, p. L1-Article in journal (Refereed)
    Abstract [en]

    Using velocity tagging we have detected hydrogen from NGC 5426 falling onto its interacting partner NGC 5427. Our observations, with the GHaFaS Fabry-Perot spectrometer, produced maps of the two galaxies in H alpha surface brightness and radial velocity. We found emission with the range of velocities associated with NGC 5426 along lines of sight apparently emanating from NGC 5427, superposed on the velocity map of the latter. After excluding instrumental effects we assign the anomalous emission to gas pulled from NGC 5426 during its passage close to NGC 5427. Its distribution, more intense between the arms and just outside the disk of NGC 5427, and weak, or absent, in the arms, suggests that the infalling gas is behind the disk, ionized by Lyman continuum photons escaping from NGC 5427. Modeling this, we estimate the distances of these gas clouds behind the plane: a few hundred parsecs to a few kiloparsecs. We also estimate the mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10 M(circle dot) per year, consistent with the high measured star formation rate across the disk of NGC 5427 and with the detected circumnuclear galactic wind.

  • 33. Font, Joan
    et al.
    Beckman, John E.
    Zaragoza-Cardiel, Javier
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Epinat, Benoit
    Amram, Philippe
    The ratio of pattern speeds in double-barred galaxies2014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 444, no 1, p. l85-L89Article in journal (Refereed)
    Abstract [en]

    We have obtained two-dimensional velocity fields in the ionized gas of a set of eight double-barred galaxies, at high spatial and spectral resolution, using their H alpha emission fields measured with a scanning Fabry-Perot spectrometer. Using the technique by which phase reversals in the non-circular motion indicate a radius of corotation, taking advantage of the high angular and velocity resolution, we have obtained the corotation radii and the pattern speeds of both the major bar and the small central bar in each of the galaxies; there are few such measurements in the literature. Our results show that the inner bar rotates more rapidly than the outer bar by a factor between 3.3 and 3.6.

  • 34. Hernandez, Olivier
    et al.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Carignan, Claude
    Beckman, John
    Gach, Jean-Luc
    Balard, Phillippe
    Amram, et al., Pillippe
    GHαFaS: Galaxy Hα Fabry-Perot System for the William Herschel Telescope2008In: Publications of the Astronomical Society of the Pacific: PASP, Vol. 120, p. 15-Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    GHαFaS, a new Fabry-Perot system, is now available at the William Herschel Telescope (WHT). It was mounted, for the first time, at the Nasmyth focus of the 4.2-m WHT on La Palma in 2007 July. Using modern technology, with a spectral resolution of the order R˜15,000, and with a seeing-limited spatial resolution, GHαFaS will provide a new look at the Hα-emitting gas over a 4.8' circular field in the nearby universe. Many science programs can be done on a 4.2-m class telescope in world-class seeing conditions with a scanning Fabry-Perot. Not only galaxies but H II regions, planetary nebulae, supernova remnants, and the diffuse interstellar medium are subjects for which unique data can be aquired rapidly. Astronomers from the Laboratoire d'Astrophysique Expérimentale (LAE) in Montréal, the Laboratoire d'Astrophysique de Marseille (LAM-OAMP), and the Instituto de Astrofísica de Canarias (IAC), have inaugurated GHαFaS by studying in detail the dynamics of some nearby spiral galaxies. A robust set of state-of-the-art tools for reducing and analyzing the data cubes obtained with GHαFaS has also been developed.

  • 35. Izumi, Takuma
    et al.
    Kohno, Kotaro
    Aalto, Susanne
    Doi, Akihiro
    Espada, Daniel
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Harada, Nanase
    Hatsukade, Bunyo
    Hattori, Takashi
    Hsieh, Pei-Ying
    Ikarashi, Soh
    Imanishi, Masatoshi
    Iono, Daisuke
    Ishizuki, Sumio
    Krips, Melanie
    Martin, Sergio
    Matsushita, Satoki
    Meier, David S.
    Nagai, Hiroshi
    Nakai, Naomasa
    Nakajima, Taku
    Nakanishi, Kouichiro
    Nomura, Hideko
    Regan, Michael W.
    Schinnerer, Eva
    Sheth, Kartik
    Takano, Shuro
    Tamura, Yoichi
    Terashima, Yuichi
    Tosaki, Tomoka
    Turner, Jean L.
    Umehata, Hideki
    Wiklind, Tommy
    ALMA OBSERVATIONS OF THE SUBMILLIMETER DENSE MOLECULAR GAS TRACERS IN THE LUMINOUS TYPE-1 ACTIVE NUCLEUS OF NGC 74692015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 811, no 1, article id 39Article in journal (Refereed)
    Abstract [en]

