A new population of soft X-ray weak quasars

被引：34

作者：

Risaliti, G

Marconi, A

Maiolino, R

Salvati, M

Severgnini, P

机构：

[1] Univ Florence, Dipartimento Astron & Sci Spazio, I-50125 Florence, Italy

[2] Osservatorio Astrofis Arcetri, I-50125 Florence, Italy

来源：

ASTRONOMY & ASTROPHYSICS | 2001年 / 371卷 / 01期

关键词：

galaxies : active; galaxies : X-rays : galaxies;

D O I：

10.1051/0004-6361:20010276

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Quasars selected in optical surveys by means of their blue or UV excess are known to be strong emitters in the X-rays, except for Broad Absorption Line (BAL) objects. In this paper we study the X-ray emission of quasars selected through their emission line spectrum rather than their blue excess. X-ray data are obtained by cross-correlating two optical samples (the Hamburg Survey Catalogue and the Palomar Transit Catalogue) with the WGA catalogue of ROSAT observations. We find that a significant fraction of objects are strongly underluminous in the X-rays. We discuss the physical nature of these sources and we propose an interpretation for their optical and X-ray properties based on a dust-poor and gas-rich absorber. Our results suggest the existence of a population of AGNs having a type 1 optical spectrum and a type 2 X-ray emission.

引用

页码：37 / 44

页数：8

共 26 条

[1] X-RAY-PROPERTIES OF OPTICALLY SELECTED QSOS [J].

AVNI, Y ;

TANANBAUM, H .

ASTROPHYSICAL JOURNAL, 1986, 305 (01) :83-99

[2] On the nature of soft X-ray weak quasi-stellar objects [J].

Brandt, WN ;

Laor, A ;

Wills, BJ .

ASTROPHYSICAL JOURNAL, 2000, 528 (02) :637-649

[3]

Brinkmann W, 1997, ASTRON ASTROPHYS, V319, P413

[4]

COMASTRI A, 1995, ASTRON ASTROPHYS, V296, P1

[5] ATLAS OF QUASAR ENERGY-DISTRIBUTIONS [J].

ELVIS, M ;

WILKES, BJ ;

MCDOWELL, JC ;

GREEN, RF ;

BECHTOLD, J ;

WILLNER, SP ;

OEY, MS ;

POLOMSKI, E ;

CUTRI, R .

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1994, 95 (01) :1-68

[6]

ENGELS D, 1998, A AS, V128, P508

[7] The contribution of faint active galactic nuclei to the hard X-ray background [J].

Fiore, F ;

La Franca, F ;

Giommi, P ;

Elvis, M ;

Matt, G ;

Comastri, A ;

Molendi, S ;

Gioia, I .

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1999, 306 (04) :L55-L60

[8] A HIGH SIGNAL-TO-NOISE RATIO COMPOSITE QUASAR SPECTRUM [J].

FRANCIS, PJ ;

HEWETT, PC ;

FOLTZ, CB ;

CHAFFEE, FH ;

WEYMANN, RJ ;

MORRIS, SL .

ASTROPHYSICAL JOURNAL, 1991, 373 (02) :465-470

[9] Exploratory ASCA observations of broad absorption line quasi-stellar objects [J].

Gallagher, SC ;

Brandt, WN ;

Sambruna, RM ;

Mathur, S ;

Yamasaki, N .

ASTROPHYSICAL JOURNAL, 1999, 519 (02) :549-555

[10]

Gilli R, 1999, ASTRON ASTROPHYS, V347, P424

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