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Astron. Astrophys. 329, 55-60 (1998)

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Far-infrared emission of intracluster dust
in the Coma galaxy cluster *

M. Stickel 1, D. Lemke 1, K. Mattila 2, L.K. Haikala 2 and M. Haas 1

1 Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
2 Helsinki University Observatory, P.O.Box 14, FIN-00014 Helsinki, Finland

Received 9 June 1997 / Accepted 14 August 1997


The ISOPHOT C200 camera aboard ISO has been used to observe the extended far infrared (FIR) emission from the Coma cluster of galaxies. Two scans with 48 [FORMULA] length across the cluster, each at 120 [FORMULA] and 185 [FORMULA], were obtained at crossing position angles. The profiles of the surface brightness ratio [FORMULA] along the two scans are quite similar in showing an enhanced 120 [FORMULA] emission within the central region of [FORMULA] 10 [FORMULA] (0.4 Mpc) diameter. This flux excess is interpreted as thermal emission from intracluster dust with a temperature slightly higher than the galactic foreground cirrus. A conservative value for the excess surface brightness at 120 [FORMULA] is [FORMULA] 0.1 MJy/sr, corresponding to a total net flux of [FORMULA] 0.7 Jy. Depending on the dust opacity and temperature, a total dust mass of [FORMULA] is inferred. The detected excess emission represents the first direct evidence from FIR observation for intracluster dust in a galaxy cluster. Since dust is destroyed effectively by the hot intracluster medium, the dust detected may result from galaxy stripping during the ongoing merging process in Coma. FIR emission from intracluster dust thus might be used as a tool to search for non-equilibrium galaxy clusters.

Key words: galaxies: clusters: individual: Coma – galaxies: clusters: general – intergalactic medium – infrared: general

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Send offprint requests to: M. Stickel (stickel@mpia-hd.mpg.de)

© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997