A5032526866- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Advanced Thermodynamic Systems and Engines
- Cosmology and Gravitation Theories
- Computational Geometry and Mesh Generation
- Advanced SAR Imaging Techniques
- Relativity and Gravitational Theory
- Geophysics and Gravity Measurements
- Genetic and phenotypic traits in livestock
- Agricultural economics and policies
- Adaptive optics and wavefront sensing
- Advanced Numerical Analysis Techniques
- Digital Image Processing Techniques
- Seismic Waves and Analysis
University of Wisconsin–Stevens Point
2011-2017
University of Alabama
2003-2010
Universitatea Nicolae Titulescu din București
2002
University of Bucharest
2002
Osservatorio Astrofisico di Torino
2002
National Institute for Astrophysics
2002
We explore the properties of Hβ emission line profile in a large, homogeneous and bright sample N∼ 470 low redshift quasars extracted from Sloan Digital Sky Survey (DR5).We approach investigation two complementary directions: composite/median spectra set diagnostic measures (asymmetry index, centroid shift kurtosis) individual quasars.The project is developed presented framework so called 4D Eigenvector 1 Parameter Space, with focus on its optical dimensions, FWHM(Hβ) relative strength FeII...
We compare broad emission line profiles and estimate ratios for all major lines between Lyα Hβ in a sample of six quasars.The sources were chosen with two criteria mind: the existence high quality optical UV spectra as well possibility to spectroscopic diversity 4D Eigenvector 1 context (4DE1).In latter sense each source occupies region (bin) FWHM(Hβ) vs. Fe ii opt strength plane that is significantly different from others.High S/N are used templates modeling other (Lyα, Civλ1549, Heiiλ1640,...
Broad emission lines in quasars enable us to "resolve" structure and kinematics of the broad-line emitting region (BLR) thought involve an accretion disk feeding a supermassive black hole. Interpretation broad line measures within 4DE1 formalism simplifies apparent confusion among such data by contrasting unifying properties so-called high low accreting Population A B sources. Hβ serves as estimator hole mass, Eddington ratio source rest frame; latter being valuable input for Civλ1549...
<i>Aims. <i/>We present new VLT ISAAC spectra for 30 quasars, which we combine with previous data to yield a sample of 53 intermediate-redshift (<i>z<i/> <i>≈<i/> 0.9–3.0) sources. The is used explore properties prominent lines in the h<i>β<i/> spectral region these very luminous quasars.<i>Methods. compare this two large low-redshift () samples search trends over almost 6dex source luminosity.<i>Results. find major trends: (1) systematic increase minimum <i>FWHM<i/> luminosity (discussed...
A significant fraction of extended radio sources presents a peculiar X-shaped morphology: in addition to the classical double lobed structure, emission is also observed along second axis symmetry form diffuse wings or tails. We re-examine origin these extensions relating morphology properties their host galaxies. The orientation shows striking connection with structure galaxy as they are preferentially aligned its minor axis. Furthermore, only galaxies high projected ellipticity....
We search fora dichotomy/bimodality between Radio Loud (RL) and Quiet (RQ) Type 1 Active Galactic Nuclei (AGN). examine several samples of SDSS QSOs with high S/N optical spectra matching FIRST/NVSS radio observations. use the data to identify weakest RL sources FRII structure define a RL/RQ boundary which corresponds log L$_{1.4GHz}$=31.6 ergs s$^{-1}$ Hz$^{-1}$. measure properties broad line H$β$ FeII emission plane 4DE1 spectroscopic diagnostic space. The quasars occupy much more...
We consider the properties of radio-loud (RL) active galactic nuclei in context eigenvector 1 (E1) parameter space. RL sources show a restricted E1 space occupation relative to radio-quiet (RQ) majority. The Fanaroff-Riley II "parent population" relatively unboosted (median radio/optical flux ratio ~490) shows most occupation. have different broad-line (and inferred black hole masses and Eddington ratios). FWHM Hβ for component are at least twice as large RQ average broad Fe λ4570...
We test the recent claim by Hu et al. that Fe ii emission in type 1 active galactic nuclei shows a systematic redshift relative to local source rest frame and broad-line Hβ. compile high signal-to-noise median composites using Sloan Digital Sky Survey spectra from both sample our own of 469 brightest DR5 spectra. Our are generated bins FWHM Hβ strength as defined 4D Eigenvector formalism. find no evidence for consistency with previous assumptions shift width (FWHM) follow virtually all...
Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies geometry/physics/kinematics for this subclass compared to radio-quiet (RQ) majority of quasars. We discuss how LD RL parent population supports notion RQ–RL dichotomy among type sources. 3C 57 is an atypical quasar that shows both uncertain radio morphology and falls region 4DE1 where are rare. present new flux optical spectroscopic measures designed verify its...
Abstract We present evidence for two populations of quasars showing distinctly different broad line structure and kinematics. The first quasar dichotomy involve differences between radio-quiet radio-loud sources. proposed an alternate population A-B based on optical, UV X-ray spectroscopic properties. One these (Pop. A: FWHM Hβ <4000 kms
Abstract Quasars show a considerable spectroscopic diversity. However, the variety of quasar spectra at low redshifts is non-random: principal component analysis applied to large samples customarily identifies two main eigenvectors. In this contribution we that range optical spectral properties observed low-z and associated with first eigenvector preserved up z ≈ 2 in sample high luminosity quasars. We also describe major effects.
We explore the relationship between radio-loud (RL) and radio-quiet (RQ) quasars using a set of optical/UV/X-ray measures that are quite independent radio measures. find RL sources to show larger average FWHM H-beta, weaker FeII emission, no soft X-ray excess CIV blueshift - all characteristics manifested by large fraction RQ (that we call Population A). log L (1.4Ghz) = 31.6 [ergs/s/Hz] (or R=70) is lower limit for showing FRII morphology. evidence hidden population below this level....
The 4D Eigenvector 1 parameter space was introduced seven years ago as an attempt at multiwavelength spectroscopic representation of quasars. It appears to be the most effective diagnostic for unifying diversity broad line AGN. This progress report shows that power 4DE1 is confirmed using optical spectra from SDSS, UV HST and X-ray XMM. Our introduction population A-B concept continues provide useful insights into quasar diversity. Largely radio-quiet, high accreting, low BH mass Pop. A...