The WISSH quasars project

Abstract

Winds accelerated by active galactic nuclei (AGNs) are invoked in the most successful models of galaxy evolution to explain the observed physical and evolutionary properties of massive galaxies. Winds are expected to deposit energy and momentum into the interstellar medium (ISM), thus regulating both star formation and supermassive black hole (SMBH) growth. We undertook a multiband observing program aimed at obtaining a complete census of winds in a sample of WISE/SDSS selected hyper-luminous (WISSH) quasars (QSOs) at z ≈ 2–4. We analyzed the rest-frame optical (i.e. LBT/LUCI and VLT/SINFONI) and UV (i.e. SDSS) spectra of 18 randomly selected WISSH QSOs to measure the SMBH mass and study the properties of winds both in the narrow line region (NLR) and broad line region (BLR) traced by blueshifted or skewed [OIII] and CIV emission lines, respectively. These WISSH QSOs are powered by SMBH with masses ≳109 M⊙ accreting at 0.4 < λEdd < 3.1. We found the existence of two subpopulations of hyper-luminous QSOs characterized by the presence of outflows at different distances from the SMBH. One population (i.e. [OIII] sources) exhibits powerful [OIII] outflows, a rest-frame equivalent width (REW) of the CIV emission REWCIV ≈ 20–40 Å, and modest CIV velocity shift (vCIVpeak) with respect to the systemic redshift (vCIVpeak <~ 2000 km s−1). The second population (i.e. Weak [OIII] sources), representing ~70% of the analyzed WISSH QSOs, shows weak or absent [OIII] emission and an extremely large blueshifted CIV emission (vCIVpeak up to ~8000 km s−1 and REWCIV <~ 20 Å). We propose two explanations for the observed behavior of the strength of the [OIII] emission in terms of the orientation effects of the line of sight and ionization cone. The dichotomy in the presence of BLR and NLR winds could be likely due to inclination effects considering a polar geometry scenario for the BLR winds. In a few cases these winds are remarkably as powerful as those revealed in the NLR in the [OIII] QSOs (Ėkin ~ 1044−45 erg s−1). We also investigated the dependence of these CIV winds on fundamental AGN parameters such as bolometric luminosity (LBol), Eddington ratio (λEdd), and UV-to-X-ray continuum slope (αOX). We found a strong correlation with LBol and an anti-correlation with αOX whereby the higher the luminosity, the steeper the ionizing continuum described by means of αOX and the larger the blueshift of the CIV emission line. Finally, the observed dependence vCIVpeak ∝ LBol0.28 ± 0.04 is consistent with a radiatively-driven-winds scenario, where a strong UV continuum is necessary to launch the wind and a weakness of the X-rayemission is fundamental to prevent overionization of the wind itself.

Prescriptions for Correcting Ultraviolet-based Redshifts for Luminous Quasars at High Redshift

“…3.1). Our measured velocity offset of the C IV line (−5097 km s −1 ) is consistent, within the errors, with the value reported in Table 6 of Vietri et al (2018) for the source (−4670 km s −1 ). Such sources may point to additional spectral parameters that should be taken into account in future prescriptions for UV-based redshift corrections.…”

Extreme Quasars as Distance Indicators in Cosmology

“…A quasars -suggests that a virialized sub-system emitting mainly LILs coexists with outflowing gas. Even at the highest luminosity the data (Sulentic et al, 2017;Vietri et al, 2018;Coatman et al, 2016) remain consistent with a scenario that posits a dichotomy within the BLR, where the blue shifted emission is produced in clumps of gas or a continuous wind (Collin-Souffrin et al, 1988;Elvis, 2000), and LILs are emitted by gas in virial motion. In this scenario, we observe a net blueshift in CIVλ1549 because of the large gas velocity field component along the radial direction, with the receding side of the flow obscured by an optically thick equatorial structure, most likely associated with the accretion disk.…”

“…The comparison between LILs and HILs has provided insightful constraints of the BLR at low-z (Marziani et al, 1996), and this is even more true if the comparison of Hβ and CIVλ1549 is carried out at high L (Sulentic et al, 2017;Bisogni et al, 2017;Shen, 2016;Vietri et al, 2018). Perhaps the most remarkable fact is that a LIL-BLR appears to remain basically virialized (Marziani et al, 2009;Sulentic et al, 2017).…”

Universal bolometric corrections for active galactic nuclei over seven luminosity decades

“…Many authors have found a correlation (although with a huge scatter) between the bolometric correction and either the Eddington ratio (λ EDD = L bol /L EDD ) or the BH mass (e.g., Vasudevan & Fabian 2007;Vasudevan et al 2009;Lusso et al 2010). We studied these dependencies using the same samples presented above, but limited only to the 745 objects for which the M BH has been measured: 21 type 1 and 15 type 2 sources by Onori et al (2017b) for the SWIFT/BAT sample (which M BH has been derived from reverberation mapping techniques and deep NIR spectroscopy, see Section 2); 11 WISSH type 1 sources (with Hβ-based virial masses provided in Vietri et al 2018); 661 COSMOS AGN by L12 (with masses obtained from virial estimators for the type 1 AGN and from M BH -M * relations plus morphological information for the type 2 sub-sample); and the 37 XXL sources (which have virial masses estimated from Hβ, Mg II and C IV broad lines). To have measurements as homogeneous as possible, we re-scaled the BH mass values of the SWIFT sample by assuming the same virial factor (f=5.5) as the other samples (rather than f=4.31 as in Ricci et al 2017c).…”