# Galaxies of the $z \sim 2$ Universe. I. Grism-Selected Rest-Frame Optical Emission Line Galaxies

## TL;DR

This study characterizes approximately 2,000 emission-line galaxies at redshift around 2, revealing their physical properties and differences from continuum-selected galaxies, providing essential data for future comparative analyses.

## Contribution

It presents the first comprehensive analysis of rest-frame optical emission-line galaxies at z~2, highlighting their properties and differences from other galaxy populations.

## Key findings

- [O III] emission is typically much brighter than [O II] and Hβ.
- Emission-line galaxies span wide ranges in stellar mass, star-formation rate, and luminosity.
- Emission-line galaxies have lower stellar masses and dust attenuation compared to continuum-selected galaxies.

## Abstract

Euclid, WFIRST, and HETDEX will make emission-line selected galaxies the largest observed constituent in the $z > 1$ universe. However, we only have a limited understanding of the physical properties of galaxies selected via their Ly$\alpha$ or rest-frame optical emission lines. To begin addressing this problem, we present the basic properties of $\sim 2,000$ AEGIS, COSMOS, GOODS-N, GOODS-S, and UDS galaxies identified in the redshift range $1.90 < z < 2.35$ via their [O II], H$\beta$, and [O III] emission lines. For these $z \sim 2$ galaxies, [O III] is generally much brighter than [O II] and H$\beta$, with typical rest-frame equivalent widths of several hundred Angstroms. Moreover, these strong emission-line systems span an extremely wide range of stellar mass ($\sim 3$ dex), star-formation rate ($\sim 2$ dex), and [O III] luminosity ($\sim 2$ dex). Comparing the distributions of these properties to those of continuum selected galaxies, we find that emission-line galaxies have systematically lower stellar masses and lower optical/UV dust attenuations. These measurements lay the groundwork for an extensive comparison between these rest-frame optical emission-line galaxies and Ly$\alpha$ emitters identified in the HETDEX survey.