The infrared luminosity of galaxy clusters

Abstract

Context. The cosmological models for the formation of the first stars and the large scale structures now raise the question of how many dust particles were released to the general diffuse gas and how these impact the star formation process. In this framework, we focus on the scale of galaxy clusters. Aims. The aim of this study is to quantify the infrared luminosity of clusters as a function of redshift and compare this with the X-ray luminosity. This can potentially constrain the origin of the infrared emission to be intracluster dust and/or dust heated by star formation in the cluster galaxies. Methods. We perform a statistical analysis of a large sample of galaxy clusters selected from existing databases and catalogues.We coadd the infrared IRAS and X-ray RASS images in the direction of the selected clusters within successive redshift intervals up to z = 1. Results. We find that the total infrared luminosity is very high and on average 20 times higher than the X-ray luminosity. If all the infrared luminosity is to be attributed to emission from diffuse intracluster dust, then the IR to X-ray ratio implies a dust-to-gas mass abundance of 5 × 10 −4 . However, the infrared luminosity shows a strong enhancement for 0.1 < z < 1, which cannot be attributed to cluster selection effects. We show that this enhancement is compatible with a star formation rate (SFR) in the member galaxies that is typical of the central Mpc of the Coma cluster at z = 0 and evolves with the redshift as (1 + z) 5 . Conclusions. It is likely that most of the infrared luminosity that we measure is generated by the ongoing star formation in the member galaxies. From theoretical predictions calibrated on extinction measurements (dust mass abundance equal to 10 −5 ), we expect only a minor contribution, of a few percent, from intracluster dust.

Infrared properties of the SDSS-maxBCG galaxy clusters

“…In addition to Montier & Giard (2005) original list of 11 507 clusters, Giard et al (2008) backed-up their analysis on two standalone catalogues -i.e. the "Northern Sky Optical Cluster Survey" (NSC, Gal et al 2003), and the SDSS-maxBCG catalogue ) -for which a richness information was available.…”

“…In order to understand the aforementioned results at 60 and 100 μm, in this work we focus on the modelisation of the IR luminosity and fluxes of galaxy clusters. The IR spectrum of galaxies, which is dominated by dust emission (Lagache et al 2005;Soifer et al 2008), is expected to make a major contribution to the IR emission detected in the direction of clusters (Giard et al 2008). Therefore, a careful modeling of the IR emission of member galaxies is needed in order to understand the global properties of clusters in the IR, and in particular to disentangle between the relative contribution of galaxies and intracluster dust.…”

“…Therefore, a careful modeling of the IR emission of member galaxies is needed in order to understand the global properties of clusters in the IR, and in particular to disentangle between the relative contribution of galaxies and intracluster dust. Given the inhomogeneity of the main dataset used by Montier & Giard (2005) and Giard et al (2008) (i.e. the 11 507 groups and clusters) in terms of cluster size and detection method, it becomes very difficult to define a global selection function of such sample, that would be necessary in order to have a suitable starting base for our work.…”

“…This concept was first used at IR wavelengths by Montier & Giard (2005) who performed a stacking analysis of the Infra Red Astronomical Satellite (IRAS) survey in the direction of more than 11 000 known galaxy clusters and groups and obtained a statistical detection of the overall clusters signal at 12, 25, 60 and 100 μm. Starting from this result, Giard et al (2008) characterised the IR luminosity evolution of the stacked sample, analysing also its correlation with their X-ray luminosities. These works constitute a first important result on the global IR properties of galaxy clusters.…”

“…This paper is organised as follows. In the next section we briefly present the statistical detection of the clusters IR emission of Montier & Giard (2005) and Giard et al (2008) and we focus in particular on the subsample of the SDSS-maxBCG catalogue. In Sect.…”