The most obscured AGN in the COSMOS field

Lanzuisi, G. and Pernar, Margareta and Delvecchio, I. and Berta, S. and Brusa, M. and Cappelluti, N. and Comastri, A. and Gilli, R. and Gruppioni, C. and Mignoli, M. and Pozzi, F. and Vietri, G. and Vignali, C. and Zamorani, G. (2015) The most obscured AGN in the COSMOS field. Astronomy and Astrophysics, 578. A120. ISSN 0004-6361

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Abstract

Highly obscured active galactic nuclei (AGN) are common in nearby galaxies, but are difficult to observe beyond the local Universe, where they are expected to significantly contribute to the black hole accretion rate density. Furthermore, Compton-thick (CT) absorbers (NH >∼ 1024 cm−2) suppress even the hard X-ray (2−10 keV) AGN nuclear emission, and therefore the column density distribution above 1024 cm−2 is largely unknown. We present the identification and multi-wavelength properties of a heavily obscured (NH >∼ 1025 cm−2), intrinsically luminous (L2−10 > 1044 erg s−1) AGN at z = 0.353 in the COSMOS field. Several independent indicators, such as the shape of the X-ray spectrum, the decomposition of the spectral energy distribution and X-ray/[NeV] and X-ray/6 μm luminosity ratios, agree on the fact that the nuclear emission must be suppressed by a >∼1025 cm−2 column density. The host galaxy properties show that this highly obscured AGN is hosted in a massive star-forming galaxy, showing a barred morphology, which is known to correlate with the presence of CT absorbers. Finally, asymmetric and blueshifted components in several optical high-ionization emission lines indicate the presence of a galactic outflow, possibly driven by the intense AGN activity (LBol/LEdd = 0.3−0.5). Such highly obscured, highly accreting AGN are intrinsically very rare at low redshift, whereas they are expected to be much more common at the peak of the star formation and BH accretion history, at z ∼ 2−3. We demonstrate that a fully multi-wavelength approach can recover a sizable sample of such peculiar sources in large and deep surveys such as COSMOS.

Item Type: Article
Keywords: galaxies: active, galaxies: nuclei, X-rays: galaxies
Date: June 2015
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2015 ESO. Received 6 March 2015. Accepted 15 April 2015. Published online 15 June 2015.
Divisions: Faculty of Science > Department of Physics
Publisher: EDP Sciences
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 06 Sep 2017 16:11
Last Modified: 07 Sep 2017 12:48
URI: http://digre.pmf.unizg.hr/id/eprint/5549

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