The UV Continuum of z > 1 Star-forming Galaxies in the Hubble Ultraviolet UltraDeep Field

Abstract

We estimate the UV continuum slope, beta, 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 <beta> = -1.382 (-1.830) +/- 0.002 (random) +/- 0.1 (systematic). We find comparable scatter in beta (standard deviation = 0.43) to local dwarf galaxies and 30% larger scatter than z > 2 galaxies. We study the trends of beta with redshift and absolute magnitude for binned sub-samples and find a modest color-magnitude relation, dbeta/dM = -0.11 +/- 0.01 and no evolution in dbeta/dM with redshift. A modest increase in dust reddening with redshift and luminosity, Delta E(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, dbeta/dz = -0.09 +/-0.01 for low luminosity (0.05 L*_{z=3}), and dbeta/dz = -0.06 +/-0.01 for medium luminosity (0.25 L*_{z=3}) galaxies.

7 pages, 4 figures, 1 table. ApJL in press

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Cited by in corpus (12)

• UVUDF: Ultraviolet Through Near-infrared Catalog and Photometric Redshifts of Galaxies in the Hubble Ultra Deep Field
• z~2-9 Galaxies Magnified by the Hubble Frontier Field Clusters II: Luminosity Functions and Constraints on a Faint-End Turnover
• The MUSE Hubble Ultra Deep Field Survey X. Ly$\alpha$ Equivalent Widths at $2.9<z<6.6$
• UV Spectral-Slopes at $z=6-9$ in the Hubble Frontier Fields: Lack of Evidence for Unusual or Pop III Stellar Populations
• UVUDF: UV Luminosity Functions at the cosmic high-noon
• Statistical correlation between the distribution of Ly$\alpha$ emitters and IGM HI at $z\sim 2.2$ mapped by Subaru/Hyper Suprime-Cam
• Distortion of the luminosity function of high-redshift galaxies by gravitational lensing
• The UV spectral slope beta and stellar population of most active star-forming galaxies at z~4
• Evolution of the UV slope of galaxies at cosmic morning (z > 4): the properties of extremely blue galaxies
• Observed UV continuum slopes ($\beta$) of galaxies at $z=0.40-0.75$ in the GOODS-north field
• UV slope of z$\sim$3 bright ($L>L^{\ast }$) Lyman-break galaxies in the COSMOS field
• Galaxy Rest-Frame UV Colors at z ~ 2-4 with HST UVCANDELS