NDLI: On the nature of X-ray “unobscured” Seyfert 2 galaxies

Content Provider	Springer Nature Link
Author	Tan, Ying Wang, JunXian Zhang, Kai
Copyright Year	2012
Abstract	We present a systematic study to reveal the effect of host galaxy contamination to the identification of X-ray “unobscured” Seyfert 2 galaxies. We compiled a sample of 14 X-ray “unobscured” Seyfert 2 galaxies and 29 X-ray obscured Seyfert 2s, with infrared [Ne II] and [O IV] emission line flux measurements. In this work we classify Seyfert 2s as “unobscured” or obscured in X-ray simply based on X-ray spectral fitting. We find that our X-ay “unobscured” Seyfert 2s have statistically higher [Ne II]/[O IV] line ratios, compared with obscured ones. Since the [Ne II]/[O IV] line ratio reflects the relative strength of star formation activity comparing with the SMBH accretion, the observed differences in [Ne II]/[O IV] line ratios clearly indicate relatively stronger X-ray contamination from star formation in the host galaxies in X-ray “unobscured” Seyfert 2s. Therefore we could attribute the X-ray “unobscured” appearance to host galaxy contamination for most (if not all) of our X-ray “unobscured” Seyfert 2s. Further analysis indicates that “unobscured” Seyfert 2s have intrinsically lower AGN luminosity but similar star formation rates, compared with obscured ones. This is also consistent with previous studies showing most X-ray “unobscured” Seyfert 2s are at lower luminosities, and relatively stronger contaminations from the host galaxies are thus expected. Finally we develop a screening criterion to distinguish potential pure Seyfert 2s from X-ray “unobscured” appearances which could be caused by strong host galaxy contamination.
Starting Page	2482
Ending Page	2491
Page Count	10
File Format	PDF
ISSN	16747348
Journal	Science in China Series G
Volume Number	55
Issue Number	12
e-ISSN	18691927
Language	English
Publisher	SP Science China Press
Publisher Date	2012-11-19
Publisher Place	Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	active galactic nuclei X-rays absorption star formation Physics Classical Continuum Physics Astronomy, Observations and Techniques
Content Type	Text
Resource Type	Article
Subject	Physics and Astronomy

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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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