Radio Emission from the Intermediate-mass Black Hole in the Globular Cluster G1 (2007)
Ulvestad, James S., Greene, Jenny E., Ho, Luis C.
We have used the Very Large Array (VLA) to search for radio emission from the globular cluster G1 (Mayall-II) in M31. G1 has been reported by Gebhardt et al. to contain an intermediate-mass black...
CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources (2007)
Healey, Stephen E., Romani, Roger W., Taylor, Gregory B., Sadler, Elaine M., Ricci, Roberto, Murphy, Tara, ...
We have assembled an 8.4 GHz survey of bright, flat-spectrum (alpha > -0.5) radio sources with nearly uniform extragalactic (|b|>10 deg) coverage for sources brighter than S_{4.8 GHz} = 65 mJy. The...
A VLBI Search for Radio Supernovae in Wolf Rayet Galaxies (2007)
Ulvestad, James S., Johnson, Kelsey E., Neff, Susan G.
We have used the VLBI High Sensitivity Array (VLBA with VLA, Green Bank Telescope, and Arecibo) to search for young radio supernovae in three nearby Wolf Rayet dwarf galaxies containing Super Star...
The Radio Quiescence of Active Galaxies with High Accretion Rates (2005)
Greene, Jenny E., Ho, Luis C., Ulvestad, James S.
We present 6 cm Very Large Array observations of the Greene & Ho (2004) sample of 19 low-mass active galaxies with high accretion rates. This is one of the only studies of a uniform sample of...
VLBA Identification of the Milliarcsecond Active Nucleus in the Seyfert Galaxy NGC 4151 (2005)
Ulvestad, James S., Wong, Diane S., Taylor, Gregory B., Gallimore, Jack F., Mundell, Carole G.
The Seyfert galaxy NGC 4151 has been imaged at resolution better than 0.1 pc using a VLBI array consisting of the VLBA and three 100m-class telescopes. A flat-spectrum 3-mJy source with a...
The Size of the Radio-Emitting Region in Low-luminosity Active Galactic Nuclei (2005)
Anderson, James M., Ulvestad, James S.
We have used the VLA to study radio variability among a sample of 18 low luminosity active galactic nuclei (LLAGNs), on time scales of a few hours to 10 days. The goal was to measure or limit the...
VLBA Imaging of Central Engines in Radio Quiet Quasars (2004)
Ulvestad, James S., Antonucci, Robert R. J., Barvainis, Richard
We have used the Very Long Baseline Array (VLBA) to image five radio-quiet quasars (RQQs) at milliarcsecond resolution, at frequencies between 1.4 and 5 GHz. These quasars have typical total flux...
POINTS (Precision Optical INTerferometer in Space) (2004)
Schumaker, Bonnie L., Ulvestad, James S., Agronin, Michael L.
POINTS is a high-precision, high-throughput interferometer intended for astromomy only. It can perform science compatable with astrophysics (AIM) and planet detection (TOPS-1). The spacecraft will be...
ARISE: A Space VLBI Mission Using an Inflatable Antenna Structure (2004)
We currently are studying an advanced space Very Long Baseline Interferometry (VLBI) mission
The Radio Continuum of the Metal-Deficient Blue Compact Dwarf Galaxy SBS0335-052 (2004)
Hunt, Leslie K., Dyer, Kristy K., Thuan, Trinh X., Ulvestad, James S.
We present new Very Large Array observations at five frequencies, from 1.4 to 22GHz, of the extremely low-metallicity blue compact dwarf SBS0335-052. The radio spectrum shows considerable absorption...
Low-Luminosity AGNs at the Highest Resolution: Jets or Accretion Flows? (2003)
Anderson, James M., Ulvestad, James S., Ho, Luis C.
Six low-luminosity active galactic nuclei have been imaged at multiple frequencies from 1.7--43 GHz (2.3--15 GHz for three of the galaxies) using the Very Long Baseline Array. In spite of dynamic...
Detection of the "Active" Nucleus of M32 (2003)
Ho, Luis C., Terashima, Yuichi, Ulvestad, James S.
M32 hosts a 2.5x10^6 solar mass central black hole, but signs of nuclear activity in this galaxy have long eluded detection. We report the first conclusive detection of the nucleus of M32 in X-rays,...
