An ISOCAM survey through gravitationally lensing galaxy clusters

Abstract

The massive cluster of galaxies Abell 2219 (z = 0.228) with two spectacular gravitational lensing arcs was observed at 14.3 μm (hereafter 15 μm) with the Infrared Space Observatory and results were published by Barvainis et al. ([CITE]). These observations have been reanalyzed using a method specifically designed for the detection of faint sources that had been applied to other clusters. Five new sources were detected and the resulting cumulative total of ten sources all have optical counterparts. The mid-infrared sources are identified with three cluster members, three foreground galaxies, an Extremely Red Object, a star and two galaxies of unknown redshift. The spectral energy distributions (SEDs) of the galaxies are fit with models from a selection, using the program GRASIL. Best-fits are obtained, in general, with models of galaxies with ongoing star formation. Infrared luminosities and star formation rates are obtained for six sources: the cluster members and the foreground galaxies. For the three cluster members the infrared luminosities derived from the model SEDs are between ~5.7 and 1.4 , corresponding to infrared star formation rates between 10 and 24 . The two cluster galaxies that have optical classifications are in the Butcher-Oemler region of the color–magnitude diagramme. The three foreground galaxies have infrared luminosities between 1.5 and 9.4 yielding infrared star formation rates between 3 and 16 . Two of the foreground galaxies are located in two foreground galaxy enhancements (Boschin et al. [CITE]). Including Abell 2219, six distant clusters of galaxies have been mapped with ISOCAM and luminous infrared galaxies (LIRGs) have been found in three of them. The presence of LIRGs in Abell 2219 strengthens the association between luminous infrared galaxies in clusters and recent or ongoing cluster merger activity.