Now showing items 1-20 of 32

• #### A 4% Geometric Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk ﻿

(Springer Nature, 1999)
The accurate measurement of extragalactic distances is a central challenge of modern astronomy, being required for any realistic description of the age, geometry and fate of the Universe. The measurement of relative ...
• #### Accelerations of Water Masers in NGC 4258 ﻿

(IOP Publishing, 2000)
The water masers in NGC4258 delineate the structure and dynamics of a sub-parsec-diameter accretion disk around a supermassive black hole. VLBA observations provide precise information about the positions in the plane of ...
• #### CHIPS: The Cosmological HI Power Spectrum Estimator ﻿

(American Astronomical Society, 2016)
Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization, and estimation of its basic physical parameters, is the principal scientific aim of many current low-frequency radio telescopes. Here ...
• #### Coexisting conical bipolar and equatorial outflows from a high-mass protostar ﻿

(Springer Nature, 1998)
The BN/KL region in the Orion molecular cloud1 is an archetype in the study of the formation of stars much more massive than the Sun2. This region contains luminous young stars and protostars, but it is difficult to study ...
• #### Delay Spectrum with Phase-Tracking Arrays: Extracting the HI power spectrum from the Epoch of Reionization ﻿

(American Astronomical Society, 2016)
The Detection of redshifted 21 cm emission from the epoch of reionization (EoR) is a challenging task owing to strong foregrounds that dominate the signal. In this paper, we propose a general method, based on the delay ...
• #### Discovery of Candidate H2O Disk Masers in Active Galactic Nuclei and Estimations of Centripetal Accelerations ﻿

(IOP Publishing, 2009)
Based on spectroscopic signatures, about one-third of known H2O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These “disk maser candidates” ...
• #### The Discovery of H2O Maser Emission in Seven AGN and at High Velocities in the Circinus Galaxy ﻿

(IOP Publishing, 2002)
We report the discovery of H2O maser emission at 1.35 cm wavelength in seven active galactic nuclei (at distances up to < 80 Mpc) during a survey conducted at the 70-m diameter antenna of the NASA Deep Space Network near ...
• #### Discovery of Water Maser Emission in Eight AGNs with 70 m Antennas of NASA’s Deep Space Network ﻿

(IOP Publishing, 2006)
We report the discovery of water maser emission in eight active galactic nuclei (AGN) with the 70-m NASA Deep Space Network (DSN) antennas at Tidbinbilla, Australia and Robledo, Spain. The positions of the newly discovered ...
• #### Discovery of Water Maser Emission in Five AGNs and a Possible Correlation Between Water Maser and Nuclear 2–10 keV Luminosities ﻿

(IOP Publishing, 2006)
We report the discovery of water maser emission in five active galactic nuclei (AGN) with the 100-m Green Bank Telescope (GBT). The positions of the newly discovered masers, measured with the VLA, are consistent with the ...
• #### Enabling a High Throughput Real Time Data Pipeline for a Large Radio Telescope Array with GPUs ﻿

(Elsevier, 2010)
The Murchison Widefield Array (MWA) is a next-generation radio telescope currently under construction in the remote Western Australia Outback. Raw data will be generated continuously at 5 GiB s$^{−1}$, grouped into 8 s ...
• #### Evidence for a Geometrically Thick Self‐Gravitating Accretion Disk in NGC 3079 ﻿

(IOP Publishing, 2005)
We have mapped, for the first time, the full velocity extent of the water maser emission in NGC 3079. The largely north-south distribution of emission, aligned with a kpc-scale molecular disk, and the segregation of blue- ...
• #### First limits on the 21 cm power spectrum during the Epoch of X-ray heating ﻿

(Oxford University Press (OUP), 2016)
We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 ...
• #### The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258 ﻿

(IOP Publishing, 2005)
A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ∼ 2 σ deviation from Keplerian motion in the projected rotation curve of the high-velocity features, corresponding to a ∼ 9 km s−1, or ...
• #### A Green Bank Telescope Search for Water Masers in Nearby Active Galactic Nuclei ﻿

(IOP Publishing, 2004)
Using the Green Bank Telescope, we have conducted a survey for 1.3 cm water maser emission toward the nuclei of nearby active galaxies, the most sensitive large survey for H2O masers to date. Among 145 galaxies observed, ...
• #### A high reliability survey of discrete Epoch of Reionization foreground sources in the MWA EoR0 field ﻿

(Oxford University Press (OUP), 2016)
Detection of the Epoch of Reionization HI signal requires a precise understanding of the intervening galaxies and AGN, both for instrumental calibration and foreground removal. We present a catalogue of 7394 extragalactic ...
• #### The IC 133 Water Vapor Maser in the Galaxy M33: A Geometric Distance ﻿

(IOP Publishing, 2004)
We report on the results of a 14 year long VLBI study of proper motions in the IC 133 H2O maser source in the galaxy M33. The method of Ordered Motion Parallax was used to model the 3-dimensional structure and dynamics of ...
• #### Line Imaging of Orion KL at 865 μm with the Submillimeter Array ﻿

(IOP Publishing, 2005)
We present the first submm (865 µm) imaging spectral line survey at one arcsecond resolution conducted with the Submillimeter Array toward Orion-KL. Within the two × two GHz bandpasses (lower and upper sidebands, 337.2–339.2GHz ...
• #### Low frequency observations of linearly polarized structures in the interstellar medium near the south Galactic pole ﻿

(American Astronomical Society, 2016)
We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg^2 centered on RA=0 h, Dec=-27 deg. The sensitivity available in our deep observations allows an in-band, ...
• #### The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology ﻿

(American Astronomical Society, 2016)
We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical ...
• #### Observational evidence for massive black holes in the centers of active galaxies ﻿

(Springer Nature, 1999)
Naturally occurring water vapor maser emission at 1.35 cm wavelength provides an accurate probe for the study of accretion disks around highly compact objects, thought to be black holes, in the centers of active galaxies. ...