Bulgeless Galaxies at Intermediate Redshift: Sample Selection, Color Properties, and the Existence of Powerful Active Galactic Nuclei

Creators: Bizzocchi, Luca; Filho, Mercedes E.; Leonardo, Elvira; Grossi, Marcus; Griffith, Roger L.; Afonso, José; Fernandes, Cristina; Retrê, João; Anton, Sonia; Bell, Eric F.; Brinchmann, Jarle; Henriques, Bruno; Lobo, Catarina; Messias, Hugo

Abstract

We present a catalog of bulgeless galaxies, which includes 19,225 objects selected in four of the deepest, largest multi-wavelength data sets available—COSMOS, AEGIS, GEMS, and GOODS—at intermediate redshift (0.4 ≤ z ≤ 1.0). The morphological classification was provided by the Advanced Camera for Surveys General Catalog (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyze the properties of the sample and the evolution of pure-disk systems with redshift. Very massive [log (M_*/M_☉) > 10.5] bulgeless galaxies contribute to ~30% of the total galaxy population number density at z ≥ 0.7, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure disks appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogs were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 active galactic nuclei (AGNs) that reside in galaxies without a classical bulge. The finding of such peculiar objects at intermediate redshift shows that while AGN growth in merger-free systems is a rare event (0.2% AGN hosts in this sample of bulgeless galaxies), it can indeed happen relatively early in the history of the universe.

Additional Information

© 2014 The American Astronomical Society. Received 2013 July 31; accepted 2013 December 14; published 2014 January 22. We thank the anonymous referee for the useful comments and suggestions. This work is based on (GO-10134, GO-09822, GO-09425.01, GO-09583.01, GO-9500) program observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This work is also based on zCOSMOS observations carried out using the Very Large Telescope at the ESO Paranal Observatory under Program ID: LP175.A-0839. This study makes use of data from AEGIS, a multiwavelength sky survey conducted with the Chandra, GALEX, Hubble, Keck, CFHT,MMT, Subaru, Palomar, Spitzer, VLA, and other telescopes and supported in part by the NSF, NASA, and the STFC. Funding for the DEEP2 survey has been provided by NSF grants AST95-09298, AST-0071048, AST-0071198, AST-0507428, and AST-0507483 as well as NASA LTSA grant NNG04GC89G. Some of the data were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Work on this paper is based on observations obtained with MegaPrime/MegaCam, a joint project of Canada-France-Hawaii Telescope (CFHT) and CEA/DAPNIA, at the CFHT, which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. We gratefully acknowledge the GOODS Team (http://cosmos.astro.caltech.edu) for providing all the imaging material available worldwide. We are also indebted to the COMBO-17 (Wolf et al. 2004) and MUSIC teams (Grazian et al. 2006) for the catalogs publicly supplied. The authors gratefully acknowledge financial support from the Science and Technology Foundation (FCT, Portugal) through research grants PTDC/CTE-AST/105287/2008, PTDC/FISAST/ 2194/2012, PEst-OE/FIS/UI2751/2011, and PEst-OE/ FIS/UI2751/2014. L.B., E.L., and M.E.F. gratefully acknowledge support from the Science and Technology Foundation (FCT, Portugal) through fellowships SFRH/BPD/62966/2009, SFRH/BPD/71278/2010, and SFRH/BPD/36141/2007.

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