The Pearson-Readhead Survey from Space
We are using the VSOP mission to observe a complete sample of Pearson-Readhead survey sources at 4.8 GHz to determine core brightness temperatures and pc-scale jet properties.
Radio↗
Engineering topics
Jones, D.
Publications and source records attributed to Jones, D..
The Sub-Parsec Structure of Accretion Disks as Revealed by VLBI Imaging of Free-Free Absorption
The physical conditions in the inner parsec of accretion disks believed to orbit the central black holes in active galactic nuclei can be probed by imaging the absorption of background radio emission by ionized gas in the disk.
Active Galaxies Accretion Disks Interferometry↗
Prospects for High Angular Resolution at Low Frequencies
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Interferometry Low Frequency↗
Space VLBI at Low Frequencies
At sufficiently low frequencies, no ground-based radio array will be able to produce high resolution images while looking through the ionosphere.
Space VLBI Interferometry Low Frequency↗
VSOP Observations of a Sub-Parsec Accretion Disk
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VLBI VSOP Active Galaxies Interferometry Accretion↗
Low Frequency Radio Astronomy from Above the Ionosphere
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VLBI low frequency interferometry surveys↗
Lunar Surface Arrays
During the latter half of the 1980's three concepts for low frequency arrays on the Moon were independently studied for NASA, leading to two workshops in 1990. The main technical challenges were those of deploying the array on the Moon, and of correlating the data on the Moon or returning all the raw data to Earth.
Lunar Moon low frequency arrays↗
The Effect of Two Lensing Galaxies on the Time Delay in PKS1830-211
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gravitational lens galaxies↗
The Effect of Two Lensing Galaxies on the Time Delay in PKS 1820-211
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Gravitational Lenses Cosmology↗
High Resolution VLBA Observations of NGC 4261
The VLBA's high angular resolution at 22 and 43 GHz allows the nuclei of nearby radio galaxies to be imaged with very high linear resolution. This is the scale on which absorption by the dense ionized inner regions of nuclear accretion disk should be detected.
Interferometry↗
The First Few Parsecs of the Jets in NGC 4261
We have imaged the nucleus of the nearby radio galaxy NGC 4261 (3C270) with the VLBA at 1.6, 8.4, 22, and 43 GHz. At 8.4 GHz our image reveals a narrow gap in emission just east of the core, which we interpret as absorption by an inner accretion disk seen nearly edge-on.
interferometry↗
The Radio Jets and Accretion Disk in NGC 4261
The structure of AGN accretion disks on sub-parsec scales can be probed through free-free absorption of synchrotron emission from the base of symmetric radio jets.
radio jets accretion disk NGC AGN↗
The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy
A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.
radio astronomy VLBJ interferometry explorer missi↗
A New Estimate of Hubble's Constant From The Gravitational Lens PKS 1830-211
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Gravitational Lens NICMOS VBLI morphology↗
A New Estimate of Hubble's Constant From The Gravitational Lens PKS 1830-211
The Einstein ring gravitational lens PKS 1830-211 consistents of two bright, milliarcsecond-scale radio components separated by 1 arcsec and connected by a fainter ring of radio emission (Rao and Subrahmanyan 1988; Jauncey et al. 1991).
Gravitational Lens PKS 1830-211 Hubble's Constant↗
The first few parsecs of the jets in NGC 4261
The double-lobed radio galaxy NGC 4261 (3C270) contains a pair of highly symmetric kpc-scale jets, as well as a two-sided morphology on parsec scales.
radio↗