The impact of large scale structure on the Lyx emission and absorption of galaxies at 2.2 < z < 2.8

Abstract

Galaxy evolution studies aim to understand how galaxies form and evolve from the initial conditions of the early universe. The modern paradigm of galaxy formation and evolution considers as a fundamental process the exchange of mass, energy, and metals between galaxies, their surrounding circumgalactic medium (CGM), and the intergalactic medium (IGM), a process known as the baryon cycle. The environment in which galaxies live play an important role in this cycle of galaxy evolution. In the "local universe", up to redshift z $\sim 1$, galaxy properties are correlated with environment or local density (e.g., \cite{Dressler1980}; \cite{Postman1984ApJ...281...95P}; \cite{kauffmann2004MNRAS.353..713K}; \cite{Cooper2006MNRAS.370..198C}; \cite{Muzzin2012ApJ...746..188M}; \cite{Hahn2015ApJ...806..162H}; \cite{Darvish2016ApJ...825..113D}). However, at earlier epochs (z > 1.5), observations that probe the relation between galaxy properties and the environment are much less definitive (see review by \cite{Overzier2016A&ARv..24...14O}), becoming a current topic of research on galaxy evolution studies. (\cite{2020Newman}) In this work, we aim to study the environmental conditions of galaxies at cosmic noon (z $\sim$ 2.2 - 2.8), and trace the impact of environment or local density over characteristic features on high redshift galaxy spectra: Lyman alpha (Ly$\alpha$) emission and Ly$\alpha$ absorption, studied in separate sections on this document. Both these studies are performed using early data from LATIS, the Lyman Alpha Tomography IMACS Survey (\cite{2020Newman}). LATIS measures the local density in which said galaxies live, enabiling the type of studies that this work aims to achieve. The survey is described in detail in Section 2. For our emission studies, we select 1258 of the 2596 galaxies from LATIS sample. In this section there are two main objectives: First, to understand how internal properties of galaxies, that modulate the production and escape of Ly$\alpha$ emission, are different in different environments. To achieve this goal we estimate a Ly$\alpha$ Equivalent Width distribution (P(EW)) based on the measurement of $M_{UV}$ and UV slope ($\beta$) from available photometry, following \cite{Oyarzun2017ApJ...843..133O} method. We find that there are not significant changes of the estimated P(EW) over different environmental conditions. Meaning that observed emission in our studied range of environment do not change due to internal processes in galaxies. The second objective is to determine changes in the Ly$\alpha$ EW distributions between groups of galaxies with different environmental conditions. We measure directly the EW in the galaxy spectra and create distributions for galaxy groups with different local densities. We find no statistically significant changes in the EW distribution of Ly$\alpha$ emission as a function of local density. For our absorption studies, we use a sample of 1771 galaxies. The main objective is to explore whether there is some change in Ly$\alpha$ absorption between groups of galaxies with different environmental conditions. We explore the differential absorption present in galaxy spectra. We find a significant decrease in HI absorption around galaxies living in the lowest density environments, which we quantify via a differential Voigt profile fitting process and their fitted parameters. This trend will be explored in more detail in the future.