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A new model framework for circumgalactic Ly α radiative transfer constrained by galaxy-Ly α forest clustering

Kakiichi, K; Dijkstra, M; (2018) A new model framework for circumgalactic Ly α radiative transfer constrained by galaxy-Ly α forest clustering. Monthly Notices of the Royal Astronomical Society , 480 (4) pp. 5140-5159. 10.1093/mnras/sty2214. Green open access

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Abstract

We present a new perturbative approach to ‘constrained Ly α radiative transfer’ (RT) through the circum- and intergalactic medium (CGM and IGM). We constrain the HI content and kinematics of the CGM and IGM in a physically motivated model, using the galaxy-Ly α forest clustering data from spectroscopic galaxy surveys in quasar fields at z ∼ 2−3. This enables us to quantify the impact of the CGM/IGM on Ly α emission in an observationally constrained, realistic cosmological environment. Our model predicts that the CGM and IGM at these redshifts transmit ≈80 per cent of Ly α photons after having escaped from galaxies. This implies that while the interstellar medium primarily regulates Ly α escape, the CGM has a non-negligible impact on the observed Ly α line properties and the inferred Ly α escape fraction, even at z ∼ 2−3. Ly α scattering in the CGM and IGM further introduces an environmental dependence in the (apparent) Ly α escape fraction, and the observed population of  Lyα emitting galaxies: the CGM/IGM more strongly suppresses direct Ly α emission from galaxies in overdense regions in the Universe, and redistributes this emission into brighter Ly α haloes. The resulting mean surface brightness profile of the Ly α haloes is generally found to be a power law ∝r−2.4. Although our model still contains arbitrariness, our results demonstrate how (integral field) spectroscopic surveys of galaxies in QSO fields constrain circumgalactic Ly α RT, and we discuss the potential of these models for studying CGM physics and cosmology.

Type: Article
Title: A new model framework for circumgalactic Ly α radiative transfer constrained by galaxy-Ly α forest clustering
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/sty2214
Publisher version: http://dx.doi.org/10.1093/mnras/sty2214
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: line: formation, radiative transfer, galaxies: high-redshift, intergalactic medium, quasars: absorption lines
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10055325
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