Star formation rates and stellar masses of Hα selected star-forming galaxies at z=0.84: a quantification of the downsizing
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2011
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American Astronomical Society
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Abstract
In this work we analyze the physical properties of a sample of 153 star-forming galaxies at z ~ 0.84, selected by their Hα flux with a narrowband filter. B-band luminosities of the objects are higher than those of local star-forming galaxies. Most of the galaxies are located in the blue cloud, though some objects are detected in the green valley and in the red sequence. After the extinction correction is applied, virtually all these red galaxies move to the blue sequence, unveiling their dusty nature. A check on the extinction law reveals that the typical extinction law for local starbursts is well suited for our sample but with E(B - V)_stars = 0.55 E(B - V)_gas. We compare star formation rates (SFRs) measured with different tracers (Hα, far-ultraviolet, and infrared), finding that they agree within a factor of three after extinction correction. We find a correlation between the ratios SFR_FUV/SFR_Hα, SFR_IR/SFR_Hα, and the EW(Hα) (i.e., weighted age), which accounts for part of the scatter. We obtain stellar mass estimations by fitting templates to multi-wavelength photometry. The typical stellar mass of a galaxy within our sample is ∼10^10 M_⨀. The SFR is correlated with stellar mass and the specific SFR decreases with it, indicating that massive galaxies are less affected by star formation processes than less massive ones. This result is consistent with the downsizing scenario. To quantify this downsizing we estimated the quenching mass M-Q for our sample at z ~ 0.84, finding that it declines from M_Q ~ 10^12 M_⨀t at z ~ 0.84 to M_Q ~ 8 x 10^10 M_⨀ at the local universe.
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© 2011. The American Astronomical Society. All rights reserved. We thank Armando Gil de Paz for helpful discussions and comments. We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2009-10368. Partially funded by the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC. V.V. acknowledges support from the AstroMadrid Program CAM S2009/ESP-1496: "Astrofísica y Desarrollos Tecnológicos en la Comunidad de Madrid" funded by the Comunidad de Madrid and the European Union. P. G. P.-G. acknowledges support from the Ramón y Cajal Program financed by the Spanish Government and the European Union. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, Caltech under NASA contract 1407. GALEX is a NASA Small Explorer launched in 2003 April. We gratefully acknowledge NASA's support for construction, operation, and scientific analysis of the GALEX mission. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan. We acknowledge Edward L. Wright for his World Wide Web Cosmology Calculator (Wright 2006), which has been used during the preparation of this paper.