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Probing the Interstellar Medium and Massive Star Formation using Submillimeter Dust Emission

Arabindo Roy

Doctor of Philosophy 2011
Graduate Department of Astronomy and Astrophysics, University of Toronto

This thesis aims to improve our understanding of the early stages of massive star formation and of the physical properties of interstellar clouds. To achieve this, I have used submillimeter continuum dust emission data obtained by the Balloon-borne Large Aperture submillimeter Telescope (BLAST) in the first science flight in 2005, with a 2-m telescope operating simultaneously at 250, 350, and 500 μm. Unfortunately, BLAST produced images of about 3.′3 resolution due to an uncharacterized optical problem.

In Chapter 2, I discuss implementation of the Lucy-Richardson (L-R) method of deconvolution to restore BLAST images to near diffraction limited resolution. Its performance and convergence have been extensively analyzed through simulations and comparison of deconvolved images with available high-resolution maps.

In Chapter 3, I study diverse phenomena in the Cygnus X region associated with high mass star-formation. To interpret the BLAST emission more fully and place the compact sources in context, archival data cubes of 13CO line emission from KOSMA, MIPS images from the Spitzer Legacy Survey of this region, and 21-cm radio continuum emission from the Canadian Galactic Plane Survey have been used. Utilizing available ancillary multiwavelength observations, the influence of OB stars and stellar clusters on Cygnus X has been studied, revisiting the well-known DR H II regions and their surroundings in the light of submillimeter continuum dust emission and CO line emission. An effort has been made to assess the evolutionary sequence of the compact sources (spatial extent of about 1 pc) on the basis of L-M diagram and subsequently to relate this sequence to independent empirical evidence and theory. Using multi-resolution observations, evidence for hierarchical substructures within molecular clouds has been examined.

Finally, in Chapter 4, a multi-wavelength power spectrum analysis of the large scale brightness fluctuations in the Galactic plane is presented. This analysis has been used to assess the level of cirrus noise which limits the detection of faint sources. A characteristic power law exponent of about −2.7 has been obtained for sub-regions of Aquila and Cygnus X. The observed relative amplitudes of power spectra at different wavelengths have been related through a spectral energy distribution, thereby determining a characteristic temperature for the Galactic diffuse emission

Reproduced with permission. library@astro.utoronto.ca
July 7, 2011