the nearby cluster of galaxies a2256 (z~0.06) is one of the rare clusters having an extented radio halo - a phenomenon which is not understood yet. this remarkable feature has sharp boundaries, covers an area of ~ 50 sq.arcmin. and has a total flux of 245 mjy at 1.44 ghz. a rosat pointing revealed a double peak of x-ray emission, sugges- ting the merging between a cluster and a group of galaxies, a possibility which is in agreement with the distribution of the galaxy velocities. subsequent deeper rosat observations provided a 2-d temperature map, clearly showing temperature gradients and thus, assessing the merging hypothesis. in this cenario, the radio halo find a natural explaination in terms of cosmic ray acceleration at the merging front. 12 iras sources are found in the field of a2256; 7 of them are associated with discrete radio sources belonging to the cluster. a2256 is a unique case of a halo cluster studied in such detail in three wavelengths for which a coherent picture is now possible. evidences found in favor of a turbulent intra-cluster medium are compelling arguments to perform iso observations in order to investigate the peculiar star formation activity, which is undoubitably triggered by the violent interactions taking place in the merging processes.
Instrument
CAM01 , PHT22
Temporal Coverage
1996-02-13T03:52:40Z/1997-02-23T11:40:37Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, PIERRE et al., 1999, 'DETAILED INSIGHTS INTO THE INTRA-CLUSTER MEDIUM OF ABELL 2256', 1.0, European Space Agency, https://doi.org/10.5270/esa-acgxtyx
