paper

The X-SHOOTER Lyman- survey at z=2 (XLS-z2) I: What makes a galaxy a Lyman- emitter?

arXiv:2102.07779 · doi:10.1093/mnras/stab1304

Abstract

We present the first results from the X-SHOOTER Lyman- survey at (XLS-). XLS- is a deep spectroscopic survey of 35 Lyman- emitters (LAEs) utilising hours of exposure time with VLT/X-SHOOTER and covers rest-frame Ly to H emission with R. We present the sample selection, the observations and the data reduction. Systemic redshifts are measured from rest-frame optical lines for 33/35 sources. In the stacked spectrum, our LAEs are characterised by an interstellar medium with little dust, a low metallicity and a high ionisation state. The ionising sources are young hot stars that power strong emission-lines in the optical and high ionisation lines in the UV. The LAEs exhibit clumpy UV morphologies and have outflowing kinematics with blue-shifted SiII absorption, a broad [OIII] component and a red-skewed Ly line. Typically 30 % of the Ly photons escape, of which one quarter on the blue side of the systemic velocity. A fraction of Ly photons escapes directly at the systemic suggesting clear channels enabling a % escape of ionising photons, consistent with an inference based on MgII. A combination of a low effective HI column density, a low dust content and young star-burst determine whether a star forming galaxy is observed as a LAE. The first is possibly related to outflows and/or a fortunate viewing angle, while we find that the latter two in LAEs are typical for their stellar mass of 10 M.

arXiv commentMain text 26 pages. Accepted for publication in MNRAS

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