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The ATLAS3D project – XIII. Mass and morphology of H i in early-type galaxies as a function of environment

Authors

  • Paolo Serra,

    Corresponding author
    1. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
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  • Tom Oosterloo,

    1. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
    2. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, the Netherlands
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  • Raffaella Morganti,

    1. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
    2. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, the Netherlands
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  • Katherine Alatalo,

    1. Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720, USA
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  • Leo Blitz,

    1. Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720, USA
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  • Maxime Bois,

    1. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
    2. Université Lyon 1, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon and Ecole Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis Laval, France
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  • Frédéric Bournaud,

    1. Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp – CNRS – Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France
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  • Martin Bureau,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
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  • Michele Cappellari,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
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  • Alison F. Crocker,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
    2. Department of Astrophysics, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003, USA
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  • Roger L. Davies,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
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  • Timothy A. Davis,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
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  • P. T. de Zeeuw,

    1. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
    2. Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, the Netherlands
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  • Pierre-Alain Duc,

    1. Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp – CNRS – Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France
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  • Eric Emsellem,

    1. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
    2. Université Lyon 1, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon and Ecole Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis Laval, France
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  • Sadegh Khochfar,

    1. Max-Planck Institut für extraterrestrische Physik, PO Box 1312, D-85478 Garching, Germany
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  • Davor Krajnović,

    1. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
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  • Harald Kuntschner,

    1. Space Telescope European Coordinating Facility, European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
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  • Pierre-Yves Lablanche,

    1. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
    2. Université Lyon 1, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon and Ecole Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis Laval, France
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  • Richard M. McDermid,

    1. Gemini Observatory, Northern Operations Centre, 670 N. A‘ohoku Place, Hilo, HI 96720, USA
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  • Thorsten Naab,

    1. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
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  • Marc Sarzi,

    1. Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL1 9AB
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  • Nicholas Scott,

    1. Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
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  • Scott C. Trager,

    1. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, the Netherlands
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  • Anne-Marie Weijmans,

    Corresponding author
    1. Dunlap Institute for Astronomy & Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada
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  • Lisa M. Young

    1. Physics Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA
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E-mail: serra@astron.nl

Dunlap Fellow.

ABSTRACT

We present the ATLAS3Di survey of a volume-limited, complete sample of 166 nearby early-type galaxies (ETGs) brighter than MK=−21.5. The survey is mostly based on data taken with the Westerbork Synthesis Radio Telescope, which enables us to detect H i down to 5 × 106–5 × 107 M within the survey volume.

We detect ∼40 per cent of all ETGs outside the Virgo galaxy cluster and ∼10 per cent of all ETGs inside it. This demonstrates that it is common for non-cluster ETGs to host H i. The morphology of the detected gas varies in a continuous way from regular, settled H i discs and rings to unsettled gas distributions (including tidal or accretion tails) and systems of clouds scattered around the galaxy. The majority of the detections consist of H i discs or rings (1/4 of all ETGs outside Virgo) so that if H i is detected in an ETG it is most likely distributed on a settled configuration. These systems come in two main types: small discs [inline image M], which are confined within the stellar body and share the same kinematics of the stars; and large discs/rings [M(H i) up to 5 × 109 M], which extend to tens of kpc from the host galaxy and are in half of the cases kinematically decoupled from the stars.

Neutral hydrogen seems to provide material for star formation in ETGs. Galaxies containing H i within ∼1Re exhibit signatures of on-going star formation in ∼70 per cent of the cases, approximately five times more frequently than galaxies without central H i. The interstellar medium (ISM) in the centre of these galaxies is dominated by molecular gas, and in ETGs with a small gas disc the conversion of H i into H2 is as efficient as in spirals.

The ETG H i mass function is characterized by M*∼ 2 × 109 M and by a slope α∼−0.7. Compared to spirals, ETGs host much less H i as a family. However, a significant fraction of all ETGs are as H i-rich as spiral galaxies. The main difference between ETGs and spirals is that the former lack the high-column-density H i typical of the bright stellar disc of the latter.

The ETG H i properties vary with environment density in a more continuous way than suggested by the known Virgo versus non-Virgo dichotomy. We find an envelope of decreasing M(H i) and M(H i)/LK with increasing environment density. The gas-richest galaxies live in the poorest environments (as found also with CO observations), where the detection rate of star formation signatures is higher. Galaxies in the centre of Virgo have the lowest H i content, while galaxies at the outskirts of Virgo represent a transition region and can contain significant amounts of H i, indicating that at least a fraction of them has joined the cluster only recently after pre-processing in groups. Finally, we find an H i morphology–density relation such that at low environment density (measured on a local scale) the detected H i is mostly distributed on large, regular discs and rings, while more disturbed H i morphologies dominate environment densities typical of rich groups. This confirms the importance of processes occurring on a galaxy-group scale for the evolution of ETGs.

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