{
  "id": "2206.12501",
  "version": "v1",
  "published": "2022-06-24T22:03:50.000Z",
  "updated": "2022-06-24T22:03:50.000Z",
  "title": "A Complex Multiphase DLA Associated with a Compact Group at z=2.431 Traces Accretion, Outflows, and Tidal Streams",
  "authors": [
    "Nikole M. Nielsen",
    "Glenn G. Kacprzak",
    "Sameer",
    "Michael T. Murphy",
    "Hasti Nateghi",
    "Jane C. Charlton",
    "Christopher W. Churchill"
  ],
  "comment": "29 pages, 10 figures. Resubmitted to MNRAS after addressing reviewer comments",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "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 $v\\sim50-300$ km s$^{-1}$ 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 ($1.66L_{\\ast}$, ${\\rm SFR}_{\\rm FUV}=11.6$ M$_{\\odot}$ yr$^{-1}$) while G2, G3, and G4 are less massive ($0.1-0.3L_{\\ast}$, ${\\rm SFR}_{\\rm FUV}=1.4-2.0$ M$_{\\odot}$ yr$^{-1}$). 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 $\\log(N(HI)/{\\rm cm}^{-2})=20.53$ and an $N(HI)$-weighted mean metallicity of $\\log(Z/Z_{\\odot})=-0.68$, with a very large MgII linewidth of $\\Delta v\\sim700$ km s$^{-1}$. The highly kinematically complex profile is well-modelled with 30 clouds across low and intermediate ionisation phases with values ${13\\lesssim\\log(N(HI)/{\\rm cm}^{-2})\\lesssim20}$ and $-3\\lesssim\\log(Z/Z_{\\odot})\\lesssim1$. 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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-06-24T22:03:50.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "tidal streams",
      "complex multiphase dla",
      "traces accretion",
      "keck cosmic web imager",
      "complex compact group environment"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 29,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}