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Peer-reviewedCC BY 4.0Monthly Notices of the Royal Astronomical Society

A VLT/CRIRES+ study of helium 1.083μm absorption features towards the inner Orion Nebula

  • Thomas J Haworth1
  • Mark McCaughrean2
  • Mario van den Ancker3
  • James E Owen4
  • John Bally5
  • Samuel Pearson6
6 affiliations
  1. 1School of Physical and Chemical Sciences, Queen Mary University of London , Mile End, London E1 4NS ,
  2. 2Max-Planck-Institut für Astronomie , Königstuhl 17, 69117 Heidelberg ,
  3. 3European Southern Observatory , Karl-Schwarzschild-Straße 2, 85748 Garching ,
  4. 4Imperial Astrophysics, Imperial College London , Blackett Laboratory, Prince Consort Road, London SW7 2AZ ,
  5. 5University of Colorado at Boulder, Center for Astrophysics and Space Astronomy , Boulder, Colorado 80309-0389 ,
  6. 6Leiden Observatory, Leiden University , 2300 RA Leiden ,
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Abstract

JWST NIRCam F115W observations towards the inner Orion Nebula revealed a diverse array of previously unknown dark features. The most likely cause was absorption or suppressed emission of the helium 1.083 μm triplet which lies in that filter. We have obtained VLT/CRIRES+ high-resolution spectrographic observations over a selection of different dark targets, confirming that the features are indeed explained by a reduction in the flux of the helium 1.083 μm triplet, a reduction that is fairly uniform across the line. The Orion Nebula is a blister H ii region, with a dense, bright ionised layer on the far side from the observer near the Orion A molecular cloud and lower density gas elsewhere. Using a simple radiative transfer model, we show that dark features arise when emission from the dense layer is absorbed by intermediate density helium (e.g. in clumps, globules, or winds from objects like proplyds) on the near side of the dense layer.

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Cite

BibTeXRIS
BibTeX
@article{haworth2026vltcrires,
  title = {{A VLT/CRIRES+ study of helium 1.083μm absorption features towards the inner Orion Nebula}},
  author = {Thomas J Haworth and Mark McCaughrean and Mario van den Ancker and James E Owen and John Bally and Samuel Pearson},
  journal = {Monthly Notices of the Royal Astronomical Society},
  year = {2026},
  month = nov,
  doi = {10.1093/mnras/stag2089},
  url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2089/9011258},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - A VLT/CRIRES+ study of helium 1.083μm absorption features towards the inner Orion Nebula
AU  - Thomas J Haworth
AU  - Mark McCaughrean
AU  - Mario van den Ancker
AU  - James E Owen
AU  - John Bally
AU  - Samuel Pearson
PY  - 2026
DA  - 2026/11/03
JO  - Monthly Notices of the Royal Astronomical Society
DO  - 10.1093/mnras/stag2089
UR  - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2089/9011258
AB  - JWST NIRCam F115W observations towards the inner Orion Nebula revealed a diverse array of previously unknown dark features. The most likely cause was absorption or suppressed emission of the helium 1.083 μm triplet which lies in that filter. We have obtained VLT/CRIRES+ high-resolution spectrographic observations over a selection of different dark targets, confirming that the features are indeed explained by a reduction in the flux of the helium 1.083 μm triplet, a reduction that is fairly uniform across the line. The Orion Nebula is a blister H ii region, with a dense, bright ionised layer on the far side from the observer near the Orion A molecular cloud and lower density gas elsewhere. Using a simple radiative transfer model, we show that dark features arise when emission from the dense layer is absorbed by intermediate density helium (e.g. in clumps, globules, or winds from objects like proplyds) on the near side of the dense layer.
SN  - 0035-8711
SN  - 1365-2966
ER  -