J/A+A/641/A17ivo://CDS.VizieR/J/A+A/641/A17doi:10.26093/cds/vizier.36410017CDSBonne L.Schneider N.Bontemps S.Clarke S. D.Gusdorf A.Lehmann A.,Steinke M.Csengeri T.Kabanovic S.Simon R.Buchbender C.Guesten R.2020-11-26T12:03:41Z2020-09-01T09:23:39ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frinterstellar-mediumradio-astronomyco-line-emissionObservations with the Herschel Space Telescope have established that most star forming gas is organised in filaments, a finding that is supported by numerical simulations of the supersonic interstellar medium (ISM) where dense filamentary structures are ubiquitous. We aim to understand the formation of these dense structures by performing observations covering the ^12^CO(4-3), ^12^CO(3-2), and various CO(2-1) isotopologue lines of the Musca filament, using the APEX telescope. The observed CO intensities and line ratios cannot be explained by PDR (photodissociation region) emission because of the low ambient far-UV field that is strongly constrained by the non-detections of the [CII] line at 158um and the [OI] line at 63um, observed with the upGREAT receiver on SOFIA, as well as a weak [CI] 609um line detected with APEX. We propose that the observations are consistent with a scenario in which shock excitation gives rise to warm and dense gas close to the highest column density regions in the Musca filament. Using shock models, we find that the CO observations can be consistent with excitation by J-type low-velocity shocks. A qualitative comparison of the observed CO spectra with synthetic observations of dynamic filament formation simulations shows a good agreement with the signature of a filament accretion shock that forms a cold and dense filament from a converging flow. The Musca filament is thus found to be dense molecular post-shock gas. Filament accretion shocks that dissipate the supersonic kinetic energy of converging flows in the ISM may thus play a prominent role in the evolution of cold and dense filamentary structures.2020A&A...641A..17Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/641/A17CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/641/A17https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/641/A17http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/641/A17https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/641/A17https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/641/A17http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/641/A17GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/641/A17/list (List of fits datacubes)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/641/A17/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/641/A17/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/641/A17/list?GETtext/xml+votable180.050000true187.20775-71.281940.0055555555555555566/41515 41518https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/641/A17?format=asciiRadiodefaultJ/A+A/641/A17/listList of fits datacubesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintNzNumber of slicesmeta.numberintbVRADLower value of VRAD intervalm/sphys.veloc;pos.heliocentricintBVRADUpper value of VRAD intervalm/sphys.veloc;pos.heliocentricintdVRADVRAD resolutionm/sspect.resolutionintsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar