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Published March 10, 2015 | Published + Submitted
Journal Article Open

A Turnover in the Galaxy Main Sequence of Star Formation at M_* ~ 10^(10) M_☉ for Redshifts z < 1.3


The relationship between galaxy star formation rates (SFRs) and stellar masses (M_*) is reexamined using a mass-selected sample of ~62,000 star-forming galaxies at z ≤ 1.3 in the COSMOS 2 deg^2 field. Using new far-infrared photometry from Herschel-PACS and SPIRE and Spitzer-MIPS 24 μm, along with derived infrared luminosities from the NRK method based on galaxies' locations in the restframe color-color diagram (NUV – r) versus (r – K), we are able to more accurately determine total SFRs for our complete sample. At all redshifts, the relationship between median SFR and M_* follows a power law at low stellar masses, and flattens to nearly constant SFR at high stellar masses. We describe a new parameterization that provides the best fit to the main sequence and characterizes the low mass power-law slope, turnover mass, and overall scaling. The turnover in the main sequence occurs at a characteristic mass of about M_0 ~ 10^(10) M_☉ at all redshifts. The low mass power-law slope ranges from 0.9-1.3 and the overall scaling rises in SFR as a function of (1 + z)^(4.12±0.10). A broken power-law fit below and above the turnover mass gives relationships of SFR ∝ M_*^(0.88±0.06) below the turnover mass and SFR ∝ M_*^(0.27±0.04) above the turnover mass. Galaxies more massive than M_* ≳ 10^(10) M_☉ have a much lower average specific star formation rate (sSFR) than would be expected by simply extrapolating the traditional linear fit to the main sequence found for less massive galaxies.

Additional Information

© 2015 American Astronomical Society. Received 2014 July 29; accepted 2015 January 5; published 2015 March 5. D.B.S. and C.M.C. acknowledge the hospitality of the Aspen Center for Physics, which is supported by the National Science Foundation grant No. PHY-1066293. C.M.C. acknowledges generous support from a McCue Fellowship through the University of California, Irvine's Center for Cosmology. K.S. gratefully acknowledges support from Swiss National Science Foundation Grant PP00P2_138979/1. K.S. acknowledges support from the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. 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; the 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, Inc. (AURA) 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. The Dark Cosmology Centre is funded by the Danish National Research Foundation.

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Published - 0004-637X_801_2_80.pdf

Submitted - 1501.01080v1.pdf


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