The Imprint of Galaxy Formation on X-ray Clusters

T. J. Ponman; D. B. Cannon; J. F. Navarro

doi:10.1038/16410

paper

The Imprint of Galaxy Formation on X-ray Clusters

arXiv:astro-ph/9810359 · doi:10.1038/16410

Abstract

It is widely believed that structure in the Universe evolves hierarchically, as primordial density fluctuations, amplified by gravity, collapse and merge to form progressively larger systems. The structure and evolution of X-ray clusters, however, seems at odds with this hierarchical scenario for structure formation. Poor clusters and groups, as well as most distant clusters detected to date, are substantially fainter than expected from the tight relations between luminosity, temperature and redshift predicted by these models. Here we show that these discrepancies arise because, near the centre, the entropy of the hot, diffuse intracluster medium (ICM) is higher tha $a c hi e v ab l e t h r o ug h g r a v i t a t i o na l co l l a p se, in d i c a t in g s u b s t an t ia l n o n - g r a v i t a t i o na l h e a t in g o f t h e I C M . W ees t ima t e t hi se x cesse n t r o p y f or t h e f i r s tt im e, an d a r g u e t ha t i t r e p r ese n t s a r e l i co f t h ee n er g e t i c w in d s t h r o ug h w hi c h f or min g g a l a x i es p o l l u t e d t h e I C M w i t hm e t a l s . E n er g e t i c a l l y, t hi s i so n l$ possible if the ICM is heated at modest redshift ($z \ltsim 2$) but prior to cluster collapse, indicating that the formation of galaxies precedes that of clusters and that most clusters have been assembled very recently.

5 pages, plus 2 postscript figures (one in colour), accepted for publication in Nature

The Imprint of Galaxy Formation on X-ray Clusters

Abstract

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