Dust Attenuation Curves at z $\sim$ 0.8 from LEGA-C: Precise Constraints on the Slope and 2175$\mathring{A}$ Bump Strength

Abstract

We present a novel approach to measure the attenuation curves of 485 individual star-forming galaxies with M${}_{\ast }$ $>$ 10${}^{10}$ M${}_{\odot }$ based on deep optical spectra from the VLT/VIMOS LEGA-C survey and multi-band photometry in the COSMOS field. Most importantly, we find that the attenuation curves in the rest-frame $3000-4500$A range are typically almost twice as steep as the Milky Way, LMC, SMC, and Calzetti attenuation curves, which is in agreement with recent studies of the integrated light of present-day galaxies. The attenuation at $4500$A and the slope strongly correlate with the galaxy inclination: face-on galaxies show less attenuation and steeper curves compared to edge-on galaxies, suggesting that geometric effects dominate observed variations in attenuation. Our new method produces $2175$A UV bump detections for 260 individual galaxies. Even though obvious correlations between UV bump strength and global galaxy properties are absent, strong UV bumps are most often seen in face-on, lower-mass galaxies (10 $<$ log${}_{10}$(M${}_{\ast }$/M${}_{\odot }$) $<$ 10.5) with low overall attenuation. Finally, we produce a typical attenuation curve for star-forming galaxies at $z\sim 0.8$; this prescription represents the effect of dust on the integrated spectral energy distributions of high-redshift galaxies more accurately than commonly used attenuation laws.

15 pages, 10 figures, 1 table. Accepted for publication in The Astrophysical Journal