The Detection of Molecular Gas in the Outskirts of NGC 6946
BRAINE, J.
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
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Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
BRAINE, J.
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
WILSON, Christine D.
Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Institute of Microbiology and Genetics
University of Exeter
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Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Institute of Microbiology and Genetics
University of Exeter
Language
en
Article de revue
This item was published in
The Astrophysical Journal. 2007, vol. 669, n° 2, p. L73-L76
American Astronomical Society
English Abstract
We present the results of a search for molecular gas emission via the CO line in the far outer disk of the nearby spiral, NGC 6946. The positions targeted were chosen to lie on or near previously-identified outer disk HII ...Read more >
We present the results of a search for molecular gas emission via the CO line in the far outer disk of the nearby spiral, NGC 6946. The positions targeted were chosen to lie on or near previously-identified outer disk HII regions. Molecular gas was clearly detected out to 1.3 R$_{25}$, with a further tentative detection at 1.4 R$_{25}$. The CO detections show excellent agreement with the HI velocities and imply beam-averaged column densities of $0.3-9\times 10^{20}$ cm$^{-2}$ and molecular gas masses of (2-70)$\times 10^{5}$ M$_{\sun}$ per 21$''$ beam (560pc). We find evidence for an abrupt decrease in the molecular fraction at the edge of the optical disk, similar to that seen previously in the azimuthally-averaged areal star formation rate. Our observations provide new constraints on the factors that determine the presence and detectability of molecular gas in the outskirts of galaxies, and suggest that neither the HI column, the metallicity or the local heating rate alone plays a dominant role.Read less <
English Keywords
galaxies: individual (NGC 6946)—galaxies: individual (NGC 1058) — galaxies: spiral — galaxies: ISM
ISM: molecules
radio lines: ISM
Origin
Hal imported