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Prospects for observing the low-density cosmic web in Lyman-alpha emission

Witstok, J, Puchwein, E, Kulkarni, G, Smit, R and Haehnelt, MG (2021) Prospects for observing the low-density cosmic web in Lyman-alpha emission. Astronomy & Astrophysics, 650. ISSN 1432-0746

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Open Access URL: https://doi.org/10.1051/0004-6361/202040187 (Published version)


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.

Item Type: Article
Uncontrolled Keywords: Astronomy & Astrophysics; cosmology: theory; diffuse radiation; EVOLUTION; FOREST; FORMING GALAXIES; INTEGRAL FIELD SPECTROSCOPY; intergalactic medium; INTERGALACTIC MEDIUM; LARGE-SCALE STRUCTURE; large-scale structure of Universe; methods: numerical; NEUTRAL HYDROGEN; Physical Sciences; POWER SPECTRUM; RADIO GALAXIES; REDSHIFT; Science & Technology; Science & Technology; Physical Sciences; Astronomy & Astrophysics; intergalactic medium; large-scale structure of Universe; diffuse radiation; cosmology: theory; methods: numerical; INTEGRAL FIELD SPECTROSCOPY; LARGE-SCALE STRUCTURE; POWER SPECTRUM; INTERGALACTIC MEDIUM; FORMING GALAXIES; NEUTRAL HYDROGEN; RADIO GALAXIES; REDSHIFT; FOREST; EVOLUTION; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
SWORD Depositor: A Symplectic
Date Deposited: 08 Nov 2022 09:43
Last Modified: 08 Nov 2022 09:43
DOI or ID number: 10.1051/0004-6361/202040187
URI: https://researchonline.ljmu.ac.uk/id/eprint/18058
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