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Published February 1, 2014 | Published + Submitted
Journal Article Open

First Hard X-Ray Detection of the Non-thermal Emission around the Arches Cluster: Morphology and Spectral Studies with NuSTAR

Abstract

The Arches cluster is a young, densely packed massive star cluster in our Galaxy that shows a high level of star formation activity. The nature of the extended non-thermal X-ray emission around the cluster remains unclear. The observed bright Fe Kα line emission at 6.4 keV from material that is neutral or in a low ionization state can be produced either by X-ray photoionization or by cosmic-ray particle bombardment or both. In this paper, we report on the first detection of the extended emission around the Arches cluster above 10 keV with the NuSTAR mission, and present results on its morphology and spectrum. The spatial distribution of the hard X-ray emission is found to be consistent with the broad region around the cluster where the 6.4 keV line is observed. The interpretation of the hard X-ray emission within the context of the X-ray reflection model puts a strong constraint on the luminosity of the possible illuminating hard X-ray source. The properties of the observed emission are also in broad agreement with the low-energy cosmic-ray proton excitation scenario.

Additional Information

© 2014 American Astronomical Society. Received 2013 September 30; accepted 2013 December 7; published 2014 January 15. This work was supported under NASA Contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). F.E.B. acknowledges support from Basal-CATA (PFB-06/2007) and CONICYT-Chile (FONDECYT 1101024 and Anillo ACT1101). R.K. thanks Eugene Churazov for fruitful discussions and valuable suggestions to the paper. Facility: NuSTAR

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Published - 0004-637X_781_2_107.pdf

Submitted - 1312.2635v1.pdf

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