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Published December 1, 2013 | Published + Submitted
Journal Article Open

The role of galaxy interaction in the SFR-M_* relation: characterizing morphological properties of Herschel-selected galaxies at 0.2 <z <1.5


Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L_(IR) ≳ 10^(11.6) L_☉) in the local universe (z ≾ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M_* relation or the "galaxy main sequence") have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M_* increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M_* relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of "disk galaxies" decreases and the fraction of "irregular" galaxies increases systematically with increasing L_(IR) out to z ≾ 1.5 and z ≾ 1.0, respectively. At L_(IR) >10^(11.5) L_☉, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M_* relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous "main-sequence galaxies" are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

Additional Information

© 2013 American Astronomical Society. Received 2013 June 3; accepted 2013 September 16; published 2013 November 12. C.-L. Hung thanks V. U and J. Chu for their help with visual classification at the early stage of this project. D. B. Sanders and C. M. Casey acknowledge the hospitality of the Aspen Center for Physics, which is supported by the National Science Foundation grant No. PHY-1066293. C. M. Casey is generously supported by a Hubble Fellowship from Space Telescope Science Institute, grant HST-HF-51268.01-A. COSMOS is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555; also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada–France–Hawaii Telescope operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France, and the University of Hawaii. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); and IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, University of Sussex (UK); and Caltech, JPL, NHSC, and University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC (UK); and NASA (USA).

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Published - 0004-637X_778_2_129.pdf

Submitted - 1309.4459v1.pdf


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