Molecular clouds in the dwarf galaxy NGC6822 Virtual Observatory Resource

Authors
  1. Schruba A.
  2. Leroy A.K.
  3. Kruijssen J.M.D.
  4. Bigiel F.
  5. Bolatto A.D.,de Blok W.J.G.
  6. Tacconi L.
  7. van Dishoeck E.F.
  8. Walter F.
  9. Published by
    CDS
Abstract

We present the Atacama Large Millimeter/submillimeter Array survey of CO(2-1) emission from the 1/5 solar metallicity, Local Group dwarf galaxy NGC 6822. We achieve high (0.9"~2pc) spatial resolution while covering a large area: four 250pcx250pc regions that encompass ~2/3 of NGC 6822's star formation. In these regions, we resolve ~150 compact CO clumps that have small radii (~2-3pc), narrow line width (~1km/s), and low filling factor across the galaxy. This is consistent with other recent studies of low-metallicity galaxies, but here shown with a 15x larger sample. At parsec scales, CO emission correlates with 8{mu}m emission better than with 24{mu}m emission and anticorrelates with H{alpha}, so that polycyclic aromatic hydrocarbon emission may be an effective tracer of molecular gas at low metallicity. The properties of the CO clumps resemble those of similar-size structures in Galactic clouds except of slightly lower surface brightness and with CO-to-H_2_ ratio ~1-2x the Galactic value. The clumps exist inside larger atomic-molecular complexes with masses typical for giant molecular clouds. Using dust to trace H_2_ for the entire complex, we find the CO-to-H_2_ ratio to be ~20-25x the Galactic value, but with strong dependence on spatial scale and variations between complexes that may track their evolutionary state. The H_2_-to-HI ratio is low globally and only mildly above unity within the complexes. The ratio of star formation rate to H_2_ is ~3-5x higher in the complexes than in massive disk galaxies, but after accounting for the bias from targeting star-forming regions, we conclude that the global molecular gas depletion time may be as long as in massive disk galaxies.

Keywords
  1. Molecular clouds
  2. Millimeter astronomy
  3. Submillimeter astronomy
  4. Galaxies
  5. CO line emission
Bibliographic source Bibcode
2017ApJ...835..278S
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/835/278
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/835/278
Document Object Identifer DOI
doi:10.26093/cds/vizier.18350278

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History

2017-10-04T08:17:33Z
Resource record created
2017-10-04T08:17:33Z
Created
2020-01-29T14:07:00Z
Updated

Contact

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CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
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cds-question@unistra.fr