The effect of radiative cooling on scaling laws of X-ray groups and clusters

We have performed cosmological simulations in a Lambda CDM cosmology with a nd without radiative cooling in order to study the effect of cooling on the cluster scaling laws. Our simulations consist of 4.1 million particles eac h of gas and dark matter within a box size of 100 h(-l) Mpc, and the run wi th cooling is the largest of its kind to have been evolved to, z = 0, Our c luster catalogs both consist of over 400 objects and are complete in mass d own to similar to 10(13) h(-1)M(circle dot). We contrast the emission-weigh ted temperature-mass (T-ew-M) and bolometric luminosity-temperature (L-bol- T-ew) relations for the simulations at z = 0. We find that radiative coolin g increases the temperature of intracluster gas and decreases its total lum inosity, in agreement with the results of Pearce et al. Furthermore, the te mperature dependence of these effects flattens the slope of the T-ew-M rela tion and steepens the slope of the L-bol-T-ew relation. Inclusion of radiat ive cooling in the simulations is sufficient to reproduce the observed X-ra y scaling relations without requiring excessive nongravitational energy inj ection.