The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240

10 pages, 6 figures

Detalles Bibliográficos
Autores: Thatte, N., Rigopoulou, D., Donnan, F. R., Garcia-Bernete, I., Pereira-Santaella, Miguel, Draine, B., Veenema, O., Kerkeni, B., Alonso-Herrero, A., Hermosa Muñoz, L., Speranza, G.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2026
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/419227
Acceso en línea:http://hdl.handle.net/10261/419227
https://api.elsevier.com/content/abstract/scopus_id/105024419846
Access Level:acceso abierto
Palabra clave:Galaxies: individual: NGC6240
Galaxies: ISM
Infrared: galaxies
Infrared: ISM
ISM: molecules
Techniques: imaging spectroscopy
astro
Astrophysics
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oai_identifier_str oai:digital.csic.es:10261/419227
network_acronym_str ES
network_name_str España
repository_id_str
dc.title.none.fl_str_mv The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
title The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
spellingShingle The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
Thatte, N.
Galaxies: individual: NGC6240
Galaxies: ISM
Infrared: galaxies
Infrared: ISM
ISM: molecules
Techniques: imaging spectroscopy
astro
Astrophysics
title_short The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
title_full The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
title_fullStr The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
title_full_unstemmed The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
title_sort The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
dc.creator.none.fl_str_mv Thatte, N.
Rigopoulou, D.
Donnan, F. R.
Garcia-Bernete, I.
Pereira-Santaella, Miguel
Draine, B.
Veenema, O.
Kerkeni, B.
Alonso-Herrero, A.
Hermosa Muñoz, L.
Speranza, G.
author Thatte, N.
author_facet Thatte, N.
Rigopoulou, D.
Donnan, F. R.
Garcia-Bernete, I.
Pereira-Santaella, Miguel
Draine, B.
Veenema, O.
Kerkeni, B.
Alonso-Herrero, A.
Hermosa Muñoz, L.
Speranza, G.
author_role author
author2 Rigopoulou, D.
Donnan, F. R.
Garcia-Bernete, I.
Pereira-Santaella, Miguel
Draine, B.
Veenema, O.
Kerkeni, B.
Alonso-Herrero, A.
Hermosa Muñoz, L.
Speranza, G.
author2_role author
author
author
author
author
author
author
author
author
author
dc.contributor.none.fl_str_mv Science and Technology Facilities Council (UK)
Comunidad de Madrid
Agencia Estatal de Investigación (España)
University of Oxford
Thatte, N. [0000-0002-6694-5184]
Rigopoulou, D. [0000-0001-6854-7545]
Donnan, F. R. [0000-0002-6460-3682]
#NODATA#
#NODATA#
#NODATA#
Veenema, O. [0009-0009-0466-9223]
Kerkeni, B. [0000-0002-5762-5058]
#NODATA#
Hermosa Muñoz, L. [0000-0002-9610-0123]
#NODATA#
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Galaxies: individual: NGC6240
Galaxies: ISM
Infrared: galaxies
Infrared: ISM
ISM: molecules
Techniques: imaging spectroscopy
astro
Astrophysics
topic Galaxies: individual: NGC6240
Galaxies: ISM
Infrared: galaxies
Infrared: ISM
ISM: molecules
Techniques: imaging spectroscopy
astro
Astrophysics
description 10 pages, 6 figures
publishDate 2026
dc.date.none.fl_str_mv 2026
2026
2026
dc.type.none.fl_str_mv info:eu-repo/semantics/article
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Publisher's version
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/419227
https://api.elsevier.com/content/abstract/scopus_id/105024419846
url http://hdl.handle.net/10261/419227
https://api.elsevier.com/content/abstract/scopus_id/105024419846
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
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https://doi.org/10.1093/mnras/staf2047
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Royal Astronomical Society
publisher.none.fl_str_mv Royal Astronomical Society
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
