非表示:
キーワード:
galaxies: clusters: general, infrared: galaxies, X-rays: galaxies: clusters, intergalactic medium, diffuse radiation, galaxies: starburst
要旨:
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.
