The HETDEX Pilot Survey & 3DHST: What Makes a Lyman-alpha Emitter?

We compare the 3D-HST H-beta emitters at z~2 to Lyman-alpha emitters found in the same redshift range by the HETDEX Pilot Survey to investigate any differences in the physical and morphological parameters that could elucidate how or why Lyman-alpha is escaping. We use one-dimensional and multi-dimensional statistics, as well as machine learning techniques to try to find differences between these datasets. However, we are unable to find statistically significant differences between these populations. This demonstrates that Lyman-alpha emitters are pulled randomly from the distribution of star-forming galaxies, and there are seemly no strong physical or morphological requirements to be a Lyman-alpha emitter. We also use this information to inform a toy model of Lyman-alpha emission that poses all star-forming galaxies are LAEs if view along certain lines of sight.