A radio and infrared investigation of Seyfert galaxies in the local universe

Castle, Ryan M. (2012) A radio and infrared investigation of Seyfert galaxies in the local universe. Masters (Research) thesis, James Cook University.

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Presented here are the results of an investigation of a newly constructed sample of local (z < 0.0303), southern-sky Seyfert galaxies. Data from the 843 MHz Sydney University Molonglo Sky Survey (SUMSS) was used, as well as near and mid/far-infrared data from the IRAS and 2MASS surveys, respectively.

The first goal of this research was to construct a complete sample of southern-sky Seyferts for use in an ongoing study of this type of AGN in the local universe. The next and main research goal in this study was to search for any previously unidentified large-scale radio emission from the Seyferts - taking advantage of the good sensitivity and (u, v) plane coverage of the Molonglo Observatory Synthesis Telescope (MOST) used in the SUMSS. This was a search for extended radio emission that could perhaps identify past epochs of activity from the nucleus. In addition, this research enables another test the unified scheme for this type of AGN by carrying out several conventional two-sample statistical tests. Radio contour maps of all sample objects are presented as well as the distances, galactocentric recession velocities, and the 843 MHz, NIR (1.25, 1.65, 2.17 μm), and MID/FIR (12, 25, 60, 100 μm) luminosities. The IR data for this sample were also used to compute several spectral indices and the spectral energy distributions (SEDs) for the sample objects, as well as to investigate the global radio-FIR correlation known to exist among all galaxies.

The most significant of the new results reported here include the identification of six radio-excess Seyferts, heretofore not identified as such in the literature, as well as a newly identified "radio-loud" type-2 Seyfert. Evidence for significant radio variability over a span of twenty years was also found for five of the sample objects by comparing data from the SUMSS to that from an earlier, smaller study using the MOST. In addition, the 2MASS Ks - band images of several of the closest type-2 Seyfert were decomposed into disk, bulge, and nuclear components in a study of the NIR properties of this type of active galaxy, increasing by nearly 50% the number of local Seyferts for which this type of analysis has been published.

Item ID: 29906
Item Type: Thesis (Masters (Research))
Keywords: Seyfert galaxies; radio emission mapping; emission analysis
Date Deposited: 25 Oct 2013 00:23
FoR Codes: 02 PHYSICAL SCIENCES > 0201 Astronomical and Space Sciences > 020103 Cosmology and Extragalactic Astronomy @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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