The UV Continuum of z > 1 Star-forming Galaxies in the Hubble Ultraviolet UltraDeep Field
Abstract
We estimate the UV continuum slope, β, for 923 galaxies in the range 1 < z < 8 in the Hubble Ultradeep Field (HUDF). These data include 460 galaxies at 1 < z < 2 down to an absolute magnitude M_UV= -14(∼ 0.006 L^*z=1; 0.02 L^*z=0), comparable to dwarf galaxies in the local universe. We combine deep HST/UVIS photometry in F225W, F275W, F336W wavebands (UVUDF) with recent data from HST/WFC3/IR (HUDF12). Galaxies in the range 1 < z < 2 are significantly bluer than local dwarf galaxies. We find their mean (median) values <β > = - 1.382(- 1.830) ± 0.002 (random) ± 0.1 (systematic). We find comparable scatter in β (standard deviation = 0.43) to local dwarf galaxies and 30% larger scatter than z > 2 galaxies. We study the trends of β with redshift and absolute magnitude for binned sub-samples and find a modest color-magnitude relation, dβ/dM = -0.11 ± 0.01, and no evolution in dβ/dM with redshift. A modest increase in dust reddening with redshift and luminosity, ΔE(B - V) ~ 0.1, and a comparable increase in the dispersion of dust reddening at z < 2, appears likely to explain the observed trends. At z > 2, we find trends that are consistent with previous works; combining our data with the literature in the range 1 < z < 8, we find a color evolution with redshift, dβ/dz = -0.09 ± 0.01 for low luminosity (0.05 L^*z=3), and dβ/dz = -0.06 ± 0.01 for medium luminosity (0.25 L^*z=3) galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2014
- DOI:
- 10.1088/2041-8205/793/1/L5
- arXiv:
- arXiv:1407.3680
- Bibcode:
- 2014ApJ...793L...5K
- Keywords:
-
- cosmology: observations;
- galaxies: evolution;
- galaxies: formation;
- galaxies: high-redshift;
- galaxies: structure;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 7 pages, 4 figures, 1 table. ApJL in press