Prospects for observing the low-density cosmic web in Lyman-αemission

Abstract

Mapping the intergalactic medium (IGM) in Lyman-α emission would yield unprecedented tomographic information on the large-scale distribution of baryons and potentially provide new constraints on the UV background and various feedback processes relevant to galaxy formation. In this work, we use a cosmological hydrodynamical simulation to examine the Lyman-α emission of the IGM resulting from collisional excitations and recombinations in the presence of a UV background. We focus on gas in large-scale-structure filaments in which Lyman-α radiative transfer effects are expected to be moderate. At low density the emission is primarily due to fluorescent re-emission of the ionising UV background as a result of recombinations, while collisional excitations dominate at higher densities. We discuss prospects of current and future observational facilities to detect this emission and find that the emission of filaments of the cosmic web are typically dominated by the halos and galaxies embedded in these filaments, rather than by the lower-density filament gas outside halos. Detecting filament gas directly would require a very long exposure with a MUSE-like instrument on the ELT. Our most robust predictions that act as lower limits indicate this would be slightly less challenging at lower redshifts (z ≲ 4). We also find that there is a large amount of variance between fields in our mock observations. High-redshift protoclusters appear to be the most promising environment to observe the filamentary IGM in Lyman-α emission.

Discovery of Faint Double-peak Hα Emission in the Halo of Low Redshift Galaxies

“…The expected signals are similar to the ones resulting from the previous simulations. Updated numerical simulations by Witstok et al (2021) at z > 2 give results consistent with the previous ones. 5.…”

Thethesanproject: Lyman-α emission and transmission during the Epoch of Reionization

“…Although radiative transfer effects on ISM to IGM scales are not included, the Ly𝛼 emissivity is clearly connected to the large-scale structure (LSS) and topology of reionization. This visualization also emphasizes the strong impact of cosmic variance on Ly𝛼 studies based on small ( 30 cMpc) reionization simulations as they may lead to biased statistics for certain quantities such as clustering and IGM transmission (for a discussion of implications for observing the postreionization cosmic web in Ly𝛼 emission see Witstok et al 2021). The resolution and box size are sufficient to provide representative galaxy populations for Ly𝛼 emission and correctly capture EoR fluctuations (Gnedin & Kaurov 2014;Iliev et al 2014).…”

How warm are non-thermal relics? Lyman-α bounds on out-of-equilibrium dark matter

“…These data can be used in combination with probes of the matter power spectrum at smaller comoving scales (k < (km/s) −1 ) via Lyman-α data, in particular from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) [62,63]. For future prospects (including higher redshifts), potentially allowing an enhanced sensitivity to the cuto˙of the spectrum see [64].…”