An analysis of the distribution of cavities in the Hı line images of the Canadian Galactic Plane Survey with a void-finder algorithm

The galactic Interstellar Medıum or ısm is one of the most studied components of the galaxy. In spite of this, no widely accepted complete dynamical model of the ısm exists. Two of the most influential models proposed by Cox and Smith, (1974) & McKee and Ostriker, (1977), differ substantially in their descriptions of the geometry of supernova remnant cavities in the ısm. No direct analysis of the geometry of cavities in the ısm has been done due to concerns over observations of neutral hydrogen (Hı) being dominated by velocity caustics. Clark et al. (2019), showed that the linear structure of Hı is most likely not caused by velocity caustics. In this thesis, we propose to extend upon her findings and present a comparison of general cavity features in the ısm to both Cox’s and McKee’s models. This was achieved by comparing the cavities found by applying a void-finding watershed-like algorithm to the velocity-channel Hı images of the Canadıan Galactıc Plane Survey data and comparing...Show moreThe galactic Interstellar Medıum or ısm is one of the most studied components of the galaxy. In spite of this, no widely accepted complete dynamical model of the ısm exists. Two of the most influential models proposed by Cox and Smith, (1974) & McKee and Ostriker, (1977), differ substantially in their descriptions of the geometry of supernova remnant cavities in the ısm. No direct analysis of the geometry of cavities in the ısm has been done due to concerns over observations of neutral hydrogen (Hı) being dominated by velocity caustics. Clark et al. (2019), showed that the linear structure of Hı is most likely not caused by velocity caustics. In this thesis, we propose to extend upon her findings and present a comparison of general cavity features in the ısm to both Cox’s and McKee’s models. This was achieved by comparing the cavities found by applying a void-finding watershed-like algorithm to the velocity-channel Hı images of the Canadıan Galactıc Plane Survey data and comparing the results with models of the ısm based on the Cox & McKee descriptions. We found evidence supporting Clark et al.’s position that narrow velocity channel images are not dominated by velocity caustics, but could not definitively support either Cox’s or McKee’s description of the ısm, even though the watershed algorithm was capable of obtaining the distribution of cavities in the model cavities.Show less

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An analysis of the distribution of cavities in the Hı line images of the Canadian Galactic Plane Survey with a void-finder algorithm