The sub-mm/radio correlation in spiral galaxies

Details The sub-mm/radio correlation in spiral galaxies The sub-mm/radio correlation in spiral galaxies

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005phdt........23b&link_type=abstract

Proquest Dissertations And Theses 2005. Section 0283, Part 0606 150 pages; [Ph.D. dissertation].Canada: Queen's University at K

Computer Science

1

Radio Correlation, Spiral Galaxies, Ngc 3044, Ngc 4157, Ngc 5775, Halo Signal-To-Noise, Galactic Dust

Scientific paper

This thesis reports the study of the dust and cosmic ray content of three edge- on spiral galaxies, NGC 3044, NGC 4157 and NGC 5775, to an unprecedented level. Observations in the sub-mm were made with the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Metre- length radio continuum emission observations were conducted with the Giant Metrewave Radio Telescope (GMRT). We have produced multi-wavelength maps of the galaxies in our study at high resolution and good signal-to-noise in both the halo and disk. These maps are the basis for the rest of the study.
Based on 450 and 850 mm observations of galaxies in our sample, we recalculated their gas-to-dust ratio which now agrees with our Galaxy's value. To our knowledge, we have produced the first spatially resolved cold-dust temperature map of any galaxy, for each galaxy in our sample. We have also produced a technique to calculate the spatial distribution of potential energy of the high-latitude dust, giving the lower limit energy required to transport dust from the disk to its current location. It is likely that one or more processes, such as perturbations in the galactic magnetic field, play a role in the ejection of the ISM, alongside supernovae.
Finally, we show that a sub-mm/radio correlation exists spatially within the disks and haloes of NGC 3044, NGC 4157 and NGC 5775 and globally between these galaxies.
This sub-mm/radio correlation is observational evidence that the conventional explanation for the famous FIR-radio correlation is incomplete or perhaps simply incorrect. An explanation, based on a review of the literature, is proposed for both the sub-mm/radio correlation and the FIR-radio correlation.
The sub-mm/radio correlation, which includes emission from the dominant cold dust component, appears to be a more fundamental phenomenon than the specific case that results in the FIR/radio correlation, because the FIR picks out only a tiny fraction of the dust mass. We find that models that link magnetic fields to dust and cosmic rays as the origin of this correlation are the most promising in explaining the correlation in diverse galactic regions.

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