On 24 February 2026,  Brian McNamara (University of Waterloo) will present “XRISM’s New Perspective on the X-ray Atmospheres of Galaxy Clusters.”

Abstract: The XRISM X-ray Observatory has observed nearly two dozen cluster and group atmospheres since its launch in 2023.  XRISM’s prime camera, Resolve, is delivering ~5eV spectral resolution from about 1 keV to beyond 6 keV.  Atmospheric radial velocities and velocity dispersions are measured to precisions of tens of km/s.  Bulk motions with speeds upward of 300 km/s are revealing complex atmospheric gas flows associated with mergers in bright clusters.  However, ratios of kinetic to thermal energy of only a few percent or less are in tension with some cosmological models.  The level of atmospheric turbulence in cooling flow clusters with powerful radio sources is surprisingly low.  No trend between jet power and atmospheric velocity dispersion has emerged.   In most systems, heating by turbulent dissipation driven by jets and bubbles would have great difficulty offsetting atmospheric cooling.  Abundance measurements of the iron-peak elements Fe, Ni, Cr and lighter elements including, Ca, Ar, S, Si are beginning to provide new insights into the cosmic history of chemical enrichment.  Finally, relatively cool (<2 keV), high velocity dispersion (~300 km/s) gas discovered in four clusters hints at an exciting new atmospheric gas component of unknown origin.   I will briefly review these and other exciting results from XRISM, and I will give my views of where this research is headed in the future.

The webinar connection details are as follows:

https://rediris.zoom.us/j/99783070475?pwd=NbKWzgrq7oOYcY6xIOHpvWp9IEJpOt.1

Passcode: 083854

Further information, including the code of conduct, is accessible on the dedicated website.