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Dense gas in low-metallicity galaxies

hal.structure.identifierFORMATION STELLAIRE 2017
dc.contributor.authorBRAINE, J.
hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR7158 / UMR_E_9005 / UM_112)]
dc.contributor.authorSHIMAJIRI, Y.
hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR7158 / UMR_E_9005 / UM_112)]
dc.contributor.authorANDRÉ, P.
hal.structure.identifierFORMATION STELLAIRE 2017
dc.contributor.authorBONTEMPS, Sylvain
hal.structure.identifierChinese Academy of Sciences [Changchun Branch] [CAS]
dc.contributor.authorGAO, Yu
dc.contributor.authorCHEN, Hao
hal.structure.identifierInstituto de RadioAstronomía Milimétrica [IRAM]
dc.contributor.authorKRAMER, C.
dc.date.issued2017
dc.identifier.issn0004-6361
dc.description.abstractEnStars form out of the densest parts of molecular clouds. Far-IR emission can be used to estimate the star formation rate (SFR) and high dipole moment molecules, typically HCN, trace the dense gas. A strong correlation exists between HCN and far-IR emission, with the ratio being nearly constant, over a large range of physical scales. A few recent observations have found HCN to be weak with respect to the far-IR and CO in subsolar metallicity (low-Z) objects. We present observations of the Local Group galaxies M 33, IC 10, and NGC 6822 with the IRAM 30 m and NRO 45 m telescopes, greatly improving the sample of low-Z galaxies observed. HCN, HCO+, CS, C2H, and HNC have been detected. Compared to solar metallicity galaxies, the nitrogen-bearing species are weak (HCN, HNC) or not detected (CN, HNCO, N2H+) relative to far-IR or CO emission. HCO+ and C2H emission is normal with respect to CO and far-IR. While 13CO is the usual factor 10 weaker than 12CO, C18O emission was not detected down to very low levels. Including earlier data, we find that the HCN/HCO+ ratio varies with metallicity (O/H) and attribute this to the sharply decreasing nitrogen abundance. The dense gas fraction, traced by the HCN/CO and HCO+/CO ratios, follows the SFR but in the low-Z objects the HCO+ is much easier to measure. Combined with larger and smaller scale measurements, the HCO+ line appears to be an excellent tracer of dense gas and varies linearly with the SFR for both low and high metallicities.
dc.description.sponsorshipVers une vision unifiée de la formation stellaire dans les galaxies : Origine de la structure filamentaire du milieu interstellaire, des cœurs pré-stellaires et des amas protostellaires vus avec Herschel - ANR-11-BS56-0010
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enAstrophysics - Astrophysics of Galaxies
dc.subject.engalaxies: individual: M 33
dc.subject.engalaxies: individual: IC 10
dc.subject.engalaxies: individual: NGC 6822
dc.subject.enLocal Group
dc.subject.engalaxies: ISM
dc.subject.enstars: formation
dc.title.enDense gas in low-metallicity galaxies
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201629781
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]
dc.identifier.arxiv1612.02196
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageA44
bordeaux.volume597
bordeaux.peerReviewedoui
hal.identifierhal-01414137
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01414137v1
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