Probing the Universe with Weak Lensing

Gravitational lenses can provide crucial information on the geometry of the Universe, on the cosmological scenario of formation of its structures as well as on the history of its components with look-back time. In this review, I focus on the most recent results obtained during the last five years from the analysis of the weak lensing regime. The interest of weak lensing as a probe of dark matter and the for study of the coupling between light and mass on scales of clusters of galaxies, large scale structures and galaxies is discussed first. Then I present the impact of weak lensing for the study of distant galaxies and of the population of lensed sources as function of redshift. Finally, I discuss the potential interest of weak lensing to constrain the cosmological parameters, either from pure geometrical effects observed in peculiar lenses, or from the coupling of weak lensing with the CMB.Comment: To appear Annual Review of Astronomy and Astrophysiscs Vol. 37. Latex and psfig.sty. Version without figure, 54 pages, 73Kb. Complete version including 13 figures (60 pages) available on ftp.iap.fr anonymous account in /pub/from_users/mellier/AnnualReview ; file ARAAmellier.ps.gz 1.6 M

An ISOCAM survey through gravitationally lensing galaxy clusters. III. New results from mid-infrared observations of th e cluster Abell 2219

The massive cluster of galaxies Abell 2219 (z = 0.228) was observed at 14.3 $\mu$m with the Infrared Space Observatory and results were published by Barvainis et al. (1999). 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. For three cluster members the infrared luminosities derived from the model SEDs are between ~5.7x10^10 Lsun and 1.4x10^11 Lsun, corresponding to infrared star formation rates between 10 and 24 Msun yr^-1. 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 1.5x10^10 Lsun and 9.4x10^10 Lsun yielding infrared star formation rates between 3 and 16 Msun yr^-1. Two of the foreground galaxies are located in two foreground galaxy enhancements (Boschin et al. 2004). 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.Comment: 8 pages, 4 figures, A&A accepted, full paper with high-resolution figures available at http://bermuda.ucd.ie/~dcoia/papers/. Reference adde

ISO's Contribution to the Study of Clusters of Galaxies

Starting with nearby galaxy clusters like Virgo and Coma, and continuing out to the furthest galaxy clusters for which ISO results have yet been published ($z=0.56$), we discuss the development of knowledge of the infrared and associated physical properties of galaxy clusters from early IRAS observations, through the "ISO-era" to the present, in order to explore the status of ISO's contribution to this field. Relevant IRAS and ISO programmes are reviewed, addressing both the cluster galaxies and the still-very-limited evidence for an infrared-emitting intra-cluster medium. ISO made important advances in knowledge of both nearby and distant galaxy clusters, such as the discovery of a major cold dust component in Virgo and Coma cluster galaxies, the elaboration of the correlation between dust emission and Hubble-type, and the detection of numerous Luminous Infrared Galaxies (LIRGs) in several distant clusters. These and consequent achievements are underlined and described. We recall that, due to observing time constraints, ISO's coverage of higher-redshift galaxy clusters to the depths required to detect and study statistically significant samples of cluster galaxies over a range of morphological types could not be comprehensive and systematic, and such systematic coverage of distant clusters will be an important achievement of the Spitzer Observatory.Comment: 22 pages, 7 figures. Accepted for publication in Space Science Reviews ISO Special Issue "ISO science legacy - a compact review of ISO major achievements", Ed.C.Cesarky & A.Salama Updated 23 Aug. 2005 in order to change some citations from astro-ph nos. to full Journal references after they were publishe

An ISOCAM survey through gravitationally lensing galaxy clusters III : new results from mid-infrared observations of the cluster Abell 2219

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{1999AJ....118..645B}). These observations have been reanalysed 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 × 1010 L⊙ and 1.4 × 1011 L⊙, corresponding to infrared star formation rates between 10 and 24 M⊙ yr-1. 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 × 1010 L⊙ and 9.4 × 1010 L⊙ yielding infrared star formation rates between 3 and 16 M⊙ yr-1. Two of the foreground galaxies are located in two foreground galaxy enhancements (Boschin et al. \cite{2004A&A...416..839B}). 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. 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 UK) and with the participation of ISAS and NASA