ATHENA Solution for the Cooling Flow Problem in Clusters of Galaxies
Abstract
The hot gas in the cores of many clusters and groups of galaxies has a cooling time shorter than 1Gyr. It is possible to probe cooling flows through the detection of cool Fe XVII and O VII emission lines. We recently detected for the first time O VII in a sample of nearby elliptical galaxy and galaxy group showing cooling of gas below 0.4 keV with high-resolution XMM-Newton grating spectra. Fe XVII and O VII appear to be produced by the same gas and provide cooling rates in agreement with theoretical predictions. In clusters of galaxy O VII as well as cooling below 0.4 has not yet been detected and Fe XVII lines also show a remarkable deficit compared to the predictions from radiative cooling flow models. AGN feedback, galactic mergers and sloshing are thought to give rise to heating and turbulence which may prevent cooling in clusters. It is possible to measure the turbulence of the hot gas in clusters by estimating the velocity widths of their X-ray emission lines. There are instrumental effects on the current X-ray satellites that significantly limit the line widths measurement and only upper-limits are so far obtained. The micro-calorimeter detectors aboard the future X-ray mission will overcome these limits and open a new frontier on the spatially-resolved measurements of turbulence in extended objects and the understanding of the interplay between feedback and cooling in clusters of galaxies. In this talk I will review the current state of art and the goals that will be reached with ASTRO-H and ATHENA.
- Publication:
-
Exploring the Hot and Energetic Universe: The first scientific conference dedicated to the Athena X-ray observatory
- Pub Date:
- September 2015
- Bibcode:
- 2015eheu.conf...19P