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Issue A&A
Volume 439, Number 1, August III 2005
Page(s) 35 - 44
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20042388



A&A 439, 35-44 (2005)
DOI: 10.1051/0004-6361:20042388

Dust emission from clusters of galaxies: statistical detection

L. A. Montier and M. Giard

Centre d'Études Spatiales des Rayonnements, 9 avenue Colonel Roche, 31022 Toulouse, France
    e-mail: montier@cesr.fr

(Received 18 November 2004 / Accepted 3 March 2005)

Abstract
The detection of the IR emission from individual galaxy clusters is a difficult task due to the extremely low level of this emission and the fluctuations of the IR sky, galactic cirrus and background galaxies. We have statistically detected a significant IR emission toward galaxy clusters at $12~\mathrm{\mu m}$, $25~\mathrm{\mu m}$, $60~\mathrm{\mu m}$ and $100~\mathrm{\mu m}$ by co-adding the IRAS maps toward a total of 11 507 galaxy clusters extracted from the CDS database. This process averages the sky fluctuations of the astrophysical sky and the survey noise to a very low level in all four bands. We have obtained an averaged central detection at all wavelengths, with an intensity of $2685 \pm 573~\mathrm{Jy/sr}$, $2127 \pm 742~\mathrm{Jy/sr}$, $16\,253 \pm 670~\mathrm{Jy/sr}$ and $34\,011 \pm 1391~\mathrm{Jy/sr}$ respectively. These detections have been confirmed against possible spurious or systematic signals using different test methods. The origin of this detected IR emission is discussed. The free-free contribution to the IR emission can be ruled out. Both the level of the emission and its spectrum favor an interpretation in terms of dust emission. However the exact location of this dust remains unknown: is this emission due to intergalactic dust, or simply the dust included in the galaxies of the clusters? This last question will be discussed in a forthcoming paper.


Key words: intergalactic medium -- galaxies: clusters: general -- infrared: stars




© ESO 2005


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