A5070332109- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Cosmology and Gravitation Theories
- Relativity and Gravitational Theory
- Radio Astronomy Observations and Technology
- Nuclear Physics and Applications
- Advanced X-ray Imaging Techniques
- Particle Detector Development and Performance
- Magnetic confinement fusion research
- X-ray Spectroscopy and Fluorescence Analysis
- Solar and Space Plasma Dynamics
- CCD and CMOS Imaging Sensors
- Calibration and Measurement Techniques
- Black Holes and Theoretical Physics
- Advanced Measurement and Metrology Techniques
- High-pressure geophysics and materials
College of Charleston
2015-2024
University of Maryland, College Park
2023-2024
Goddard Space Flight Center
2024
Massachusetts Institute of Technology
2023
University of South Carolina
2013-2019
Pennsylvania State University
2001-2010
Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna
2010
Osservatorio astronomico di Bologna
2010
University of Bologna
2010
University of Washington
2009
A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of exciting science opportunities next decade. The Large Synoptic Survey Telescope (LSST) have an effective aperture 6.7 meters and imaging camera field view 9.6 deg^2, be devoted ten-year 20,000 deg^2 south +15 deg. Each pointing imaged 2000 times fifteen second exposures six broad from 0.35 1.1 microns, total point-source depth r~27.5. LSST Science Book describes basic...
We present catalogs for the ~2 Ms Chandra Deep Field-North, currently deepest X-ray observation of Universe in 0.5-8.0 keV band. Five hundred and three (503) sources are detected over an ~448 sq.arcmin area up to seven bands; 20 these lie Hubble Field-North. Source positions determined using matched-filter centroiding techniques; median positional uncertainty is ~0.3 arcsecs. The colors indicate a broad variety source types, although absorbed AGNs (including some possible Compton-thick...
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...
An extremely deep X-ray survey (≈1 Ms) of the Hubble Deep Field North (HDF-N) and its environs (≈450 arcmin2) has been performed with Advanced CCD Imaging Spectrometer on board Chandra X-Ray Observatory. This is one two deepest surveys ever performed; for point sources near aim point, it reaches 0.5–2.0 2–8 keV flux limits ≈3 × 10-17 ≈2 10-16 ergs cm-2 s-1, respectively. Here we provide source catalogs, along details observations, data reduction, technical analysis. Observing conditions,...
We present results from a 221.9 ks Chandra exposure of the HDF-N and its vicinity, concentrating on 8.6' X 8.7' area covered by Caltech Faint Field Galaxy Redshift Survey (the `Caltech area'). The minimum detectable fluxes in 0.5-2 keV 2-8 bands are 1.3e-16 cgs 6.5e-16 cgs, respectively total 82 sources detected. More than 80% extragalactic X-ray background band is resolved. Redshifts available for 96% with R<23; redshift range 0.1-3.5 most having z < 1.5. Eight located itself, including two...
We report the discovery of X-ray broad absorption lines (BALs) from BALQSO APM 08279+5255 originating material moving at relativistic velocities with respect to central source. The large flux magnification by a factor ~ 100 provided gravitational lens effect combined redshift (z = 3.91) quasar have facilitated acquisition first high signal-to-noise spectrum containing BALs. Our analysis places rest-frame energies two observed 8.1 and 9.8 keV. detection each these is significant > 99.9%...
We use gravitational microlensing of the four images z=0.658 quasar RXJ1131-1231 to measure sizes optical and X-ray emission regions quasar. The (face-on) scale length disk at rest frame 400 nm is 1.3 10^15cm, while half-light radius 0.3-17 keV 2.3 10^14cm. formal uncertainties are factors 1.6 2.0, respectively. With exception lower limit on size, results very stable against any changes in priors used analysis. Based Hbeta line-width, we estimate that black hole mass ~10^8 Msun, which...
