The Compton-thick AGN in the CDF-N

I. Georgantopoulos; A. Akylas; A. Georgakakis; M. Rowan-Robinson

paper

The Compton-thick AGN in the CDF-N

arXiv:0909.0224

Abstract

We present X-ray spectral analysis of the brightest sources (f_{2-10 keV}>10^{-15} $c g s) in t h e C han d r a D ee pF i e l d N or t h . O u r s am pl eco n s i s t so f 222 so u r ces; f or t h e v a s t maj or i t y (171) e i t h er a s p ec t r osco p i cor a p h o t o m e t r i cr e d s hi f t i s a v ai l ab l e . O u r g o a l i s t o d i sco v er t h e C o m pt o n - t hi c k A GN ina d i r ec tw a y i . e . t h r o ug h t h e i r X - r a y s p ec t r a . C o m pt o n - t hi c k A GN g i v e a w a y t h e i r p r ese n ce in X - r a y se i t h er d i r ec tl y t h r o ug h t h e ab sor pt i o n t u r n o v er r e d s hi f t e d in t h e C han d r a p a ss ban d, or t h r o ug ha f l a t, r e f l ec t i o n - d o mina t e d, s p ec t r u m . T h e ab o v ese l ec t i o n cr i t er ia y i e l d 10 C o m pt o n - t hi c k A GN c an d i d a t eso f w hi c h t h e nin e a r er e f l ec t i o n d o mina t e d . T h e I R or s u b - mm d a t a w h er e a v ai l ab l e, cor r o b or a t e t h e p r ese n ceo f ah e a v i l y o b sc u r e d n u c l e u s inm os t c a ses . A l l t h e f i v ec an d i d a t e C o m pt o n - t hi c k so u r ces w i t ha v ai l ab l e 24 mi cr o n d a t a p r ese n t v er y hi g h v a l u eso f t h e f_{24} / f_{R} f l ux r a t i os ug g es t in g t ha tt h ey a r e d u s t o b sc u r e d g a l a x i es . T h e l o w f_{x} / f_{I R} r a t i o a l sos ug g es tt h e p r ese n ceo f o b sc u r e d n u c l e iinman y c a ses . F o u r o f t h ec an d i d a t e C o m pt o n - t hi c k so u r ces a r e a ssoc ia t e d w i t h s u b - mm g a l a x i es a t hi g h r e d s hi f t sz$ \sim2$. The number count vs. flux distribution of the candidate Compton-thick AGN as well as their distribution with redshift agree reasonably well with the predictions of the X-ray background synthesis models of Gilli et al.

13 pages, to appear in Astronomy & Astrophysics

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