The soft-X-ray emission of Ark 120. XMM-Newton, NuSTAR, and the importance of taking the broad view
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Date
2014
Journal Title
Journal ISSN
Volume Title
Publisher
OXFORD UNIV PRESS
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 similar to 0.3 keV and an optical depth of similar to 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.
Description
Keywords
accretion, accretion discs, galaxies: active, galaxies: individual: Ark 120, ACTIVE GALACTIC NUCLEI, BLACK-HOLE SPIN, LINE REGION SIZES, SUZAKU OBSERVATIONS, CENTRAL MASSES, SKY SURVEY, SPECTRA, EXCESS, PHOTOIONIZATION, SEYFERT-1