A5086367166- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- GNSS positioning and interference
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Particle accelerators and beam dynamics
- Antenna Design and Optimization
- Cosmology and Gravitation Theories
- Ionosphere and magnetosphere dynamics
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Soil Moisture and Remote Sensing
- Magnetic confinement fusion research
- Antenna Design and Analysis
National Radio Astronomy Observatory
2016-2025
Rhodes University
2019-2024
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
New Mexico Institute of Mining and Technology
1982-2006
U.S. National Science Foundation
2001
Virginia Tech
1996
United States Naval Research Laboratory
1993
University of California, Berkeley
1987
Center for Astrophysics Harvard & Smithsonian
1987
The NRAO VLA Sky Survey (NVSS) covers the sky north of J2000.0 δ = -40° (82% celestial sphere) at 1.4 GHz. principal data products are (1) a set 2326 4° × continuum "cubes" with three planes containing Stokes I, Q, and U images plus (2) catalog almost 2 106 discrete sources stronger than S ≈ 2.5 mJy. all have θ 45'' FWHM resolution nearly uniform sensitivity. Their rms brightness fluctuations σ 0.45 mJy beam-1 0.14 K (Stokes I) 0.29 0.09 Q U). uncertainties in right ascension declination...
My life has been an interesting voyage. I became astronomer because could not imagine living on Earth and trying to understand how the Universe works. scientific career revolved around observing motions of stars within galaxies ...Read More
Since its commissioning in 1980, the Very Large Array (VLA) has consistently demonstrated scientific productivity. However, fundamental capabilities have changed little since particularly key areas of sensitivity, frequency coverage, and velocity resolution. These limitations been addressed by a major upgrade array, which began 2001 will be completed at end 2012. When completed, Expanded VLA -- EVLA provide complete coverage from 1 to 50 GHz, continuum sensitivity typically microJy/beam (in...
We develop an absolute flux density scale for centimeter-wavelength astronomy by combining accurate ratios determined the Very Large Array between planet Mars and a set of potential calibrators with Rudy thermophysical emission model Mars, adjusted to established Wilkinson Microwave Anisotropy Probe. The radio sources 3C123, 3C196, 3C286, 3C295 are found be varying at level less than ∼5% per century all frequencies 1 50 GHz, hence suitable as standards. present polynomial expressions their...
The Very Large Array (VLA) Low-frequency Sky Survey (VLSS) has imaged 95% of the 3*pi sr sky north declination = -30 degrees at a frequency 74 MHz (4 meter wavelength). resolution is 80" (FWHM) throughout, and typical RMS noise level ~0.1 Jy/beam. point-source detection limit 0.7 Jy/beam so far nearly 70,000 sources have been catalogued. This survey used system added to VLA in 1998. It required new imaging algorithms remove large ionospheric distortions this very low throughout entire ~11.9...
The flux density scale of Perley and Butler (2013) is extended downwards to ~50 MHz by utilizing recent observations with the Karl G. Jansky Very Large Array (VLA) 20 sources between 220 48.1 GHz, legacy VLA at 73.8 MHz. derived spectral densities are placed on an absolute Baars et al. (1977) values Cygnus A (3C405) for frequencies below 2 Mars-based polynomials 3C286, 3C295, 3C196 from above GHz. Polynomial expressions presented all sources, accuracy limited primary standards 3 -- 5% over...
We used the Karl G. Jansky Very Large Array (VLA) to image one primary beam area at 3 GHz with 8 arcsec FWHM resolution and 1.0 microJy/beam rms noise near pointing center. The P(D) distribution from central 10 arcmin of this confusion-limited constrains count discrete sources in 1 < S(microJy/beam) range. At level brightness-weighted differential S^2 n(S) is converging rapidly, as predicted by evolutionary models which faintest radio are star-forming galaxies; ~96$% background originating...
view Abstract Citations (359) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multifrequency Radio Observations of Cygnus A: Spectral Aging in Powerful Galaxies Carilli, C. L. ; Perley, R. A. Dreher, J. W. Leahy, P. We present a detailed analysis the radio spectrum across lobes These observations provide first critical test synchrotron spectral aging theory. The results are good agreement with jet model for powerful galaxies, involving...
The authors have discovered a new gravitational lens system which consists of quasar at z = 1.695 nearly centered on 15 mag spiral galaxy, 2237+0305, 0.0394. At 2arcsec resolution, only single optical image the is visible; its centroid located within approximately 0arcsec.3 center galaxy. "Snapshot" observations VLA yielded no detectable radio radiation, placing an upper limit about 0.5 mJy combined flux density galaxy and λ 6 cm. discuss simple model that accounts for these observations.
view Abstract Citations (268) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The jet and filaments in Cygnus A. Perley, R. ; Dreher, J. W. Cowan, Multiconfiguration VLA observations of A at 1.4 5 GHz have been used to produce detailed maps exceptional dynamic range. radio extends from the core into northwest lobe. broad lobes reveal an unexpected wealth filamentary structure. Two new hot spots are identified. pressure cluster gas which Cyg is...
