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MUSE searches for galaxies near very metal-poor gas clouds at z~3 : new constraints for cold accretion models.

Fumagalli, M. and Cantalupo, S. and Dekel, A. and Morris, S. L. and O'Meara, J. M. and Prochaska, J. X. and Theuns, T. (2016) 'MUSE searches for galaxies near very metal-poor gas clouds at z~3 : new constraints for cold accretion models.', Monthly notices of the Royal Astronomical Society., 462 (2). pp. 1978-1988.


We report on the search for galaxies in the proximity of two very metal-poor gas clouds at z ∼ 3 towards the quasar Q0956+122. With a 5-hour Multi-Unit Spectroscopic Explorer (MUSE) integration in a ∼500 × 500 kpc2 region centred at the quasar position, we achieve a ≥80 per cent complete spectroscopic survey of continuum-detected galaxies with mR ≤ 25 mag and Lyα emitters with luminosity LLyα ≥ 3 × 1041 erg s− 1. We do not identify galaxies at the redshift of a z ∼ 3.2 Lyman limit system (LLS) with log Z/Z⊙ = −3.35 ± 0.05, placing this gas cloud in the intergalactic medium or circumgalactic medium of a galaxy below our sensitivity limits. Conversely, we detect five Lyα emitters at the redshift of a pristine z ∼ 3.1 LLS with log Z/Z⊙ ≤ −3.8, while ∼0.4 sources were expected given the z ∼ 3 Lyα luminosity function. Both this high detection rate and the fact that at least three emitters appear aligned in projection with the LLS suggest that this pristine cloud is tracing a gas filament that is feeding one or multiple galaxies. Our observations uncover two different environments for metal-poor LLSs, implying a complex link between these absorbers and galaxy haloes, which ongoing MUSE surveys will soon explore in detail. Moreover, in agreement with recent MUSE observations, we detected a ∼ 90 kpc Lyα nebula at the quasar redshift and three Lyα emitters reminiscent of a ‘dark galaxy’ population.

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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:18 July 2016
Date deposited:31 August 2016
Date of first online publication:25 July 2016
Date first made open access:31 August 2016

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