J/A+A/638/A44ivo://CDS.VizieR/J/A+A/638/A44doi:10.26093/cds/vizier.36380044CDSBeuther H.Wang Y.Soler J.D.Linz H.Henshaw J.Vazquez-Semadeni E.,Gomez G.Ragan S.Henning T.Glover S.C.O.Lee M.-Y.Guesten R.2020-10-01T13:41:25Z2020-06-09T08:08:55ZCDS support team

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

cds-question@unistra.frmolecular-cloudsinfrared-sourcesAtomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained. Identify and characterize the cloud formation signatures in atomic and molecular gas. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employ spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in ^13^CO in the 1-0 and 3-2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers, estimates of the mass flow rates, velocity structure functions, a Histogram of Oriented Gradients (HOG) study as well as comparisons to simulations. The central IRDC is embedded in a more diffuse envelope of cold neutral medium (CNM) traced by HI self-absorption (HISA) and molecular gas. The spectral line data as well as the HOG and structure function analysis indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and position-velocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent with gas flows being dominated by the formation of hierarchical structures. The observations and analysis are consistent with a picture where the IRDC G28 is formed at the center of two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar, gravitationally driven collapse of the cloud, external compression by, e.g., spiral arm shocks or supernovae explosions cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows.2020A&A...638A..44Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/638/A44CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/634/A83 : THOR DR2 source list (Wang+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/638/A44https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/638/A44http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/638/A44https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/638/A44https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/638/A44http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/638/A44GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/638/A44/list (List of fits files)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/638/A44/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/638/A44/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/638/A44/list?GETtext/xml+votable180.050000true280.70688-4.02230.0055555555555555566/12974 30258https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/638/A44?format=asciiInfrareddefaultJ/A+A/638/A44/listList of fits filesrecnoRecord 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 pixels along Z-axismeta.numberintObs.dateObservaiton datestime.epochnullablebVRADLower value of VRAD intervalkm/sphys.velocintBVRADUpper value of VRAD intervalkm/sphys.velocfloatdVRADVRAD resolutionm/sspect.resolutionintsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fits