ABSTRACT We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low-redshift ( <?CDATA $0.2\lt z\lt 0.3$?> ) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities ${L}_{6}\gtrsim {10}^{23.2}\,{\rm{W}}\,{\mathrm{Hz}}^{-1}$?> that primarily generated in the active galactic nucleus (AGN) responsible for excess optical luminosity defines bona fide QSO; and...
We used the 1.4 GHz NVSS to study radio sources in two color-selected QSO samples: a volume-limited sample of 1313 QSOs defined by M_i < -23 redshift range 0.2 z 0.45 and magnitude-limited 2471 with m_r 18.5 1.8 2.5. About 10% were detected above 2.4 mJy catalog limit are powered primarily AGNs. The space density low-redshift evolves as rho proportional (1+z)^6. In both ranges flux-density distributions luminosity functions stronger than power laws, no features suggest more one kind source....
Maps with high dynamic range are presented of a well-defined sample powerful core-dominated radio sources, all which have 5-GHz core flux densities > 1 Jy. The maps were made at frequency 1.64 GHz from combined VLA A and B configuration data. novel technique for producing variable sources data taken different epochs is described. It found that, on average, BL Lac objects not more than the quasars in sample. This provides no support view that Lacs those seen such small angles to line sight...
view Abstract Citations (176) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Magnetic Fields in the Hydra A Cluster Taylor, Gregory B. ; Perley, Richard A. Sensitive, high-resolution VLA polarimetric observations are presented for radio galaxy A, an outstanding example of a high-luminosity source embedded within cooling flow cluster. We find extremely high Faraday rotation measures (RMs), throughout central regions this source, with strong...
We present radio images at 20 cm of 22 galaxies and one quasar made with National Radio Astronomy Observatory (NRAO) Very Large Array. The sources are drawn from the z <0.5 subset complete sample defined by Laing et al. [MNRAS, 204, 151 (1983)]. have resolutions 1.1-5.8 arcsec, chosen to give about 50 beamwidths across each source, sufficient sampling aperture plane represent accurately largest-scale structure. With current ages, nearly all members LRL high-sensitivity VLA or Westerbork.
VLA maps of total intensity and fractional polarization at λ3.6 cm are presented for 11 radio galaxies, part a sample 29 nearby galaxies with P178 > 1.5 × 1025 W Hz−1 sr−1. Ten have classical double structure. The hotspots in all these well resolved. We discovered one-sided jet 3C 135, as imaging the known jets 98, 111 445 high resolution. There also possible five remaining six doubles. eleventh object, 15, is imaged here first time. It dominated by bright jet, weak counterjet detected.
Accurate positions of 404 compact radio sources used as calibrators by the VLA are presented. In addition, structure and polarization each source at both 4885 1465 MHz given. Eighty-five percent have spectral indices flatter than 0.5; all these dominated an unresolved core. Half flat-spectrum contain nearby, associated diffuse a level exceeding approximately 0.4% core brightness 20 cm.
VLA maps of total intensity and fractional polarization at 3.6 cm are presented for eight radio galaxies, part a sample 30 nearby FRII sources with |$P_{178}\gt 2 \times 10^{25}\enspace \text {W} \enspace \text{Hz}^{-1}\enspace\text {sr}^{-1}$|. High-sensitivity images the hotspots (with resolutions 0.25 0.75 arcsec average noise levels ∼ µJy) show strikingly different complex structures. Jets found in six sources.
view Abstract Citations (205) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-resolution VLA observations of the radio jet in NGC 6251. Perley, R. A. ; Bridle, H. Willis, G. The has been used at resolutions 1.15-15 arcsec range 1370, 1480, 1662, and 4885 MHz, 50 1446 1662 to observe galaxy expands a variable rate, exhibiting several stages confinement reexpansion. A counterjet detected over 56 kpc direction opposite that main jet. There...
view Abstract Citations (150) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Catalog of Small-Diameter Radio Sources in the Galactic Plane Zoonematkermani, S. ; Helfand, D. J. Becker, R. H. White, L. Perley, A. survey plane longitude range -20^deg^ <= l 120^deg^ for latitudes |b| 0.8^deg^ has been carried out at 1400 MHz using VLA B configuration. We present here a catalog 1992 discrete sources detected this which is ~ 75% complete to...