154 research outputs found
Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261
We report dual-frequency very long baseline interferometry (VLBI)
observations at 22 and 43 GHz toward the nucleus of a nearby radio galaxy NGC
4261. In particular, we present a VLBI image of the 22 GHz H2O maser line and
its location in the circumnuclear region of NGC 4261. H2O maser emission is
marginally detected above the three times the rms level within a velocity range
of approximately 2250-2450 km/s, slightly red-shifted with respect to the
systemic velocity. H2O maser emission is located approximately 1 milliarcsecond
(mas) east of the brightest continuum component at 22 GHz, where the continuum
spectrum is optically thick, that is at the free-free absorbed receding jet by
ionized gas. A positional coincidence between H2O maser emission and an ionized
gas disk implies that the H2O maser emission arises from the near side of the
disk, amplifying continuum emission from the background receding jet. If the
disk axis is oriented 64 degree relative to the line of sight, the H2O maser
emission is expected to be at a mean radius of 0.3 pc in the disk. The broad
line width of the H2O maser emission can be attributed to complex kinematics in
the immediate vicinity of the supermassive black hole (SMBH), including ongoing
gas infall onto the SMBH, turbulence, and outflow. This is analogous to the
multi-phase circumnuclear torus model in the nearest radio-loud H2O megamaser
source NGC 1052. An alternative explanation for H2O maser association is the
shock region between the jet and the ambient molecular clouds. However, this
explanation fails to describe the explicit association of H2O maser emission
only with the free-free absorbed receding jet.Comment: 10 pages, 5 figures, submitted to PAS
Free-Free Absorption and the Unified Scheme
We report Very-Long-Baseline Array (VLBA) observations at 2.3, 8.4, and 15.4
GHz towards nine GHz-Peaked Spectrum (GPS) sources. One Seyfert 1 galaxy, one
Seyfert 2 galaxy, three radio galaxies, and four quasars were included in our
survey. We obtained spatial distributions of the Free-Free Absorption (FFA)
opacity with milliarcsec resolutions for all sources. It is found that type-1
(Seyfert 1 and quasars) and type-2 (Seyfert 2 and radio galaxies) sources
showed different distributions of the FFA opacities. The type-1 sources tend to
show more asymmetric opacity distributions towards a double lobe, while those
of the type-2 sources are rather symmetric. Our results imply that the
different viewing angle of the jet causes the difference of FFA opacity along
the external absorber. This idea supports the unified scheme between quasars
and radio galaxies, proposed by Barthel (1989).Comment: 17 pages, including 8 figures. Proceedings of the 3rd Compact Steep
Spectrum and GHz Peaked Spectrum Sources, 2002, Greece. Submitted to the
Publications of Astronomical Society of Australi
Dense Plasma Torus in the GPS Galaxy NGC 1052
We report results from nearly simultaneous pentachromatic VLBI observations
towa rds a nearby GPS galaxy NGC 1052. The observations at 1.6 and 4.8 GHz with
VSOP, and at 2.3, 8.4, and 15.4 GHz wit h VLBA, provide linear resolutions of
pc. Convex spectra of a double-sided jet imply that synchrotron
emission is obscured through foreground cold dense plasma, in terms of
free--free absorption (FFA). We found a central condensation of the plasma
which covers about 0.1 pc and 1 pc of the approaching and receding jets,
respectively. A simple model with a geometrically thick plasma torus
perpendicular to the jets is established to explain the asymmetric distribution
of FFA opacities.Comment: 9 pages, 4 figures, other comment
Decomposition Characteristics of Benzene, Toluene and Xylene in an Atmospheric Pressure DC Corona Discharge II. Characteristics of Deposited By-products and Decomposition Process
