The X-ray spectra of optically selected Seyfert 2 galaxies: are there any Seyfert 2 galaxies with no absorption?

被引:73
作者
Pappa, A
Georgantopoulos, I
Stewart, GC
Zezas, AL
机构
[1] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England
[2] Natl Observ Athens, Inst Astron & Astrophys, Athens, Greece
关键词
galaxies : active; galaxies : Seyfert; galaxies : starburst; X-rays : galaxies;
D O I
10.1046/j.1365-8711.2001.04609.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present an X-ray spectral analysis of a sample of eight bona fide Seyfert 2 galaxies, selected on the basis of their high [O III]lambda 5007 flux, from the Ho et al. spectroscopic sample of nearby galaxies. We find that, in general, the X-ray spectra of our Seyfert 2 galaxies are complex, with some of our objects having spectra different from the 'typical' spectrum of X-ray selected Seyfert 2 galaxies. Two (NGC 3147 and 4698) show no evidence for intrinsic absorption. We suggest that this is a result of the fact that when the torus suppresses the intrinsic medium and hard energy flux, underlying emission from the host galaxy, originating in circumnuclear starbursts, and scattering from warm absorbers contributes in these energy bands more significantly. Our ASCA data alone cannot discriminate whether low-absorption objects are Compton-thick active galactic nuclei (AGNs) with a strong scattered component or lack an obscuring torus. The most striking example of our low absorption Seyfert 2 is NGC 4698. Its spectrum could be explained by either a dusty warm absorber or a lack of broad-line clouds so that its appearance as a Seyfert 2 is intrinsic and not a result of absorption.
引用
收藏
页码:995 / 1006
页数:12
相关论文
共 56 条
[1]  
ALONSOHERRERO A, 1997, MNRAS, V291, P557
[2]   UNIFIED MODELS FOR ACTIVE GALACTIC NUCLEI AND QUASARS [J].
ANTONUCCI, R .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1993, 31 :473-521
[3]   A three-dimensional diagnostic diagram for Seyfert 2 galaxies: Probing X-ray absorption and Compton thickness [J].
Bassani, L ;
Dadina, M ;
Maiolino, R ;
Salvati, M ;
Risaliti, G ;
Della Ceca, R ;
Matt, G ;
Zamorani, G .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1999, 121 (02) :473-482
[4]   THE CAMBRIDGE-CAMBRIDGE ROSAT SERENDIPITY SURVEY .1. X-RAY-LUMINOUS GALAXIES [J].
BOYLE, BJ ;
MCMAHON, RG ;
WILKES, BJ ;
ELVIS, M .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1995, 272 (02) :462-468
[5]  
COLLINSOUFFRIN S, 1987, ASTRON ASTROPHYS, V179, P30
[6]  
COMASTRI A, 1995, ASTRON ASTROPHYS, V296, P1
[7]  
COMASTRI A, 2001, P C XRAY ASTR 1999 S
[8]   H I IN THE GALAXY [J].
DICKEY, JM ;
LOCKMAN, FJ .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1990, 28 :215-261
[9]   DESTRUCTION MECHANISMS FOR INTER-STELLAR DUST [J].
DRAINE, BT ;
SALPETER, EE .
ASTROPHYSICAL JOURNAL, 1979, 231 (02) :438-455
[10]  
EHLE M, 1995, ASTRON ASTROPHYS, V295, P289