The soft-X-ray emission of Ark 120. XMM–Newton, NuSTAR, and the importance of taking the broad view

Creators: Matt, G.; Marinucci, A.; Guainazzi, M.; Brenneman, L. W.; Elvis, M.; Lohfink, A.; Arèvalo, P.; Boggs, S. E.; Cappi, M.; Christensen, F. E.; Craig, W. W.; Fabian, A. C.; Fuerst, F.; Hailey, C. J.; Harrison, F. A.; Parker, M.; Reynolds, C. S.; Stern, D.; Walton, D. J.; Zhang, W. W.

Abstract

We present simultaneous XMM–Newton and NuSTAR observations of the 'bare' Seyfert 1 galaxy, Ark 120, a system in which ionized absorption is absent. The NuSTAR hard-X-ray spectral coverage allows us to constrain different models for the excess soft-X-ray emission. Among phenomenological models, a cutoff power law best explains the soft-X-ray emission. This model likely corresponds to Comptonization of the accretion disc seed UV photons by a population of warm electrons: using Comptonization models, a temperature of ∼0.3 keV and an optical depth of ∼13 are found. If the UV-to-X-ray OPTXAGNF model is applied, the UV fluxes from the XMM–Newton Optical Monitor suggest an intermediate black hole spin. Contrary to several other sources observed by NuSTAR, no high-energy cutoff is detected with a lower limit of 190 keV.

Additional Information

© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. First published online: February 18, 2014. We thank the anonymous referee for useful comments which helped us to improve the clarity of the paper, and Chris Done for comments and advices on the OPTXAGNF model. This work has 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 NUSTARDAS jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). The work is also based on observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). GM and AM acknowledge financial support from Italian Space Agency under grant ASI/INAF I/037/12/0-011/13 and from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n.312789.

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Submitted - 1401.5235v1.pdf

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