5 research outputs found
A Complex Multiphase DLA Associated with a Compact Group at z=2.431 Traces Accretion, Outflows, and Tidal Streams
As part of our program to identify host galaxies of known z=2-3 MgII
absorbers with the Keck Cosmic Web Imager (KCWI), we discovered a compact group
giving rise to a z=2.431 DLA with ultra-strong MgII absorption in quasar field
J234628+124859. The group consists of four star-forming galaxies within 8-28
kpc and km s of each other, where tidal streams are weakly
visible in deep HST imaging. The group geometric centre is D=25 kpc from the
quasar (D=20-40 kpc for each galaxy). Galaxy G1 dominates the group
(, M yr) while G2,
G3, and G4 are less massive (,
M yr). Using a VLT/UVES quasar spectrum covering the HI Lyman
series and metal lines such as MgII, SiIII, and CIV, we characterised the
kinematic structure and physical conditions along the line-of-sight with
cloud-by-cloud multiphase Bayesian modelling. The absorption system has a total
and an -weighted mean metallicity of
, with a very large MgII linewidth of km s. The highly kinematically complex profile is
well-modelled with 30 clouds across low and intermediate ionisation phases with
values and
. Comparing these properties to the
galaxy properties, we infer a wide range of gaseous environments, including
metal-rich outflows, metal-poor IGM accretion, and tidal streams from
galaxy--galaxy interactions. This diversity of structures forms the intragroup
medium around a complex compact group environment at the epoch of peak star
formation activity. Surveys of low redshift compact groups would benefit from
obtaining a more complete census of this medium for characterising evolutionary
pathways.Comment: 29 pages, 10 figures. Accepted for publication in MNRAS 28 June 202
Gravitational lensing reveals cool gas within 10-20 kpc around a quiescent galaxy
While quiescent galaxies have comparable amounts of cool gas in their outer circumgalactic medium (CGM) compared to star-forming galaxies, they have significantly less interstellar gas. However, open questions remain on the processes causing galaxies to stop forming stars and stay quiescent. Theories suggest dynamical interactions with the hot corona prevent cool gas from reaching the galaxy, therefore predicting the inner regions of quiescent galaxy CGMs are devoid of cool gas. However, there is a lack of understanding of the inner regions of CGMs due to the lack of spatial information in quasar-sightline methods. We present integral-field spectroscopy probing 10–20 kpc (2.4–4.8 Re) around a massive quiescent galaxy using a gravitationally lensed star-forming galaxy. We detect absorption from Magnesium (MgII) implying large amounts of cool atomic gas (108.4–109.3 M⊙ with T~104 Kelvin), in comparable amounts to star-forming galaxies. Lens modeling of Hubble imaging also reveals a diffuse asymmetric component of significant mass consistent with the spatial extent of the MgII absorption, and offset from the galaxy light profile. This study demonstrates the power of galaxy-scale gravitational lenses to not only probe the gas around galaxies, but to also independently probe the mass of the CGM due to it’s gravitational effect