ODIN: The LAE Ly{\alpha} Luminosity Function over Cosmic Time and Environmental Density

TL;DR

This paper presents methods to measure the Lyα luminosity function of galaxies across different environments and cosmic times, revealing environmental effects and evolution of the function from redshift 4.5 to 2.4.

Contribution

It introduces algorithms for accurately computing the LAE luminosity function and applies them to ODIN survey data, exploring environmental dependence and evolution over cosmic time.

Findings

Environmental effects on LAE luminosity function observed

LF steepens at faint end from z~4.5 to 2.4

Number density of LAEs decreases over time

Abstract

The ubiquity and relative ease of discovery make $2\lesssim z\lesssim 5$ Ly$\alpha$ emitting galaxies (LAEs) ideal tracers for cosmology. In addition, because Ly$\alpha$ is a resonance line, but frequently observed at large equivalent width, it is potentially a probe of galaxy evolution. The LAE Ly$\alpha$ luminosity function (LF) is an essential measurement for making progress on both of these aspects. Although several studies have computed the LAE LF, very few have delved into how the function varies with environment. The large area and depth of the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey makes such measurements possible at the cosmic noon redshifts of z~2.4, ~3.1, and ~4.5. In this initial work, we present algorithms to rigorously compute the LAE LF and test our methods on the ~16,000 ODIN LAEs found in the extended COSMOS field. Using these limited samples, we find slight evidence that protocluster environments either suppress the numbers of very faint and very bright LAEs or enhance medium-bright LAEs in comparison to the field. We also find that the LF decreases in number density and evolves towards a steeper faint-end slope over cosmic time from z~4.5 to z~2.4.