The impact of cooling flows on the T_X-L_Bol relation for the most luminous clusters

Abstract

We examine the effects of cooling flows on the T_X–L_Bol relation for a sample of the most X-ray luminous (L_Bol > 10⁴⁵ erg s⁻¹) clusters of galaxies known. Using high-quality ASCA X-ray spectra and ROSAT images we explicitly account for the effects of cooling flows on the X-ray properties of the clusters and show that this reduces the previously noted dispersion in the T_X–L_Bol relationship. More importantly, the slope of the relationship is flattened from L_Bol ∝ T³_X to approximately L_Bol ∝ T²_X, in agreement with recent theoretical models which include the effects of shocks and pre-heating on the X-ray gas. We find no evidence for evolution in the T_X–L_Bol relation within z ∼ 0.3. Our results demonstrate that the effects of cooling flows must be accounted for before cosmological parameters can be determined from X-ray observations of clusters. The results presented here should provide a reliable basis for modelling the T_X–L_Bol relation at high X-ray luminosities.

galaxies: clusters: general, cooling flows, intergalactic medium, X-rays: galaxies