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The ALMA view of UV irradiated cloud edges: unexpected structures and processes

dc.contributor.authorGOICOECHEA, Javier
dc.contributor.authorCUADRADO, S.
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorPETY, J.
hal.structure.identifierConsejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain] [CSIC]
dc.contributor.authorAGUADO, A.
hal.structure.identifierOnsala Space Observatory [OSO]
dc.contributor.authorBLACK, J. H.
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorBRON, E.
hal.structure.identifierInstituto de Ciencia de Materiales de Madrid [ICMM]
dc.contributor.authorCERNICHARO, J.
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
hal.structure.identifierAMOR 2018
dc.contributor.authorCHAPILLON, E.
hal.structure.identifierObservatorio Astronomico Nacional, Madrid
dc.contributor.authorFUENTE, A.
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorGERIN, M.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorJOBLIN, C.
dc.date.issued2018
dc.date.conference2017-03-20
dc.description.abstractEnFar-UV photons (E<13.6 eV) from hot massive stars regulate, or at least influence, the heating, ionization, and chemistry of most of the neutral interstellar medium. Investigating the interaction between FUV radiation and interstellar matter thus plays an important role in astrochemistry. We have used ALMA to mosaic a small field of the Orion Bar where the critical transition from atomic to molecular gas takes place. These observations provide an unprecedented sharp view of this transition layer (~1" resolution or ~414 AU). The resulting images (so far in the rotational emission of CO, HCO+, H13CO+, SO+, SO, and reactive ions SH+ and HOC+) show the small-scale structure in gas density and temperature, and the steep abundance gradients. The images reveal a pattern of high-density substructures, photo-ablative gas flows and instabilities at the edge of the molecular cloud. We have also used the IRAM 30m telescope to carry out a line-survey of the illuminated edge of the Bar in the mm domain. Our observations reveal the presence of complex organic molecules that were not expected in such a harsh environment. In particular, we have reported the first detection of the unstable cis conformer of formic acid (HCOOH) in the ISM. The energy barrier to internal rotation (the conversion from trans to cis) is approximately 4827 cm-1. Hence, this detection is surprising. The low inferred trans-to-cis abundance ratio of 2.8+/-1.0 supports a photoswitching mechanism: a given conformer absorbs a FUV stellar photon that radiatively excites the molecule to electronic states above the interconversion barrier. Subsequent fluorescent decay leaves the molecule in a different conformer form. This mechanism, which we have specifically studied with ab initio quantum calculations, was not considered so far in astrochemistry although it can affect the structure of a variety of molecules in PDRs. (abridged)
dc.language.isoen
dc.subject.enAstrophysics - Astrophysics of Galaxies
dc.title.enThe ALMA view of UV irradiated cloud edges: unexpected structures and processes
dc.typeCommunication dans un congrès
dc.identifier.doi10.1017/S1743921317007761
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Cosmologie et astrophysique extra-galactique [astro-ph.CO]
dc.identifier.arxiv1707.08869
bordeaux.page210-217
bordeaux.conference.title: "Astrochemistry VII, Through the Cosmos from Galaxies to Planets". Proceedings of the IAU Symposium No. 332, 2017, Puerto Varas, Chile. M. Cunningham, T. Millar and Y. Aikawa, eds. p210-217
bordeaux.countryCL
bordeaux.conference.cityPuerto Varas
bordeaux.peerReviewedoui
hal.identifierhal-01582589
hal.version1
hal.invitednon
hal.proceedingsoui
hal.conference.end2017-03-24
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01582589v1
bordeaux.COinSctx_ver=Z39.88-2004&amp;rft_val_fmt=info:ofi/fmt:kev:mtx:journal&amp;rft.date=2018&amp;rft.spage=210-217&amp;rft.epage=210-217&amp;rft.au=GOICOECHEA,%20Javier&amp;CUADRADO,%20S.&amp;PETY,%20J.&amp;AGUADO,%20A.&amp;BLACK,%20J.%20H.&amp;rft.genre=unknown


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