NEATH: II. N2H+ as a tracer of imminent star formation in quiescent high-density gas
Star formation activity in molecular clouds is often found to be correlated with the amount of material above a column density threshold of ∼1022 cm−2. Attempts to connect this column density threshold to a volume density above which star formation can occur are limited by the fact that the volume...
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| Main Authors: | , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
December 2023
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2023, Volume: 526, Issue: 4, Pages: 4952-4960 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stad3089 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stad3089
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| Author Notes: | F.D. Priestley, P.C. Clark, S.C.O. Glover, S.E. Ragan, O. Fehér, L.R. Prole and R.S. Klessen |
| Summary: | Star formation activity in molecular clouds is often found to be correlated with the amount of material above a column density threshold of ∼1022 cm−2. Attempts to connect this column density threshold to a volume density above which star formation can occur are limited by the fact that the volume density of gas is difficult to reliably measure from observations. We post-process hydrodynamical simulations of molecular clouds with a time-dependent chemical network, and investigate the connection between commonly observed molecular species and star formation activity. We find that many molecules widely assumed to specifically trace the dense, star-forming component of molecular clouds (e.g. HCN, HCO+, CS) actually also exist in substantial quantities in material only transiently enhanced in density, which will eventually return to a more diffuse state without forming any stars. By contrast, N2H+ only exists in detectable quantities above a volume density of , the point at which CO, which reacts destructively with N2H+, begins to deplete out of the gas phase on to grain surfaces. This density threshold for detectable quantities of N2H+ corresponds very closely to the volume density at which gas becomes irreversibly gravitationally bound in the simulations: the material traced by N2H+ never reverts to lower densities, and quiescent regions of molecular clouds with visible N2H+ emission are destined to eventually form stars. The N2H+ line intensity is likely to directly correlate with the star formation rate averaged over time-scales of around a Myr. |
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| Item Description: | Im Text ist "2" tiefgestellt und "+" hochgestellt Gesehen am 09.02.2024 Veröffentlicht: 10. Oktober 2023 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stad3089 |