A NuSTAR observation of the center of the Coma Cluster

TL;DR

This study uses NuSTAR X-ray observations to analyze the thermal and non-thermal emissions in the core of the Coma Cluster, setting upper limits on non-thermal inverse Compton emission and mapping temperature distribution.

Contribution

First NuSTAR observation of the Coma Cluster core providing constraints on non-thermal emission and detailed temperature mapping.

Findings

Thermal emission dominates the spectrum.

Upper limit on non-thermal IC emission is $5.1 imes 10^{-12}$ erg cm$^{-2}$ s$^{-1}$.

Temperature map shows a gradient from hot northwest to cooler southeast.

Abstract

We present the results of a 55ks NuSTAR observation of the core of the Coma Cluster. The global spectrum can be explained by thermal gas emission, with a conservative 90% upper limit to non-thermal inverse Compton (IC) emission of $5.1 \times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$ in a 12 arcmin $\times$ 12 arcmin field of view . The brightness of the thermal component in this central region does not allow more stringent upper limits on the IC component when compared with non-imaging instruments with much larger fields of view where claims of detections have been made. Future mosaic NuSTAR observations of Coma will further address this issue. The temperature map shows a relatively uniform temperature distribution with a gradient from the hot northwest side to the cooler southeast, in agreement with previous measurements. The temperature determination is robust given the flat effective area and low background in the 3-20 keV band, making NuSTAR an ideal instrument to measure high temperatures in the intracluster medium.