A5008513014- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Ionosphere and magnetosphere dynamics
- GNSS positioning and interference
- Stellar, planetary, and galactic studies
- Radio Wave Propagation Studies
- Astrophysics and Star Formation Studies
- Antenna Design and Optimization
- Earthquake Detection and Analysis
- Dark Matter and Cosmic Phenomena
- Particle accelerators and beam dynamics
- Particle Detector Development and Performance
- Lightning and Electromagnetic Phenomena
- Precipitation Measurement and Analysis
- Pulsars and Gravitational Waves Research
- Superconducting and THz Device Technology
Los Alamos National Laboratory
2012-2025
University of New Mexico
1996-2022
Boeing (United States)
1998
Space Telescope Science Institute
1995
National Radio Astronomy Observatory
1988-1994
New Mexico Institute of Mining and Technology
1993
Istituto di Radioastronomia di Bologna
1989
SKA Observatory
1986-1988
University of Manchester
1986-1988
The central radio source in M87 provides the best opportunity to study jet formation because it has a large angular size for gravitational radius of black hole and bright that is well resolved by VLBI observations. We present intensive monitoring observations from 2007 2008, plus roughly annual span 17 years, all made with Very Long Baseline Array at 43 GHz resolution about 30 60 Rs. Our high-dynamic-range images clearly show wide-opening-angle structure counter-jet. counter-jet are nearly...
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles energies exceeding 10^12 electron Volts (eV) and are bright sources very-high-energy (VHE) gamma-ray emission, it not yet known where VHE emission originates. Here we report on radio observations galaxy M87, revealing period extremely strong flares accompanied by increase flux from its nucleus. These results...
view Abstract Citations (163) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observation of a Ring Structure in SiO Maser Emission from Late-Type Stars Diamond, P. J. ; Kemball, A. Junor, W. Zensus, Benson, Dhawan, V. We have used the National Radio Astronomy Observatory (NRAO) Very Long Baseline Array (VLBA) to make first full high-resolution synthesis images 43 GHz masers around late-type stars. Our observations stars TX Cam and U Her...
VLBA and Global VLBI observations of M87 at 43 GHz, some new previously published, are used to study the structural evolution jet with a spatial resolution under 100 Schwarzschild radii. The images, taken between 1999 2004, have an angular 0.00043" x 0.00021". An edge-brightened structure indication large opening angle base seen in all five epochs. In addition, probable counter-jet is latter three A 22 GHz image also confirms many structures higher frequency, including counter-jet....
The X-ray intensity of knot HST-1, 0.85" from the nucleus radio galaxy M87, has increased by more than a factor 50 during last 5 years. optical increase is similar and our limited data indicate commensurate activity. We give primary results Chandra Observatory monitoring program consider some implications this extreme variability in relativistic jet. find that support 'modest beaming synchrotron' model as indicated earlier papers. Based on model, decay lightcurve appears to be dominated...
view Abstract Citations (141) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Subluminal Motion and Limb Brightening in the Nuclear Jet of M87 Reid, M. J. ; Biretta, A. Junor, W. Muxlow, T. B. Spencer, R. E. We conducted an 18 station VLBI observation to map nucleus at cm wavelength. The resulting image has a dynamic range greater than 2000 1 resolves continuous, well-collimated, nuclear jet both along perpendicular axis. displays complicated...
We present Chandra X-ray monitoring of the M87 jet in 2002, which shows that intensity HST-1, an optical knot 0.8" from core, increased by a factor two 116 days and four 2 yrs. There was also significant flux decrease over months, with suggestive evidence for softening spectrum. From this variability behavior, we argue bulk emission HST-1 comes synchrotron emission. None other conceivable processes can match range observed characteristics. By estimating model parameters various relativistic...
We have imaged the inner 0.1 pc of archetypal radio jet in nearby galaxy, 3C274 (Virgo A), with two epochs intercontinental, very- long-baseline interferometry (VLBI) at a wavelength 1.3 cm. These images highest linear resolution (1.6 x 10^-2^ pc) achieved on an extragalactic jet. At this resolution, we find ~4 mas (0.3 long composed several components. A lower image detects to ~25 (2 from presumed core. The appears well collimated (opening angle ~20^deg^), and has morphology similar that...
