The cosmic web can potentially be observed in direct emission through the Lyman-alpha line. While luminous Lyman-alpha emitters are already an established powerful tracer of the matter distribution in the high-redshift universe, the implications of …
The diffuse filaments of the cosmic web can potentially be observed in emission through the Lyman-alpha line. While luminous Lyman-alpha emitters are already an established powerful tracer of the matter distribution in the high-redshift universe, the …
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.
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 …
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.
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.
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. This will ensure the code’s relevance in the future and application to new simulations that would not have been able to be processed with prior code due to the larger memory requirement due to an intermediate interpolation step.