A5048400063- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Relativity and Gravitational Theory
- Scientific Research and Discoveries
- Advanced Measurement and Metrology Techniques
- History and Developments in Astronomy
- Particle Accelerators and Free-Electron Lasers
- Statistics Education and Methodologies
- Geophysics and Gravity Measurements
- Advanced X-ray Imaging Techniques
- Nuclear Physics and Applications
- CCD and CMOS Imaging Sensors
- Solar and Space Plasma Dynamics
University of North Texas
2015-2024
Pennsylvania State University
2005-2009
Pacific States University
2008
Tel Aviv University
1998-2005
[abridged] We present point-source catalogs for the 4Ms Chandra Deep Field-South (CDF-S), which is deepest survey to date and covers an area of 464.5 arcmin^2. provide a main source catalog, contains 740 X-ray point sources that are detected with wavdetect at false-positive probability threshold 1E-5 also satisfy binomial-probability source-selection criterion P<0.004; this approach designed maximize number reliable detected. A total 300 main-catalog new compared previous 2Ms CDF-S sources....
We present X-ray source catalogs for the $\approx7$ Ms exposure of Chandra Deep Field-South (CDF-S), which covers a total area 484.2 arcmin$^2$. Utilizing WAVDETECT initial detection and ACIS Extract photometric extraction significance assessment, we create main catalog containing 1008 sources that are detected in up to three bands: 0.5-7.0 keV, 0.5-2.0 2-7 keV. A supplementary is also provided including 47 lower-significance have bright ($K_s\le23$) near-infrared counterparts. identify...
Reverberation mapping of nearby active galactic nuclei has led to estimates broad-line-region (BLR) sizes and central-object masses for some 37 objects date. However, successful reverberation yet be performed quasars either high luminosity (above L_opt~10^{46} erg/s) or redshift (z>0.3). Over the past six years, we have carried out, at Hobby-Eberly Telescope, rest-frame-ultraviolet spectrophotometric monitoring a sample redshifts z=2.2--3.2, with luminosities L_opt~10^{46.4}--10^{47.6}...
Utilizing 21 new Chandra observations as well archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample 59 most optically luminous quasars in universe (Mi ≈ -29.3 to -30.2) spanning redshift range z 1.5-4.5. Our full consists 32 from Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3) quasar catalog, two additional objects DR3 area that were missed by SDSS selection criteria, 25 comparably at ≳ 4. This is largest such date. By jointly fitting...
Most galaxy evolutionary models require quasar feedback to regulate star formation in their host galaxies. In particular, at high redshift, expect that associated with quasar-driven outflows is so efficient the gas largely swept away or heated up, hence suppressing massive We observationally investigate this phenomenon by using VLT-SINFONI integral field spectroscopy of luminous 2QZJ002830.4-281706 z = 2.4. The spectra sample optical emission lines redshifted into near-IR. [OIII]λ5007...
AGN-driven outflows are invoked by galaxy evolutionary models to quench star formation and explain the origin of relations observed locally between super massive black holes their host galaxies. This work aims detect presence extended ionised in luminous quasars where we expect maximum activity both hole accretion. Currently, there only a few studies based on spatially resolved observations at high redshift, $z>2$. We analyse sample six (${\rm L>10^{47} \ erg/s}$) $z\sim2.4$, H-band using...
We present point-source catalogs for the ~2 Ms exposure of Chandra Deep Field-South (CDF-S); this is one two most-sensitive X-ray surveys ever performed. The survey covers an area ~436 arcmin^2 and reaches on-axis sensitivity limits ~1.9x10^{-17} ~1.3x10^{-16} ergs/cm^2/s 0.5-2.0 2-8 keV bands, respectively. Four hundred sixty-two point sources are detected in at least three bands that were searched; 135 these new compared to previous ~1 CDF-S detections. Source positions determined using...
We present Spitzer IRS low resolution, mid-IR spectra of a sample 25 high luminosity QSOs at 2
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3–3.2, including new XMM-Newton observations four these sources. find a significant correlation between normalized accretion rate (L/LEdd) and photon index (Γ) for 35 moderate- to high-luminosity RQ AGNs, our Within limits sample, we show that measurement Γ LX can provide an estimate L/LEdd black hole mass (MBH) with mean uncertainty factor ≲3 on predicted values...
We present new XMM-Newton observations of two luminous and high accretion rate radio-quiet active galactic nuclei (AGNs) at z ~ 2. Together with archival X-ray rest-frame optical spectra three sources similar properties, as well 25 moderate-luminosity AGNs < 0.5, we investigate, for the first time, dependence hard (≳2 keV) power-law photon index on broad Hβ emission-line width across ~3 orders magnitude in AGN luminosity. Provided that rates five can be estimated by extrapolating well-known...
We present new near-infrared spectroscopic measurements of the Hβ region for a sample 29 luminous high-redshift quasars. have measured width in those sources and added archival to create 92 active galactic nuclei (AGNs) which rest-frame UV N V λ1240 C IV λ1549 emission lines are available. Our spans 6 orders magnitude luminosity includes 31 radio-loud AGNs. It also 10 narrow-line Seyfert 1 galaxies one broad absorption line quasar. find that metallicity, indicated by V/C ratio, is primarily...
