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Spatially resolving a starburst galaxy at hard x-ray energies: NuSTAR, CHANDRA and VLBA observations of NGC 253

Wik, D. R. and Lehmer, B. D. and Hornschemeier, A. E. and Yukita, M. and Ptak, A. and Zezas, A. and Antoniou, V. and Argo, M. K. and Bechtol, K. and Boggs, S. and Christensen, F. and Craig, W. and Hailey, C. and Harrison, F. A. and Krivonos, R. and Maccarone, T. J. and Stern, D. and Venters, T. and Zhang, W. W. (2014) Spatially resolving a starburst galaxy at hard x-ray energies: NuSTAR, CHANDRA and VLBA observations of NGC 253. Astrophysical Journal, 797 (2). Art. No. 79. ISSN 0004-637X. doi:10.1088/0004-637X/797/2/79.

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Prior to the launch of NuSTAR, it was not feasible to spatially resolve the hard (E > 10 keV) emission from galaxies beyond the Local Group. The combined NuSTAR data set, comprised of three similar to 165 ks observations, allows spatial characterization of the hard X-ray emission in the galaxy NGC 253 for the first time. As a follow up to our initial study of its nuclear region, we present the first results concerning the full galaxy from simultaneous NuSTAR, Chandra, and Very Long Baseline Array monitoring of the local starburst galaxy NGC 253. Above similar to 10 keV, nearly all the emission is concentrated within 100 '' of the galactic center, produced almost exclusively by three nuclear sources, an off-nuclear ultraluminous X-ray source (ULX), and a pulsar candidate that we identify for the first time in these observations. We detect 21 distinct sources in energy bands up to 25 keV, mostly consisting of intermediate state black hole X-ray binaries. The global X-ray emission of the galaxy-dominated by the off-nuclear ULX and nuclear sources, which are also likely ULXs-falls steeply (photon index greater than or similar to 3) above 10 keV, consistent with other NuSTAR-observed ULXs, and no significant excess above the background is detected at E > 40 keV. We report upper limits on diffuse inverse Compton emission for a range of spatial models. For the most extended morphologies considered, these hard X-ray constraints disfavor a dominant inverse Compton component to explain the. gamma-ray emission detected with Fermi and H.E.S.S. If NGC 253 is typical of starburst galaxies at higher redshift, their contribution to the E > 10 keV cosmic X-ray background is < 1%.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wik, D. R.0000-0001-8952-676X
Lehmer, B. D.0000-0003-2192-3296
Hornschemeier, A. E.0000-0001-8667-2681
Yukita, M.0000-0001-6366-3459
Ptak, A.0000-0001-5655-1440
Zezas, A.0000-0001-8952-676X
Antoniou, V.0000-0001-7539-1593
Boggs, S.0000-0001-9567-4224
Christensen, F.0000-0001-5679-1946
Harrison, F. A.0000-0003-2992-8024
Krivonos, R.0000-0003-2737-5673
Maccarone, T. J.0000-0003-0976-4755
Stern, D.0000-0003-2686-9241
Zhang, W. W.0000-0002-1426-9698
Additional Information:© 2014 American Astronomical Society. Received 2014 June 27, accepted for publication 2014 October 8. Published 2014 December 1. We thank the referee for insightful suggestions that improved the paper. This research was supported by an appointment (DRW) to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with the National Aeronautics and Space Administration (NASA) 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 NASA. 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). This work was also funded by a Chandra grant for Program #13620679 (PI: Hornschemeier). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme and operated under license.
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NASA Postdoctoral ProgramUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20150401-103251427
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56279
Deposited By: Joy Painter
Deposited On:01 Apr 2015 19:09
Last Modified:10 Nov 2021 20:57

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