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spelling The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240Thatte, N.Rigopoulou, D.Donnan, F. R.Garcia-Bernete, I.Pereira-Santaella, MiguelDraine, B.Veenema, O.Kerkeni, B.Alonso-Herrero, A.Hermosa Muñoz, L.Speranza, G.Galaxies: individual: NGC6240Galaxies: ISMInfrared: galaxiesInfrared: ISMISM: moleculesTechniques: imaging spectroscopyastroAstrophysics10 pages, 6 figuresWe have carried out a detailed analysis of the 3.4 μm spectral feature arising from Polycyclic Aromatic Hydrocarbons (PAH), using James Webb Space Telescope archival data. For the first time in an external galaxy (NGC 6240), we have identified two distinct spectral components of the PAH 3.4 μm feature: a shorter wavelength component at 3.395 μm, which we attribute to short aliphatic chains tightly attached to the aromatic rings of the PAH molecules; and a longer wavelength feature at 3.405 μm that arises from longer, more fragile, aliphatic chains that are weakly attached to the parent PAH molecule. These longer chains are more easily destroyed by far-ultraviolet photons (>5 eV) and PAH thermal emission only occurs where PAH molecules are shielded from more energetic photons by dense molecular gas. We see a very strong correlation in the morphology of the PAH 3.395 μm feature with the PAH 3.3 μm emission, the latter arising from robust aromatic PAH molecules. We also see an equally strong correlation between the PAH 3.405 μm morphology and the warm molecular gas, as traced by H<inf>2</inf> vibrational lines. We show that the flux ratio PAH 3.395/PAH 3.405 < 0.3 corresponds strongly to regions where the PAH molecules are shielded by dense molecular gas, so that only modestly energetic UV photons penetrate to excite the PAHs. Our work shows that PAH 3.405 μm and PAH 3.395 μm emission features can provide robust diagnostics of the physical conditions of the interstellar medium in external galaxies, and can be used to quantify the energies of the photon field penetrating molecular clouds.NT and DR acknowledge support from UK Science and Technology Facilities Council (STFC) through grant ST/W000903/1. FRD acknowledges support from STFC through studentship ST/W507726/1. IG-B was supported by the Programa Atracci´on de Talento Investigador ‘Cesar Nombela’ via grant 2023-T1/TEC-29030 funded by the Community of Madrid. AA-H and LHM acknowledge financial support by grant PID2021-124665NB-I00 funded by the Spanish Ministry of Science and Innovation and the State Agency of Research MCIN/AEI/10.13039/501100011033, PID2021-124665NB-I00, and ERDF A way of making Europe. MP-S acknowledges support under grants RYC2021-033094-I, CNS2023-145506, and PID2023- 146667NB-I00 funded by MCIN/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR. Computational resources were provided by the Advanced Research Computing (ARC) facility at the University of Oxford [1]. We gratefully acknowledge the use of ARC for supporting the quantum chemical calculations performed in this work.Peer reviewedRoyal Astronomical SocietyScience and Technology Facilities Council (UK)Comunidad de MadridAgencia Estatal de Investigación (España)University of OxfordThatte, N. [0000-0002-6694-5184]Rigopoulou, D. [0000-0001-6854-7545]Donnan, F. R. [0000-0002-6460-3682]#NODATA##NODATA##NODATA#Veenema, O. [0009-0009-0466-9223]Kerkeni, B. [0000-0002-5762-5058]#NODATA#Hermosa Muñoz, L. [0000-0002-9610-0123]#NODATA#Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202620262026info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/419227https://api.elsevier.com/content/abstract/scopus_id/105024419846reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2021-124665NB-I00info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2021-124665NB-I00info:eu-repo/grantAgreement/AEI//RYC2021-033094-Iinfo:eu-repo/grantAgreement/AEI//CNS2023-145506info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2023-146667NB-I00https://doi.org/10.1093/mnras/staf2047Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/4192272026-05-22T06:33:51Z
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