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# The Origin of the Observed Lyman alpha EW Distribution of Dwarf Galaxies at z~2

C. Snapp-Kolas, B. Siana, T. Gburek, A. Alavi, N. Emami, J. Richard, D. P. Stark, C. Scarlata

Submitted on 31 October 2022

## Abstract

We present a rest-UV selected sample of 32 lensed galaxies at $z\sim 2$ observed with joint Keck/LRIS rest-UV and Keck/MOSFIRE rest-optical spectra behind the clusters Abell 1689, MACS J0717, and MACS J1149. The sample pushes towards the faintest UV luminosities observed ($-19\le {\mathrm{M}}_{\mathrm{U}\mathrm{V}}\le -17$) at this redshift. The fraction of dwarf galaxies identified as Ly$\alpha$ emitters () is ${\mathrm{X}}_{\mathrm{L}\mathrm{A}\mathrm{E}}={25}_{-10}^{+15}\mathrm{%}$. We use the Balmer lines and UV continuum to estimate the intrinsic EW allowing us to distinguish the effects of the ionizing spectra and Ly$\alpha$ escape fraction on the observed EW distribution. Fainter galaxies (${\mathrm{M}}_{\mathrm{U}\mathrm{V}}>-19$) show larger intrinsic EWs and escape fractions than brighter galaxies. Only galaxies with intrinsic EWs greater than 40 have escape fractions larger than 0.05. We find an anti-correlation between the escape fraction and ${\mathrm{A}}_{\mathrm{V}}$ as well as UV spectral slope. The volumetric escape fraction of our sample is ${f}_{\mathrm{e}\mathrm{s}\mathrm{c}}^{\mathrm{L}\mathrm{y}\alpha }={4.59}_{-1.4}^{+2.0}\mathrm{%}$ in agreement with measurements found elsewhere in the literature. About half of the total integrated Ly$\alpha$ luminosity density comes from galaxies with .

## Preprint

Comment: 11 pages, 13 figures

Subject: Astrophysics - Astrophysics of Galaxies