@article{10902/34240,
year = {2019},
month = {9},
url = {https://hdl.handle.net/10902/34240},
abstract = {NGC 3147 has been considered the best case of a true type 2 AGN: an unobscured AGN,
based on the unabsorbed compact X-ray continuum, which lacks a broad-line region (BLR).
However, the very low luminosity of NGC 3147 implies a compact BLR, which produces very
broad lines, hard to detect against the dominant background host galaxy. Narrow (0.1 arcsec × 0.1 arcsec) slit HST spectroscopy allowed us to exclude most of the host galaxy light, and
revealed an H α line with an extremely broad base (FWZI∼27 000 km s−1). The line profile
shows a steep cut-off blue wing and an extended red wing, which match the signature of a
mildly relativistic thin accretion disc line profile. It is indeed well fit with a nearly face on thin
disc, at i ∼ 23º , with an inner radius at 77 ± 15 rg, which matches the prediction of 62+¹⁸
−₁₄ rg from the RBLR–L1/2 relation. This result questions the very existence of true type 2 AGN. Moreover, the detection of a thin disc, which extends below 100 rg in an L/LEdd ∼ 10−⁴ system, contradicts the current view of the accretion flow configuration at extremely low accretion rates.},
organization = {We thank the anonymous referee and H. Tran for the 2003 Keck spectrum of NGC 3147. SB acknowledges financial support from the Italian Space Agency under grant ASI-INAF 2017-14-H.O. FJC acknowledges financial support through grant AYA2015-64346-C2- 1P (MINECO/FEDER).},
publisher = {Oxford University Press},
publisher = {Monthly Notices of the Royal Astronomical Society: Letters, 2019, 488(1), L1-L5},
title = {HST unveils a compact mildly relativistic broad-line region in the candidate true type 2 NGC 3147},
author = {Bianchi, Stefano and Antonucci, Robert and Capetti, Alessandro and Chiaberge, Marco and Laor, Ari and Bassani, Loredana and Carrera Troyano, Francisco Jesús and La Franca, Fabio and Marinucci, Andrea and Matt, Giorgio and Middei, Riccardo and Panessa, Francesca},
}