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 and without radiative cooling in order to study the effect of cooling on the cluster scaling laws. Our simulations consist of 4.1 million particles each of gas and dark matter within a box size of 100 h(-l) Mpc, and the run with cooling is the largest of its kind to have been evolved to, z = 0, Our cluster catalogs both consist of over 400 objects and are complete in mass down to similar to 10(13) h(-1)M(circle dot). We contrast the emission-weighted temperature-mass (T-ew-M) and bolometric luminosity-temperature (L-bol-T-ew) relations for the simulations at z = 0. We find that radiative cooling increases the temperature of intracluster gas and decreases its total luminosity, in agreement with the results of Pearce et al. Furthermore, the temperature dependence of these effects flattens the slope of the T-ew-M relation and steepens the slope of the L-bol-T-ew relation. Inclusion of radiative cooling in the simulations is sufficient to reproduce the observed X-ray scaling relations without requiring excessive nongravitational energy injection.