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Molecular gas in the galaxy M83: I. The molecular gas distribution
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
2004 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 413, 505-523 p.Article in journal (Refereed) Published
Abstract [en]

We present 12CO  J=1-0 and J=2-1 Swedish-ESO Submillimetre Telescope (SEST) observations of the barred spiral galaxy M 83 (NGC 5236). The size of the CO maps is

and they cover the entire optical disk. The grid spacing is 11´´ for CO( J=1-0) and 11´´ or 7´´ for CO( J=2-1) depending on the position in the galaxy. In total we have obtained spectra in 1900 and 2574 positions in the CO( J=1-0) and CO( J=2-1) lines, respectively. The CO emission is strongly peaked toward the nucleus, which breaks up into two separate components in the CO( J=2-1) data due to the higher spatial resolution. Emission from the bar is strong, in particular on the leading edges of the bar. The molecular gas arms are clearly resolved and can be traced for more than 360°. Emission in the inter-arm regions is detected. The average CO ( J=2-1)/( J=1-0) line ratio is 0.77. The ratio is lower than this on the spiral arms and higher in the inter-arm regions. The arms show regularly spaced concentrations of molecular gas, Giant Molecular Associations (GMA's), whose masses are of the order 

. The total molecular gas mass is estimated to be 

. This mass is comparable to the total HI mass, but H 2 dominates in the optical disk. In the disk, H 2 and HI show very similar distributions, including small scale clumping. We compare the molecular gas distribution with those of other star formation tracers, such as B and H  images.

Place, publisher, year, edition, pages
2004. Vol. 413, 505-523 p.
Keyword [en]
galaxies: individual: M 83; NGC 5236 -- galaxies: spiral -- galaxies: structure -- galaxies: ISM -- radio lines: galaxies -- galaxies: abundances
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-23097DOI: 10.1051/0004-6361:20031507OAI: oai:DiVA.org:su-23097DiVA: diva2:190138
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2011-06-28Bibliographically approved
In thesis
1. Molecular gas in the galaxy M83: Its distribution, kinematics, and relation to star formation
Open this publication in new window or tab >>Molecular gas in the galaxy M83: Its distribution, kinematics, and relation to star formation
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The barred spiral galaxy M83 (NGC5236) has been observed in the 12CO J=1–0 and J=2–1 millimetre lines with the Swedish-ESO Submillimetre Telescope (SEST). The sizes of the CO maps are 100×100, and they cover the entire optical disk. The CO emission is strongly peaked toward the nucleus. The molecular spiral arms are clearly resolved and can be traced for about 360º. The total molecular gas mass is comparable to the total Hi mass, but H2 dominates in the optical disk.

Iso-velocity maps show the signature of an inclined, rotating disk, but also the effects of streaming motions along the spiral arms. The dynamical mass is determined and compared to the gas mass. The pattern speed is determined from the residual velocity pattern, and the locations of various resonances are discussed. The molecular gas velocity dispersion is determined, and a trend of decreasing dispersion with increasing galactocentric radius is found.

A total gas (H2+Hi+He) mass surface density map is presented, and compared to the critical density for star formation of an isothermal gaseous disk. The star formation rate (SFR) in the disk is estimated using data from various star formation tracers. The different SFR estimates agree well when corrections for extinctions, based on the total gas mass map, are made. The radial SFR distribution shows features that can be associated with kinematic resonances. We also find an increased star formation efficiency in the spiral arms. Different Schmidt laws are fitted to the data. The star formation properties of the nuclear region, based on high angular resolution HST data, are also discussed.

Place, publisher, year, edition, pages
Stockholm: Institutionen för astronomi, 2004. 42 p.
Keyword
Molecular gas, Galaxies, Galaxies individual: M83, Star formation, Galactic dynamics
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-148 (URN)91-7265-864-9 (ISBN)
Public defence
2004-05-28, Sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00
Opponent
Supervisors
Available from: 2004-05-06 Created: 2004-05-06Bibliographically approved

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