Volume 578, June 2015
|Number of page(s)||6|
|Published online||15 June 2015|
The most obscured AGN in the COSMOS field
Dipartimento di Fisica e AstronomiaUniversità di Bologna,
Viale Berti Pichat 6/2,
2 INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 Physics Department, University of Zagreb, Bijenicka cesta 32, 10002 Zagreb, Croatia
4 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
5 INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
Received: 6 March 2015
Accepted: 15 April 2015
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.
Key words: galaxies: active / galaxies: nuclei / X-rays: galaxies
© ESO, 2015
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.