    We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type. 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.'' 5x0.'' 4 = 165 x 132 pc) at submillimeter wavelengths. Utilizing the wide. bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO+(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 mu m continuum. The region consists of the central similar to 1 '' component and the surrounding starburst ring with a radius of similar to 1.'' 5-2.'' 5. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated toward the central similar to 1 '', suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO+(4-3) and HCN(4-3)/CS(7-6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4-3)/HCO+(4-3) ratio at the AGN position of NGC 7469 (1.11 +/- 0.06) is almost half of the corresponding value of the low-luminosity type. 1 Seyfert galaxy NGC 1097 (2.0 +/- 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (similar to 1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.

  • 36. Izumi, Takuma
    et al.
    Kohno, Kotaro
    Aalto, Susanne
    Espada, Daniel
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Harada, Nanase
    Hatsukade, Bunyo
    Hsieh, Pei-Ying
    Imanishi, Masatoshi
    Krips, Melanie
    Martin, Sergio
    Matsushita, Satoki
    Meier, David S.
    Nakai, Naomasa
    Nakanishi, Kouichiro
    Schinnerer, Eva
    Sheth, Kartik
    Terashima, Yuichi
    Turner, Jean L.
    SUBMILLIMETER-HCN DIAGRAM FOR ENERGY DIAGNOSTICS IN THE CENTERS OF GALAXIES2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 818, no 1, article id 42Article in journal (Refereed)
    Abstract [en]

    Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4-3)/HCO+(4-3) and/or HCN(4-3)/CS(7-6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN. enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO+ and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even greater than or similar to 10 are a plausible explanation for the submillimeter HCN. enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish. these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral-neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.

  • 37. Izumi, Takuma
    et al.
    Kohno, Kotaro
    Martin, Sergio
    Espada, Daniel
    Harada, Nanase
    Matsushita, Satoki
    Hsieh, Pei-Ying
    Turner, Jean L.
    Meier, David S.
    Schinnerer, Eva
    Imanishi, Masatoshi
    Tamura, Yoichi
    Curran, Max T.
    Doi, Akihiro
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Krips, Melanie
    Lundgren, Andreas A.
    Nakai, Naomasa
    Nakajima, Taku
    Regan, Michael W.
    Sheth, Kartik
    Takano, Shuro
    Taniguchi, Akio
    Terashima, Yuichi
    Tosaki, Tomoka
    Wiklind, Tommy
    Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 10972013In: PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, ISSN 0004-6264, Vol. 65, no 5, p. UNSP 100-Article in journal (Refereed)
    Abstract [en]

    We present the first 100 pc scale view of the dense molecular gas in the central similar to 1.3 kpc of the type-1 Seyfert NGC 1097, traced by HCN (J = 4-3) and HCO+ (J = 4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we consider the characteristics of the dense gas around this AGN, and search for the mechanism of HCN enhancement. We find a high HCN (J = 4-3) to HCO+ (J = 4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (nu(2) = 1(1f), J = 4-3) to HCN (J = 4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J = 4-3) to CS (J = 7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined with similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones, similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J = 4-3 and 1-0 data from ALMA, and J = 3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 <= [HCN]/[HCO+] <= 20: non-LTE analysis) in the nucleus, and that the high-J lines (J = 4-3 and 3-2) are emitted from dense (10(4.5) cm(-3) <= n(H2) <= 10(6) cm(-3)), hot (70 K <= T-kin <= 550 K) regions. Finally we propose that high-temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than pure gas-phase PDR/XDR chemistry.

  • 38.
    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.

  • 39.
    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).

  • 40.
    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.

  • 41. Knapen, J.
    et al.
    Sharp, R.
    Ryder, S.
    Falcon-Barroso, J.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gutiérrez, L.
    The central region of M83: massive star formation, kinematics, and the location and origin of the nucleus2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 408, no 2, p. 797-811Article in journal (Refereed)
    Abstract [en]

    We report new near-IR integral field spectroscopy of the central starburst region of the barred spiral galaxy M83 obtained with Cambridge Infra-Red Panoramic Survey Spectrograph (CIRPASS) on Gemini-South, which we analyse in conjunction with GHαFaS Fabry–Perot data, an Anglo-Australian Telescope (AAT) IRIS2 Ks-band image, and near- and mid-IR imaging from the Hubble and Spitzer space telescopes. The bulk of the current star formation activity is hidden from optical view by dust extinction, but is seen in the near- and mid-IR to the north of the nucleus. This region is being fed by inflow of gas through the bar of M83, traced by the prominent dust lane entering into the circumnuclear region from the north. An analysis of stellar ages confirms that the youngest stars are indeed in the north-west. A gradual age gradient, with older stars further to the south, characterizes the well-known star-forming arc in the central region of M83, and is consistent with a stable scenario where gas inflow into the central regions is facilitated by the galactic bar.