VLBI Imaging of Seyfert Galaxies (2003)
The advent of the Very Long Baseline Array and its phase-referencing capability have enabled milliarcsecond-scale imaging of radio sources at sub-millijansky sensitivity, opening the door to...
A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra (2002)
Ulvestad, James S., Ho, Luis C.
(Abridged) We have searched for nuclear radio emission from a statistically complete sample of 40 Sc galaxies within 30 Mpc that are optically classified as star-forming objects, in order to...
Astronomy Astrophysics manuscript no. January 23, 2002 (2002)
Neil M. Nagar, Heino Falcke, Andrew S. Wilson, James S. Ulvestad
This paper presents the results of a high resolution radio imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs) at D 19 Mpc. We rst report new 2 cm (150 mas resolution...
Neil M. Nagar, Andrew S. Wilson, Heino Falcke, James S. Ulvestad, Carole G. Mundell
There is now strong evidence that many LLAGNs contain accreting massive black holes and that the nuclear radio emission is dominated by parsec-scale jets launched by these black holes. Here, we...
Ulvestad, James S., Ho, Luis C.
The low-luminosity active galactic nuclei in NGC 3147, NGC 4203, and NGC 4579 have been imaged at four frequencies with the Very Long Baseline Array. The galaxies are unresolved at all frequencies,...
Statistical Properties of Radio Emission from the Palomar Seyfert Galaxies (2001)
Ulvestad, James S., Ho, Luis C.
We have carried out an analysis of the radio and optical properties of a statistical sample of 45 Seyfert galaxies from the Palomar spectroscopic survey of nearby galaxies. We find that the space...
Radio Continuum Survey of an Optically-Selected Sample of Nearby Seyfert Galaxies (2001)
Ho, Luis C., Ulvestad, James S.
We have used the Very Large Array (VLA) to conduct a survey for radio continuum emission in the sample of 52 Seyfert nuclei selected from the optical spectroscopic galaxy catalog of Ho, Filippenko,...
Heino Falcke, Neil M. Nagar, Andrew S. Wilson, James S. Ulvestad
We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio ux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected...
Falcke, Heino, Nagar, Neil M., Wilson, Andrew S., Ulvestad, James S.
We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected...
Cicrumnuclear Supernova Remnants and HII Regions in NGC 253 (2000)
Archival VLA data has been used to produce arcsecond-resolution 6- and 20-cm images of the region surrounding the nuclear 200-pc (~15") starburst in NGC 253. Twenty-two discrete sources stronger than...
VLA and VLBA observations of compact radio cores in LINER galaxies (1999)
Heino Falcke, Luis C. Ho, James S. Ulvestad, Andrew S. Wilson, Neil M. Nagar
. A VLA survey of nearby LINER galaxies at 15 GHz has revealed the presence of a compact radio core in many sources. The cores seem to be correlated with the optical activity. Follow-up VLBA...
Goals of the ARISE Space VLBI Mission (1999)
Supermassive black holes, with masses of 10^6 to more than 10^9 solar masses, are among the most spectacular objects in the Universe, and are laboratories for physics in extreme conditions. The...
VLA and VLBA observations of compact radio cores in LINER galaxies (1998)
Falcke, Heino, Ho, Luis C., Ulvestad, James S., Wilson, Andrew S., Nagar, Neil M.
A VLA survey of nearby LINER galaxies at 15 GHz has revealed the presence of a compact radio core in many sources. The cores seem to be correlated with the optical activity. Follow-up VLBA...
Future Space Vlbi Missions (1998)
This paper describes the history of the Space VLBI technique, and its natural extension to future Space VLBI programs. Two specific future missions, VSOP-2 and ARISE, are discussed. Finally, some...
Future Space Vlbi Missions (1998)
This paper describes the history of the Space VLBI technique, and its natural extension to future Space VLBI programs. Two specific future missions, VSOP-2 and ARISE, are discussed. Finally, some...
ARISE: A Space VLBI Mission Using an Inflatable Antenna Structure (1996)
James S. Ulvestad, Roger P, Joel G. Smith, James S. Roger P
We currently are studying an advanced space Very Long Baseline mission called ARISE (Advanced Radio between Space and Earth). One or two spacecraft Earth orbit would form interferometers on baselines...