{
  "id": "2306.10099",
  "version": "v1",
  "published": "2023-06-16T18:00:00.000Z",
  "updated": "2023-06-16T18:00:00.000Z",
  "title": "The magnetic fields of starburst galaxies. I. Identification and characterization of the thermal polarization in the galactic disk and outflow",
  "authors": [
    "Enrique Lopez-Rodriguez"
  ],
  "comment": "21 pages, 14 figures, 4 tables. Submitted to ApJ with positive review by the anonymous referee. Comments are welcome",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Far-infrared polarized emission by means of magnetically aligned dust grains is an excellent tracer of the magnetic fields (B-fields) in the cold phase of the galactic outflows in starburst galaxies. We present a comprehensive study of the B-fields in three nearby ($3.5$-$17.2$ Mpc) starbursts (M82, NGC 253, and NGC 2146) at $5$ pc-$1.5$ kpc resolutions using publicly available $53$-$890$ $\\mu$m imaging polarimetric observations with SOFIA/HAWC+, JCMT/POL-2, and ALMA. We find that the polarized spectral energy distributions (SEDs) of the full galaxies are dominated by the polarized SEDs of the outflows with dust temperatures of $T_{\\rm{d,outflow}}^{\\rm{PI}}\\sim45$ K and emissive index of $\\beta_{\\rm{outflow}}^{\\rm{PI}}\\sim2.3$. The disks are characterized by low $T_{\\rm{d,disk}}^{\\rm{PI}}=[24,31]$ K and $\\beta_{\\rm{disk}}^{\\rm{PI}}\\sim1$. We show that disk- and outflow-dominated galaxies can be better distinguished by using polarized SEDs instead of total SEDs. We compute the $53$-$850$ $\\mu$m polarization spectrum of the disk and outflow and find that dust models of the diffuse ISM can reproduce the fairly constant polarization spectrum of the disk, $\\langle P_{\\rm{disk}} \\rangle=1.2\\pm0.5$%. The dust models of heterogenous clouds and two temperature components are required to explain the polarization spectrum of the outflow ($2$-$4$% at $53$ $\\mu$m, $\\sim1$% at $850$ $\\mu$m, and a minimum within $89$-$154$ $\\mu$m). We conclude that the polarized dust grains in the outflow arise from a dust population with higher dust temperature and emissivities than those from the total flux. The B-fields of the outflows have maximum extensions within $89$-$214$ $\\mu$m reaching heights of $\\sim4$ kpc, and flatter polarized fluxes than total fluxes. The extension of the B-field permeating the circumgalactic medium increases with increasing the star formation rate.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-06-16T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "magnetic fields",
      "starburst galaxies",
      "thermal polarization",
      "galactic disk",
      "polarization spectrum"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 21,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}