We present new X-ray temperatures and improved X-ray luminosity estimates for 15 new and archival XMM-Newton observations of galaxy clusters at intermediate redshift with mass and luminosities near the galaxy group/cluster division (, L 2 × 1044 erg s–1, 0.3 z 0.6). These clusters have weak-lensing mass measurements based on Hubble Space Telescope observations of clusters representative of an X-ray-selected sample (the ROSAT 160SD survey). The angular resolution of XMM-Newton allows us to disentangle the emission of these galaxy clusters from nearby point sources, which significantly contaminated previous X-ray luminosity estimates for 6 of the 15 clusters. We extend cluster scaling relations between X-ray luminosity, temperature, and weak-lensing mass for low-mass, X-ray-selected clusters out to redshift ~0.45. These relations are important for cosmology and the astrophysics of feedback in galaxy groups and clusters. Our joint analysis with a sample of 50 clusters in a similar redshift range but with larger masses (M 500 21.9 × 1014 M ☉, 0.15 ≤ z ≤ 0.55) from the Canadian Cluster Comparison Project finds that within r 2500, M∝L 0.44 ± 0.05, T∝L 0.23 ± 0.02, and M∝T 1.9 ± 0.2. The estimated intrinsic scatter in the M-L relation for the combined sample is reduced to σlog (M|L) = 0.10, from σlog (M|L) = 0.26 with the original ROSAT measurements. We also find an intrinsic scatter for the T-L relation, σlog (T|L) = 0.07 ± 0.01.
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