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NuSTAR Hard X-ray Survey of the Galactic Center Region I: Hard X-ray Morphology and Spectroscopy of the Diffuse Emission

Mori, Kaya and Forster, Karl and Grefenstette, Brian W. and Harrison, Fiona A. and Madsen, Kristin K. and Mao, Peter H. and Miyasaka, Hiromasa and Rana, Vikram (2015) NuSTAR Hard X-ray Survey of the Galactic Center Region I: Hard X-ray Morphology and Spectroscopy of the Diffuse Emission. Astrophysical Journal, 814 (2). Art. No. 94. ISSN 0004-637X. doi:10.1088/0004-637X/814/2/94.

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We present the first sub-arcminute images of the Galactic Center above 10 keV, obtained with NuSTAR. NuSTAR resolves the hard X-ray source IGR J17456–2901 into non-thermal X-ray filaments, molecular clouds, point sources, and a previously unknown central component of hard X-ray emission (CHXE). NuSTAR detects four non-thermal X-ray filaments, extending the detection of their power-law spectra with Γ ~ 1.3–2.3 up to ~50 keV. A morphological and spectral study of the filaments suggests that their origin may be heterogeneous, where previous studies suggested a common origin in young pulsar wind nebulae (PWNe). NuSTAR detects non-thermal X-ray continuum emission spatially correlated with the 6.4 keV Fe Kα fluorescence line emission associated with two Sgr A molecular clouds: MC1 and the Bridge. Broadband X-ray spectral analysis with a Monte-Carlo based X-ray reflection model self-consistently determined their intrinsic column density (~10^(23) cm^(−2)), primary X-ray spectra (power-laws with Γ ~ 2) and set a lower limit of the X-ray luminosity of Sgr A* flare illuminating the Sgr A clouds to L_X ≳ 10^(38) erg s^(−1). Above ~20 keV, hard X-ray emission in the central 10 pc region around Sgr A* consists of the candidate PWN G359.95–0.04 and the CHXE, possibly resulting from an unresolved population of massive CVs with white dwarf masses M_(WD) ~ 0.9 M_⊙. Spectral energy distribution analysis suggests that G359.95–0.04 is likely the hard X-ray counterpart of the ultra-high gamma-ray source HESS J1745–290, strongly favoring a leptonic origin of the GC TeV emission.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Mori, Kaya0000-0002-9709-5389
Forster, Karl0000-0001-5800-5531
Grefenstette, Brian W.0000-0002-1984-2932
Harrison, Fiona A.0000-0003-2992-8024
Madsen, Kristin K.0000-0003-1252-4891
Miyasaka, Hiromasa0000-0002-8074-4186
Rana, Vikram0000-0003-1703-8796
Additional Information:© 2015 American Astronomical Society. Received 2015 June 8; accepted 2015 October 14; published 2015 November 19. 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). R. Krivonos acknowledges support from Russian Science Foundation through grant 14–22-00271. G. Ponti acknowledges support via an EU Marie Curie IntraEuropean fellowship under contract no. FP-PEOPLE-2012-IEF-331095, the Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luft- und Raumfahrt (BMWI/DLR, FKZ 50 OR 1408) and the Max Planck Society. F.E. Bauer acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007, FONDECYT 1141218, "EMBIGGEN" Anillo ACT1101), and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. S. Zhang is supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program—Grant "NNX13AM31." D. Barret acknowledges support from the French Space Agency (CNES). We thank Tahir Yaqoob for useful discussions on the MYTorus model.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Russian Science Foundation14-22-00271
Marie Curie FellowshipFP-PEOPLE-2012-IEF-331095
Bundesministerium für Wirtschaft und Technologie (BMWi)BMWI/DLR, FKZ 50 OR 1408
Max Planck SocietyUNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)Anillo ACT1101
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoMinistry for the Economy, Development, and Tourism’s Millennium Science InitiativeIC120009
NASA Earth and Space Science FellowshipNNX13AM31
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Subject Keywords:Galaxy: center; radiation mechanisms: non-thermal; X-rays: general; X-rays: ISM
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-19
Issue or Number:2
Record Number:CaltechAUTHORS:20151223-064848832
Persistent URL:
Official Citation:Kaya Mori et al 2015 ApJ 814 94
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63162
Deposited By: Ruth Sustaita
Deposited On:23 Dec 2015 18:37
Last Modified:10 Nov 2021 23:12

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