NuSTAR HARD X-RAY SURVEY OF THE GALACTIC CENTER REGION. I. HARD X-RAY MORPHOLOGY AND SPECTROSCOPY OF THE DIFFUSE EMISSION

Journal Article · Tue Dec 01 00:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/814/2/94· OSTI ID:22521873

Mori, Kaya; Hailey, Charles J.; Perez, Kerstin; Nynka, Melania; Zhang, Shuo; Canipe, Alicia M. ^[1]; Krivonos, Roman; Tomsick, John A.; Barrière, Nicolas; Boggs, Steven E.; Craig, William W. ^[2]; Hong, Jaesub ^[3]; Ponti, Gabriele ^[4]; Bauer, Franz ^[5]; Alexander, David M. ^[6]; Baganoff, Frederick K. ^[7]; Barret, Didier ^[8]; Christensen, Finn E. ^[9]; Forster, Karl ^[10]; Giommi, Paolo ^[11] ; others, and

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1. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
2. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
3. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
4. Max-Planck-Institut f. extraterrestrische Physik, HEG, Garching (Germany)
5. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile)
6. Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
7. Kavli Institute for Astrophysics and Space Research, Massachusets Institute of Technology, Cambridge, MA 02139 (United States)
8. Université de Toulouse, UPS-OMP, IRAP, Toulouse (France)
9. DTU Space—National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
10. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
11. ASI Science Data Center, Via del Politecnico snc I-00133, Roma (Italy)

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{sup 23} cm{sup −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{sub X} ≳ 10{sup 38} erg s{sup −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{sub WD} ∼ 0.9 M{sub ⊙}. 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.

• OSTI ID: 22521873
• Journal Information: Astrophysical Journal, Vol. 814, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CLOUDS
COSMIC GAMMA SOURCES
ENERGY SPECTRA
FILAMENTS
FLUORESCENCE
HARD X RADIATION
KEV RANGE
LUMINOSITY
MASS
MILKY WAY
MONTE CARLO METHOD
MORPHOLOGY
NEBULAE
PULSARS
TEV RANGE
WHITE DWARF STARS
X-RAY SPECTRA