Galaxy Rest-Frame UV Colors at z ~ 2-4 with HST UVCANDELS

Abstract

We present an analysis of rest-frame UV colors of 17,243 galaxies at $z\sim 2-4$ in the HST UVCANDELS fields: GOODS-N, GOODS-S, COSMOS, and EGS. Here, we study the rest-frame UV spectral slope, $\beta$, measured via model spectra obtained via spectral energy distribution (SED) fitting, ${\beta }_{SED}$, and explore its correlation with various galaxy parameters (photometric redshift, UV magnitude, stellar mass, dust attenuation, star formation rate [SFR], and specific SFR) obtained via SED fitting with Dense Basis. We also obtain measurements for $\beta$ via photometric power-law fitting and compare them to our SED-fit-based results, finding good agreement on average. While we find little evolution in $\beta$ with redshift from $z=2-4$ for the full population, there are clear correlations between $\beta$ (and related parameters) when binned by stellar mass. For this sample, lower stellar mass galaxies (log[$M_{\ast }$] = 7.5-8.5 $M_{\odot }$) are typically bluer (${\beta }_{SED}=-2.0\pm 0.2$ / ${\beta }_{PL}=-2.1\pm 0.4$), fainter ($MUV=-17.8_{-0.6}^{+0.7}$) less dusty ($Av=0.4\pm 0.1$ mag), exhibit lower rates of star formation (log[SFR]=$0.1\pm 0.2M_{\odot }/$ yr) and higher specific star formation rates (log[sSFR]=$-8.2\pm 0.2{\mathrm{yr}}^{-1}$) than their high-mass counterparts. Higher-mass galaxies (log[$M_{\ast }$] $=10.0-12.0M_{\odot }$) are on average redder (${\beta }_{SED}=-0.9_{-0.5}^{+0.8}$ / ${\beta }_{PL}=-1.0_{-0.5}^{+0.8}$), brighter ($MUV=-19.6_{-1.2}^{+1.0}$), dustier ($Av=0.9_{-0.4}^{+0.5}$ mag), have higher SFRs (log[SFR]=$1.2_{-1.1}^{+0.6}{M}_{\odot }$ yr), and lower sSFRs (log[sSFR]=$-9.1_{-1.1}^{+0.5}{yr}^{-1}$). This study's substantial sample size provides a benchmark for demonstrating that the rest-frame UV spectral slope correlates with stellar mass-dependent galaxy characteristics at $z\sim 2-4$, a relationship less discernible with smaller datasets typically available at higher redshifts.

13 pages, 5 tables, 7 figures, published in ApJ

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