    Detailed analyses of the Paβ ionized gas kinematics and near-IR imaging confirm that the kinematic centre coincides with the photometric centre of M83, and that these are offset significantly, by about 3 arcsec or 60 pc, from the visible nucleus of the galaxy. We discuss two possible options, the first of which postulates that the kinematic and photometric centre traces a galaxy nucleus hidden by a substantial amount of dust extinction, in the range AV= 3–10 mag. By combining this information with kinematic results and using arguments from the literature, we conclude that such a scenario is, however, unlikely, as is the existence of other ‘hidden’ nuclei in M83.

    We thus concur with recent authors and favour a second option, in which the nucleus of the galaxy is offset from its kinematic and photometric centre. This is presumably a result of some past interaction, possibly related to the event which lies at the origin of the disturbance of the outer disc of the galaxy. We find some indications for a disturbance in the Hα velocity field which would confirm the influence of the m= 1 perturbation in the gravitational potential, but note that further high-quality stellar kinematic data are needed to confirm this scenario.

  • 42.
    Lindblad, Per-Olof
    et al.
    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).
    Hjelm, Maja
    Stockholm University, Faculty of Science, Department of Astronomy.
    Nelson, Charles H.
    On a Method to Resolve the Nuclear Activity in Galaxies as Applied to the Seyfert 2 Galaxy NGC 13582010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 723, no 1, p. 342-352Article in journal (Refereed)
    Abstract [en]

    Nuclear regions of galaxies generally host a mixture of components with different excitations, compositions, and kinematics. Derivation of emission line ratios and kinematics could then be misleading if due correction is not made for the limited spatial and spectral resolutions of the observations. The aim of this paper is to demonstrate, with application to a long-slit spectrum of the Seyfert 2 galaxy NGC 1358, how line intensities and velocities, together with modeling and knowledge of the point-spread function, may be used to resolve the differing structures. In the situation outlined above, the observed kinematics differs for different spectral lines. From the observed intensity and velocity distributions of a number of spectral lines, and with some reasonable assumptions about the structure of different subcomponents to diminish the number of free parameters, the true line ratios and velocity structures may be deduced. A preliminary solution for the nuclear structure of NGC 1358 is obtained, involving a nuclear point source and an emerging outflow of high excitation, ending with shock and postshock cloud as revealed by the velocities, as well as a nuclear emission-line disk rotating in the potential of a stellar bulge and expressing a radial excitation gradient. The method results in a likely scenario for the nuclear structure of the Seyfert 2 galaxy NGC 1358. For definitive results, an extrapolation of the method to two dimensions combined with the use of integral field spectroscopy will be necessary.

  • 43. Marquart, Thomas
    et al.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergvall, Nils
    Stockholm University, Faculty of Science, Department of Astronomy.
    Cumming, Robert
    Stockholm University, Faculty of Science, Department of Astronomy.
    Amram, Philippe
    Star-gas decoupling and a non-rotating stellar core in He 2-10: Integral field spectroscopy with FLAMES/ARGUS2007In: Astronomy and Astrophysics, Vol. 474, no L9Article in journal (Refereed)
    Abstract [en]

    Aims.We study the two-dimensional distribution and kinematics of the stellar and gaseous components in the centre of the blue compact dwarf galaxy He 2-10. The aim is to compare the kinematics of gas and stars in order to determine whether they are consistent with one another, or if stars and gas can be decoupled due to gravitational perturbations and feedback from star formation. Methods: We have used the integral field unit ARGUS, part of FLAMES on the European Southern Observatory's Very Large Telescope, to target the Ca ii λλ8498,8542,8662 Å triplet in the central 300 × 480 parsecs of He 2-10. The selected wavelength regime includes several prominent spectral features, including the Paschen series and the [S iii] emission-line, which we have used to derive the kinematics of the ionised interstellar medium. Results: We find no systematic trend in the velocities of the stars over the observed field of view and conclude that the stellar kinematics is governed by random motions. This is in contrast to the motions the ionised interstellar medium, where we find spatial velocity variations up to 60 km s-1. Our gas velocity field is consistent with previous studies of both the molecular gas and the feedback-driven outflow in He 2-10. We interpret the kinematic decoupling between the stars and the gas as He 2-10 being in the process of transformation to a dwarf elliptical galaxy.

