相关论文: Revisited abundance diagnostics in quasars: Fe II/…
We present spectra of six luminous quasars at z ~ 2, covering rest wavelengths 1600-3200 A. The fluxes of the UV Fe II emission lines and Mg II 2798 doublet, the line widths of Mg II, and the 3000 A luminosity were obtained from the…
The enrichment of Fe, relative to alpha-elements such as O and Mg, represents a potential means to determine the age of quasars and probe the galaxy formation epoch. To explore how \ion{Fe}{2} emission in quasars is linked to physical…
Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from quasars has a major cosmological motivation. Both Fe and Mg are produced by short-lived massive stars. In addition, Fe is produced by accreting white dwarf supernovae…
The Fe II/Mg II emission line flux ratio in quasar spectra serves as a proxy for the relative Fe to alpha-element abundances in the broad line regions of quasars. Due to the expected different enrichment timescales of the two elements, they…
It has been suggested in the literature that the (Fe/alpha) abundance ratio may be used as a chronometer, due to a delay in this ratio reaching its solar value as predicted by galactic chemical evolution models. Using grids of…
We present an analysis of Mg II $\lambda2798$ and Fe II UV emission lines for archival Sloan Digital Sky Survey (SDSS) quasars to explore diagnostics of the magnesium-to-iron abundance ratio in a broad-line region cloud. Our sample consists…
Broad Fe II emission is a prominent feature of the optical and ultraviolet spectra of quasars. We report on a systematical investigation of optical Fe II emission in a large sample of 4037 z < 0.8 quasars selected from the Sloan Digital Sky…
We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 A. The redshift ranges from z = 0.061 to 0.555 and the luminosity from M_{B} = -22.69 to -26.32. We describe the procedure of generating the…
The Eddington ratio is a key parameter that governs the diversity of quasar properties. It can be scaled with a strong anti-correlation between optical Fe II and [O III] emission. In search of such indicators in the far-UV band, the HST…
Fe II emission is a well-known contributor to the UV spectra of active galactic nuclei and the modeling of this part may affect the results obtained for the MgII$\lambda2800$ emission, which is one of the lines used for black hole mass…
To investigate the chemical abundance of broad-line region clouds in quasars at high redshifts, we performed near-infrared spectroscopy of six luminous quasars at z ~ 2.7 with the WINERED spectrograph mounted on the New Technology Telescope…
The abundance of alpha-process elements such as magnesium and carbon relative to iron measured from the broad emission lines of QSOs can serve as a diagnostic of the star formation and chemical enrichment histories of their host galaxies.…
We present a set of new theoretical Fe II templates for bright quasars covering a wavelength range of 1000-10000 \AA\, based on the recent atomic database available in the C23.00 version of the photoionization code CLOUDY. We compute a grid…
We present results of the analysis of near infrared spectroscopic observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of the ultraviolet FeII/MgII emission line strength in order to estimate the beginning of intense…
We investigate the spectral properties of the UV ($\lambda\lambda$2650-3050 \AA) and optical ($\lambda\lambda$4000-5500 \AA) Fe II emission features in a sample of 293 type 1 active galactic nuclei (AGNs) from Sloan Digital Sky Survey…
We investigate FeII emission in Broad Line Region (BLR) of AGNs by analyzing the FeII(UV), FeII(4570) and MgII emission lines in 884 quasars in the Sloan Digital Sky Survey (SDSS) Quasar catalog in a redshift range of 0.727 < z < 0.804.…
We present results from analysis of spectra from a sample of ~900 quasars from the Sloan Digital Sky Survey. These objects were selected for their intermediate redshift (1.2<z<1.8), placing MgII and UV FeII in the optical band pass,…
Understanding the Fe II emission from Active Galactic Nuclei (AGN) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving both quasar classification schemes such as…
We present evidence for a skewed distribution of UV FeII emission in quasars within candidate overdense regions spanning spatial scales of ~ 50 Mpc at 1.11 < z < 1.67, compared to quasars in field environments at comparable redshifts. The…
We investigate the strength of ultraviolet Fe II emission in fainter quasars compared with brighter quasars for 1.0 <= z <= 1.8, using the SDSS (Sloan Digital Sky Survey) DR7QSO catalogue and spectra of Schneider et al., and the SFQS (SDSS…