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Title: First hard x-ray detection of the non-thermal emission around the arches cluster: Morphology and spectral studies with NuSTAR

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 scenarioþ.
Authors:
; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ; ; ;  [5] ; ; ;  [6] ;  [7] ;  [8] ;  [9]
  1. Space Science Lab, University of California, Berkeley, CA 94720 (United States)
  2. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catlica de Chile, Casilla 306, Santiago 22 (Chile)
  3. MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 (United States)
  4. DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
  5. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
  6. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
  7. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  8. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  9. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22348091
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC RADIATION; DETECTION; EMISSION; EXCITATION; GALAXIES; HARD X RADIATION; KEV RANGE; LIMITING VALUES; LUMINOSITY; PHOTOIONIZATION; PROTONS; REFLECTION; SPATIAL DISTRIBUTION; SPECTRA; STAR CLUSTERS; STARS