Volume 439, Number 2, August IV 2005
|465 - 477
|Cosmology (including clusters of galaxies)
|29 July 2005
Tracing the X-ray emitting intra-cluster medium of clusters of galaxies beyond r
AIM - Unité Mixte de Recherche CEA - CNRS - Université Paris VII - UMR N° 7158 CEA/Saclay; DSM/DAPNIA/Service d'Astrophysique, CEA/Saclay, L'Orme des Merisiers, Bât. 709, 91191 Gif-sur-Yvette, France e-mail: firstname.lastname@example.org
Accepted: 2 May 2005
We present in this paper a study of a sample of 14 nearby clusters of galaxies () observed with the ROSAT/PSPC. We only select clusters with low galactic absorption ( 1020 cm-2) in order to trace the hot X-ray emitting intra-cluster medium (ICM) out to large radii. We convert the X-ray surface brightness profiles of the clusters into emission measure profiles scaled to the classical scaling relations based on the spherical collapse model. We sort the clusters into different temperature bins and stack the scaled emission measure (ScEM) profiles of clusters belonging to the same bin together. This method enhances the statistics of the profiles – especially in outer regions. The stacked profiles allow us to observe a signal out to radii . In the center () we find that the ScEM profiles deviate from predicted scaling laws. Hotter clusters have systematically a higher ScEM than cooler clusters. This result is in very good agreement with current studies on the relation and the entropy-temperature relation () found recently. At radii we find that the ScEM profiles agree well within the error bars, suggesting self-similarity. Fitting beta-models to the overall ScEM profiles, we find for the different subsamples and , which is higher than the canonical value of often found. The beta-model is generally a better representation for hotter than for cooler clusters. We see indications for continuous steepening of the profiles with increasing radius: at radii the profiles are systematically below the beta-model curve with . We discuss our results with respect to the observed X-ray luminosity relation, the gas mass relation and the total mass relation. We also address implications on the origin of the observed relation. Furthermore, we discuss the observed steepness of the X-ray profiles, which falls off more rapidly than predicted from the NFW-profile for cold dark matter halos.
Key words: galaxies: clusters: general / cosmology: observations / dark matter / large-scale structure of Universe / X-rays: galaxies: clusters
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.