Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21941903f&link_type=abstract
American Astronomical Society, AAS Meeting #219, #419.03
Astronomy and Astrophysics
Astronomy
Scientific paper
The rest-frame ultraviolet (UV) color is one of the most accessible diagnostics of galaxy properties at high redshift. Here we present an analysis of the evolution of the rest-UV colors of galaxies in the epoch 4 < z < 8. We use the new deep and wide data available in the GOODS-S field from the CANDELS Hubble Space Telescope Multi-Cycle Treasury program, as well as existing data in the HUDF and ERS fields to select galaxies via photometric redshifts. Our sample consists of 2800 galaxies, with > 110 galaxies at z = 7 - 8. We parameterize the rest-UV color via the UV spectral slope β, which we measure while performing spectral energy distribution fitting, measuring the slope of the best-fit model spectrum in the defined wavelength windows. We use simulations to show that this new method results in a smaller average scatter on β than when using solely a single color. We find that the typical UV spectral slope evolves significantly from -1.8 at z = 4 to -2.3 at z = 7. This evolution of β with redshift can be explained by an increase in dust extinction in a typical galaxy in our sample, from very little at z = 7, to Av 0.4 mag at z = 4, possibly due to an increasing dust contribution from low-mass (< 3 M&sun;) AGB stars at z < 7. Finally, we find that β = -2.6 +/- 0.3 for faint (L < 0.25 L*) galaxies at z = 7. This redder value than previous claims in the literature, along with the reduced error bar due to the deeper data and new measurement method, casts further doubt upon the existence of "exotic” stellar populations in these galaxies.
Dickinson Marc
Ferguson Harry
Finkelstein Steven L.
Giavalisco Mauro
Koekemoer Anton
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