A5054254501- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- GNSS positioning and interference
- Adaptive optics and wavefront sensing
- Antenna Design and Optimization
- Ionosphere and magnetosphere dynamics
- Particle Accelerators and Free-Electron Lasers
- Superconducting and THz Device Technology
- Dark Matter and Cosmic Phenomena
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Cosmology and Gravitation Theories
- Geomagnetism and Paleomagnetism Studies
- SAS software applications and methods
University of New Mexico
2016-2025
Las Cumbres Observatory Global Telescope Network
2018-2024
UNSW Sydney
1999-2023
University of Arizona
2019-2023
New Mexico State University
2018-2023
Arcetri Astrophysical Observatory
2019-2023
National Radio Astronomy Observatory
2008-2020
University of Oxford
2014
Max Planck Society
2014
Max Planck Innovation
2014
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...
We present the first results from a very deep Chandra X-ray observation of core Perseus cluster galaxies. A pressure map reveals clear thick band high around inner radio bubbles. The gas in must be expanding outward and sharp front to it is identified as shock front, yet we see no temperature jump across it; indeed there more soft emission behind than it. conclude that this region either thermal conduction operates efficiently or co-existing relativistic plasma seen mini-halo mediating...
We report subarcsec-resolution X-ray imaging of the core Perseus cluster around galaxy NGC 1275 with Chandra Observatory. The ROSAT-discovered holes associated radio lobes have bright rims which are cooler than surrounding gas and not due to shocks. themselves may contain some hotter gas. map strong photoelectric absorption across Northern lobe rim a small infalling irregular galaxy, known as high velocity system. Two outer holes, one was previously known, identified recently found spurs...
We present preliminary results from a deep observation lasting almost 200 ks of the centre Perseus cluster galaxies around NGC 1275. The X-ray surface brightness intracluster gas beyond inner 20 kpc, which contains radio bubbles, is very smooth apart some low-amplitude quasi-periodic ripples. A clear density jump at radius 24 kpc to north-east, about 10 out bubble rim, appears be due weak shock driven by northern bubble. similar front may exist both bubbles but masked elsewhere rim emission...
Magnetic fields in galaxy clusters have been measured using a variety of techniques, including: studies synchrotron relic and halo radio sources within clusters, inverse Compton X-ray emission from surveys Faraday rotation measures polarized both behind Cluster Cold Fronts images. These measurements imply that most cluster atmospheres are substantially magnetized, with typical field strengths order 1 microGauss high areal filling factors out to Mpc radii. There is likely, however, be...
Using Chandra X-ray observations of 9 nearby, luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from data and estimated black hole masses, power emerging these systems in relativistic jets. The jet powers, inferred energies timescales required to inflate cavities observed surrounding emitting gas, can be related by law model. A significant fraction (2.2^{+1.0}_{-0.7} per cent, for...
The aim of the present work is to constrain Coma cluster magnetic field strength, its radial profile and power spectrum by comparing Faraday Rotation Measure (RM) images with numerical simulations field. We have analyzed polarization data for seven radio sources in observed Very Large Array at 3.6, 6 20 cm, derived Measures kiloparsec scale resolution. Random three dimensional models been simulated various values central intensity B_0 power-law slope eta, where eta indicates how scales...
We report on the discovery of a supermassive binary black hole system in radio galaxy 0402+379, with projected separation between two holes just 7.3 pc. This is closest pair yet found by more than 2 orders magnitude. These results are based recent multifrequency observations using Very Long Baseline Array (VLBA), which reveal compact, variable, flat-spectrum, active nuclei within elliptical host 0402+379. Multiepoch from VLBA also provide constraints total mass and dynamics system. Low...
Abstract Compact symmetric objects (CSOs) are jetted active galactic nuclei (AGN) with overall projected size <1 kpc. The classification was introduced to distinguish these from the majority of compact AGN in centimeter-wavelength very long baseline interferometry observations, where observed emission is relativistically boosted toward observer. original criteria for CSOs were (i) evidence on both sides center activity and (ii) However, some jet axes close line sight appear have been...
view Abstract Citations (242) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Compact Symmetric Objects and the Evolution of Powerful Extragalactic Radio Sources Readhead, A. C. S. ; Taylor, G. B. Pearson, T. J. Wilkinson, P. N. Multifrequency radio observations compact symmetric objects 0108 + 388, 0710 439 2352 495, high-resolution VLA primary hot spot in Cygnus A, are used to investigate dependence on external density size, pressure,...
