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Molecular gas in the galaxy M83: Its distribution, kinematics, and relation to star formation
Stockholm University, Faculty of Science, Department of Astronomy.
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 [en]
Molecular gas, Galaxies, Galaxies individual: M83, Star formation, Galactic dynamics
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-148ISBN: 91-7265-864-9 (print)OAI: oai:DiVA.org:su-148DiVA: diva2:190142
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
List of papers
1. Molecular gas in the galaxy M83: I. The molecular gas distribution
Open this publication in new window or tab >>Molecular gas in the galaxy M83: I. The molecular gas distribution
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.

Keyword
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:nbn:se:su:diva-23097 (URN)10.1051/0004-6361:20031507 (DOI)
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2017-12-13Bibliographically approved
2. Molecular gas in the galaxy M83: II. Kinematics of the molecular gas
Open this publication in new window or tab >>Molecular gas in the galaxy M83: II. Kinematics of the molecular gas
2004 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 244, 865-881 p.Article in journal (Refereed) Published
Abstract [en]

We present the kinematics of the molecular gas in the barred spiral galaxy M 83 (NGC 5236). The study is based on 12CO( J= 1-0 and 2-1) observations with the Swedish-ESO Submillimetre Telescope (SEST). Iso-velocity maps of the entire optical disk, 10   10 or 13  13 kpc, are produced. They show the pattern of an inclined, rotating disk, but also the effects of streaming motions along the spiral arms. A dynamical mass of about 6  10

is estimated by fitting the rotation curve of an exponential disk model to these data. The gas constitutes about 13% of the disk mass. The pattern speed is determined from the residual velocity pattern. 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 (H 2 +

 + He) mass surface density map is presented, and compared to the critical density for star formation of an isothermal gaseous disk. The critical density is exceeded in the spiral arms, but not in the interarm regions. The locations of Giant Molecular Associations (GMAs) and

 regions are consistent with this scenario of dynamically induced star formation.

Keyword
galaxies: individual: M 83 (NGC 5236) -- galaxies: spiral -- galaxies: kinematics and dynamics -- galaxies: structure -- galaxies: ISM -- radio lines: galaxies
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-23098 (URN)10.1051/0004-6361:20040230 (DOI)
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2017-12-13Bibliographically approved
3. Molecular gas in the galaxy M83: III. Its relation to star formation in the disk
Open this publication in new window or tab >>Molecular gas in the galaxy M83: III. Its relation to star formation in the disk
(English)Manuscript (preprint) (Other academic)
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-23099 (URN)
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2011-06-28Bibliographically approved
4. Star formation in the nuclear region of M83: The HST/NICMOS view
Open this publication in new window or tab >>Star formation in the nuclear region of M83: The HST/NICMOS view
2004 (English)In: The Interplay among Black Holes, Stars and ISM in Galactic Nuclei: Proceedings of the 222th Symposium of the International Astronomical Union / [ed] T. Storchi-Bergmann, L. C. Ho & H. R. Schmitt, Cambridge: Cambridge University Press , 2004, 219-220 p.Conference paper, Published paper (Refereed)
Abstract [en]

The nuclear region of the barred spiral galaxy M83 has been imaged at near-infrared wavelengths with the HST NICMOS, showing a new region of star formation activity.

Place, publisher, year, edition, pages
Cambridge: Cambridge University Press, 2004
Series
Proceedings of the International Astronomical Union, ISSN 1743-9213 ; 222
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-23100 (URN)10.1017/S1743921304002133 (DOI)0-521-84803-2 (ISBN)
Conference
International Astronomical Union, Symposium, March 1-5, 2004, Gramado, Rio Grande do Sul, Brazil
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2011-07-01Bibliographically approved

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