# Lyman-alpha

## The Impact of the IGM on Lyman-alpha Emitting Galaxies' Spectra

Introduction Lyman-$\alpha$ spectra can provide insights into the small-scale structure and kinematics of neutral hydrogen (HI) within galaxies as well as the ionization state of the intergalactic medium (IGM). The former defines the intrinsic spectrum of a galaxy, which is modified by the latter. These two effects are degenerate: While at low redshifts, double peaked Lyman-$\alpha$ spectra are the norm, we find more and more spectra only showing a red peak at high redshifts.

## The Lyman-alpha Cosmic Web

While Lyman-alpha emitters (LAEs) are already a popular astrophysical and cosmological tracer of the high-z (2) universe, diffuse Lyman- alpha observations outside of galaxies could become a powerful probe of the filamentary structure of the cosmic …

## Simulating Lyman-alpha Emitters

Below plots show first results of our new radiative transfer code for meshless structures applied to individual halos in the IllustrisTNG simulations. Lyman-alpha emitter after radiative transfer. Surface brightness in erg/s/cm$^2$/arcsec$^2$. Lyman-alpha emitter after radiative transfer. Artificially lowered neutral hydrogen density by a factor of $10$, revealing the radiative transfer smoothing out the emission from the star forming regions. Surface brightness in erg/s/cm$^2$/arcsec$^2$. The neutral hydrogen column density responsible for scattering out the injected photons in star forming regions.

## IGM Interaction of Lyman-alpha Emitters Spectra

Lyman-alpha emitters (LAEs) show a rich variety of spectral shapes due to the emission line’s resonant nature and typically high optical depths. While there is a large body of literature exploring how small-scale density and velocity distributions can explain this variety of features in spectra, the intergalactic medium (IGM) has often been neglecting as a contributing factor for such features. Above sketch helps visualizing how the IGM density and velocity structure along a line-of-sight give rise to an attenuation profile possibly shaping the arising spectrum.

## Radiative Transfer on Voronoi Meshes

An increasing amount of astrophysical and cosmological simulations are carried out on a moving unstructed mesh defined by the Voronoi tessellation. Photons are spawned in a Monte Carlo fashion from emitting gas cells. At each scattering the contribution reaching the observer along specified lines of sight is computed. Lately, we expanded the priorly used code in Behrens et al., 2019 ( public version here) to work on such meshless structure.

## Clustering Distortions from Lyman-alpha Radiative Transfer - A short introduction

The dimensionally split power spectrum/two-point correlation are standard tools for constraining the cosmological model from redshift surveys. Given the Lyman-alpha emission line, I will try to motivate what significant distortions from the line's …

## Clustering Distortions from Lyman-alpha Radiative Transfer

Lyman-alpha based emission line surveys are prone to errors in their interpretation due to the complex radiative transfer for this line. We address this issue by running full radiative transfer simulations on the Illustris simulations and generate …

## Clustering Distortions from Lyman-alpha Radiative Transfer

Introduction Lyman-$\alpha$ emitters and their intensity map are powerful probes of the large-scale structure. Given typically very high optical depths, scatterings with neutral hydrogen have a non-negligible impact on the observed distribution of Lyman-$\alpha$ photons. To study this in detail, we run a suit of radiative transfer (RT) simulations on the Illustris simulation and investigate two possible distortion effects arising from RT in real space as well as in redshift space for the two-point correlation function.

## Cosmological radiative transfer simulations of Lyman-alpha emission: the impact on the galaxy clustering

Lyman-alpha emitters and their intensity map are powerful probes of the large-scale structure at optical and near-infrared wavelength as HETDEX plans. However, the fact that the Lyman-alpha photons are scattered due to the neutral hydrogen has …