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Evidence for a black hole from high rotation velocities in a sub-parsec region of NGC4258
MANY galaxies are thought to contain massive black holes— exceeding ten million solar masses—at their centres1,2, but firm observational evidence has proved to be surprisingly elusive. The best
A geometric distance to the galaxy NGC4258 from orbital motions in a nuclear gas disk
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
A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant*
We present initial results from a time series BVI survey of two fields in NGC 4258 using the HST ACS. This galaxy was selected because of its accurate maser-based distance, which is anticipated to
A Warped Accretion Disk and Wide-Angle Outflow in the Inner Parsec of the Circinus Galaxy
We present the first VLBI maps of H2O maser emission (λ1.3 cm) in the nucleus of the Circinus galaxy, constructed from data obtained with the Australia Telescope Long Baseline Array. The maser
We report a new geometric maser distance estimate to the active galaxy NGC 4258. The data for the new model are maser line-of-sight (LOS) velocities and sky positions from 18 epochs of very long
wsclean: an implementation of a fast, generic wide-field imager for radio astronomy
Astronomical widefield imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new
Vlbi imaging of water maser emission from the nuclear torus of ngc 1068
We have made the first VLBI synthesis images of the H2O maser emission associated with the central engine of the Seyfert galaxy NGC 1068. Emission extends about ±300 km s-1 from the systemic
Q0906+6930: The Highest Redshift Blazar
We report the discovery of a radio-loud flat-spectrum QSO at z = 5.47 with properties similar to those of the EGRET γ-ray blazars. This source is the brightest radio QSO at z > 5, with a parsec-scale
The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies
Abstract The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the