Plume, René, Eden, David J., Currie, Malcolm J., Morgan, Lawrence K., Jiang, Xue-Jian, DiFrancesco, James, Imanishi, Masatoshi, Kim, Kee-Tae, Liu, Tie, Rani, Raffaele, and others. (2026) MAJORS II: HCO+ & HCN Abundances in W40. Monthly Notices of the Royal Astronomical Society, . Article Number tag186. ISSN 0035-8711. (doi:10.1093/mnras/stag186) (KAR id:112922)
|
PDF
Author's Accepted Manuscript
Language: English 
This work is licensed under a Creative Commons Attribution 4.0 International License.
|
|
|
Download this file (PDF/1MB) |
Preview |
| Request a format suitable for use with assistive technology e.g. a screenreader | |
| Official URL: https://doi.org/10.1093/mnras%2Fstag186 |
|
Abstract
We present observations of HCN and HCO+ J = 3 → 2 in the central 424″ × 424″ region of the W40 massive star forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N( H2) and TK, assuming a constant density, and using the radex radiative transfer code we found that the HCN and HCO+ abundances range from X(HCN) = 0.4 − 7.0 × 10−8 and X( HCO+) = 0.4 − 7.3 × 10−9. Additional modelling using the nautilus chemical evolution code, that takes H2 density variations into account, however, suggests the HCN and HCO+ abundances may be fairly constant. Careful modelling of three different positions finds X(HCN) = 1.3 − 1.7 × 10−8, X( HCO+) = 1.3 − 3.1 × 10−9. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO+ emission, with H2 densities in the range 5 × 104–5 × 105 cm−3– suggesting that the HCN and HCO+ emission does indeed arise from dense gas. High UV intensity (e.g. Go > a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where AV < 6, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.
| Item Type: | Article |
|---|---|
| DOI/Identification number: | 10.1093/mnras/stag186 |
| Additional information: | For the purpose of open access, the author(s) has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising. |
| Uncontrolled keywords: | surveys, stars: formation, ISM: clouds, ISM: abundances, ISM: molecules |
| Subjects: | Q Science > QB Astronomy |
| Institutional Unit: | Schools > School of Engineering, Mathematics and Physics > Physics and Astronomy |
| Former Institutional Unit: |
There are no former institutional units.
|
| Funders: | Science and Technology Facilities Council (https://ror.org/057g20z61) |
| Depositing User: | James Urquhart |
| Date Deposited: | 30 Jan 2026 12:22 UTC |
| Last Modified: | 02 Feb 2026 13:09 UTC |
| Resource URI: | https://kar.kent.ac.uk/id/eprint/112922 (The current URI for this page, for reference purposes) |
University of Kent Author Information
Urquhart, James S..
| Creator's ORCID: |
 https://orcid.org/0000-0002-1605-8050
|
|---|---|
| CReDIT Contributor Roles: |
- Link to SensusAccess
- Export to:
- RefWorks
- EPrints3 XML
- BibTeX
- CSV
- Depositors only (login required):
Altmetric
Altmetric
