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The WISSH quasars project: revealing ultra-massive black-holes and powerful winds in the most luminous AGN
13 giugno 2017 @ 11:45 - 12:45
The systematic investigation of hyper-luminous quasars shining at the golden epoch of AGN activity offers the unique opportunity of studying the power and the effect of AGN feedback at its extreme.
The WISE/SDSS selected hyper-luminous (WISSH) quasar survey is an extensive
multi-band observing program (from millimeter wavelengths to hard X rays) designed to accurately probe the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows.
Our on-going project aims at constraining both AGN and host galaxy ISM and star-formation properties in a large sample of ~90 broad-line quasars at the brightest end of the AGN luminosity function (L_bol > 1e14 L_sun), and at the peak of their number density (z ~ 2.5 – 3.5).
I will review the most important results of the near-IR spectroscopic follow-up of WISSH quasars (available for ~40% of the sample) performed with the LUCI at LBT and SINFONI.
We found that WISSH quasars are typically powered by highly accreting (0.3-3 Ledd), ten billion solar masses SMBHs, demonstrating that WISSH provides a simple and valuable tool to complete the census of the extreme SMBH population in the universe. We also succeeded in discovering [OIII] emission lines with a broad, skewed profile and exceptional luminosities (> 6e44 erg/s), tracing very powerful ionized outflows (up to ~4% of L_bol) in ~30% of the sample.
Remarkably, the remaining 70% of quasars lacks [OIII] emission but shows strong winds traced by 3,000-8,000 km/s blueshifts of the high-ionization (CIV) with respect to low-ionization (Hbeta) broad emission lines, revealing strong radiatively driven winds that dominate the BLR kinematics. Finally, I will discuss the possible causes behind this intriguing dichotomy which involve fundamental parameters such as bolometric luminosity, SMBH mass, Eddington ratio and the shape of the UV-X-ray spectrum.