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PhD Defense - Jianning Zeng

Jianning ZengJianning successfully defended her dissertation on April 22, 2009.

Extended Emission Surrounding Nearby Seyfert Galaxies

We present the results from a search for and survey of any extended X- ray emission surrounding a class of Active Galactic Nuclei (AGN) known as “Seyfert-2” galaxies using data collected using Chandra X-ray observatory (CXO). The mirrors of this work was therefore to determine whether CXO observations help constrain current theories for AGN by probing the smallest spatial scales (> 100 pc) possible. Our sample consists of all the CXO observations of Seyfert-2 galaxies performed using the ACIS-S3 detector during the first 8 years of operation (28 objects). We find extended X-ray emission in all our Seyfert-2 sample of galaxies with a range of luminosities (1038 ∼ 1041 erg s−1 ). For 18 objects, the morphology is predominately bi-conical centered on the nucleus and typically extending out to a few kpc. Only a single cone is seen in 8 of the remaining ob jects, which may be indicative of intrinsically anisotropic emission. Where data is available, the X-ray cones do appear to occupy the same solid angle as the extended [OIII] emission line gas previously detected in these objects.

Our data suggest that the luminosity of the extended emission is typically a few percent of that of the nuclear source. Our findings are therefore broadly consist with current theories of AGN, but the low signal to noise for many of the observations combined with obscuration and possible contamination prevent any definitive tests of “Unified Schemes” being performed. Unfortunately this is likely to be the case for the foreseeable future.