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On the connection between the intergalactic medium and galaxies: the H I–galaxy cross-correlation at z ≲ 1

Tejos, N.; Morris, S.L.; Finn, C.W.; Crighton, N.H.M.; Bechtold, J.; Jannuzi, B.T.; Schaye, J.; Theuns, T.; Altay, G.; Le Fèvre, O.; Ryan-Webeer, E.; Davé, R.

On the connection between the intergalactic medium and galaxies: the H I–galaxy cross-correlation at z ≲ 1 Thumbnail


N. Tejos

C.W. Finn

N.H.M. Crighton

J. Bechtold

B.T. Jannuzi

J. Schaye

G. Altay

O. Le Fèvre

E. Ryan-Webeer

R. Davé


We present a new optical spectroscopic survey of 1777 ‘star-forming’ (‘SF’) and 366 ‘non-star-forming’ (‘non-SF’) galaxies at redshifts z ∼ 0-1 (2143 in total), 22 AGN and 423 stars, observed by instruments such as the Deep Imaging Multi-Object Spectrograph, the Visible Multi-Object Spectrograph and the Gemini Multi-Object Spectrograph, in three fields containing five quasi-stellar objects (QSOs) with Hubble Space Telescope (HST) ultraviolet spectroscopy. We also present a new spectroscopic survey of 173 ‘strong’ (1014 ≤ NHI≲ 1017 cm−2) and 496 ‘weak’ (1013 ≲ NHI < 1014 cm−2) intervening H i (Lyα) absorption-line systems at z ≲ 1 (669 in total), observed in the spectra of eight QSOs at z ∼ 1 by the Cosmic Origins Spectrograph and the Faint Object Spectrograph on the HST. Combining these new data with previously published galaxy catalogues such as the Very Large Telescope Visible Multi-Object Spectrograph Deep Survey and the Gemini Deep Deep Survey, we have gathered a sample of 654 H i absorption systems and 17 509 galaxies at transverse scales ≲50 Mpc, suitable for a two-point correlation function analysis. We present observational results on the H i–galaxy (ξag) and galaxy–galaxy (ξgg) correlations at transverse scales r⊥ ≲ 10 Mpc, and the H i–H i autocorrelation (ξaa) at transverse scales r⊥ ≲ 2 Mpc. The two-point correlation functions are measured both along and transverse to the line of sight, ξ(r⊥, r∥). We also infer the shape of their corresponding ‘real-space’ correlation functions, ξ(r), from the projected along the line-of-sight correlations, assuming power laws of the form ξ(r) = (r/r0)−γ. Comparing the results from ξag, ξgg and ξaa, we constrain the H i–galaxy statistical connection, as a function of both H i column density and galaxy star formation activity. Our results are consistent with the following conclusions: (i) the bulk of H i systems on ∼ Mpc scales have little velocity dispersion (≲120 km s−1) with respect to the bulk of galaxies (i.e. no strong galaxy outflow/inflow signal is detected); (ii) the vast majority (∼100 per cent) of ‘strong’ H i systems and ‘SF’ galaxies are distributed in the same locations, together with 75 ± 15 per cent of ‘non-SF’ galaxies, all of which typically reside in dark matter haloes of similar masses; (iii) 25 ± 15 per cent of ‘non-SF’ galaxies reside in galaxy clusters and are not correlated with ‘strong’ H i systems at scales ≲2 Mpc; and (iv) >50 per cent of ‘weak’ H i systems reside within galaxy voids (hence not correlated with galaxies), and are confined in dark matter haloes of masses smaller than those hosting ‘strong’ systems and/or galaxies. We speculate that H i systems within galaxy voids might still be evolving in the linear regime even at scales ≲2 Mpc.


Tejos, N., Morris, S., Finn, C., Crighton, N., Bechtold, J., Jannuzi, B., …Davé, R. (2014). On the connection between the intergalactic medium and galaxies: the H I–galaxy cross-correlation at z ≲ 1. Monthly Notices of the Royal Astronomical Society, 437(3), 2017-2075.

Journal Article Type Article
Publication Date Jan 21, 2014
Deposit Date Nov 1, 2013
Publicly Available Date Dec 20, 2013
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 437
Issue 3
Pages 2017-2075
Keywords Galaxies: formation, Intergalactic medium, Quasars: absorption lines, Large-scale structure of Universe.


Published Journal Article (6.5 Mb)

Copyright Statement
This article has been published in the Monthly Notices of the Royal Astronomical Society <br /> &copy; 2013 The Authors.<br /> Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.

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