The WISSH quasars project

I. Powerful ionised outflows in hyper-luminous quasars

¹ INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monte Porzio Catone (Roma), Italy
e-mail: manuela.bischetti@oa-roma.inaf.it
² Università degli Studi di Roma “Tor Vergata”, via Orazio Raimondo 18, 00173 Roma, Italy
³ Università degli Studi di Roma “La Sapienza”, Piazzale Aldo Moro 5, 00185 Roma, Italy
⁴ European Southern Observatory (ESO), Alonso de Cordova 3107, Cassilla 19001, Vitacura, Santiago 19, Chile
⁵ Dipartimento di Fisica e Astronomia, Università di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Firenze), Italy
⁶ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁷ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
⁸ Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁹ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹⁰ INAF–Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy
¹¹ European Southern Observatory, Karl-Schwarzschild-str. 2, 85748 Garching bei München, Germany

Received: 13 July 2016
Accepted: 9 December 2016

Abstract

Models and observations suggest that both the power and effects of AGN feedback should be maximised in hyper-luminous (L_Bol > 10⁴⁷ erg s^-1) quasars, i.e. objects at the brightest end of the AGN luminosity function. In this paper, we present the first results of a multiwavelength observing programme, focusing on a sample of WISE/SDSS selected hyper-luminous (WISSH) broad-line quasars at z ≈ 1.5–5. The WISSH quasars project has been designed to reveal the most energetic AGN-driven outflows, estimate their occurrence at the peak of quasar activity, and extend the study of correlations between outflows and nuclear properties up to poorly investigated, extreme AGN luminosities, i.e. L_Bol ~ 10⁴⁷ − 10⁴⁸ erg s^-1. We present near-infrared, long-slit LBT/LUCI1 spectroscopy of five WISSH quasars at z ≈ 2.3 − 3.5, showing prominent [OIII] emission lines with broad (FWHM ~1200–2200 km s^-1) and skewed profiles. The luminosities of these broad [OIII] wings are the highest measured so far, with L_[OIII]^broad ≳ 5 × 10⁴⁴ erg s^-1, and reveal the presence of powerful ionised outflows with associated mass outflow rates Ṁ ≳ 1700M_⊙ yr^-1 and kinetic powers Ė_kin ≳ 10⁴⁵ erg s^-1. Although these estimates are affected by large uncertainties because of the use of [OIII] as a tracer of ionised outflows and the very basic outflow model adopted here, these results suggest that in our hyper-luminous targets the AGN is highly efficient at pushing large amounts of ionised gas outwards. Furthermore, the mechanical outflow luminosities measured for WISSH quasars correspond to higher percentages (~1–3%) of L_Bol than those derived for AGN with lower L_Bol. Our targets host very massive (M_BH ≳ 2 × 10⁹M_⊙) black holes that are still accreting at a high rate (i.e. a factor of ~0.4–3 of the Eddington limit). These findings clearly demonstrate that WISSH quasars offer the opportunity to probe the extreme end of both luminosity and supermassive black holes (SMBH) mass functions and revealing powerful ionised outflows that are able to affect the evolution of their host galaxies.