558 research outputs found
VLBI Imagings of Kilo-parsec Knot in 3C 380
We investigate observational properties of a kilo-parsec scale knot in
radio-loud quasar 3C 380 by using two epoch archival data obtained by Very Long
Baseline Interferometry (VLBI) at 5 GHz on 1998 July and 2001 April. We succeed
in obtaining the highest spatial resolution image of the bright knot K1 located
at 732 milliarcseconds, or more than 20 kpc de-projected, downstream from the
nucleus three times better than previously obtained highest resolution image by
Papageorgiou et al. (2006). Our images reveal, with new clarity, "inverted
bow-shock" structure in K1 facing the nucleus and its morphology resembles a
conical shock wave. By comparing the two epoch images directly, we explore the
kinematics of K1 and obtain the upper limit of apparent velocity, 0.25 mas/yr
or 9.8 c of K1 for the first time. The upper limit of apparent velocity is
marginally smaller than superluminal motions seen in the core region. Further
new epoch VLBI observations are necessary to measure the proper motion at K1.Comment: 15 pages, 4 figures, accepted for publication in PAS
Evidence for nuclear radio jet and its structure down to <100 Schwarzschild radii in the center of the Sombrero galaxy (M 104, NGC 4594)
Abridged: We investigated the detailed radio structure of the nucleus of the
Sombrero galaxy using high-resolution, quasi-simultaneous, multi-frequency,
phase-referencing VLBA observations. We obtained the VLBI images toward this
nucleus, with unprecedented sensitivities and resolutions, at the seven
frequencies between 1.4 and 43 GHz, where those at 15, 24 and 43 GHz are the
first clear VLBI detections. At 43 GHz, the nuclear structure was imaged on a
linear scale under 100 Schwarzschild radii. For the first time, we have
discovered the presence of the extended structure in this nucleus, which is
directing from the radio core in two sides toward northwest/southeast
directions. The nuclear structure shows a clear spatial gradient on the radio
spectra, which is similar to that commonly seen in more luminous AGN with
powerful relativistic jets. Moreover, the radio core shows a
frequency-dependent size with an elongated shape, and the position of the core
also tends to be frequency dependent. A set of these new findings provide
evidence that the central engine of the Sombrero is powering radio jets. Based
on the observed brightness ratio of jet-to-counter jet, core position shift and
its comparison with a theoretical model, we constrained the following
fundamental physical parameters for the M 104 jets: (1) the northern side is
the approaching jet, whereas the southern side is receding: (2) the inclination
angle of the jet is relatively close to our line-of-sight, probably less than
~25degrees: (3) the jet intrinsic velocity is highly sub-relativistic at a
speed less than ~0.2c. The derived pole-on nature of the M 104 jet is in
accordance with the previous argument that M 104 contains a true type II AGN,
i.e., the broad line region of this nucleus is actually absent or intrinsically
weak, if the plane of the presumed circumnuclear torus is perpendicular to the
axis of the radio jets.Comment: 12 pages, 9 figures, 4 tables, accepted for publication in Ap
High-Sensitivity 86GHz (3.5mm) VLBI Observations of M87: Deep Imaging of the Jet Base at a 10 Schwarzschild-Radius Resolution
We report on results from new high-sensitivity, high-resolution 86GHz (3.5
millimeter) observations of the jet base in the nearby radio galaxy M87,
obtained by the Very Long Baseline Array in conjunction with the Green Bank
Telescope. The resulting image has a dynamic range exceeding 1500 to 1, the
highest ever achieved for this jet at this frequency, resolving and imaging a
detailed jet formation/collimation structure down to ~10 Schwarzschild radii
(Rs). The obtained 86GHz image clearly confirms some important jet features
known at lower frequencies, i.e., a wide-opening angle jet base, a
limb-brightened intensity profile, a parabola-shape collimation profile and a
counter jet. The limb-brightened structure is already well developed at <
0.2mas (< 28Rs, projected) from the core, where the corresponding apparent
opening angle becomes as wide as ~100 degrees. The subsequent jet collimation
near the black hole evolves in a complicated manner; there is a "constricted"
structure at tens Rs from the core, where the jet cross section is locally
shrinking. We suggest that an external pressure support from the inner part of
radiatively-inefficient accretion flow may be dynamically important in
shaping/confining the footprint of the magnetized jet. We also present the
first VLBI 86GHz polarimetric experiment for this source, where a highly
polarized (~20%) feature is detected near the jet base, indicating the presence
of a well-ordered magnetic field. As a by-product, we additionally report a
43/86 GHz polarimetric result for our calibrator 3C 273 suggesting an extreme
rotation measure near the core.Comment: Accepted for publication in ApJ. 39 pages, 11 figures, 3 table
Left Hemihepatectomy for Hepatocellular Carcinoma Following Esophagectomy with Retrosternal Gastric Tube Reconstruction for Esophageal Cancer
Approximately 4% of patients with esophageal cancer develop a second primary malignancy in the upper gastrointestinal trunk. However, hepatectomy following esophagectomy for esophageal cancer has rarely been reported. We report the case of a 70-year-old man who underwent an esophagectomy for esophageal cancer with retrosternal gastric tube reconstruction. Nine years later, he developed hepatocellular carcinoma with tumor thrombus involving the left portal vein, and was successfully treated with left hemihepatectomy. Special attention should be paid to avoiding incidental injury of the gastric tube as well as the right gastroepiploic artery during the hepatectomy
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