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arXiv · 1803.05912

The redshift evolution of rest-UV spectroscopic properties in Lyman Break Galaxies at z ~ 2-4

Xinnan Du·Alice E. Shapley·Naveen A. Reddy·Tucker Jones·Daniel P. Stark·Charles C. Steidel·Allison L. Strom·Gwen C. Rudie·Dawn K. Erb·Richard S. Ellis·Max Pettini
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Abstract

We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ~ 2-4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Ly$α$ equivalent width (EW), and various galaxy properties, we study the evolutionary trends among Ly$α$, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Ly$α$ and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Ly$α$, LIS lines, and dust extinction are redshift-independent, as is the decoupling of Ly$α$ and HIS line strengths, and the bulk outflow kinematics as traced by LIS lines. Stronger Ly$α$ emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in average Ly$α$ strength with redshift, and the variation in Ly$α$ strength at fixed redshift, can be explained in terms of variations in neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Ly$α$ and CIII] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Ly$α$ photons at the highest Ly$α$ EWs. The challenge now is to understand the observed evolution in neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6.

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Xinnan Du, Alice E. Shapley, Naveen A. Reddy, Tucker Jones, Daniel P. Stark, Charles C. Steidel, Allison L. Strom, Gwen C. Rudie, Dawn K. Erb, Richard S. Ellis, Max Pettini. 2018-04-20. The redshift evolution of rest-UV spectroscopic properties in Lyman Break Galaxies at z ~ 2-4. https://doi.org/10.3847/1538-4357%2Faabfcf

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