This is the second in a series of papers aiming to test how the mass (M BH ), accretion rate (Ṁ ) and spin (a * ) of super massive black holes (SMBHs) determine the observed properties of type-I active galactic nuclei (AGN). Our project utilizes a sample of 39 unobscured AGN at z 1.55 observed by VLT/X-shooter, selected to map a large range in M BH and L/L Edd and covers the most prominent UV-optical (broad) emission lines, including Hα, Hβ, Mg II λ2798, and C IV λ1549. This paper focuses on single-epoch, "virial" M BH determinations from broad emission lines and examines the implications of different continuum modeling approaches in line width measurements. We find that using a local power-law continuum instead of a physically-motivated thin disk continuum leads to only slight underestimation of the FWHM of the lines and the associated M BH (FWHM). However, the line dispersion σ line and associated M BH (σ line ) are strongly affected by the continuum placement and provides less reliable mass estimates than FWHM-based methods. Our analysis shows that Hα, Hβ and Mg II can be safely used for virial M BH estimation. The C IV line, on the other hand, is not reliable in the majority of the cases, this may indicate that the gas emitting this line is not virialized. While Hα and Hβ show very similar line widths, the mean FWHM(Mg II) is about 30% narrower than FWHM(Hβ). We confirm several recent suggestions to improve the accuracy in C IV-based mass estimates, relying on other UV emission lines. Such improvements do not reduce the scatter between C IV-based and Balmer-line-based mass estimates.

Supermassive black holes reside in the nuclei of most galaxies. Accurately determining their mass is key to understand how the population evolves over time and how the black holes relate to their host galaxies [1][2][3] . Beyond the local universe, the mass is commonly estimated assuming virialized motion of gas in the close vicinity to the active black holes, traced through broad emission lines 4, 5 . However, this procedure has uncertainties associated with the unknown distribution of the gas clouds. Here we show that the comparison of black hole masses derived from the properties of the central accretion disc with the virial mass estimate provides a correcting factor, for the virial mass estimations, that is inversely proportional to the observed width of the broad emission lines. Our results suggest that line-of-sight inclination of gas in a planar distribution can account for this effect. However, radiation pressure effects on the distribution of gas can also reproduce our findings. Regardless of the physical origin, our findings contribute to mitigate the uncertainties in current black hole mass estimations and, in turn, will help to further understand the evolution of distant supermassive black holes and their host galaxies.Active Supermassive black holes (SMBHs) are powered by accretion flows, probably in the form of accretion discs (ADs) that convert gravitational energy into radiation 6 . Gas in the Broad Line Region (BLR), located in the vicinity of the SMBH and moving at Keplerian velocities of thousands of kilometres per second, is photo-ionized by the AD producing broad emission lines. Under virial equilibrium, the observed width of these lines (in terms of full width at half maximum, FWHM obs ) can be used as a proxy for the virial velocity (VBLR) and MBH can be expressed as:Here, G is the gravitational constant, RBLR is the mean BLR distance to the SMBH and f is the virial factor that accounts for the differences between the unknown VBLR and FWHM obs that are mostly caused by the BLR gas distribution of each object. Since even in the closest active galaxies the BLR cannot be resolved with current capabilities, RBLR is estimated from reverberation mapping (RM) experiments that show a strong correlation between the typical distance to the Hβ emitting region and the continuum luminosity (the RBLR − L relation) 7,8 . f is assumed to be constant for all systems and is usually determined by requiring RM-based masses (from Equation 1) to agree, on average, with masses estimated from the relation between MBH and the stellar velocity dispersion found in local galaxies [9][10][11] . This indirect technique to determine MBH is known as the "single epoch virial method" 4, 5 .

The physics of active super massive black holes (BHs) is governed by their mass (M BH ), spin (a * ) and accretion rate (Ṁ ). This work is the first in a series of papers with the aim of testing how these parameters determine the observable attributes of active galactic nuclei (AGN). We have selected a sample in a narrow redshift range, centered on z ∼ 1.55, that covers a wide range in M BH andṀ , and are observing them with X-shooter, covering rest wavelengths ∼1200-9800Å. The current work covers 30 such objects and focuses on the origin of the AGN spectral energy distribution (SED). After estimating M BH andṀ based on each observed SED, we use thin AD models and a Bayesian analysis to fit the observed SEDs in our sample. We are able to fit 22/30 of the SEDs. Out of the remaining 8 SEDs, 3 can be fit by the thin AD model by correcting the observed SED for reddening within the host galaxy and 4 can be fit by adding a disc wind to the model. In four of these 8 sources, Milky Way-type extinction, with the strong 2175Å feature, provides the best reddening correction. The distribution in spin parameter covers the entire range, from −1 to 0.998, and the most massive BHs have spin parameters greater than 0.7. This is consistent with the "spin-up" model of BH evolution. Altogether, these results indicate that thin ADs are indeed the main power houses of AGN, and earlier claims to the contrary are likely affected by variability and a limited observed wavelength range.

We present Reverberation Mapping (RM) results for 17 high-redshift, high-luminosity quasars with good quality R-band and emission line light curves. We are able to measure statistically significant lags for Lyα (11 objects), SiIV (5 objects), CIV (11 objects), and CIII] (2 objects). Using our results and previous lag determinations taken from the literature, we present an updated CIV radiusluminosity relation and provide for the first time radius-luminosity relations for Lyα, SiIV and CIII]. While in all cases the slope of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low luminosity end. We find that the emissivity weighted distance from the central source of the Lyα, SiIV and CIII] line emitting regions are all similar, which corresponds to about half that of the Hβ region. We also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the Lyα light curve and one in the SiIV light curve, in that they do not seem to follow the variability of the UV continuum. Finally, we compute RM black hole masses for those quasars with highly significant lag measurements and compare them with CIV single-epoch (SE) mass determinations. We find that the RM-based black hole mass determinations seem smaller than those found using SE calibrations.

We present the active galactic nucleus (AGN) catalog and optical spectroscopy for the second data release of the Swift BAT AGN Spectroscopic Survey (BASS DR2). With this DR2 release we provide 1449 optical spectra, of which 1182 are released for the first time, for the 858 hard-X-ray-selected AGNs in the Swift BAT 70-month sample. The majority of the spectra (801/1449, 55%) are newly obtained from Very Large Telescope (VLT)/X-shooter or Palomar/Doublespec. Many of the spectra have both higher resolution (R > 2500, N ∼ 450) and/or very wide wavelength coverage (3200–10000 Å, N ∼ 600) that are important for a variety of AGN and host galaxy studies. We include newly revised AGN counterparts for the full sample and review important issues for population studies, with 47 AGN redshifts determined for the first time and 790 black hole mass and accretion rate estimates. This release is spectroscopically complete for all AGNs (100%, 858/858), with 99.8% having redshift measurements (857/858) and 96% completion in black hole mass estimates of unbeamed AGNs (722/752). This AGN sample represents a unique census of the brightest hard-X-ray-selected AGNs in the sky, spanning many orders of magnitude in Eddington ratio (L/L Edd = 10−5–100), black hole mass (M BH = 105–1010 M ⊙), and AGN bolometric luminosity (L bol = 1040–1047 erg s−1 ).