Gaseous by-products and deposited material obtained from the decomposition of benzene, toluene and xylene in an atmospheric pressure DC corona discharge were minutely investigated by gas chromatograph mass spectrometry and infrared absorption spectroscopy, and the decomposition processes of benzene, toluene and xylene were estimated. It was found that carbon dioxide (CO2), carbon monoxide (CO), formic acid (HCOOH) and formic anhydride ((CHO)2) were the major gaseous by-products from benzene, toluene and xylene, while acetic formic anhydride (CH3COOCHO) and acetic acid (CH3COOH) were the major by-products from toluene and xylene. Benzaldehyde (C6H5CHO) and methyl benzaldehyde (CH3CH4CHO) were produced from toluene and xylene, respectively. It was hypothesized that the decomposition of benzene, toluene, and xylene was initiated by the production of phenyl radicals, phenyl and benzyl radicals, and methyl benzyl and methyl phenyl radicals, respectively. These radicals are deposited on electrodes, wall, etc., resulting in the polymerization of aromatic rings and the substitution of function groups. Also, those radicals are decomposed and converted into by-products described above. In addition, it is probably that benzyl and methyl benzyl radicals are precursors of C6H5CHO and CH3C6H4CHO, respectively, and that C6H5CHO and CH3C6H4CHO are decomposed, contributing to by-product production and deposition. Furthermore, some intermediate by-products, produced by the cleavage of the aromatic ring in benzene, toluene and xylene decomposition and containing O=C-O, C=O, O-H, and C-H groups, may be deposit on the electrodes
ALMA Detection of 321 GHz water maser emission in the radio galaxy NGC 1052
The Atacama Large Millimeter/submillimeter Array (ALMA) serendipitously
detected HO emission at 321 GHz in NGC
1052. This is the first submillimeter maser detection in a radio galaxy and the
most luminous 321-GHz HO maser known to date with the isotropic luminosity
of 1090 . The line profile consists of a broad velocity component
with FWHM km s straddling the systemic velocity and a
narrow component with FWHM km s blueshifted by 160 km
s. The profile is significantly different from the known 22-GHz maser which shows a broad profile redshifted by 193 km s. The
submillimeter maser is spatially unresolved with a synthesized beam of
and coincides with the
continuum core position within 12 pc. These results indicate amplification of
the continuum emission through high-temperature ( K) and dense ( cm) molecular gas in front of the coreComment: 3 figures, Accepted for publication in Publications of Astronomical
Society of Japa
Neuronal Insulin Receptor Signaling: A Potential Target for the Treatment of Cognitive and Mood Disorders
Spontaneous Vacuolar Degeneration of the Thyroid Follicular Epithelium in Cynomolgus Monkeys
Vacuolar degeneration of the thyroid follicular epithelium was observed in two untreated
female cynomolgus monkeys assigned to control groups. In light microscopy, large vacuoles
containing a homogenous substance occupied the basal region of the epithelium, and the
nuclei had shifted toward the apical region. The vacuoles showed negative reactions to PAS
and thyroglobulin. Electron microscopic observation revealed dilatation of the rough
endoplasmic reticulum corresponding to the vacuoles. The plasma TSH, T3 and T4 levels
determined for the samples kept frozen were within the normal ranges, suggesting that the
thyroid function was kept intact
Positional Coincidence of H2O Maser and a Plasma Obscuring Torus in Radio Galaxy NGC 1052
We present multi-frequency simultaneous VLBA observations at 15, 22 and 43
GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three
continuum images reveal a double-sided jet structure, whose relative intensity
ratios imply that the jet axis is oriented close to the sky plane. The steeply
rising spectra at 15-43 GHz at the inner edges of the jets strongly suggest
that synchrotron emission is absorbed by foreground thermal plasma. We detected
H2O maser emission in the velocity range of 1550-1850 km/s, which is redshifted
by 50-350 km/s with respect to the systemic velocity of NGC 1052. The
redshifted maser gas appears projected against both sides of the jet, in the
same manner as the HI seen in absorption. The H2O maser gas are located where
the free-free absorption opacity is large. This probably imply that the masers
in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus
of NGC 4258. Such circumnuclear structure can be the sence of accreting onto
the central engine.Comment: 18 pages, 7 figures, accepted for publication in Ap
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