Ly{\alpha} Halos around [O III]-Selected Galaxies in HETDEX

TL;DR

This study analyzes the extended Lyα emission around [O III]-selected galaxies at redshifts 1.9 to 2.35, revealing differences in surface brightness profiles compared to Lyα-emitting galaxies, and suggests outer halo photons originate outside the galaxies.

Contribution

First measurement of Lyα halos around [O III]-selected galaxies at z~2, showing differences from Lyα emitters and indicating external origins of outer halo photons.

Findings

Lyα halos extend up to 800 kpc around galaxies.

Inner surface brightness is ten times fainter than in Lyα emitters.

Outer Lyα halo photons likely originate outside the central galaxies.

Abstract

We present extended Lyman-{\alpha} (Ly{\alpha}) emission out to 800 kpc of 1034 [O III]-selected galaxies at redshifts 1.9<z<2.35 using the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). The locations and redshifts of the galaxies are taken from the 3D-HST survey. The median-stacked surface brightness profile of Ly{\alpha} emission of the [O III]-selected galaxies agrees well with that of 968 bright Ly{\alpha}-emitting galaxies (LAEs) at r>40 kpc from the galaxy centers. The surface brightness in the inner parts (r<10 kpc) around the [O III]-selected galaxies, however, is ten times fainter than that of the LAEs. Our results are consistent with the notion that photons dominating the outer regions of the Ly{\alpha} halos are not produced in the central galaxies but originate outside of them.