NuSTAR's Hard Look at Clusters and Relics: Bullet Cluster First Results
Abstract
Mergers between massive galaxy clusters are the most energetic events since the Big Bang, driving shocks and turbulence in the intracluster medium (ICM) that heats the gas and accelerates relativistic particles. Many disturbed clusters host radio halos, and detecting the corresponding inverse Compton (IC) emission is crucial for nailing down the average strength of the ICM magnetic field and thus the total energetics of its relativistic component. However, the lack of X-ray sensitivity at energies above 10 keV make robust measurements of >10 keV shock temperatures and IC emission extremely challenging. At present, IC detections are of low significance and/or are controversial, primarily due to natural uncertainties in the background of non-imaging instruments. NuSTAR's unprecedented spatial resolution and sensitivity above 10 keV promises to reduce these uncertainties and allow unambiguous confirmation or rejection of previous measurements. The first target of NuSTAR's galaxy cluster program is the Bullet cluster, which exhibits a luminous radio halo and potentially very hot (>15 keV) gas in a shock. We present preliminary results from the first 150 ks observation of the Bullet with NuSTAR, including images and spatially resolved spectra. Along with our expectations for the combination of this data with that from additional pointings, we summarize the remainder of the cluster program, including simulations of future targets.
- Publication:
-
American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22124420W