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We present a numerical approach to investigate the relationship between magnetic fields and Faraday rotation effects in clusters of galaxies. can infer structure strength intra-cluster by comparing our simulations with observed polarization properties extended cluster radio sources such as galaxies halos. find observations require field which fluctuates over wide range spatial scales (at least one order magnitude). If several polarized are located at different projected positions galaxy...
We present the first results of VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey 1127 sources with flat radio spectra. Through automated data reduction imaging routines, we have produced publicly available I, Q, U images detected polarized flux density from 37% sources. also developed an algorithm to use each source's I image automatically classify it as pointlike source, core jet, compact symmetric object (CSO) candidate, or complex source. Using Sloan Digital Sky (SDSS),...
The first station of the Long Wavelength Array (LWA1) was completed in April 2011 and is currently performing observations resulting from its call for proposals addition to a continuing program commissioning characterization observations. instrument consists 258 dual-polarization dipoles, which are digitized combined into beams. Four independently-steerable beams available, each with two tunings 16 MHz bandwidth that can be independently tuned any frequency between 10 88 MHz. system...
The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed detect predicted O(100) mK sky-averaged absorption of cosmic microwave background by hydrogen in neutral pre- and intergalactic medium just after cosmological Age. spectral signature would be associated with emergence a diffuse Lyα from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection this feature, an unexpectedly large amplitude 530 mK, centred at 78 MHz. Verification result independent...
We present the first statistical study of X-ray cavities in distant clusters galaxies (z > 0.3). With aim providing further insight into how AGN feedback operates at higher redshift, we have analysed Chandra observations Massive Cluster Survey (MACS) and searched for surface-brightness depressions associated with Brightest Galaxy (BCG). The MACS sample consists most luminous within 0.3 < z 0.7 (median L_(X,RASS) = 7*10^44 erg/s), out 76 clusters, find 13 "clear" 7 "potential" (detection rate...
LWA1 is a new radio telescope operating in the frequency range 10-88 MHz, located central New Mexico. The consists of 258 pairs dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one instrument's "all dipoles" modes, facilitating all-sky imaging. Notable features instrument include high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to...
Abstract We use a sample of 54 compact symmetric objects (CSOs) to confirm that there are two unrelated CSO classes: an edge-dimmed, low-luminosity class (CSO 1), and edge-brightened, high-luminosity 2). Using blind tests, we show 2s consist three subclasses: 2.0, having prominent hot spots at the leading edges narrow jets and/or lobes; 2.2, without with broad 2.1, which exhibit mixed properties. Most do not evolve into larger jetted active galactic nuclei (AGN), but spend their whole life...
Abstract Compact symmetric objects (CSOs) are compact (<1 kpc), jetted active galactic nuclei (AGN), whose jet axes not aligned close to the line of sight, and observed emission is predominantly relativistically boosted toward us. Two classes CSOs have previously been identified: approximately one-fifth edge dimmed rest brightened. We designate these as CSO 1s 2s, respectively. This paper focuses almost exclusively on 2s. Using complete samples 2s we present three independent lines...
We extend our earlier work on cluster cores with distinct radio bubbles, adding more active i.e. those Ghz emission, to sample, and also investigating ``ghost bubbles,'' without GHz emission. have determined k, which is the ratio of total particle energy that electrons radiating between 10 MHz GHz. Constraints ages bubbles confirm factor, volume filling f lies within range 1 < k/f 1000. In assumption there pressure equilibrium radio-emitting plasma surrounding thermal X-ray gas, none lobes...
We have found broad Hα and Hβ line emission in spectra of BL Lacertae taken on 1995 May 21 June 1: those occasions Lac did not meet the defining criteria for class named after it. The luminosity, ~2 × 1041 h-2 erg s-1 H0 = 100 h km Mpc-1, is significantly above detection threshold older published which do show line. Several possible explanations increase luminosity are discussed. continuum was at faint end its commonly observed range: V ~ 16.0 21. polarization, measured 1, also near low...