Volume 370, Number 3, May II 2001
|Page(s)||900 - 908|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 May 2001|
The BeppoSAX High Energy Large Area Survey
IV. On the soft X-ray properties of the hard X-ray-selected HELLAS sources
Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, 40127 Bologna, Italy
2 Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
3 Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Monteporzio, Italy
4 BeppoSAX Science Data Center, Via Corcolle 19, 00131 Roma, Italy
5 Dipartimento di Fisica, Università degli Studi "Roma Tre", Via della Vasca Navale 84, 00146 Roma, Italy
Corresponding author: C. Vignali, email@example.com
Accepted: 16 February 2001
We present a comprehensive study of the soft X-ray properties of the BeppoSAX High-Energy Large Area Survey (HELLAS) sources. A large fraction (about 2/3) of the hard X-ray selected sources is detected by ROSAT. The soft X-ray colors for many of these objects, along with the 0.5-2 keV flux upper limits for those undetected in the ROSAT band, do imply the presence of absorption. The comparison with the ROSAT Deep Survey sources indicates that a larger fraction of absorbed objects among the HELLAS sources is present, in agreement with their hard X-ray selection and the predictions of the X-ray background synthesis models. Another striking result is the presence of a soft (additional) X-ray component in a significant fraction of absorbed objects.
Key words: surveys / galaxies: active / galaxies: nuclei / galaxies: starburst X / rays: galaxies
© ESO, 2001
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