Related papers: Fe II Diagnostic Tools for Quasars
The abundance, temperature, and clustering of metals in the intergalactic medium are important parameters for understanding their cosmic evolution and quantifying their impact on cosmological analysis with the Ly $\alpha$ forest. The…
Several observed spectral properties of quasars are believed to be influenced by quasar orientation. In this investigation we examine the effect of orientation on the Mg II line located at 2798 {\AA} in a sample of 36 radio-loud quasars,…
Infrared OH lines at 1.55 - 1.56 um in the H-band were obtained with the Phoenix high-resolution spectrograph at the 2.1m telescope of the Kitt Peak National Observatory for a sample of 14 metal-poor stars. Detailed analyses of the sample…
[Fe II] emission lines are prominent in the infrared (IR), and they are important diagnostic tools for radiative atomic shocks. We investigate the emission characteristics of [Fe II] lines using a shock code developed by Raymond (1979) with…
The lifetime of quasars is fundamental for understanding the growth of supermassive black holes, and is an important ingredient in models of the reionization of the intergalactic medium. However, despite various attempts to determine quasar…
The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a…
The line strength indices Hb, Mg2, and <Fe>, together with their gradients and dependence on the galaxy luminosity (mass), observed in elliptical galaxies are customarily considered as reliable indicators of systematic differences in age…
One of the puzzles in understanding the spectra of active galactic nuclei (AGN) is the origin of the FeII emission. FeI emission, if present, will help reveal the physical conditions of the emitting gas. In an attempt to verify the presence…
We present an analysis of the chemical and ionization conditions in a sample of 100 weak Mg II absorbers identified in the VLT/UVES archive of quasar spectra. Using a host of low ionization lines associated with each absorber in this…
The centre of NGC 4151 has been observed in the J-band with the SMIRFS integral field unit (IFU) on the UK Infrared Telescope. A map of [Fe II] emission is derived, and compared with the distributions of the optical narrow line region and…
Quasars are variable and their variability can both constrain their physical properties and help to identify them. We look for ways to efficiently identify quasars exhibiting consistent variability over multi-year time-scales, based on a…
The variability of quasars across multiple wavelengths is a useful probe of physical conditions in active galactic nuclei. In particular, variable accretion rates, instabilities, and reverberation effects in the accretion disk of a…
We use a sample of Type 1 active galactic nuclei (AGNs) spectra in order to investigate which atomic processes are responsible for some observed properties of the FeII emission lines and how they are connected with macroscopic physical…
We describe a method for determination of physical conditions in the broad line regions of a significant subsample of Seyfert-1 nuclei and quasars. Several diagnostic ratios based on intermediate (AlIII 1860, SiIII 1892) and high (CIV 1549,…
Context. The study of old, metal-poor stars deepens our knowledge on the early stages of the universe. In particular, the study of these stars gives us a valuable insight into the masses of the first massive stars and their emission of…
The Mg II emission line is visible in the optical band for intermediate redshift quasars (0.4 < z < 1.6) and it is thus an extremely important tool to measure the black hole mass and to understand the structure of the Broad Line Region. We…
Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant \alpha. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible…
We have compared the optical emission line ratios of type 2 quasars from Zakamska et al. with standard AGN photoionization model predictions, Seyfert 2s, HII galaxies, and narrow line FRII radio galaxies. Moderate to high ionization narrow…
We present measurements of elemental abundances in solar flares with the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO). EVE observes both high temperature Fe emission lines (Fe XV-Fe XXIV) and continuum emission…
Supernovae remnants are known to be luminous sources of infrared [FeII] emission. By studying how the luminosity scales with age, environment and other relevant factors, we can construct an [FeII] luminosity function for supernovae…