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Cosmic web Lyα emission in a sample of overdense regions

  • Davide Tornotti
  • Michele Fumagalli
  • Matteo Fossati
  • Roland Bacon
  • Fabrizio Arrigoni Battaia
  • Rajeshwari Dutta
  • Michele Fulghieri
  • Celine Peroux
  • Marc Rafelski
  • Mitchell Revalski
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Abstract

We present a complete and homogeneous analysis of the Lyα emission properties of the cosmic web at 3 ≲ z ≲ 5 as a function of the overdensity of Lyα emitters (LAEs) in the MUSE Ultra Deep Field (MUDF) and the MUSE Extremely Deep Field (MXDF). We identify 41 overdensities, probing environments that are δ≈ 2 − 10 times denser than the field. We search for extended emission down to surface brightness (SB) levels of 3 − 5 × 10−20 erg s−1 cm−2 arcsec−2, revealing filamentary structures beyond the scale of the circumgalactic medium, confirming that LAEs act as signposts of the cosmic web. A trend with overdensity emerges: non-detections are mainly at δ< 2, a ≈ 1 dex scatter in SB appears for 2 ≲ δ≲ 3.5, and detections reach a maximum intrinsic SB of ≈ 2 × 10−19 erg s−1 cm−2 arcsec−2 for δ≳ 3.5. Emitting regions occupy a fraction of projected area fs ≈ 0.20 − 0.25 inside filaments, yielding a cosmological incidence for Lyα emission in the cosmic web ℓ(Lyα) of ≈ 1.22, which is similar to the one of partially-neutral Lyman limit systems. This analysis indicates that the emitting gas is partially ionized at moderate densities (nH ≈ 10−3 − 10−1 cm−3), likely tracing the denser spines of intergalactic filaments and embedded substructures. Finally, we forecast how oriented stacking in larger samples of overdensities from shallower observations could yield an expanded view of the cosmic web before the next-generation wide-field spectroscopic instruments become operational.

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Cite

BibTeXRIS
BibTeX
@misc{tornotti2026cosmic,
  title = {{Cosmic web Ly$α$ emission in a sample of overdense regions}},
  author = {Davide Tornotti and Michele Fumagalli and Matteo Fossati and Roland Bacon and Fabrizio Arrigoni Battaia and Rajeshwari Dutta and Michele Fulghieri and Celine Peroux and Marc Rafelski and Mitchell Revalski},
  howpublished = {HAL},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2609.20938},
  eprint = {2609.20938},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05830187v1},
}
RIS
TY  - UNPB
TI  - Cosmic web Lyα emission in a sample of overdense regions
AU  - Davide Tornotti
AU  - Michele Fumagalli
AU  - Matteo Fossati
AU  - Roland Bacon
AU  - Fabrizio Arrigoni Battaia
AU  - Rajeshwari Dutta
AU  - Michele Fulghieri
AU  - Celine Peroux
AU  - Marc Rafelski
AU  - Mitchell Revalski
PY  - 2026
DA  - 2026/10/13
PB  - HAL
DO  - 10.48550/arxiv.2609.20938
UR  - https://hal.science/hal-05830187v1
AB  - We present a complete and homogeneous analysis of the Lyα emission properties of the cosmic web at 3 ≲ z ≲ 5 as a function of the overdensity of Lyα emitters (LAEs) in the MUSE Ultra Deep Field (MUDF) and the MUSE Extremely Deep Field (MXDF). We identify 41 overdensities, probing environments that are δ≈ 2 − 10 times denser than the field. We search for extended emission down to surface brightness (SB) levels of 3 − 5 × 10^−20 erg s^−1 cm^−2 arcsec^−2, revealing filamentary structures beyond the scale of the circumgalactic medium, confirming that LAEs act as signposts of the cosmic web. A trend with overdensity emerges: non-detections are mainly at δ< 2, a ≈ 1 dex scatter in SB appears for 2 ≲ δ≲ 3.5, and detections reach a maximum intrinsic SB of ≈ 2 × 10^−19 erg s^−1 cm^−2 arcsec^−2 for δ≳ 3.5. Emitting regions occupy a fraction of projected area f_s ≈ 0.20 − 0.25 inside filaments, yielding a cosmological incidence for Lyα emission in the cosmic web ℓ(Lyα) of ≈ 1.22, which is similar to the one of partially-neutral Lyman limit systems. This analysis indicates that the emitting gas is partially ionized at moderate densities (n_H ≈ 10^−3 − 10^−1 cm^−3), likely tracing the denser spines of intergalactic filaments and embedded substructures. Finally, we forecast how oriented stacking in larger samples of overdensities from shallower observations could yield an expanded view of the cosmic web before the next-generation wide-field spectroscopic instruments become operational.
ER  -