A Study of the Neutral Hydrogen Content of Blue Compact Dwarf Galaxies

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MacHattie, Jeremy
Galaxy , Astronomy , Neutral , Hydrogen , Galactic , Dwarf , Astrophysics
The results of a study of the neutral hydrogen (HI) content and distribution within a sample of 18 blue compact dwarf galaxies (BCDs) are presented. An investigation of the behaviour of the gas-to-dust ratio (GDR) as a function of metallicity (Z) is also presented. Observations of these BCDs was performed using the Very Large Array (VLA) in 2009, a year in which the array was undergoing a technological upgrade to the the Karl G. Jansky VLA (JVLA). The observations were reduced and images processed using the Astronomical Image Processing Software (AIPS), and data cubes for each galaxy were produced. The results include detections of eleven HI lines (two new detections) and ten background continuum sources (two new discoveries). All detections are at a higher resolution and/or sensitivity than previous measurements. These detections spanned a large range of line widths and HI masses; some masses comparable to those in normal galaxies. Of particular interest was the discovery of a compact absorption feature in the dwarf galaxy Haro 11. A paper submitted to the Monthly Notices of the Royal Astronomical Society (MNRAS) Letters on this discovery is presented. Another significant result was the discovery of a highly extended and massive HI region in the dwarf galaxy CGCG 297-017. For those galaxies with no detected HI line or radio continuum, an upper limit to the flux density was computed, which was used to derive upper limits to the HI mass or star-formation rate (SFR) respectively. Three HI flux density upper limits are new results, and seven continuum flux density upper limits are also new. The GDR-Z relation at low metallicities shows a potential power law or broken power law relation with a turning point at Z=7.96 or Z=8.05. To within error, these turning points and power law indices of the broken power law fits are consistent with other work.
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