ODIN: The LAE Lyα Luminosity Function over Cosmic Time and Environmental Density
Gautam Nagaraj, Robin Ciardullo, Caryl Gronwall, Vandana Ramakrishnan, Kyoung-Soo Lee, Eric Gawiser, Nicole M. Firestone, Govind Ramgopal, J. Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Francisco Javier Castander, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Arjun Dey, Biprateep Dey, Peter Doel, Jaime Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Hiram K. Herrera-Alcantar, Klaus Honscheid, Mustapha Ishak, Robert Kehoe, David Kirkby, T. Kisner, Anthony Kremin, Martin Landriau, Laurent Le Guillou, Michael Levi, Christophe Magneville, Marc Manera, Paul Martini, Aaron M. Meisner, Ramon Miquel, John Moustakas, Nathalie Palanque-Delabrouille, Francisco Prada, Ignasi Perez-Rafols, Graziano Rossi, Lado Samushia, Eusebio Sanchez, David J. Schlegel, Michael F. Schubnell, Hee-Jong Seo, Joseph H. Silber, David Sprayberry, Gregory Tarle, Francisco Valdes, Benjamin A. Weaver, Martin White, Rongpu Zhou, Hu Zou
TL;DR
The study addresses how the Lyα-emitting galaxy luminosity function (LF) depends on environmental density across cosmic time. It develops rigorous algorithms to compute the LAE LF and applies them to ~16,000 ODIN LAEs in the Extended COSMOS field. The analysis finds slight evidence that protocluster environments suppress very faint and very bright LAEs or boost medium-bright LAEs relative to the field, and shows the LF declines in number density with time while the faint-end slope steepens from $z \sim 4.5$ to $z \sim 2.4$. These results demonstrate the feasibility of environment-resolved LF measurements with wide-area, narrow-band surveys like ODIN, informing models of galaxy evolution and large-scale structure.
Abstract
The ubiquity and relative ease of discovery make $2\lesssim z\lesssim 5$ Ly$α$ emitting galaxies (LAEs) ideal tracers for cosmology. In addition, because Ly$α$ is a resonance line, but frequently observed at large equivalent width, it is potentially a probe of galaxy evolution. The LAE Ly$α$ 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.