The distribution of molecular clouds along the Southern Galactic Plane

  • Kerem Osman Çubuk

Student thesis: Doctoral ThesisDoctor of Philosophy


This thesis presents the data of the Mopra Southern Galactic Plane CO Survey and various analyses undertaken using the survey data. The survey covers a large region of the sky from l = 250 to 355 and |b| < 1, with some extensions an area of 221 degin total.

These data have been taken at 0.6 arcminute spatial resolution and 0.1 km s−1spectralresolution, providing an unprecedented view of the molecular gas clouds of the Southern Galactic Plane in the 109-115 GHz J = 1-0 transitions of 12CO, 13CO, C18O and C17O.The total measured 12CO and 13CO fluxes for the entire survey are found to be 1.5 x 10^8 K km/s and 1.8 x 10^7 K km/s, respectively. The total molecular cloud mass value is then calculated using a canonical X-factor value. The total mass limits were determined assuming all the flux originates from the near and far distance solutions to the Galactic rotation curve. According to these analyses, the lowest and the highest mass limits of the molecular clouds were found to be 2.8 x 10^8 M_solar and 1.5 x 10^9 M_solar, respectively.

A new molecular cloud catalogue has been produced using a dendrogram-based algorithm. Various properties of each cloud have been derived using a combination of a Galactic rotation curve and a parallax-based distance estimator to obtain distances for each cloud. The total mass derived for the individual clouds identified is 3.8 x 10^8 M_solar. The catalogue clouds were then placed on top of the widely used Milky Way images to show the veracity of the images. The molecular cloud distribution coincides well with the spiral arm locations.

The total mass in the Galaxy has been estimated to be ~1 x 10^9 M_solar assuming a symmetrical molecular mass distribution between Northern and Southern Hemispheres.

Date of AwardDec 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsArmagh Observatory and Planetarium
SupervisorMichael Burton (Supervisor)


  • Molecular clouds
  • galaxies
  • astrophysics
  • survey
  • Milky Way
  • carbon monoxide

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