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Deep Spitzer/IRAC Data for z ∼ 10 Galaxies Reveal Blue Balmer Break Colors: Young Stellar Populations at ∼500 Myr of Cosmic Time.

Authors :
Stefanon, Mauro
Bouwens, Rychard J.
Labbé, Ivo
Illingworth, Garth D.
Gonzalez, Valentino
Oesch, Pascal A.
Source :
Astrophysical Journal. 2/1/2023, Vol. 943 Issue 2, p1-10. 10p.
Publication Year :
2023

Abstract

We present the deepest constraints yet on the median rest-UV+optical spectral energy distribution (SED) of z ∼ 10 galaxies prior to James Webb Space Telescope science operations. We constructed stacks based on four robust J 125 dropouts, previously identified across the GOODS fields. We used archival Hubble Space Telescope/Wide Field Camera 3 data and the full-depth Spitzer/IRAC mosaics from the GREATS program, the deepest coverage at ∼3–5 μ m to date. The most remarkable feature of the SED is a blue IRAC [3.6]–[4.5] = −0.18 ± 0.25 mag color. We also find a nearly flat H 160 − [3.6] = 0.07 ± 0.22 mag color, corresponding to a UV slope β = −1.92 ± 0.25. This is consistent with previous studies and indicative of minimal dust absorption. The observed blue IRAC color and SED fitting suggest that z ∼ 10 galaxies have very young (few × 10 Myr) stellar populations, with 80% of stars being formed in the last ≲160 Myr (2 σ). While an exciting result, the uncertainties on the SED are too large to allow us to place strong constraints on the presence of a nebular continuum in z ∼ 10 galaxies (as might be suggested by the blue [3.6]–[4.5] < 0 mag color). The resulting sSFR is consistent with the specific accretion rate of dark matter halos, indicative of a star formation efficiency showing quite limited evolution at such early epochs. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
0004637X
Volume :
943
Issue :
2
Database :
Academic Search Index
Journal :
Astrophysical Journal
Publication Type :
Academic Journal
Accession number :
161580315
Full Text :
https://doi.org/10.3847/1538-4357/aca470