相关论文: Subparsec-scale HI in the nucleus of NGC 4151

Sensitive high angular and linear resolution radio images of the 240-pc radio jet in NGC4151, imaged at linear resolutions of 0.3 to 2.6 pc using the VLBA and phased VLA at 21 cm, are presented and reveal for the first time a faint, highly…

We observed the nuclear region of NGC 4261 (3C270) with the VLBA at two frequencies (1.6 and 8.4 GHz) simultaneously. We find that the position angle of the parsec-scale radio axis agrees, within the errors, with the position angle of the…

Using a combination of observations involving the VLA, MERLIN and global VLBI networks we have made a detailed study of the radio continuum and the neutral hydrogen (HI) kinematics and distribution within the central kiloparsec of the radio…

We have used the VLBA to produce a high dynamic range image of the nucleus of NGC 6251 at 1.6 GHz and snapshot images at 5.0, 8.4, and 15.3 GHz to search for emission from a parsec-scale counterjet. Previous VLBI images at 1.6 GHz have set…

We present results of VLA and VLBA observations of the 1.420 GHz neutral hydrogen absorption associated with the Compact Symmetric Object 1946+708 (z=0.101). We find significant structure in the gas on parsec scales. The peak column density…

One of the most important problems in the study of AGN is understanding the detailed geometry, physics, and evolution of the central engines and their environments. The leading models involve an accretion disk and torus around a central…

We present an HI absorption survey of the central 250 pc of the Galaxy. Very Large Array (VLA) observations were made at 21 cm in the DnC and CnB configurations and have a resolution of ~15"(0.6 pc at the Galactic Center (GC) distance) and…

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 monochromatic radio power of ~10^{37} ergs/s has…

We report on high sensitivity, spectral line VLBI observations of the HI absorption feature in the radio galaxy NGC4261. Although absorption is only detectable on the most sensitive baseline, it can be unambiguously associated with the…

In the last several years, a number of compact extragalactic radio sources have been found to exhibit neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Models proposed to explain this phenomenon involve…

We present sub-arcsecond, Multi-Element Radio Linked Interferometer (MERLIN) observations of the decimetre radio continuum structure and neutral hydrogen (HI) absorption from the nuclear region of the starburst galaxy NGC 4194 (the Medusa…

A sub-parsec scale radio counterjet has been detected in the nucleus of the closest radio galaxy, Centaurus A (NGC 5128), with VLBI imaging at 2.3 and 8.4 GHz. This is one of the first detections of a VLBI counterjet and provides new…

We present sensitive, high resolution Very Long Baseline Array (VLBA) observations of the central 0.3 arcsec of PKS 2322-123 at 1.3 and 5 GHz. These observations reveal straight and symmetric jets emerging from both sides of an inverted…

A number of extragalactic radio sources which exhibit symmetric jets on parsec scales have now been found to have neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Understanding the spatial distribution…

We report the GMRT detection of HI 21cm absorption from the $z \sim 3.39$ damped Lyman-$\alpha$ absorber (DLA) towards PKS 0201+113, the highest redshift at which 21cm absorption has been detected in a DLA. The absorption is spread over…

We present MERLIN observations of Galactic 21-cm HI absorption at an angular resolution of c. 0.1-0.2 arcsec and a velocity resolution of 0.5 km/s, in the direction of three moderately low latitude (-8< b <-12 deg) extragalactic radio…

We present 0.15 arcsec (56 pc) resolution MERLIN observations of neutral hydrogen (HI) 21 cm absorption detected towards the arcsecond-scale radio jet of the Seyfert 1.5 galaxy Markarian 6. Absorption is detected only towards a bright,…

(Abridged) We discuss multiple VLBI continuum and spectral line observations and WSRT spectroscopy of NGC 1052. Sub-parsec scale features move outward at approximately 0.26c in bi-symmetric jets, most likely oriented near the plane of the…

We have observed the supernova remnant (SNR) G290.1-0.8 in the 21-cm HI line and the 20-cm radio continuum using the Australia Telescope Compact Array (ATCA). The HI data were combined with data from the Southern Galactic Plane Survey to…

We present new, high angular resolution (~0.22") MERLIN observations of neutral hydrogen (HI) absorption and 21-cm radio continuum emission across the central ~900 parsecs of the ultraluminous infrared galaxy, Arp220. Spatially resolved HI…