MAGiiCAT VI. The Mg ii Intragroup Medium Is Kinematically Complex

Abstract

By comparing Mg II absorption in the circumgalactic medium (CGM) of group environments to isolated galaxies, we investigated the impact of environment on the CGM. A Mg II absorber is associated with a group if there are two or more galaxies at the absorption redshift within a projected distance of D = 200 kpc from a background quasar and a line-of-sight velocity separation of 500 km s −1 . We compiled a sample of 29 group environments consisting of 74 galaxies (2 − 5 galaxies per group) at 0.113 < z gal < 0.888. The group absorber median equivalent width ( W r (2796) = 0.65 ± 0.13 Å) and covering fraction ( f c = 0.89 +0.05 −0.09 ) are larger than isolated absorbers (1.27σ and 2.2σ, respectively) but median column densities are statistically consistent. A pixel-velocity two-point correlation function analysis shows that group environment kinematics are statistically comparable to isolated environments (0.8σ), but with more power for high velocity dispersions similar to outflow kinematics. Group absorbers display more optical depth at larger velocities. A superposition model in which multiple galaxies contribute to the observed gas matches larger equivalent width group absorbers, but overpredicts the kinematics significantly due to large velocity separations between member galaxies. Finally, galaxy-galaxy groups (similar member galaxy luminosities) may have larger absorber median equivalent widths (1.7σ) and velocity dispersions (2.5σ) than galaxy-dwarf groups (disparate luminosities). We suggest the observed gas is coupled to the group rather than individual galaxies, forming an intragroup medium. Gas may be deposited into this medium by multiple galaxies via outflowing winds undergoing an intergalactic transfer between member galaxies or from tidal stripping of interacting members.

The MUSE Ultra Deep Field (MUDF). II. Survey design and the gaseous properties of galaxy groups at 0.5 &lt; z &lt; 1.5

“…Bordoloi et al (2011) found marginally more extended Mg ii absorption profiles compared to a sample of more isolated galaxies, concluding that the absorbing gas is more likely to be associated to the individual galaxies rather than the intragroup medium. Nielsen et al (2018) similarly found an enhanced equivalent width of Mg ii absorbers in a sample of 29 galaxy groups with respect to an isolated galaxy sample. These authors have complemented these results with a kinematical analysis of the absorption profiles and concluded that the absorbers originate from an intragroup medium rather than from individual galaxies.…”

“…Several studies have used the Mg ii doublet to trace gas with similar column densities to that detected through 21-cm atomic hydrogen observations (e.g. Bergeron 1986;Kacprzak et al 2008;Steidel et al 1994;Chen & Tinker 2008;Chen et al 2010;Gauthier 2013;Bordoloi et al 2014a;Nielsen et al 2015;Schroetter et al 2016;Nielsen et al 2018;Rubin et al 2018a,b). These studies have found that Mg ii absorbers trace the CGM of galaxies and possibly outflowing gas up to a distance of ∼ 100 kpc (Kacprzak et al 2008;Chen et al 2010).…”

MUSE-ALMA haloes V: physical properties and environment of z ≤ 1.4 H i quasar absorbers

“…Lanzetta & Bowen 1990;Bergeron & Boissé 1991;Bouché et al 2006;Chen et al 2010). We compared our groups to several other MUSE studies from the literature and the Mg ii absorbers compilation MAG iiCAT (Nielsen et al 2013) of isolated galaxies as well as galaxy groups (Nielsen et al 2018). Fig.9 shows that MUSE-ALMA Halos systems are in agreement with this relation, especially with other absorption-related groups.…”

“…Combined with highresolution UV spectroscopy of quasars, these studies have revealed relevant features interpreted as galactic outflows (Schroetter et al 2016;Rahmani et al 2018b;Schroetter et al 2019), warped accretion discs (Rahmani et al 2018a) and galactic fountains (Bouché et al 2016). Alongside the detection of kinematic traces of gas inflows and outflows, new studies detected multiple galaxies associated with one absorber (Bielby et al 2017;Péroux et al 2017;Klitsch et al 2018;Nielsen et al 2018;Péroux et al 2019;Muzahid et al 2019). These findings point towards a more complex view of the gaseous halos of galaxies: from the halo gas of single systems, through tidal streams and halo substructures (Whiting et al 2006; Kacprzak et al 2010) to intra-group gas (Bielby et al 2017;Fossati et al 2019).…”

Ultraviolet signatures of the multiphase intracluster and circumgalactic media in the romulusc simulation

“…RomulusC is among the highest resolution hydrodynamic cosmological simulations of a galaxy cluster run to date, with a Plummer equivalent gravitational force resolution of 250 pc (a 350 pc spline kernel is used), a maximum SPH resolution of 70 pc, and gas and dark matter mass resolutions of 2.12 × 10 5 and 3.39 × 10 5 M respectively. At this resolution, RomulusC is one of only two cluster cosmological simulations currently in production that is capable of resolving the multiphase structure of gas in the ICM (see also Nelson et al (2019)). Lower mass halos and galaxies, including their interaction with the ICM, are also followed The color scaling of the images in the bottom row is roughly consistent with the sensitivity of existing instruments.…”