Related papers: CIV 1549 as an Eigenvector 1 Parameter for Active …
Using a sample of 3814 quasars from the Sloan Digital Sky Survey, we confirm that high-ionization, broad, emission lines such as CIV are significantly blueshifted with respect to low-ionization, broad, emission lines such as MgII. CIV…
Single-epoch virial black hole (BH) mass estimators utilizing broad emission lines have been routinely applied to high-redshift quasars to estimate their BH masses. Depending on the redshift, different line estimators (Halpha, Hbeta, MgII,…
We revisit the Quasar Main Sequence (QMS) by investigating the impact of the stellar component from the host galaxy (HG) on the emission line spectra of the active galactic nuclei (AGN). We first detect spectra with broad emission lines…
Our analysis is aimed at characterizing the properties of the integrated spectrum of active galactic nuclei (AGNs) such as the ubiquity of the Fe K{\alpha} emission in AGNs and the dependence of the spectral parameters on the X-ray…
We present the emission properties of a sample of 3,579 type 1 AGN, selected based on the detection of broad H-alpha emission. The sample covers the range of black hole mass 10^6<M_BH/M_Sun<10^9.5 and luminosity in Eddington units 10^-3 <…
We present a multiwavelength spectral study of the quasar HE0359-3959, which has been identified as an extreme radiating source at intermediate redshift (z=1.5209). Along the spectral range, the different ionic species give information…
We have compiled a sample of 165 radio galaxies from the literature to study the properties of the extended emission line regions and their interaction with the radio source over a large range of redshift 0<z<5.2. For each source, we have…
We surveyed the HST UV spectra of 49 low-redshift quasars for z < 1 CIV candidates, relying solely on the characteristic wavelength separation of the doublet. After consideration of the defining traits of CIV doublets (e.g., consistent line…
In large optical survey at high redshifts ($z>2$), the CIV broad emission line is the most practical alternative to estimate the mass ($M_{\text{BH}}$) of active super-massive black holes (SMBHs). However, mass determinations obtained with…
A new, complete sample of 14,584 broad-line AGNs at $z<0.35$ is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release.…
We have investigated the distribution and evolution of ~3100 intergalactic HI absorbers with HI column densities log N(HI) = [12.75, 17.0] at 1.9 < z < 3.2, using 18 high resolution, high S/N quasar spectra obtained from the ESO VLT/UVES…
From a parent catalog of 561 changing-look active galactic nuclei (CL-AGNs) identified by Guo et al. (2025), we investigate the evolutionary sequence of broad emission lines using a redshift-selected subset (0.35 < z < 0.45) of 54 CL-AGNs…
We have investigated the broad-line Balmer decrements (Halpha/Hbeta) for a large, homogeneous sample of Seyfert 1 galaxies and QSOs using spectroscopic data obtained in the Sloan Digital Sky Survey. The sample, drawn from the Fourth Data…
We investigate the relationship between the rest-frame equivalent width (EW) of the C IV \lambda1549 broad-emission line, monochromatic luminosity at rest-frame 5100 A, and the Hbeta-based Eddington ratio in a sample of 99 ordinary quasars…
Recently, the CIII] and CIV emission lines have been observed in galaxies in the early Universe ($z>5$), providing new ways to measure their redshift and study their stellar populations and AGN. We explore the first blind CII], CIII] and…
The study of narrow-line Seyfert 1 galaxies (NLS1s) is now mostly limited to low redshift ($z<0.8$) because their definition requires the presence of the H$\beta$ emission line, which is redshifted out of the spectral coverage of major…
We use the Sloan Digital Sky Survey (SDSS) Quasar Data Release 12 (DR12Q), containing nearly 300,000 AGNs, to calculate the monochromatic luminosities at 5100\AA, 3000\AA, and 1350\AA, derived from the broad-band extinction-corrected SDSS…
We present the first result of a programme to search for large flux variations in the X-ray sources of the XMM Serendipitous Survey compared to previous ROSAT observations. An increase in X-ray flux by a factor >10 was discovered from the…
We present a census of local active galactic nuclei (AGN) at a redshift of $z\leq0.025$ selected using the high-ionization [Ne v] $\lambda14.32\,\mu$m emission line from the Infrared Database of Extragalactic Observables from Spitzer…
We present a census of the active black hole population at 1<z<2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood fitting technique. The study of the active black…