Volume 600, April 2017
|Number of page(s)||14|
|Published online||13 April 2017|
A high spectral resolution map of the nuclear emitting regions of NGC 7582
1 INAF–Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate (LC), Italy
2 Centre for Space Science and Technology, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
3 Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
4 Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
5 INAF–Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
6 INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
Received: 20 December 2016
Accepted: 13 February 2017
We present the results of the spatial and spectral analysis of the deep (~ 200 ks) Chandra HETG observation of the changing look AGN NGC 7582. During this long Chandra observation, NGC 7582 was in a highly obscured state. Therefore, we also consider a short (~ 24 ks) Suzaku observation, which caught NGC 7582 in a Compton thick state. This allows us to determine the underlying continuum model and the amount of absorption [NH = (1.2 ± 0.2) × 1024 cm-2]. A wealth of emission lines (from Mg, Si, S, and Fe) are detected in the Chandra data, which allows us to map the structure of the circumnuclear emitters. The high resolution spectrum reveals that the soft X-ray emission originates in a hybrid gas, which is ionized in part by the strong circumnuclear star-forming activity and in part by the central AGN. The high resolution images confirm that the emitting region is highly inhomogeneous and extends up to a few hundred pc from the nuclear source. The X-ray images are more extended in the lower energy lines (Ne and Mg) than in the higher energy lines (Si, Fe); the former are dominated by the collisionally ionized gas from the starburst and the latter by the photoionized AGN emission. This is supported by the analysis of the He-like triplets in the grating spectra. We deduce that a low density (ne ~ 0.3−1 cm-3) photoionized gas is responsible for the strong forbidden components, which is likely to originate from extended AGN narrow line region gas at distances of 200–300 pc from the black hole. We also detect an absorption feature at ~ 6.7 keV that is consistent with the rest frame energy of the resonance absorption line from Fe xxv (Elab = 6.7 keV), which traces the presence of a sub-parsec scale ionized circumnuclear absorber. The emerging picture is in agreement with our new view of the circumnuclear gas in AGN, where the medium is clumpy and stratified in both density and ionization. These absorbers and emitters are located on different scales, from the sub-pc broad line region gas out to the kpc scale of the galactic absorber.
Key words: galaxies: individual: NGC 7582 / X-rays: galaxies / galaxies: active
© ESO, 2017
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