{
  "id": "2411.14530",
  "version": "v1",
  "published": "2024-11-21T19:00:03.000Z",
  "updated": "2024-11-21T19:00:03.000Z",
  "title": "Time evolution of o-H$_2$D$^+$, N$_2$D$^+$, and N$_2$H$^+$ during the high-mass star formation process",
  "authors": [
    "G. Sabatini",
    "S. Bovino",
    "E. Redaelli",
    "F. Wyrowski",
    "J. S. Urquhart",
    "A. Giannetti",
    "J. Brand",
    "K. M. Menten"
  ],
  "comment": "13 pages, 5 figures, 3 tables. Accepted for publication in A&A",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "Deuterium fractionation is a well-established evolutionary tracer in low-mass star formation, but its applicability to the high-mass regime remains an open question. The abundances and ratios of deuterated species have often been proposed as reliable evolutionary indicators for different stages of the high-mass star formation. We investigate the role of N$_2$H$^+$ and key deuterated molecules as tracers of the different stages of the high-mass star formation, and test whether their abundance ratios can serve as reliable evolutionary indicators. We conducted APEX observations of o-H$_2$D$^+$ (1$_{10}$-1$_{11}$), N$_2$H$^+$ (4-3), and N$_2$d$^+$ (3-2) in 40 high-mass clumps at different evolutionary stages, selected from the ATLASGAL survey. Molecular column densities ($N$) and abundances ($X$), were derived through spectral line modelling, both under local thermodynamic equilibrium (LTE) and non-LTE conditions. The $N$(o-H$_2$D$^+$) show the smallest deviation from LTE results when derived under non-LTE assumptions. In contrast, N$_2$D$^+$ shows the largest discrepancy between the $N$ derived from LTE and non-LTE. In all the cases discussed, we found that $X$(o-H$_2$D$^+$) decreases more significantly with time than in the case of $X$(N$_2$D$^+$); whereas $X$(N$_2$H$^+$) increases slightly. Therefore, the validity of the recently proposed $X$(o-H$_2$D$^+$)/$X$(N$_2$D$^+$) ratio as a reliable evolutionary indicator was not observed for this sample. While the deuteration fraction derived from N$_2$D$^+$ and N$_2$H$^+$ clearly decreases with clump evolution, the interpretation of this trend is complex, given the different distribution of the two tracers. Our results suggest that a careful consideration of the observational biases and beam-dilution effects are crucial for an accurate interpretation of the evolution of the deuteration process during the high-mass star formation process.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-11-21T19:00:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high-mass star formation process",
      "reliable evolutionary indicator",
      "time evolution",
      "molecular column densities",
      "local thermodynamic equilibrium"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}