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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2011

Dust-obscured star formation and the contribution of galaxies escaping UV/optical color selections at z similar to 2

L. Riguccini
  • Fonction : Auteur
E. Le Floc'H
  • Fonction : Auteur
H. Aussel
M. Salvato
  • Fonction : Auteur
P. Capak
H. Mccracken
  • Fonction : Auteur
J. Kartaltepe
D. Sanders
N. Scoville
  • Fonction : Auteur

Résumé

Context. A substantial amount of the stellar mass growth across cosmic time occurred within dust-enshrouded environments. So far, identification of complete samples of distant star-forming galaxies from the short wavelength range has been strongly biased by the effect of dust extinction. Nevertheless, the exact amount of star-forming activity that took place in high-redshift dusty galaxies but that has currently been missed by optical surveys has barely been explored. Aims. Our goal is to determine the number of luminous star-forming galaxies at 1.5 less than or similar to z less than or similar to 3 that are potentially missed by the traditional color selection techniques because of dust extinction. We also aim at quantifying the contribution of these sources to the IR luminosity and cosmic star formation density at high redshift. Methods. We based our work on a sample of 24 mu m sources brighter than 80 mu Jy and taken from the Spitzer survey of the COSMOS field. Almost all of these sources have accurate photometric redshifts. We applied to this mid-IR selected sample the BzK and BM/BX criteria, as well as the selections of the IRAC peakers and the Optically-Faint IR-bright (OFIR) galaxies. We analyzed the fraction of sources identified with these techniques. We also computed 8 mu m rest-frame luminosity from the 24 mu m fluxes of our sources, and considering the relationships between L-8 (mu m) and L-Pa alpha and between L-8 (mu m) and L-IR, we derived rho(IR) and then rho(SFR) for our MIPS sources. Results. The BzK criterion offers an almost complete (similar to 90%) identification of the 24 mu m sources at 1.4 \textless z \textless 2.5. In contrast, the BM/BX criterion misses 50% of the MIPS sources. We attribute this bias to the effect of extinction, which reddens the typical colors of galaxies. The contribution of these two selections to the IR luminosity density produced by all the sources brighter than 80 mu Jy are on the same order. Moreover the criterion based on the presence of a stellar bump in their spectra (IRAC peakers) misses up to 40% of the IR luminosity density, while only 25% of the IR luminosity density at z similar to 2 is produced by OFIR galaxies characterized by extreme mid-IR to optical flux ratios. Conclusions. Color selections of distant star- forming galaxies must be used with care given the substantial bias they can suffer. In particular, the effect of dust extinction strongly affects the completeness of identifications at the bright end of the bolometric luminosity function, which implies large and uncertain extrapolations to account for the contribution of dusty galaxies missed by these selections. In the context of forthcoming facilities that will operate at long wavelengths (e.g., JWST, ALMA, SAFARI, EVLA, SKA), this emphasizes the importance of minimizing the extinction biases when probing the activity of star formation in the early Universe.

Dates et versions

hal-01438065 , version 1 (17-01-2017)

Identifiants

Citer

L. Riguccini, E. Le Floc'H, O. Ilbert, H. Aussel, M. Salvato, et al.. Dust-obscured star formation and the contribution of galaxies escaping UV/optical color selections at z similar to 2. Astronomy and Astrophysics - A&A, 2011, 534, ⟨10.1051/0004-6361/201116950⟩. ⟨hal-01438065⟩
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