A Chandra Study of Temperature Distributions of the Intracluster Medium in 50 Galaxy Clusters

Abstract

To investigate the spatial distribution of the intracluster medium temperature in galaxy clusters in a quantitative way and probe the physics behind it, we analyze the X-ray spectra from a sample of 50 clusters that were observed with the Chandra ACIS instrument over the past 15 years and measure the radial temperature profiles out to 0.45r 500. We construct a physical model that takes into consideration the effects of gravitational heating, thermal history (such as radiative cooling, active galactic nucleus feedback, and thermal conduction), and work done via gas compression, and use it to fit the observed temperature profiles by running Bayesian regressions. The results show that in all cases our model provides an acceptable fit at the 68% confidence level. For further validation, we select nine clusters that have been observed with both Chandra (out to ≳0.3r 500) and Suzaku (out to ≳1.5r 500) and fit their Chandra spectra with our model. We then compare the extrapolation of the best fits with the Suzaku measurements and find that the model profiles agree with the Suzaku results very well in seven clusters. In the remaining two clusters the difference between the model and the observation is possibly caused by local thermal substructures. Our study also implies that for most of the clusters the assumption of hydrostatic equilibrium is safe out to at least 0.5r 500 and the non-gravitational interactions between dark matter and its luminous counterparts is consistent with zero.

The Megaparsec-scale Gas-sloshing Spiral in the Remnant Cool Core Cluster Abell 1763

“…The abundance was fixed at the standard value of 0.3 Z . Similar to the results presented in Zhu et al (2016), the temperature of the cluster as a function of radius was found to be flat out to r 500 .…”

The Merger Dynamics of the Galaxy Cluster Abell 1775: New Insights from Chandra and XMM-Newton for a Cluster Simultaneously Hosting a WAT and a NAT Radio Sources

“…We find that the azimuthally averaged projected gas temperature shows a small increase from 3.20 +0.15 −0.16 keV in the innermost region (< 0 .6 or 48.6 kpc) to 4.15 ± 0.17 keV at ∼ 1 (∼ 81 kpc), and a gradual descent in 2 , which agrees with the temperature profile obtained with the Chandra ACIS data in the W sector ( §3.2). This profile is similar to those obtained in other galaxy clusters, which typically show an outward temperature increase in the inner regions to a peak value at ∼ 0.2r 500 and then a continuous temperature drop out to about r 500 (Zhu et al 2016), implying that within about 0.2r 500 the thermodynamic effect of the gravity has been greatly modified by the effects of non-gravitational processes (essentially radiative cooling and AGN feedback), while in outer regions the gravity dominates the gas thermodynamics (Zhu et al 2021). The azimuthally averaged projected metal abundance shows a significant peak of 0.89 +0.18 −0.16 Z in the innermost region (< 0 .6 or 48.6 kpc) and a monotonous outward decrease to a very low value (∼ 0.1 Z ) in the outermost annuli.…”

“…The gas and total gravitational masses of Abell 1775 can be determined by applying a revised thermodynamical ICM (RTI) model provided by Zhu et al (2016Zhu et al ( , 2021, which takes into account the effects of both gravitating and non-gravitational processes (e.g., feedback and radiation). In the RTI model, the total gravitational mass is described by using the generalized NFW profile (Navarro, Frenk & White 1997)…”

Discovering the most elusive radio relic in the sky: diffuse shock acceleration caught in the act?

“…However, a Dressler and Shectman three-dimensional test of the galaxy redshifts suggests that the cluster is disturbed (Lopes et al 2018). The radius of the cluster is R 500 = 1.56 ± 0.06, 1.1 +0.3 −0.1 Mpc depending on the mass estimate, which is debated between the values M 500 = 11.7 ± 1.4, 4.0 +5.2 −1.1 , and 3.73 +0.18 −0.19 , in units of 10 14 M , derived from radial velocity distribution, Chandra and Planck data, respectively (Planck Collaboration XXVII 2016; Zhu et al 2016;Lopes et al 2018). At larger radii, R 200 = 2.2 ± 0.1 Mpc and M 200 = 12.7 ± 1.5 × 10 14 M (Lopes et al 2018;Oh et al 2018).…”