Salim, Samir and Dickinson, Mark and Rich, R. Michael and Charlot, Stéphane and Lee, Janice C. and Schiminovich, David and Pérez-González, Pablo G. and Ashby, Matthew L. N. and Papovich, Casey and Faber, S. M. and Ivison, Rob J. and Frayer, David T. and Walton, Josiah M. and Weiner, Benjamin J. and Chary, Ranga-Ram and Bundy, Kevin and Noeske, Kai and Koekemoer, Anton M. (2009) Mid-IR Luminosities and UV/Optical Star Formation Rates at z < 1.4. Astrophysical Journal, 700 (1). pp. 161-182. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090918-092255124
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Ultraviolet (UV) nonionizing continuum and mid-infrared (IR) emission constitute the basis of two widely used star formation (SF) indicators at intermediate and high redshifts. We study 2430 galaxies with z < 1.4 in the Extended Groth Strip with deep MIPS 24 μm observations from FIDEL, spectroscopy from DEEP2, and UV, optical, and near-IR photometry from the AEGIS. The data are coupled with dust-reddened stellar population models and Bayesian spectral energy distribution (SED) fitting to estimate dust-corrected star formation rates (SFRs). In order to probe the dust heating from stellar populations of various ages, the derived SFRs were averaged over various timescales—from 100 Myr for "current" SFR (corresponding to young stars) to 1-3 Gyr for long-timescale SFRs (corresponding to the light-weighted age of the dominant stellar populations). These SED-based UV/optical SFRs are compared to total IR luminosities extrapolated from 24 μm observations, corresponding to 10-18 μm rest frame. The total IR luminosities are in the range of normal star-forming galaxies and luminous IR galaxies (10^(10)-10^(12) L_⊙). We show that the IR luminosity can be estimated from the UV and optical photometry to within a factor of 2, implying that most z < 1.4 galaxies are not optically thick. We find that for the blue, actively star-forming galaxies the correlation between the IR luminosity and the UV/optical SFR shows a decrease in scatter when going from shorter to longer SFR-averaging timescales. We interpret this as the greater role of intermediate age stellar populations in heating the dust than what is typically assumed. Equivalently, we observe that the IR luminosity is better correlated with dust-corrected optical luminosity than with dust-corrected UV light. We find that this holds over the entire redshift range. Many so-called green valley galaxies are simply dust-obscured actively star-forming galaxies. However, there exist 24 μm detected galaxies, some with L_(IR)>10^(11) L_⊙, yet with little current SF. For them a reasonable amount of dust absorption of stellar light (but presumably higher than in nearby early-type galaxies) is sufficient to produce the observed levels of IR, which includes a large contribution from intermediate and old stellar populations. In our sample, which contains very few ultraluminous IR galaxies, optical and X-ray active galactic nuclei do not contribute on average more than ~50% to the mid-IR luminosity, and we see no evidence for a large population of "IR excess" galaxies.
|Additional Information:||2009. The American Astronomical Society Received 2008 December 29; accepted 2009 May 19; published 2009 June 30. S.S. thanks Christopher N. A. Willmer, Jeffrey A. Newman, and Alison L. Coil for help with and access to additional DEEP2 data, Delphine Marcillac for providing IR templates, and Emanuele Daddi, David Elbaz, Amelia M. Stutz, and Arjun Dey for valuable feedback and discussions. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. We acknowledge NSF grants AST-0071198 and AST- 0507483 awarded to University of California at Santa Cruz and Berkeley. This study makes use of data from the 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. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Facilities: GALEX,Keck:II (DEIMOS),CFHT(MegaPrime/ MegaCam), MMT (MegaCam), Hale (WIRC), Spitzer (MIPS).|
|Subject Keywords:||galaxies: active; galaxies: evolution; galaxies: fundamental parameters; infrared: galaxies; surveys; ultraviolet: galaxies|
|Official Citation:||Mid-IR Luminosities and UV/Optical Star Formation Rates at z < 1.4 Samir Salim, Mark Dickinson, R. Michael Rich, Stéphane Charlot, Janice C. Lee, David Schiminovich, Pablo G. Pérez-González, Matthew L. N. Ashby, Casey Papovich, S. M. Faber, Rob J. Ivison, David T. Frayer, Josiah M. Walton, Benjamin J. Weiner, Ranga-Ram Chary, Kevin Bundy, Kai Noeske, and Anton M. Koekemoer 2009 ApJ 700 161-182 doi: 10.1088/0004-637X/700/1/161.|
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|Deposited By:||Tony Diaz|
|Deposited On:||25 Sep 2009 18:11|
|Last Modified:||26 Dec 2012 11:24|
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