We present 0.5–2 keV, 2–8 4–8 and 0.5–8 keV (hereafter soft, hard, ultra-hard, full bands, respectively) cumulative differential number-count (log N–log S) measurements for the recently completed ≈4 Ms Chandra Deep Field-South (CDF-S) survey, deepest X-ray survey to date. implement a new Bayesian approach, which allows reliable calculation of number counts down flux limits that are factors ≈1.9–4.3 times fainter than previously investigations. In soft band (SB), most sensitive bandpass in...
We present an investigation into how well the properties of accretion flow on to a supermassive black hole may be coupled those overlying hot corona. To do so, we specifically measure characteristic spectral index, Γ, power-law energy distribution, over range 2–10 keV, for X-ray selected, broad-lined radio-quiet active galactic nuclei (AGN) up z ∼ 2 in Cosmic Evolution Survey (COSMOS) and Extended Chandra Deep Field South (E-CDF-S). test previously reported dependence between Γ mass, full...
We present new spectroscopic and photometric data of the type Ibn supernovae 2006jc, 2000er 2002ao. discuss general properties this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring traces evolution class objects during first few days after shock breakout. An overall similarity in is found among members group, would be unexpected if energy these core-collapse events was dominated by interaction between ejecta circumstellar medium. Type appear to...
Negative feedback from active galactic nuclei (AGN) is considered a key mechanism in shaping galaxy evolution. Fast, extended outflows are frequently detected the AGN host galaxies at all redshifts and luminosities, both ionised molecular gas. However, these only "potentially" able to quench star formation we still missing decisive evidence of negative action. Here present Spectrograph for INtegral Field Observations Near Infrared (SINFONI) H- K-band integral-field spectroscopic observations...
We present an X-ray and multiwavelength study of 33 weak emission-line quasars (WLQs) 18 that are analogs the extreme WLQ, PHL 1811, at –2.9. New Chandra 1.5–9.5 ks exploratory observations were obtained for 32 objects while others have archival observations. Significant fractions these luminous type 1 distinctly compared to typical quasars, including 16 (48%) WLQs 17 (94%) 1811 with average weakness factors 39, respectively. measure a relatively hard () effective power-law photon index...
We investigate the population of high-redshift ($3\leq z < 6$) AGN selected in two deepest X-ray surveys, 7 Ms \textit{Chandra} Deep Field-South and 2 Field-North. Their outstanding sensitivity spectral characterization faint sources allow us to focus on sub-$L_*$ regime (log$L_{\mathrm{X}}\lesssim44$), poorly sampled by previous works using shallower data, obscured population. Taking fully into account individual photometric-redshift probability distribution functions, final sample consists...
We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release Sloan Digital Sky Survey and present infrared, optical, radio observations subsample four objects at z 4. These emission-line (WLQs) constitute prominent tail Lyα + N v equivalent width distribution, we compare them to more typical properties low-redshift active galactic nuclei weak/absent lines, namely BL Lac objects. find that WLQs exhibit hot (T ∼ 1000 K) thermal dust have...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
We present measurements of the evolution normal-galaxy X-ray emission from $z \approx$ 0-7 using local galaxies and galaxy samples in 6 Ms Chandra Deep Field-South (CDF-S) survey. The majority CDF-S are observed at rest-frame energies above 2 keV, where is expected to be dominated by binary (XRB) populations; however, hot gas provide small contributions observed- frame < 1 keV 1$. show that a single scaling relation between luminosity ($L_{\rm X}$) star-formation rate (SFR) insufficient for...
X-ray emission from QSOs has been used to assess SMBH accretion properties up $z$~6. However, at $z>6$ only ~15 are covered by sensitive observations, preventing a statistically significant investigation of the in first Gyr Universe. We present new Chandra observations 10 QSOs, selected have virial black-hole mass estimates Mg II line spectroscopy. Adding archival data for an additional 15 we investigate QSO population Universe, focusing particular on $L_{UV}-L_{X}$ relation, which is traced...
Vera C. Rubin Observatory is a ground-based astronomical facility under construction, joint project of the National Science Foundation and U.S. Department Energy, designed to conduct multi-purpose 10-year optical survey southern hemisphere sky: Legacy Survey Space Time. Significant flexibility in strategy remains within constraints imposed by core science goals probing dark energy matter, cataloging Solar System, exploring transient sky, mapping Milky Way. The survey's massive data...
We present new H- and K-band spectroscopy of 15 high-luminosity active galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained with Gemini South. combined the data spectra an additional 29 sources to obtain a sample 1045.2 < λ Lλ(5100 Å) 1047.3 ergs s−1 black hole (BH) mass range, using reverberation mapping relationships based on Hβ method, 108.8-1010.7 M☉. do not find correlation L/LEdd MBH, but we , which might be due selection effects. The distribution is broad covers range ~0.07-1.6,...
We present Spitzer rest-frame mid-infrared spectroscopy of twelve z~2 mm-bright type 1 QSOs, selected from unlensed and lensed QSO samples covering a range AGN optical luminosities L_5100=10^45 to 10^47 erg/s. On top the continuum, we detect PAH emission luminous star formation in nine objects individually as well composite spectrum for full sample. luminosity rest frame far-infrared correlate extend similar correlation lower local QSOs. This provides strong evidence intense hosts these...
We present new near-infrared spectroscopic measurements for 29 luminous high-redshift active galactic nuclei (AGNs) and use the data to discuss size other properties of narrow-line regions (NLRs) in those sources. The high-resolution spectra have been used carefully model Fe II blends provide reliable [O III] λ5007, II, Hβ measurements. find that about two-thirds all very high luminosity sources show strong λ5007 lines, while remaining objects no or weak such lines. While emitters are also...