Quasar Properties from the Sloan Digital Sky Survey. II. The Quasars Obtained by the SDSS-IV in the First Two Years

Abstract

This work aims to measure the properties of continuum and emission lines around C iv, Mg ii, Hβ, and Hα for the quasars observed by the extended Baryon Oscillation Spectroscopic Survey (eBOSS) during the first two years. We determine the quasar redshifts based on narrow [O iii] λ5007, broad Mg ii λ2799, and/or C iv λ1548 emission lines. The comparisons between the visual inspection redshifts included in DR14Q and the redshifts determined by us suggest that the visual inspection redshifts would be robust. We also infer the virial black hole mass of quasars based on C iv, Mg ii, Hβ, and/or Hα broad emission lines, using empirical relationships reported by previous studies. Systematic differences are remarkable among different line-based mass estimators reported by previous studies. Using the empirical relationship (Equation (1)), we improve the line-based mass estimators by recalibrating new coefficient (a, b), so that different line-based mass estimators are more consistent. We find that (a, b) = (0.96, 0.5), (0.91, 0.5), (0.82, 0.5), and (0.77, 0.5) are the best choices for the Hα-, Hβ-, Mg ii-, and C iv-based mass estimators, respectively. All these above properties are publicly available. We also find that the line and continuum luminosities are tightly correlated with each other. The Balmer lines show a negative Baldwin effect, while the metal lines display a positive Baldwin effect. In addition, we find that tight correlations are indwelled in different line luminosities.

Detections of inflowing gas from narrow absorption lines at parsec scales

“…The Mg ii emission line properties are measured from the spectra subtracted by the contin- uum+iron fits. We used two Gaussian functions to fit the Mg ii emission features, of which one, with FWHM > 1200 km s −1 (e.g., Shen et al 2011;Chen et al 2019), is for the broad Mg ii component, and the other one, whose FWHM is determined from the [O ii] emission lines, is for the narrow Mg ii component. During the fits of emission lines, we exclude the spectral data around the strong Mgii λλ2796,2803 absorption doublets.…”

“…where the calibrated coefficients (a, b) = (0.82, 0.5) are empirical values (e.g., Chen et al 2019), and the L 3000 is the monochromatic luminosity of each quasar at 3000 Å, which is estimated from the fitted power law. The bolometric luminosity of the quasars is directly derived from the monochromatic luminosity with standard bolometric correction, namely, L bol = 5.15L 3000 (Richards et al 2006).…”

“…The Eddington ratios of the nine quasars with inflowing Mg ii NALs are shown. We calculate the Eddingtong ratios for all the quasars with z em < 1.07 included in Chen et al (2018a), where their black hole mass is available from previous works (e.g., Shen et al 2011;Chen et al 2018bChen et al , 2019. The results are shown in Figure 6, which includes 2724 quasars.…”

The first high-redshift changing-look quasars

“…For equation (1), Vestergaard & Peterson (2006) measure γ = 0.53 and the offset as a = 0.660, and these estimates are widely adopted (e.g. Shen et al 2011;Chen et al 2019;Yao et al 2019). Kozłowski (2017) have similar values to Vestergaard & Peterson (2006) , with (a, γ ) = (0.64, 0.53), but note that there is a problem with the C IV FWHMs for those quasars that are reported in both the DR7 Quasar catalogue and DR12 Quasar catalogue.…”

Feii strength in NLS1s – dependence on the viewing angle and FWHM(Hβ)

“…Having a lower-than typical mass is a result of how the black hole mass (M BH ) is estimated. One of the methods to estimate the M BH is the dynamical method that involves the use of the virial relation (Chen et al 2019). According to this, the M BH is a function of (i) the size of the emitting region, here, the broad-line region (BLR); and (ii) the FWHM(Hβ) of the virialized gas.…”