{
  "id": "2309.16510",
  "version": "v1",
  "published": "2023-09-28T15:16:33.000Z",
  "updated": "2023-09-28T15:16:33.000Z",
  "title": "Variations of the HCO$^{+}$, HCN, HNC, N$_2$H$^+$ and NH$_{3}$ deuterium fractionation in high-mass star-forming regions",
  "authors": [
    "A. G. Pazukhin",
    "I. I. Zinchenko",
    "E. A. Trofimova",
    "C. Henkel",
    "D. A. Semenov"
  ],
  "comment": "13 pages + appendix (25 pages total), 11 figures. Accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We use spectra and maps of the $J=1-0$ and $J=2-1$ DCO$^{+}$, DCN, DNC, $\\rm N_2D^+$ lines and $1_{11}-1_{01}$ ortho- and para-NH$_{2}$D lines, obtained with the IRAM-30m telescope, as well as observations of their hydrogenated isotopologues to study deuteration processes in five high-mass star-forming regions. The temperature was estimated from CH$_3$CCH lines, also observed with the IRAM-30m telescope, and from NH$_3$ lines, observed with the 100-m radio telescope in Effelsberg, as well as using the integrated intensity ratios of the $J=1-0$ H$^{13}$CN and HN$^{13}$C lines and their main isotopologues. Applying a non-LTE radiative transfer model with RADEX, the gas density and the molecular column densities were estimated. D/H ratios are $0.001-0.05$ for DCO$^{+}$, $0.001-0.02$ for DCN, $0.001-0.05$ for DNC and $0.02-0.4$ for NH$_{2}$D. The D/H ratios decrease with increasing temperature in the range of $\\rm 20-40 \\,K$ and slightly vary at densities $n(\\rm H_2) \\sim 10^4-10^6\\, cm^{-3}$. The deuterium fraction of $\\rm N_2H^{+}$ is $0.008-0.1$ at temperatures in the range of $\\rm 20-25\\, K$ and at a density of $\\sim 10^5\\, \\rm cm^{-3}$. We also estimate relative abundances and find $ \\sim 10^{-11}-10^{-9}$ for DCO$^{+}$ and DNC, $ \\sim 10^{-11}-10^{-10}$ for $\\rm N_2D^+$ and $ \\sim 10^{-10}-10^{-8}$ for NH$_{2}$D. The relative abundances of these species decrease with increasing temperature. However, the DCN/H$_2$ ratio is almost constant ($\\sim 10^{-10}$). The observational results agree with the predictions of chemical models (although in some cases there are significant differences).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-09-28T15:16:33.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high-mass star-forming regions",
      "deuterium fractionation",
      "iram-30m telescope",
      "d/h ratios",
      "variations"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}