98 research outputs found
The Diverse Properties of GPS Sources
We discuss the morphology and kinematics of five gigahertz-peaked spectrum
(GPS) sources that have been observed with the VLBA. We find a wide range of
observed properties including core-jet structure, superluminal motion,
variability, extended structure, and polarization, all of which appear to
deviate from commonly-accepted GPS paradigms (e.g., O'Dea 1998). We suggest
that the observed low frequency cutoff in GPS sources may be primarily due to
free-free absorption rather than synchrotron self-absorption.Comment: Proceedings of the 6th European VLBI Network Symposium, Ros E.,
Porcas R.W., Lobanov, A.P., & Zensus, J.A. (eds), MPIfR, Bonn, Germany. (4
pages, 5 figures, needs evn2002.cls style file
Острый панкреатит с точки зрения врача-интенсивиста
The paper considers the basic principles of the pathophysiology, as well as the diagnosis and treatment of patients with severe acute pancreatitis. Key words: acute pancreatitis, pathophysiology, diagnosis, treatment.В статье рассматриваются основные принципы патофизиологии острого панкреатита, диагностика и лечение больных с тяжелой формой острого панкреатита. Ключевые слова: острый панкреатит, патофизиология, диагностика, лечение
VLBI imaging of extremely high redshift quasars at 5 GHz
We present very long baseline interferometry (VLBI) images of ten very high
redshift (z>3) quasars at 5 GHz. The sources 0004+139, 0830+101, 0906+041,
0938+119 and 1500+045 were observed in September 1992 using a global VLBI
array, while 0046+063, 0243+181, 1338+381, 1428+423 and 1557+032 were observed
in October 1996 with the European VLBI Network and Hartebeesthoek, South
Africa. Most of the sources are resolved and show asymmetric structure. The
sample includes 1428+423, the most distant radio loud quasar known to date
(z=4.72). It is barely resolved with an angular resolution of about 2.0*1.4
mas.Comment: Astronomy and Astrophysics, in press, Latex2e, 10 pages, 3 figures
(and lots of sub-figures
VSOP observation of the quasar PKS 2215+020: a new laboratory for core-jet physics at z=3.572
We report results of a VSOP (VLBI Space Observatory Programme) observation of
a high redshift quasar PKS 2215+020 (z=3.572). The ~1 milliarcsecond resolution
image of the quasar reveals a prominent `core-jet' structure on linear scales
from 5/h to 300/h pc ($H_0=100*h km/(s*Mpc). The brightness temperatures and
sizes of bright features identified in the jet are consistent with emission
from relativistic shocks dominated by adiabatic energy losses. The jet is
powered by the central black hole with estimated mass of ~4*10^9 solar masses.
Comparisons with VLA and ROSAT observations indicate a possible presence of an
extended radio/X-ray halo surrounding 2215+020.Comment: 15 pages, 6 figures, aastex macros; accepted for publication in The
Astrophysical Journal, V.546, N.2 *(January 10 2001
Observations of the bright radio sources in the North Celestial Pole region at the RATAN-600 radio telescope
A survey of the North Celestial Pole region using the RATAN-600 radio
telescope at five frequencies in the range 2.3 to 21.7 GHz is described.
Sources were chosen from the NVSS catalogue. The flux densities of 171 sources
in the Declination range +75 to +88 are presented; typical flux density errors
are 5-10 percent including calibration errors. About 20 percent of the sources
have flat spectra or a flat component.Comment: 21 pages, 7 figures; to be published in Astronomy and Astrophysics
(without last figure with the spectra of the observed sources
FIRST-based survey of Compact Steep Spectrum sources I. MERLIN images of arc-second scale objects
Compact Steep Spectrum (CSS) sources are powerful extragalactic radio sources
with angular dimensions of the order of a few arcseconds or less. Such a
compactness is apparently linked to the youth of these objects. The majority of
CSSs investigated so far have been known since the early 1980s. This paper is
the first in a series where we report the results of an observational campaign
targeted on a completely new sample of CSSs which are significantly weaker than
those investigated before. The ultimate goal of that campaign is to find out
how ``weak'' CSSs compare to ``strong'', classical ones, especially with regard
to the morphologies. Here we present an analysis of morphological and physical
properties of five relatively large sources based on MERLIN observations at 1.6
and 5 GHz.Comment: 8 pages, 7 figures, A&A in pres
A Possible Periodicity in the Radio Lightcurves of 3C454.3
During the period 1966.5 - 2006.2 the 15GHz and 8GHz lightcurves of 3C454.3
(z=0.859) show a qsasi-periodicity of ~12.8 yr (~6.9 yr in the rest frame of
the source) with a double-bump structure. This periodic behaviour is
interpreted in terms of a rotating double-jet model in which the two jets are
created from the black holes in a binary system and rotate with the period of
the orbital motion. The periodic variations in the radio fluxes of 3C454.3 are
suggested to be mainly due to the lighthouse effects (or the variation in
Doppler boosting) of the precessing jets which are caused by the orbital
motion. In addition, variations in the mass-flow rates accreting onto the black
holes may be also involved.Comment: 15 pages, 11 figure
A kinematic study of the compact jet in quasar B3 1633+382
We present a study of the motion of compact jet components in quasar B3
1633+382. Through analyzing 14 epochs of VLBI observations of three components
(B1, B2, and B3) at 22 GHz, we find two different possibilities of component
classification. Thus two corresponding kinematical models can be adopted to
explain the evolutionary track of components. One is a linear motion, while
another is a helical model. Future observations are needed to provide new
kinematical constraints for the motion of these components in this source.Comment: 7 pages, 3 figures; Accepted for publication in A&
The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
The contribution of the Unresolved Extragalactic Radio Sources to the diffuse
brightness of the sky was evaluated using the source number - flux measurements
available in literature. We first optimized the fitting function of the data
based on number counts distribution. We then computed the brightness
temperature at various frequencies from 151 MHz to 8440 MHz and derived its
spectral dependence. As expected the frequency dependence can be described by a
power law with a spectral index , in agreement with the
flux emitted by the {\it steep spectrum} sources. The contribution of {\it flat
spectrum} sources becomes relevant at frequencies above several GHz. Using the
data available in literature we improved our knowledge of the brightness of the
unresolved extragalactic radio sources. The results obtained have general
validity and they can be used to disentangle the various contributions of the
sky brightness and to evaluate the CMB temperature.Comment: Accepted for publication in the Astrophysical Journa
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