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Title:
Constraining the AGN contribution in a multiwavelength study of Seyfert galaxies
Authors:
Melendez Hernandez, Marcio Baal
Affiliation:
AA(The Catholic University of America)
Publication:
Proquest Dissertations And Theses 2008. Section 0043, Part 0606 126 pages; [Ph.D. dissertation].United States - - District of Columbia: The Catholic University of America; 2008. Publication Number: AAT 3311968. Source: DAI-B 69/05, Nov 2008
Publication Date:
00/2008
Origin:
UMI
Keywords:
Seyfert galaxies, Active galactic nuclei, Star formation, Galaxies
Comment:
Publication Number: AAT 3311968; ISBN: 9780549650645; Advisor: Kraemer, Steven B.
Bibliographic Code:
2008PhDT.........9M

Abstract

I have studied the relationship between high- and low-ionization mid-infrared emission lines with the aim of constraining the active galactic nuclei (AGN) and star formation contributions for a sample of 100 Seyfert galaxies. I investigated the correlation between the [O IV] l25.89 μm emission line luminosities, obtained from Spitzer spectra, with the X-ray continua in the 14- 195 keV band, obtained with the SWIFT /Burst Alert Telescope (BAT). I find the [O IV] to be an accurate and truly isotropic indicator of the power of the AGN. Consequently, I have used the [O IV] to deconvolve the contributions of the AGN and star formation in the low-ionization [Ne II] l12.81 μm emission line, and mid- and far-infrared continuum luminosities of Seyfert 1 and Seyfert 2 galaxies. I investigated the ionization state of the emission-line gas in Seyfert galaxies using the [O IV]/[Ne II] emission ratio. I find that Seyfert 2 galaxies have, on average, lower ratios than those of Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGN, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. Although I cannot dismiss the former, I find that Seyfert 1 and Seyfert 2 galaxies have similar luminosity distributions. Using [Ne II] as a tracer of star formation I find a higher average star formation rate for Seyfert 2 galaxies, 7.7±0.3M[Special characters omitted.] yr-1, than for Seyfert 1 galaxies, 5.0±0.4M[Special characters omitted.] yr -1 . For comparison, I examined the mid- and far-infrared continua and find that Seyfert 1 and Seyfert 2 galaxies are dominated by hot dust and cool dust components, respectively. Overall, these results test the unified model of AGN, and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.
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