M87 has one of the largest angular size black holes known. It also a bright jet that is well resolved across near core using high frequency VLBI. As such it best object to observe study launch region jets where physical sizes structures interest scale with gravitational radius. Modern numerical simulations suggest formation extends over 100-1000 Rs. been observed resolution about 60 Rs at 43 GHz VLBA every 3 weeks through 2007, and 5 days between January April 2008. A preliminary movie, made...
M87 is the best source in which to study a jet at high resolution gravitational units because it has very mass black hole and nearby. The angular size of second only Sgr A*, does not have strong jet. structure edge brightened with wide opening angle base weak counterjet. We roughly annual observations for 17 years plus intensive monitoring three week intervals year five day 2.5 months made Very Long Baseline Array (VLBA) 43 GHz. inner shows complex dynamics, apparent motions both along...
view Abstract Citations (40) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Violent Interaction Between the Dwarf Galaxy UGC 7636 and Giant Elliptical NGC 4472 McNamara, Brian R. ; Sancisi, Renzo Henning, Patricia A. Junor, William We present new U, B, R, H I imagery of Virgo Cluster giant elliptical galaxy its interacting dwarf companion 7636. Using a composite image reconstruction technique, we show that trail debris ~5 arcmin in length...
We briefly review the observed structure and evolution of M87 jet on scales less, similar1 parsec (pc; 1 pc = 3.09 x 10(16) m). Filamentary features, limb-brightening, side-to-side oscillation are common characteristics pc-scale, kpc-scale jets. The most prominent emission features both subpc appear stationary (v/c < 0.1). Nonetheless, based jet's flux evolution, presence superluminal motion, absence a visible counter-jet, we argue for an underlying relativistic flow, consistent with unified...
We present evidence for X-ray variability from the core and knot A in M87 jet based on data two observations with Einstein Observatory High Resolution Imager (HRI) three ROSAT HRI. The intensity showed a 16 per cent increase 17 months (1979–80); 12 3 years 1992 to 1995; drop last half of 1995. appears have decreased by between June 1995 December. Although is consistent general expectations AGN, changes provide constraints emission process geometry. Thus we predict that morphology will differ...
<i>Aims. <i/>We report new Very Long Baseline Array (VLBA) polarimetric observations of the compact steep-spectrum (CSS) sources 3C 119, 318, and 343 at 5 8.4 GHz. <i>Methods. analysed our VLBA derived milliarcsecond-resolution images total intensity, polarisation, rotation measure (<i>RM<i/>) distributions. <i>Results. <i/> The CSS source associated with a possible quasar, has rest-frame <i>RM<i/> values up to ~10 200 rad m<sup>-2<sup/> in region that coincides change direction inner jet....
We present multifrequency radio observations of the prototypical compact steep-spectrum quasar 3C 147, and report enormous differential Faraday rotation between two extended components on opposite sides quasar. This indicates that large amounts thermal gas are present, demonstrates directly existence asymmetries in gaseous environment this source. suggest a consistent picture for comment evolution sources general.
Summary To investigate the nature of extragalactic radio sources with extended emission on only one side active nucleus, we have observed a sample suspected candidates both VLA and MERLIN. In this paper, present observations 13 which were either being ‘one-sided’ or known to lobes very different surface brightnesses. Many found sides nucleus. Using our as well those available in literature, compiled 4C quasars having one-sided structure. We then compared some their properties are two-sided,...
We present VLA 5-GHz and MERLIN 408-MHz observations of a sample steep-spectrum low-frequency-variable sources. The radio show that the vast majority sources have linear sizes typical compact steep spectrum A classification based on their arcsecond-scale structure allows us to separate them into two classes, namely with an unresolved component lobe-dominated All but three existence (subarcsecond) components which are required by models explain source variability as due propagation effects in...
Abstract Impulsive phenomena in the Earth's atmosphere produce acoustic and gravity waves which perturb ionosphere. Such perturbations are often measured using total electron content fluctuations (TEC), derived from ground‐based Global Positioning System data. Using TEC data Japanese GEONET ground network after Tōhoku earthquake on 11 March 2011, we demonstrate capabilities of a new framework methodologies for analyzing ionospheric perturbations. The consists several techniques: calculating...
As part of a search for high-luminosity radio galaxies with one-sided structures, the galaxy 0500 + 630 has been imaged both VLA and MERLIN its optical spectrum determined using Isaac Newton Telescope on La Palma. The is found to have redshift 0.290 ± 0.004. observations show source be highly asymmetric, an overall structure which cannot understood easily by ascribing it either orientation relativistic beaming effects or asymmetric distribution gas in central region. A comparison this...