We present results from a monitoring campaign performed with the Chandra X-ray Observatory of gravitationally lensed quasars RX J1131-1231 and HE 1104-1805. detect significant variability in all images both quasars. The flux detected image A is particular interest because its high amplitude (a factor ~ 20). interpret it as arising microlensing since uncorrelated that other ratios show larger changes than optical we would expect for more compact emission regions. differences between 1104-1805...
We use gravitational microlensing to determine the size of X-ray and optical emission regions quadruple lens system Q 2237+0305. The half-light radius, log(R1/2, V/cm) = 16.41 ± 0.18 (at λrest 2018 Å), is significantly larger than observed soft, (1.1–3.5 keV in rest frame), hard, (3.5–21.5 band emission. There weak evidence that hard component more compact with . This wavelength-dependent structure agrees recent results found other systems using techniques, favors geometries which corona...
We present four new seasons of optical monitoring data and six epochs X-ray photometry for the doubly-imaged lensed quasar Q J0158-4325. The high-amplitude, short-period microlensing variability which this system is known has historically precluded a time delay measurement by conventional methods. attempt to circumvent limitation application Monte Carlo analysis technique, but we are only able prove that must have expected sign (image A leads image B). Despite our failure robustly measure...
The Advanced X-ray Imaging Satellite (AXIS) is a Probe-class concept that will build on the legacy of Chandra Observatory by providing low-background, arcsecond-resolution imaging in 0.3-10 keV band across 450 arcminute$^2$ field view, with an order magnitude improvement sensitivity. AXIS utilizes breakthroughs construction lightweight segmented optics using single-crystal silicon, and developments fabrication large-format, small-pixel, high readout rate CCD detectors good spectral...
The quasar PKS 0637-753, the first celestial X-ray target of Chandra Observatory, has revealed asymmetric structure extending from 3 to 12 arcsec west quasar, coincident with inner portion jet previously detected in a 4.8 GHz radio image (Tingay et al. 1998). At redshift z=0.651, is largest (~100 kpc) and most luminous (~10^{44.6} ergs/s) few so far X-rays. This letter presents high resolution jet, 42 ks data when 0637-753 was on-axis ACIS-S near optimum focus. For morphology closely matches...
For the population of quasi-stellar objects (QSOs) with broad ultraviolet absorption lines, we are just beginning to accumulate X-ray observations enough counts for spectral analysis at CCD resolution. From a sample eight QSOs (including four line [BAL] and three mini-BAL QSOs) ASCA or Chandra spectra more than 200 counts, general patterns emerging. Their power-law continua typical normal Γ ≈ 2.0, signatures significant column density [NH (0.1-4) × 1023 cm-2] intrinsic, absorbing gas clear....
The high-resolution X-ray spectrum of NGC 3783 shows several dozen absorption lines and a few emission from the H-like He-like ions O, Ne, Mg, Si, S, as well Fe XVII-Fe XXIII L-shell transitions. We have reanalyzed Chandra HETGS using better flux wavelength calibrations, along with more robust methods. Combining each element, we clearly demonstrate existence determine that they are blueshifted relative to systemic velocity by -610 ± 130 km s-1. find Ne in High-Energy Grating be resolved FWHM...
We provide X-ray constraints and perform the first spectral analyses for bright SCUBA sources (f850 μm ≥ 5 mJy; signal-to-noise ratio ≥4) in an 84 × area of 2 Ms Chandra Deep Field North survey containing Hubble North. emission is detected from seven 10 submillimeter this region down to 0.5–8.0 keV fluxes ≈1 10-16 ergs cm-2 s-1, corresponding X-ray–detected source density 360 deg-2; our suggest that equates fraction population ≳36%, although systematic effects may be present. Two have nearby...
