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Astron. Astrophys. 360, 457-462 (2000)
Sub-mm and X-ray background: Two unrelated phenomena?
P. Severgnini 1,
R. Maiolino 2,
M. Salvati 2,
D. Axon 3,
A. Cimatti 2,
F. Fiore 4,
R. Gilli 1,5,
F. La Franca 6,
A. Marconi 2,
G. Matt 6,
G. Risaliti 1 and
C. Vignali 7,8
1 Università di Firenze, Dipartimento di Astronomia, Largo E. Fermi 5, 50125 Firenze, Italy
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3 University of Hertfordshire, Department of Physical Sciences, College Lane, Hatfield, Herts AL10 8 AB, UK
4 Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Monteporzio Catone, Italy
5 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Postsdam, Germany
6 Università degli Studi "Roma Tre", Dipartimento di Fisica, Via della Vasca Navale 84, 00146 Roma, Italy
7 Università di Bologna, Dipartimento di Astronomia, Via Ranzani 1, 40127 Bologna, Italy
8 Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
Received 30 March 2000 / Accepted 13 June 2000
Abstract
Obscured AGNs are thought to contribute a large fraction of the
hard X-ray background (2-10 keV), and have also been proposed as the
powerhouse of a fraction of the SCUBA sources which make most of the
background at 850µm, thus providing a link between the
two spectral windows. We have tackled this issue by comparing data at
2-10 keV and at 850µm for a sample of 34 sources at
fluxes (or limiting fluxes) which resolve most of the background in
the two bands. We present here new SCUBA observations, and new
correlations between separate data sets retrieved from the literature.
Similar correlations presented by others are added for completeness.
None of the 11 hard X-ray (2-10 keV) sources has a counterpart at 850
µm, with the exception of a Chandra source in the SSA13
field, which is a candidate type 2, heavily absorbed QSO at high
redshift. The ratios ![[FORMULA]](img1.gif)
(mostly upper
limits) of the X-ray sources are significantly lower than the value
observed for the cosmic background. In particular, we obtain that 2-10
keV sources brighter than ![[FORMULA]](img2.gif)
, which make
at least 75% of the background in this band, contribute for less than
7% to the submillimeter background. Out of the 24 SCUBA sources, 23
are undetected by Chandra. The ratios
(mostly lower limits) of these SCUBA sources indicate that most of
them must be powered either by starburst activity, or by an AGN which
is obscured by a column ![[FORMULA]](img3.gif)
, with a
reflection efficiency in the hard X rays significantly lower than
1% in most cases. However, AGNs of this type could not contribute
significantly to the 2-10 keV background.
Key words: galaxies:
active 
submillimeter
infrared:
galaxies
X-rays:
galaxies
cosmology: diffuse radiation
Send offprint requests to: P. Severgnini (paolas@arcetri.astro.it)
Contents
- 1. Introduction
- 2. Observations and data reduction
- 3. Results and cross-correlation of other surveys
- 4. Comparison with AGN and starburst templates
- 5. Discussion
- 6. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: August 17, 2000
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