October 29, 1998
We present results of ultra-deep ISOCAM observations through a cluster-lens at 7 and 15 micron with the Infrared Space Observatory (ISO) satellite. These observations reveal a large number of luminous Mid-Infrared (MIR) sources. Cross-identification in the optical and Near-Infrared (NIR) wavebands shows that about half of the 7 micron sources are cluster galaxies. The other 7 micron and almost all 15 micron sources are identified as lensed distant galaxies. Thanks to the gravitational amplification they constitute the faintest MIR detected sources, allowing us to extend the number counts in both the 7 and 15 micron bands. In particular, we find that the 15 micron counts have a steep slope alpha_15 = -1.5 +/- 0.3 and are large, with N_15 (>30 microJy}) = 13 +/- 5 per square arcmin. These numbers rule out non-evolutionary models and favour very strong evolution. Down to our counts limit, we found that the resolved 7 and 15 microns background radiation intensity is respectively (2 +/-0.5) 10^(-9) and (5 +/-1) 10^(-9) W m^(-2) sr^(-1).
Similar papers 1
October 18, 1999
We present imaging results and source counts from a deep ISOCAM cosmological survey at 15 microns, through gravitationally lensing galaxy clusters. We take advantage of the cluster gravitational amplification to increase the sensitivity of our survey. We detect a large number of luminous mid-IR sources behind the cluster lenses, down to very faint fluxes, which would have been unreachable without the gravitational lensing effect. These source counts, corrected for lensing dis...
January 12, 1999
We present imaging results and source counts from an ISOCAM deep and ultra-deep cosmological survey through gravitationally lensing clusters of galaxies at 7 and 15 microns. A total area of about 53 sq.arcmin was covered in maps of three clusters. The lensing increases the sensitivity of the survey. A large number of luminous mid-infrared (MIR) sources were detected behind the lenses, and most could be unambiguously identified with visible counterparts. Thanks to the gravitat...
May 21, 2003
ISOCAM was used to perform a deep survey through three gravitationally lensing clusters of galaxies. Nearly seventy sq. arcmin were covered over the clusters A370, A2218 and A2390. We present maps and photometry at 6.7 & 14.3 microns, showing a total of 145 mid-IR sources and the associated source counts. The 15 micron counts reach the faintest level yet recorded. All sources have counterparts in the optical or near-IR. Models of the clusters were used to correct for the effe...
August 13, 1998
We present the first results of mid-infrared (MIR) ultra-deep observations towards the lensing cluster Abell 2390 using the ISOCAM infrared camera on-board ESA's Infrared Space Observatory (ISO) satellite. They reveal a large number of luminous MIR sources. Optical and near-infrared (NIR) cross-identification suggests that almost all 15 microns sources and about half of the 7 microns are identified with distant lensed galaxies. Thanks to the gravitational amplification these ...
July 13, 2004
The gravitationally lensing clusters A370, A2218, A1689 and CL0024+1654 were observed with the Infrared Space Observatory (ISO) using ISOCAM at 6.7 and 14.3 microns (hereafter 7 and 15 microns respectively). A total of 178 sources were detected in the whole set, 70 of them being cluster objects. The spectral energy distribution of a subset of sources was calculated using GRASIL. The results for the total infrared luminosity and the estimation of the star formation rate are pr...
June 16, 2004
We describe the results of observations of galaxy clusters conducted with ISOCAM on-board the Infrared Space Observatory. Our research is aimed at understanding the processes driving galaxy evolution in dense environments, free from the bias of dust extinction. The results reveal quite a complex picture: the star-formation activity of cluster galaxies does not show a simple evolution with redshift, but also depends on the dynamical status and evolutionary history of the clust...
November 4, 1999
We present the results of the extragalactic surveys performed at 15 and 175 microns using the ISOCAM and ISOPHOT instruments on-board the Infrared Space Observatory (ISO). The number counts at both wavelengths present a strong evolution. The preliminary study of the individual galaxies responsible for this evolution suggest that more star formation was hidden by dust at redshifts around z=1-2 and imply that the population of luminous IR galaxies detected by IRAS in the local ...
November 30, 1998
We present a comprehensive study of ISO cluster galaxies in connection with other wavelengths. First results show that infrared galaxies detected by ISOCAM concentrate on the edge of clusters. Surprisingly, they are not emission lines galaxies but very luminous elliptical, merging or interacting ones, which suggests non-trivial connections between star formation rate, optical and mid-IR properties. However, no correlation has been found between the MIR/optical star formation ...
January 20, 1999
We present the first results of a study of faint 12 micron sources detected with the Infrared Space Observatory (ISO) in four deep, high galactic latitude fields. The sample includes 50 such sources in an area of 0.1 square degrees down to a 5 sigma flux limit of about 500 microJy. From optical identifications based on the US Naval Observatory (USNO) catalogue and analysis of the optical/IR colours and Digital Sky Survey (DSS) images, we conclude that 37 of these objects are ...
December 8, 1999
I present results from a deep 12 micron extragalactic survey conducted with the ISOCAM instrument. The survey covers about 0.1 sq. deg. in four fields and reaches a 5 sigma flux limit of about 500 microJy. 50 sources are identified to this flux limit. Of these, 37 are classified as galaxies on the basis of optical/mid-IR colours using identifications from the USNO-A photographic survey. Number counts for these objects exceed those predicted for no-evolution models in simple m...