Infrared color selection of massive galaxies atz > 3
- Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu, F-91191 Gif-sur-Yvette (France)
- Department of Physics, Anhui Normal University, Wuhu, Anhui, 241000 (China)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)
- INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (Italy)
- Center for Astrophysics and Planetary Science, Racah Institute of Physics,The Hebrew University, Jerusalem, 91904 (Israel)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom)
- Department of Astronomy, University of Massachusetts, Amherst, MA (United States)
- Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States)
We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H{sub 160} (H) and Infrared Array Camera (IRAC) 4.5 μm bands, specifically H−[4.5]>2.25 mag. These galaxies, called “HIEROs,” include two major populations that can be separated with an additional J − H color. The populations are massive and dusty star-forming galaxies at z>3 (JH−blue) and extremely dusty galaxies at z≲3 (JH−red). The 350 arcmin{sup 2} of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to [4.5]<24 mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on JH−blue (z>3) HIEROs, which have a median photometric redshift 〈z〉∼4.4 and stellar mass M{sub ∗}∼10{sup 10.6} M{sub ⊙} and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ∼240 M{sub ⊙} yr{sup −1}, leading to a specific SFR, sSFR≡SFR/M{sub ∗}∼4.2 Gyr{sup −1}, suggesting that the sSFRs for massive galaxies continue to grow at z>2 but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including ∼20% as compact as quiescent (QS) galaxies at similar redshifts, JH−blue HIEROs represent perfect star-forming progenitors of the most massive (M{sub ∗}≳10{sup 11.2} M{sub ⊙}) compact QS galaxies at z∼3 and have the right number density. HIEROs make up ∼60% of all galaxies with M{sub ∗}>10{sup 10.5} M{sub ⊙} identified at z>3 from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations. While HIEROs make up 15%–25% of the total SFR density at z∼4–5, they completely dominate the SFR density taking place in M{sub ∗}>10{sup 10.5} M{sub ⊙} galaxies, and HIEROs are therefore crucial to understanding the very early phase of massive galaxy formation.
- OSTI ID:
- 22879401
- Journal Information:
- Astrophysical Journal, Vol. 816, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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