2025ApJ...985..174M

We present an analysis of rest-frame ultraviolet (UV) colors of 17,243 galaxies at z ∼ 2-4 in the Hubble Space Telescope UVCANDELS fields: GOODS-N, GOODS-S, COSMOS, and EGS. Here, we study the rest-frame UV spectral slope, β, measured via model spectra obtained via spectral energy distribution (SED) fitting, β_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 β 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 β with redshift from z = 2-4 for the full population, there are clear correlations between β (and related parameters) when binned by stellar mass. For this sample, lower-stellar-mass galaxies (log[M_*] = 7.5-8.5 M_⊙) are typically bluer (${\beta }_{{\rm{SED}}}=-2.{0}_{-0.2}^{+0.2}$ / ${\beta }_{{\rm{PL}}}=-2.{1}_{-0.4}^{+0.4}$), fainter (${M}_{{\rm{UV}}}=-17.{8}_{-0.6}^{+0.7}$), and less dusty (${A}_{{\rm{v}}}=0.{4}_{-0.1}^{+0.1}$ mag), and they exhibit lower rates of star formation (log[SFR]=$0.{1}_{-0.2}^{+0.2}{M}_{\odot }\,{{\rm{yr}}}^{-1}$) and higher specific star formation rates (log[sSFR] = $-8.{2}_{-0.2}^{+0.2}\,{{\rm{yr}}}^{-1}$) than their high-mass counterparts. Higher-mass galaxies (log[M_*] = 10.0-12.0 M_⊙) are on average redder (${\beta }_{{\rm{SED}}}=-0.{9}_{-0.5}^{+0.8}$/${\beta }_{{\rm{PL}}}=-1.{0}_{-0.5}^{+0.8}$), brighter (${M}_{{\rm{UV}}}=-19.{6}_{-1.2}^{+1.0}$), and dustier (${A}_{{\rm{v}}}=0.{9}_{-0.4}^{+0.5}$ mag), and they have higher SFRs (log[SFR] = $1.{2}_{-1.1}^{+0.6}{M}_{\odot }\,{{\rm{yr}}}^{-1}$) and lower sSFRs (log[sSFR] = $-9.{1}_{-1.1}^{+0.5}\,{{\rm{yr}}}^{-1}$). 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 ∼ 2-4, a relationship less discernible with the smaller data sets typically available at higher redshifts.