  • 44. Martin, S.
    et al.
    Kohno, K.
    Izumi, T.
    Kripsi, M.
    Meier, D. S.
    Aladro, R.
    Matsushita, S.
    Takano, S.
    Turner, J. L.
    Espada, D.
    Nakajima, T.
    Terashima, Y.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hsieh, P. -Y
    Imanishi, M.
    Lundgren, A.
    Nakai, N.
    Schinnerer, E.
    Sheth, K.
    Wiklind, T.
    Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 10972015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 573, article id A116Article in journal (Refereed)
    Abstract [en]

    Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods. We carried out 3 mm ALMA observations that include seven different molecular species, namely HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO, as well as the C-13 isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc (similar to 30 '') of the galaxy at a resolution of similar to 2.2 '' x 1.5 '' (150 pc x 100 pc). Results. HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation effects, where a high density gas component (similar to 10(6) cm(-3)) may be more prominent in SB galaxies. However, the most promising are the differences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.

  • 45. Nilsson, R.
    et al.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Thebault, Ph.
    Liseau, R.
    VLT imaging of the beta Pictoris gas disk2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 544, p. A134-Article in journal (Refereed)
    Abstract [en]

    Context. Circumstellar debris disks older than a few Myr should be largely devoid of primordial gas remaining from the protoplanetary disk phase. Tracing the origin of observed atomic gas in Keplerian rotation in the edge-on debris disk surrounding the similar to 12 Myr old star beta Pictoris requires more detailed information about its spatial distribution than has previously been acquired by limited slit spectroscopy. Especially indications of asymmetries and presence of Ca II gas at high disk latitudes call for additional investigation to exclude or confirm its connection to observed dust structures or suggested cometary bodies on inclined eccentric orbits. Aims. We set out to recover a complete image of the Fe I and Ca II gas emission around beta Pic by spatially resolved, high-resolution spectroscopic observations to better understand the morphology and origin of the gaseous disk component. Methods. The multiple fiber facility FLAMES/GIRAFFE at the Very Large Telescope (VLT), with the large integral-field-unit ARGUS, was used to obtain spatially resolved optical spectra (from 385.9 to 404.8 nm) in four regions covering the northeast and southwest side of the disk. Emission lines from Fe I (at 386.0 nm) and Ca II (at 393.4 and 396.8 nm) were mapped and could be used to fit a parametric function for the disk gas distribution, using a gas-ionisation code for gas-poor debris disks. Results. Both Fe I and Ca II emission are clearly detected, with the former dominating along the disk midplane, and the latter revealing vertically more extended gas. The surface intensity of the Fe I emission is lower but more extended in the northeast (reaching the 210 AU limit of our observations) than in the southwest, while Ca II shows the opposite asymmetry. The modelled Fe gas disk profile shows a linear increase in scale height with radius, and a vertical profile that suggests dynamical interaction with the dust. We also qualitatively demonstrate that the Ca II emission profile can be explained by optical thickness in the disk midplane, and does not require Ca to be spatially separated from Fe.

  • 46.
    Nilsson, Ricky
    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.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Thébault, Philippe
    Liseau, René
    VLT imaging of the β Pictoris gas diskArticle in journal (Refereed)
  • 47. Peletier, R. F.
    et al.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Allard, E. L.
    Knapen, Johan
    Sarzi, M.
    van de Ven, G.
    Falcón Barroso, Jesús
    Cappellari, M.
    de Zeeuw, P. T.
    Emsellem, Eric
    Stars and gas in the inner parts of galaxies seen in SAURON integral field observations2007In: New Astronomy Reviews, ISSN 1387-6473, Vol. 51, no 1-2, p. 29-33Article in journal (Refereed)
    Abstract [en]

    We give two examples of spiral galaxies that show non-circular gas motions in the inner kiloparsecs, from SAURON integral field spectroscopy. We use harmonic decomposition of the velocity field of the ionized gas to study the underlying mass distribution, employing linear theory. The higher order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model. We also present maps of a number of strong absorption lines in M 100, derive simple stellar populations and correlate them with features in the gas kinematics.

