MUSE Analysis of Gas around Galaxies (MAGG) – IV. The gaseous environment of z ∼ 3–4 Ly α emitting galaxies

Abstract

We study the link between galaxies and H i-selected absorption systems at z ∼ 3 − 4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field spectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\rm N_{\rm HI}\gtrsim 10^{16.5}~\rm cm^{-2}$. We identify 127 Lyα emitting galaxies (LAEs) around the absorbers, corresponding to a detection rate of 82±16 per cent. The luminosity function of these LAEs is ≈5 times higher in normalization than the field population and we detect a significant clustering of galaxies with respect to the gas, confirming that high column density absorbers and LAEs trace each other. Between 30 and 40 per cent of the absorbers are associated with multiple LAEs, which lie preferentially along filaments. Galaxies in groups also exhibit a three times higher covering factor of optically-thick gas compared to isolated systems. No significant correlations are identified between the emission properties of LAEs and the absorption properties of optically-thick gas clouds, except for a weak preference of brighter and multiple galaxies to reside near broad absorbers. Based on the measured impact parameters and the covering factor, we conclude that the near totality of optically-thick gas in the Universe can be found in the outer circumgalactic medium (CGM) of LAEs or in the intergalactic medium (IGM) in proximity to these galaxies. Thus, LAEs act as tracers of larger scale structures within which both galaxies and optically-thick clouds are embedded. The patchy and inhomogeneous nature of the CGM and IGM explains the lack of correlations between absorption and emission properties. This implies that very large samples are needed to unveil the trends that encode the properties of the baryon cycle.

The Bimodal Absorption System Imaging Campaign (BASIC). I. A Dual Population of Low-metallicity Absorbers at z < 1

“…The authors also interpret the absorber as located within a gaseous filament possibly accreting onto one of the nearby galaxies. The latest MAGG results (the characterized environments of 61 absorbers) in Lofthouse et al (2023) similarly show that LLSs at these high redshifts are either located in regions close to galaxies (3-4 R vir ) or likely in filaments of the IGM. Although it is outside of the LLS column density range, we also note the detection of an SLLS (…”

The MUSE Ultra Deep Field (MUDF). III. Hubble Space Telescope WFC3 Grism Spectroscopy and Imaging

“…These observational challenges have made the study of quasar fields particularly insightful because the quasar light is selectively absorbed by the IGM and CGM as it travels to the observer, which reveals the gas in and around galaxies that reside in field, cluster, and group environments (Bechtold 2001;Khare 2013;Chen et al 2020;Dutta et al 2020Dutta et al , 2021Lofthouse et al 2023). In the past, these studies were limited by the requirement that sources needed to be preselected for targeting with long-slit or fixed aperture multi-object spectroscopy, which can bias the galaxy sample.…”

The Study of the Circumgalactic Medium with Quasar Pairs

“…Morphology, inclination, azimuthal angle with respect to the major axis of a galaxy, and environment of galaxies also influence the quantity of gas that the quasar sight line intercepts; therefore the connection between them and the properties of absorption lines are widely investigated (e.g., Kacprzak et al 2007;Bordoloi et al 2011;Kacprzak et al 2011;Cunnama et al 2014; Barnes et al 2014;Tumlinson et al 2017;Lan & Mo 2018;Ho et al 2020;Lee et al 2021). In the last few years, blind searches for galaxies associated with absorbers also revealed that the absorber's properties are related to the gravitational interactions in the group populations, galaxy's outflows, intergalactic medium accretions, star formation rates, and gas distributions within a galaxy group (e.g., Fossati et al 2019;Nielsen et al 2020;Bielby et al 2020;Dutta et al 2020;Muzahid et al 2021;Nielsen & Kacprzak 2022;Lofthouse et al 2023). In addition, one absorber might be associated with multiple galaxies within a group as well (e.g., Bielby et al 2020;Lofthouse et al 2023).…”

“…In the last few years, blind searches for galaxies associated with absorbers also revealed that the absorber's properties are related to the gravitational interactions in the group populations, galaxy's outflows, intergalactic medium accretions, star formation rates, and gas distributions within a galaxy group (e.g., Fossati et al 2019;Nielsen et al 2020;Bielby et al 2020;Dutta et al 2020;Muzahid et al 2021;Nielsen & Kacprzak 2022;Lofthouse et al 2023). In addition, one absorber might be associated with multiple galaxies within a group as well (e.g., Bielby et al 2020;Lofthouse et al 2023).…”