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Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet

Beckett, Alexander; Morris, Simon L; Fumagalli, Michele; Tejos, Nicolas; Jannuzi, Buell; Cantalupo, Sebastiano

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Michele Fumagalli

Nicolas Tejos

Buell Jannuzi

Sebastiano Cantalupo


We examine to what extent disc and outflow models can reproduce observations of H I gas within a few virial radii of galaxies in pairs and groups. Using highly sensitive HST/COS and FOS spectra of the Q0107 quasar triplet covering Ly α for z≲1, as well as a deep galaxy redshift survey including VIMOS, DEIMOS, GMOS, and MUSE data, we test simple disc and outflow models against the H I absorption along three lines-of-sight (separated by 200–500 kpc) through nine galaxy groups in this field. These can be compared with our previous results in which these models can often be fit to the absorption around isolated galaxies. Our models can reproduce ≈ 75 per cent of the 28 identified absorption components within 500 km s−1 of a group galaxy, so most of the H I around groups is consistent with a superposition of the CGM of the individual galaxies. Gas stripped in interactions between galaxies may be a plausible explanation for some of the remaining absorption, but neither the galaxy images nor the galaxy and absorber kinematics provide clear evidence of such stripped material, and these unexplained absorbers do not preferentially occur around close pairs of galaxies. We find H I column densities typically higher than at similar impact parameters around isolated galaxies (≈ 2.5σ), as well as more frequent detections of O VI than around isolated galaxies (30 per cent of sightlines to 7 per cent).


Beckett, A., Morris, S. L., Fumagalli, M., Tejos, N., Jannuzi, B., & Cantalupo, S. (2023). Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet. Monthly Notices of the Royal Astronomical Society, 521(1), 1113-1143.

Journal Article Type Article
Acceptance Date Feb 4, 2023
Online Publication Date Mar 2, 2023
Publication Date 2023-05
Deposit Date May 23, 2023
Publicly Available Date May 23, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 521
Issue 1
Pages 1113-1143


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Copyright Statement
© The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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