Joint HST, VLT/MUSE, and XMM-Newton observations to constrain the mass distribution of the two strong lensing galaxy clusters: MACS J0242.5-2132 and MACS J0949.8+1708

We present the strong lensing analysis of two galaxy clusters: MACS J0242.5-2132 (MACS J0242, z = 0.313) and MACS J0949.8+1708 (MACS J0949, z = 0.383). Their total matter distributions are constrained, thanks to the powerful combination of observations with the Hubble Space Telescope (HST) and the Multi-Unit Spectroscopic Explorer instrument. Using these observations, we precisely measure the redshift of six multiple image systems in MACS J0242 and two in MACS J0949. We also include four multiple image systems in the latter cluster identified in HST imaging without MUSE redshift measurements. For each cluster, our best-fit mass model consists of a single cluster-scale halo and 57 (170) galaxy-scale halos for MACS J0242 (MACS J0949). Multiple images positions are predicted with a rms 0.39 arcsec and 0.15 arcsec for MACS J0242 and MACS J0949 models, respectively. From these mass models, we derive aperture masses of M(R <200 kpc) = 1.67^+0.03_-0.05 × 10¹⁴ M_☉ and M(R<200 kpc) = 2.00^+0.05_-0.20 × 10¹⁴ M_☉. Combining our analysis with X-ray observations from the XMM-Newton Observatory, we show that MACS J0242 appears to be a relatively relaxed cluster, whereas conversely, MACS J0949 shows a relaxing post-merger state. At 200 kpc, X-ray observations suggest the hot gas fraction to be, respectively, f_g = 0.115^+0.003_-0.004 and 0.053^+0.007_-0.006 for MACS J0242 and MACS J0949. MACS J0242 being relaxed, its density profile is very well fitted by a Navarro-Frenk-White distribution, in agreement with X-ray observations. Finally, the strong lensing analysis of MACS J0949 suggests a flat dark matter density distribution in the core, between 10 and 100 kpc. This appears consistent with X-ray observations.