A spectroscopic survey of Ly$\alpha$ emitters and Ly$\alpha$ luminosity function at Redshifts 3.7 and 4.8

TL;DR

This study presents a large spectroscopic survey of Ly$ extalpha$ emitters at redshifts 3.7 and 4.8, measuring their luminosity functions and analyzing their evolution over cosmic time.

Contribution

It provides one of the largest spectroscopic samples of LAEs at these redshifts and derives reliable Ly$ extalpha$ luminosity functions, confirming slow evolution from z~3.1 to 5.7.

Findings

Ly$ extalpha$ luminosity functions decrease mildly from z~3.1 to 5.7.

LF declines rapidly beyond z>5.7, indicating effects of cosmic reionization.

Sample is among the most luminous LAEs at these redshifts.

Abstract

We present a spectroscopic survey of Ly$\alpha$ emitters (LAEs) at $z\sim3.7$ and $z\sim4.8$. The LAEs are selected using the narrowband technique based on the combination of deep narrowband and broadband imaging data in two deep fields, and then spectroscopically confirmed with the MMT multi-fiber spectrograph Hectospec. The sample consists of 71 LAEs at $z\sim3.7$ and 69 LAEs at $z\sim4.8$ over $\sim 1.5$ deg$^2$, making it one of the largest spectroscopically confirmed sample of LAEs at the two redshifts. Their Ly$\alpha$ luminosities are measured using the secure redshifts and deep photometric data, and span a range of $\sim 10^{42.5}$ - $10^{43.6} \,\rm erg\, s^{-1}$, so these LAEs represent the most luminous galaxies at the redshifts in terms of Ly$\alpha$ luminosity. We estimate and correct sample incompletenesses and derive reliable Ly$\alpha$ luminosity function (LF)s at $z\sim3.7$ and 4.8 based on the two spectroscopic samples. We find that our Ly$\alpha$ LFs are roughly consistent (within a factor of $2-3$) with previous measurements at similar redshifts that were derived from either photometric samples or spectroscopic samples. By comparing with previous studies in different redshifts, we find that the Ly$\alpha$ LFs decrease mildly from $z\sim3.1$ to $z\sim5.7$, supporting the previous claim of the slow LF evolution between $z\sim2$ and $z\sim6$. At $z>5.7$, the LF declines rapidly towards higher redshift, partly due to the effect of cosmic reionization.