2012ApJ...755..148G -
Astrophys. J., 755, 148 (2012/August-3)
The rest-frame UV-to-optical colors and spectral energy distributions of z ∼ 4-7 galaxies.
GONZALEZ V., BOUWENS R.J., LABBE I., ILLINGWORTH G., OESCH P., FRANX M. and MAGEE D.
Abstract (from CDS):
We use the ultra-deep HUDF09 and the deep Early Release Science data from the HST WFC3/IR camera, along with the wide-area Spitzer/IRAC data from GOODS-S to derive spectral energy distributions (SEDs) of star-forming galaxies from the rest-frame UV to the optical over a wide luminosity range (M1500 ∼ -21 to M1500∼ -18) from z ∼ 7 to z ∼ 4. The sample contains ∼400 z ∼ 4, ∼120 z ∼ 5, ∼60 z ∼ 6, and 36 z ∼ 7 galaxies. Median stacking enables the first comprehensive SED study of very faint high-z galaxies at multiple redshifts (e.g., [3.6] = 27.4±0.1 AB mag for the M1500∼ -18 sources at z ∼ 4). At z ∼ 4, we study the stacked SEDs over a range of 5 mag reaching down to ∼0.06L*_ z = 4_. We use all available SEDs and template fits to derive rest-frame UV-to-optical colors (U - V) at all redshifts and luminosities. We find that this color does not vary significantly with redshift at a fixed luminosity. The UV-to-optical color does show a weak trend with luminosity, becoming redder at higher luminosities. This is most likely due to dust. At z ≳ 5, we find blue [3.6]-[4.5] colors ∼ -0.3 mag that are most likely due to rest-frame optical emission lines contributing to the flux in the IRAC filter bandpasses. Such contributions would lower both ages and masses by ∼2 x. The scatter in our derived SEDs remains large, but the results are most consistent with a lack of any evolution in the SEDs with redshift at a given luminosity. The uniformity of the SEDs suggests a self-similar mode of evolution over a timespan from 0.7 Gyr to 1.5 Gyr after the big bang that encompasses very substantial growth in the stellar mass density in the universe (from ∼4x106 to ∼2x107 M☉/Mpc3).
Abstract Copyright:
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Journal keyword(s):
galaxies: evolution - galaxies: high-redshift
Simbad objects:
2
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