A Spectral Atlas of Lyman Alpha Emitters at z = 5.7 and z = 6.6

TL;DR

This study provides a comprehensive spectral atlas of Ly-alpha emitters at redshifts 5.7 and 6.6, revealing their properties, evolution, and the ionized bubble environments during the epoch of reionization.

Contribution

It offers the first large, uniform spectroscopic samples of LAEs at these redshifts, analyzing their line profiles, luminosities, and implications for cosmic reionization.

Findings

Lower-luminosity LAEs show decreasing line width with redshift.

High-luminosity LAEs may create large ionized bubbles.

Double-peaked LAEs require transmission on the blue side.

Abstract

We present two uniformly observed spectroscopic samples of Ly-alpha emitters (LAEs) (127 at z = 5.7 and 82 at z = 6.6), which we use to investigate the evolution of the LAE population at these redshifts. The observations cover a large field (44 sq. deg) in the North Ecliptic Pole (HEROES), as well as several smaller fields. We have a small number of exotic LAEs in the samples: double-peaked Ly-alpha profiles; very extended red wings; and one impressive lensed LAE cross. We also find three broad-line AGNs. We compare the Ly-alpha line width measurements at the two redshifts, finding that the lower-luminosity LAEs show a strong evolution of decreasing line width with increasing redshift, while the high-luminosity LAEs do not, with a transition luminosity of log L(Ly-alpha) = 43.25 erg s-1 . Thus, at z = 6.6, the high-luminosity LAEs may be producing large ionized bubbles themselves, or they may be residing in overdense galaxy sites that are producing such bubbles. In order to avoid losses in the red wing, the radius of the ionized bubble must be larger than 1 pMpc. The double-peaked LAEs also require transmission on the blue side. For the four at z = 6.6, we use models to estimate the proximity radii, Ra , where the ionizing flux of the galaxy is sufficient to make the surroundings have a low enough neutral fraction to pass the blue light. Since the required Ra are large, multiple ionizing sources in the vicinity may be needed.