The ATLAS3D project – XVIII. CARMA CO imaging survey of early-type galaxies

MNRAS 432, 1796–1844 (2013) doi:10.1093/mnras/sts299 Advance Access publication 2013 May 14 The ATLAS3D project – XVIII. CARMA CO imaging survey of early-type galaxies Katherine Alatalo,1,2‹ Timothy A. Davis,3 Martin Bureau,4 Lisa M. Young,5 Leo Blitz,1 Alison F. Crocker,6,7 Estelle Bayet,4 Maxime Bois,8 Frédéric Bournaud,9 Michele Cappellari,4 Roger L. Davies,4 P. T. de Zeeuw,3,10 Pierre-Alain Duc,9 Eric Emsellem,3,11 Sadegh Khochfar,12 Davor Krajnović,3 Harald Kuntschner,3 Pierre-Yves Lablanche,3,11 Raffaella Morganti,13,14 Richard M. McDermid,15 Thorsten Naab,12 Tom Oosterloo,13,14 Marc Sarzi,16 Nicholas Scott,17 Paolo Serra13 and Anne-Marie Weijmans18 † 1 Department of Astronomy, University of California, Hearst Field Annex, Berkeley, CA 94720-3411, USA 3 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany 4 Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH 5 Physics Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA 6 Department of Astronomy, Lederle Graduate Research Tower B 619E, University of Massachusetts, Amherst, MA 01003, USA 7 Physics Department, University of Toledo, 2801 West Bancroft, Toledo, OH 43606, USA 8 Observatoire de Paris, LERMA and CNRS, 61 Av. de l’Observatoire, F-75014 Paris, France 9 Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp – CNRS – Université Paris Diderot, F-91191 Gif-sur-Yvette Cedex, France 10 Sterrewacht Leiden, Leiden University, Postbus 9513, NL-2300 RA Leiden, the Netherlands 11 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 12 Max-Planck-Institut für Extraterrestrische Physik, PO Box 1312, D-85478 Garching, Germany 13 Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, NL-7990 AA Dwingeloo, the Netherlands 14 Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, the Netherlands 15 Gemini Observatory, Northern Operations Centre, 670 North A‘ohoku Place, Hilo, HI 96720, USA 16 Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL1 9AB 17 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia 18 Dunlap Institute for Astronomy & Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada Accepted 2012 October 19. Received 2012 October 19; in original form 2012 July 1 ABSTRACT We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS3D molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a 12 CO(1–0) integrated flux of 18.5 Jy km s−1 ,1 and it represents the largest, best studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g − r colour image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50 per cent), rings (15 per cent), bars+rings (10 per cent), spiral arms (5 per cent) and mildly (12.5 per cent) and strongly (7.5 per cent) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted  E-mail: † Dunlap Fellow. 1 18.5 Jy km s−1 is drawn from the IRAM 30-m survey, and as the interferometric data indicate that the 30-m molecular gas masses are generally underestimates; the true limit is likely slightly higher.  C 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society 2 NASA Herschel Science Center, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125, USA The CARMA ATLAS3D CO survey of ETGs 1797 molecular gas mass across the sample of 2.48 × 1010 M , or approximately 8.3 × 108 M per minor merger within the sample, consistent with minor merger stellar mass ratios. Key words: surveys – ISM: molecules – galaxies: elliptical and lenticular, cD – galaxies: evolution – galaxies: ISM – galaxies: star formation. 1 I N T RO D U C T I O N 2 The current paper presents in detail the observations used in Paper X to discuss the origin of the CO. 2 THE CARMA SAMPLE The sample of ETGs chosen for the CARMA survey was extracted from the ATLAS3D survey. All ATLAS3D galaxies were observed with the IRAM 30-m telescope in CO(1–0) and CO(2–1), mostly by Combes et al. (2007) and Paper IV, though a few were The bimodality in the morphological classification of galaxies has long been known (Hubble 1926). Late-type galaxies (LTGs) typically have exponential discs, spiral structure and blue colours. Earlytype galaxies (ETGs) are more ellipsoidal, with smoother isophotes and red colours. One scenario for producing this galaxy bimodality is via mergers. Simulations have shown that a merger between two LTGs often creates an ETG (Toomre & Toomre 1972; Springel, Di Matteo & Hernquist 2005). ETGs are also much more likely to be found on the ‘red-sequence’ portion of the colour–magnitude diagram (CMD; Baldry et al. 2004; Faber et al. 2007), presumably due to the loss of most of their star-forming material. ETGs have been shown to be deficient in star formation relative to LTGs at a given mass (Visvanathan & Sandage 1977; Bower, Lucey & Ellis 1992), and therefore should be molecular and atomic gas poor (Lees et al. 1991). Recently, it has, however, become clear that they are not devoid of cold gas, containing reservoirs of dust (e.g. Hawarden et al. 1981; Jura 1986; Knapp et al. 1989), neutral atomic gas (e.g. Knapp, Turner & Cunniffe 1985; Sage & Welch 2006; Oosterloo et al. 2010) and molecular gas (e.g. Sage & Wrobel 1989; Welch & Sage 2003; Combes, Young & Bureau 2007). The ATLAS3D sample is a complete, volume-limited sample of 260 local ETGs brighter than MK = −21.5, covering distances to 42 Mpc with some restrictions on declination and Galactic latitude (Cappellari et al. 2011, hereafter Paper I). The survey was designed to help us understand ETG formation and evolution. Optical integral-field spectroscopy with Spectroscopic Areal Unit for Research on Optical Nebulae (SAURON) on the William Herschel Telescope (WHT) has been obtained over the central 41 × 33 arcsec2 region of all ATLAS3D galaxies, revealing their internal stellar kinematics, stellar population properties and ionized gas distributions and kinematics. The ATLAS3D sample has also been completely observed in CO J = 1–0 and 2–1 with the Institut de Radioastronomie Millimetrique (IRAM) 30-m telescope (Young et al. (...truncated)