CLASH-X: a comparison of lensing and X-ray techniques for measuring the mass profiles of galaxy clusters Academic Article uri icon


  • We present profiles of temperature, gas mass, and hydrostatic mass estimated from new and archival X-ray observations of CLASH clusters. We compare measurements derived from XMM and Chandra observations with one another and compare both to gravitational lensing mass profiles derived with CLASH Hubble Space Telescope and Subaru Telescope lensing data. Radial profiles of Chandra and XMM measurements of electron density and enclosed gas mass are nearly identical, indicating that differences in hydrostatic masses inferred from X-ray observations arise from differences in gas-temperature measurements. Encouragingly, gas temperatures measured in clusters by XMM and Chandra are consistent with one another at ~100–200 kpc radii, but XMM temperatures systematically decline relative to Chandra temperatures at larger radii. The angular dependence of the discrepancy suggests that additional investigation on systematics such as the XMM point-spread function correction, vignetting, and off-axis responses is yet required. We present the CLASH-X mass-profile comparisons in the form of cosmology-independent and redshift-independent circular-velocity profiles. We argue that comparisons of circular-velocity profiles are the most robust way to assess mass bias. Ratios of Chandra hydrostatic equilibrium (HSE) mass profiles to CLASH lensing profiles show no obvious radial dependence in the 0.3–0.8 Mpc range. However, the mean mass biases inferred from the weak-lensing (WL) and SaWLens data are different. As an example, the weighted-mean value at 0.5 Mpc is 〈b〉 = 0.12 for the WL comparison and 〈b〉 = −0.11 for the SaWLens comparison. The ratios of XMM HSE mass profiles to CLASH lensing profiles show a pronounced radial dependence in the 0.3–1.0 Mpc range, with a weighted mean mass bias value rising to 〈b〉 gsim 0.3 at ~1 Mpc for the WL comparison and 〈b〉 ≈ 0.25 for the SaWLens comparison. The enclosed gas mass profiles from both Chandra and XMM rise to a value ≈1/8 times the total-mass profiles inferred from lensing at ≈0.5 Mpc and remain constant outside of that radius, suggesting that M_gas × 8 profiles may be an excellent proxy for total-mass profiles at ≳ 0.5 Mpc in massive galaxy clusters.


publication date

  • January 1, 2014