Journal Article

Galaxy Rest-frame UV Colors at z ∼ 2–4 with HST UVCANDELS

Windhorst, Rogier A, Finkelstein, Steven L, Taamoli, Sina, Yung, L. Y. Aaron, Bagley, Micaela B, Grogin, Norman A, Wang, Xin, Hathi, Nimish P, Alavi, Anahita, Prichard, Laura, Morales, Alexa M, Nedkova, Kalina V, Teplitz, Harry I, Rafelski, Marc, Sunnquist, Ben, Koekemoer, Anton M

2025

Overview

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, βSED, 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 ( βSED=−2.0−0.2+0.2 / βPL=−2.1−0.4+0.4 ), fainter ( MUV=−17.8−0.6+0.7 ), and less dusty ( Av=0.4−0.1+0.1 mag), and they exhibit lower rates of star formation (log[SFR]= 0.1−0.2+0.2M⊙yr−1 ) and higher specific star formation rates (log[sSFR] = −8.2−0.2+0.2yr−1 ) than their high-mass counterparts. Higher-mass galaxies (log[M*] = 10.0–12.0 M⊙) are on average redder ( βSED=−0.9−0.5+0.8 / βPL=−1.0−0.5+0.8 ), brighter ( MUV=−19.6−1.2+1.0 ), and dustier ( Av=0.9−0.4+0.5 mag), and they have higher SFRs (log[SFR] = 1.2−1.1+0.6M⊙yr−1 ) and lower sSFRs (log[sSFR] = −9.1−1.1+0.5yr−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.

• Publisher: IOP Publishing
• Subject: Correlation / Cosmic dust / Galaxies / Galaxy distribution / Hubble Space Telescope / Parameters / Photometry / Red shift / Space telescopes / Spectral energy distribution / Star & galaxy formation / Star formation / Star formation rate / Stars / Stars & galaxies / Stellar mass