XMM-NEWTONOBSERVATIONS OF THREE LOW X-RAY LUMINOSITY GALAXY CLUSTERS

Abstract

We present new XMM-Newton measurements of the X-ray luminosities (Lx ) and temperatures (Tx ) for three clusters of galaxies. Two are low Lx (<3 × 1043 erg s–1) clusters, RXJ0110.3+1938 (z = 0.317) and RXJ1011.0+5339 (z = 0.329). These clusters were selected from the 160 Square Degree Survey, a survey of extended sources serendipitously discovered in pointed ROSAT observations. The third cluster, KDCS 112, was included by chance in one of our pointings, and is an optically selected cluster from the DEEPRANGE survey. It has a similar redshift and X-ray luminosity as the first two. We estimate the optical richness (Λcl) of all three clusters. RXJ1011.0+5339 was missed by DEEPRANGE because it is optically poor. However, KDCS112 was missed in the 160SD even though it is brighter in the X-rays than its neighbor RXJ1011.0+5339, because it fell below the 160SD flux limit. The ROSAT flux of RXJ1011.0+5339 was overestimated due to point-source contamination; it is among the lowest luminosity groups with a known X-ray temperature at moderate redshift. These clusters represent a pilot study to probe the Lx -Tx relation at moderate redshifts and low Lx , a regime where feedback processes may increase the scatter or change the mean Lx -Tx relation. The X-ray luminosities and temperatures of the clusters are consistent with the Lx -Tx relationship in galaxy clusters at low redshift, albeit with large scatter. We place a upper limit on the scatter in the Lx -Tx relation of ~0.1 in δlog Tx for moderate redshift clusters, similar to that of low-redshift clusters.