The evolution of the UV luminosity and stellar mass functions of Lyman-alpha emitters from z~2 to z~6

Santos, Sérgio and Sobral, David and Butterworth, Josh and Paulino-Afonso, Ana and Ribeiro, Bruno and Cunha, Elisabete da and Calhau, João and Khostovan, Ali Ahmad and Matthee, Jorryt and Haro, Pablo Arrabal (2021) The evolution of the UV luminosity and stellar mass functions of Lyman-alpha emitters from z~2 to z~6. Monthly Notices of the Royal Astronomical Society, 505 (1). 1117–1134. ISSN 0035-8711

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Abstract

We measure the evolution of the rest-frame UV luminosity function (LF) and the stellar mass function (SMF) of Lyman-alpha (Lya) emitters (LAEs) from z~2 to z~6 by exploring ~4000 LAEs from the SC4K sample. We find a correlation between Lya luminosity (LLya) and rest-frame UV (M_UV), with best-fit M_UV=-1.6+-0.2 log10(LLya/erg/s)+47+-12 and a shallower relation between LLya and stellar mass (Mstar), with best-fit log10( Mstar/Msun)=0.9+-0.1 log10(LLya/erg/s)-28+-4.0. An increasing LLya cut predominantly lowers the number density of faint M_UV and low Mstar LAEs. We estimate a proxy for the full UV LFs and SMFs of LAEs with simple assumptions of the faint end slope. For the UV LF, we find a brightening of the characteristic UV luminosity (M_UV*) with increasing redshift and a decrease of the characteristic number density (Phi*). For the SMF, we measure a characteristic stellar mass (Mstar*/Msun) increase with increasing redshift, and a Phi* decline. However, if we apply a uniform luminosity cut of log10 (LLya/erg/s) >= 43.0, we find much milder to no evolution in the UV and SMF of LAEs. The UV luminosity density (rho_UV) of the full sample of LAEs shows moderate evolution and the stellar mass density (rho_M) decreases, with both being always lower than the total rho_UV and rho_M of more typical galaxies but slowly approaching them with increasing redshift. Overall, our results indicate that both rho_UV and rho_M of LAEs slowly approach the measurements of continuum-selected galaxies at z>6, which suggests a key role of LAEs in the epoch of reionisation.