We report on an observation of the broad absorption line (BAL) quasar PG 1115+080 performed with XMM-Newton observatory. Spectral analysis reveals second case a relativistic X-ray-absorbing outflow in BAL quasar. The first was revealed recent APM 08279+5255 Chandra X-Ray Observatory. As 08279+5255, observed flux is greatly magnified by gravitational lensing. relatively high redshift (z = 1.72) places redshifted energies resonant features sensitive portion spectral response. spectrum...
We present the results from an X-ray and optical survey of a sample 17 radio jets in active galactic nuclei performed with Chandra Hubble Space Telescope. The was selected is unbiased toward detection at shorter wavelengths, but preferentially it includes beamed sources. find that emission common on kiloparsec scales, over half (10/17) exhibiting least one knot images. A similar rate found for emission, although not all knots have counterparts vice versa. distributions radio-to-X-ray...
We present 4-7 ks Chandra observations of 35 Broad Absorption Line (BAL) quasars from the Large Bright Quasar Survey, largest sample sensitive, 0.5-8.0 keV X-ray this class to date. The limited ranges in both redshift (z=1.42-2.90) and UV luminosity (a factor ~12) also make it relatively uniform. Of targets, 27 are detected for a detection fraction 77%, we confirm previous studies that find BAL be generally weak. Five eight non-detections known low-ionization quasars, confirming reports...
The core-dominated radio-loud quasar PKS 0637-752 (z = 0.654) was the first celestial object observed with Chandra X-ray Observatory, offering early surprise of detection a remarkable jet. Several observations variety detector configurations contribute to total exposure time Advanced CCD Imaging Spectrometer (ACIS; Garmire et al. 2000, in preparation) about 100ks. A spatial analysis all available data, making use Chandra's resolving power 0.4 arcsec, reveals jet that extends 10 arcsec west...
Quasar accretion disc winds observed via broad absorption lines (BALs) in the UV produce strong continuous X-rays. The X-ray absorber is believed to serve critically as a radiative shield keep outflow ionizations low enough for driving. However, previous studies have shown that ‘mini-BAL’ and narrow line (NAL) outflows dramatically less than BALs. Here, we examine rest-frame spectra of eight mini-BAL quasars with speeds range 0.1–0.2c test hypothesis these extreme require shield. We find...
We review results from our monitoring observations of several lensed quasars performed in the optical, UV, and X-ray bands. Modeling multi-wavelength light curves provides constraints on extent emission regions. One important analysis is that optical sizes as inferred microlensing are significantly larger than those predicted by theoretical-thin-disk estimate. In a few cases we also constrain slope size-wavelength relation. Our size soft hard regions indicate some objects sample region more...
Past X-ray observations of the nearby luminous quasar PDS 456 (at $z=0.184$) have revealed a wide angle accretion disk wind (Nardini et al. 2015), with an outflow velocity $\sim-0.25c$, as observed through its blue-shifted iron K-shell absorption line profile. Here we present three new XMM-Newton 456; one in September 2018 where was bright and featureless, two 2019, 22 days apart, occurring when five times fainter strong lines from were present. During second 2019 observation, broad...
We present the first grating-resolution X-ray spectra of Seyfert 1 galaxy NGC 3783, obtained with High Energy Transmission Grating Spectrometer on Chandra X-Ray Observatory. These reveal many narrow absorption lines from H-like and He-like ions O, Ne, Mg, Si, S, Ar as well Fe XVII-Fe XXI L-shell lines. have also identified several weak emission lines, mainly O Ne. The are blueshifted by a mean velocity ≈440 ± 200 km s-1 not resolved, indicating dispersion within absorbing gas few hundred...
We report results from Chandra observations of the X-ray jet 3C 273 during calibration phase in 2000 January. The zeroth-order images and spectra two 40 ks exposures with High-Energy Transmission Grating Low-Energy + Advanced CCD Imaging Spectrometer-S show a complex structure. brightest optical knots are detected resolved 0.2-8 keV energy band. morphology tracks well optical. However, while brightness decreases along jet, outer parts tend to be increasingly bright increasing wavelength....