Quasars are some of the brightest astronomical objects and are a subclass of active galactic nuclei. They have been the subject of much research in the astronomical community, and their properties have been studied extensively over the past several decades. In this article, we will take a look at the findings of a recent study on quasars, which was conducted by Wei-Rong Huang and published in 2023.
The study, titled “Quasar Properties from the Sloan Digital Sky Survey. III. The Quasars Obtained by the SDSS-IV”, focuses on the properties of quasars that were newly obtained by the Sloan Digital Sky Survey (SDSS) during its fourth stage (SDSS-IV). The authors of the study measured the main properties of emission lines around the C IV, Mg II, Hβ, and Hα spectral regions, and estimated the quasar redshifts from narrow [O III], broad Mg II, and broad C IV emission lines.
One of the key findings of the study is that the redshifts estimated from the fits of the broad C IV, Mg II, Hβ, and Hα emission lines are robust. The authors also calculated the virial black hole mass using empirical relationships provided by previous works, and found that there are systematic biases among the different line-based mass estimators.
The study also found that about 10% of the quasar spectra have strong associated C IV λλ1548, 1551 absorption lines, and at least one strong Mg II λλ2796, 2803 associated absorption line is overlaid on the profile of the Mg II emission line for about 5% of the quasar spectra. The authors found that about 89%, 99%, 98%, and 97% of the fits have reduced χ2 < 3 in the C IV, Mg II, Hβ, and Hα spectral regions, respectively.
The main results of the study are the determination of the quasar redshifts by the fitting results of the narrow [O III], broad C IV, or broad Mg II emission lines. The authors also updated the catalog of quasar properties, which includes the main characteristics of emissions around the C IV, Mg II, Hβ, and Hα spectral regions for 225,082 quasars that are newly included in Data Release 16 of the Quasar Catalog (DR16Q) with respect to DR14Q.
Source : Wei-Rong Huang et al 2023 ApJS 264 52 https://doi.org/10.3847/1538-4365/aca6e2