  • 48.
    Pinol-Ferrer, Nuria
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundgren, A.
    van de Ven, G.
    Physical condition of the molecular gas at the centre of NGC 10972011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 414, no 1, p. 529-537Article in journal (Refereed)
    Abstract [en]

    We have used the X(CO) conversion factor, local thermodynamic equilibrium and large velocity gradient approximation to parametrize the cold and warm phases of the interstellar medium from five different low transitions of the CO molecule in the central 21 arcsec (kpc) region of NGC 1097. We have applied a one-component model and derived a typical kinetic temperature of about 33 K, a molecular hydrogen density of 4.9 x 10(3) M(circle dot) pc(-3) and a CO column density of 1.2 x 10(-2) M(circle dot) pc(-2). A two-component model results in 85 per cent cold-to-total gas fraction in the presence of a 90 K warm counterpart. Furthermore, we 'resolve' the spatially unresolved single-dish observations by selecting velocity channels that in an interferometric velocity map correspond to specific regions. We have selected five such regions and found that the physical properties in these regions are comparable to those derived from the full line profile. This implies that the central kpc of NGC 1097 is rather homogeneous in nature and, although the regions are not uniquely located within the ring, the star formation along the ring is homogeneously distributed (in agreement with recent Herschel observations). We have further revised the mass-inflow rate on to the supermassive black hole in this prototype low-ionization nuclear emission-line region/Seyfert 1 galaxy and found that accounting for the total interstellar medium and applying a careful contribution of the disc thickness and corresponding stability criterion increases the previous estimations by a factor of 10. Finally, we have calculated the X(CO) conversion factor for the centre of NGC 1097 using an independent estimation of the surface density to the CO emission and obtained X(CO) = (2.8 +/- 0.5) x 10(20) cm(-2) (K km s(-1))(-1) at a radius 10.5 arcsec and X(CO) = (5.0 +/- 0.5) x 10(20) cm(-2) (K km s(-1))(-1) at a radius 7.5 arcsec. With the approach and analysis described in this paper, we have demonstrated that important physical properties can be derived to a resolution beyond the single-dish resolution element; however, caution is necessary while interpreting the results.

  • 49.
    Pinol-Ferrer, Nuria
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lindblad, Per Olof
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Analytic gas orbits in an arbitrary rotating galactic potential using the linear epicyclic approximation2012In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 421, no 2, p. 1089-1102Article in journal (Refereed)
    Abstract [en]

    A code, EPIC5, has been developed which computes, in the two-dimensional case, the initially circular orbits of guiding centra in an arbitrary axisymmetric potential with an arbitrary, weak perturbing potential in solid body rotation. This perturbing potential is given by its Fourier expansion. The analytic solution solves the linear epicyclic approximation of the equations of motion. To simulate the motion of interstellar matter and to damp the Lindblad resonances, in these equations we have introduced a friction which is proportional to the deviation from circular velocity. The corotation resonance is also damped by a special parameter. The program produces, in just a few seconds, orbital and density maps, as well as line-of-sight velocity maps for a chosen orientation of the galaxy. We test EPIC5 by comparing its results with previous simulations and observations from the literature, which gives satisfactory agreement. The aim is that this program should be a useful complement to elaborate numerical simulations. Particularly so are its abilities to quickly explore the parameter space, to construct artificial galaxies and to isolate various single agents important for developing the structure of interstellar matter in disc galaxies. The EPIC5 code can be obtained from npi@astro.su.se.

  • 50.
    Piñol-Ferrer, Nuria
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Carignan, Claude
    Font, Joan
    Hernandez, Olivier
    Karlsson, Roland
    Stockholm University, Faculty of Science, Department of Astronomy.
    van de Ven, Glenn
    Bar pattern speed and position of the circumnuclear ringin NGC 10972014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 438, no 2, p. 971-982Article in journal (Refereed)
    Abstract [en]

    We present the first galactic-scale model of the gas dynamics of the prototype barred Seyfert 1 galaxy NGC 1097. We use large scale FaNTOmM Fabry-Perot interfer-ometric data covering the entire galactic disc and combined the distribution andkinematics maps with high resolution two-dimensional spectroscopy from the Gemini telescope. We build a dynamical model for the gravitational potential by applying the analytic solution to the equations of motion, with in the epicyclic approximation. Our model reproduces all the significant kinematic and structural signatures of thisgalaxy. We find that the primary bar is 7.9±0.6 kpc long and has a pattern speedof 36 ± 2 km s−1 kpc−1. This places the corotation radius at 8.6±0.5 kpc, the outer Lindblad resonance at 14.9±0.9 kpc and two inner Lindblad resonances at 60±5 pcand 2.9±0.1 kpc. These derivations lead to a ratio of the corotation radius over barlength of 1.0–1.2, which is in concordance with simulations of barred galaxies. Our model presents evidence that the circumnuclear ring in this galaxy is not located near any of the resonance radii in this galaxy. The ring might have once formed at the outer inner Lindblad resonance radius, and it has been migrating inward, toward the centre of the galactic gravitational potential.

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