Huang, J.-S. and Faber, S. M. and Daddi, E. and Laird, E. S. and Lai, K. and Omont, A. and Wu, Y. and Younger, J. D. and Bundy, K. and Cattaneo, A. and Chapman, S. C. and Conselice, C. J. and Dickinson, M. and Egami, E. and Fazio, G. G. and Im, M. and Koo, D. and Le-Floc’h, E. and Papovich, C. and Rigopoulou, D. and Smail, I. and Song, M. and Van-de-Werf, P. P. and Webb, T. M. A. and Willmer, C. N. A. and Willner, S. P. and Yan, L. (2009) Infrared Spectrograph Spectroscopy and Multi-Wavelength Study of Luminous Star-Forming Galaxies at z ≃ 1.9. Astrophysical Journal, 700 (1). pp. 183-198. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090902-141912333
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We analyze a sample of galaxies chosen to have F_(24μm) > 0.5 mJy and satisfy a certain IRAC color criterion. Infrared Spectrograph (IRS) spectra yield redshifts, spectral types, and polycyclic aromatic hydrocarbons (PAH) luminosities, to which we add broadband photometry from optical through IRAC wavelengths, MIPS from 24-160 μm, 1.1 mm, and radio at 1.4 GHz. Stellar population modeling and IRS spectra together demonstrate that the double criteria used to select this sample have efficiently isolated massive star-forming galaxies at z ~ 1.9. This is the first starburst (SB)-dominated ultraluminous infrared galaxies (ULIRG) sample at high redshift with total infrared luminosity measured directly from FIR and millimeter photometry, and as such gives us the first accurate view of broadband spectral energy distributions for SB galaxies at extremely high luminosity and at all wavelengths. Similar broadband data are assembled for three other galaxy samples—local SB galaxies, local active galactic nucleus (AGN)/ULIRGs, and a second 24 μm-luminous z ~ 2 sample dominated by AGN. L_(PAH)/L_(IR) for the new z ~ 2 SB sample is the highest ever seen, some three times higher than in local SBs, whereas in AGNs this ratio is depressed below the SB trend, often severely. Several pieces of evidence imply that AGNs exist in this SB-dominated sample, except two of which even host very strong AGN, while they still have very strong PAH emission. The Advanced Camera for Surveys images show that most objects have very extended morphologies in the rest-frame ultraviolet band, thus extended distribution of PAH molecules. Such an extended distribution prevents further destruction PAH molecules by central AGNs. We conclude that objects in this sample are ULIRGs powered mainly by SB; and the total infrared luminosity density contributed by this type of objects is 0.9-2.6 × 10^7 L_☉ Mpc^(–3).
|Additional Information:||© 2009. The American Astronomical Society. Received 2008 September 25; accepted 2009 April 29; published 2009 July 1. This work is based in part 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.|
|Subject Keywords:||cosmology: observations; galaxies: starburst; infrared: galaxies|
|Official Citation:||Infrared Spectrograph Spectroscopy and Multi-Wavelength Study of Luminous Star-Forming Galaxies at z 1.9 J.-S. Huang, S. M. Faber, E. Daddi, E. S. Laird, K. Lai, A. Omont, Y. Wu, J. D. Younger, K. Bundy, A. Cattaneo, S. C. Chapman, C. J. Conselice, M. Dickinson, E. Egami, G. G. Fazio, M. Im, D. Koo, E. Le Floc'h, C. Papovich, D. Rigopoulou, I. Smail, M. Song, P. P. Van de Werf, T. M. A. Webb, C. N. A. Willmer, S. P. Willner, and L. Yan 2009 ApJ 700 183-198 doi: 10.1088/0004-637X/700/1/183|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||14 Sep 2009 19:27|
|Last Modified:||26 Dec 2012 11:18|
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