1,581 research outputs found
VLBI observation of giant radio galaxy J1313+696 at 2.3/8.4 GHz
We report the result of VLBI observation of the giant radio galaxy J1313+696
(4C +69.15) at 2.3/8.4 GHz, only the core component of the giant radio galaxy
was detected in the VLBI observation at the dual frequencies. The result shows
a steep spectrum core with () between
2.3 GHz and 8.4 GHz. The steep spectrum core may be a sign of renewed activity.
Considering also the upper limit flux density of 2.0 mJy at 0.6 GHz from Konar
et al. 2004 the core has a GHz-peaked spectrum, implying that the core is
compact and absorbed. Further high resolution VLBI observations are needed to
identify if the steep spectrum core is consisting of a core and steep spectrum
jet.Comment: 3 pages, 3 figure
The CMB Dipole and Circular Galaxy Distribution
The validity of Hubble's law defies the determination of the center of the
big bang expansion, even if it exists. Every point in the expanding universe
looks like the center from which the rest of the universe flies away. In this
article, the author shows that the distribution of apparently circular galaxies
is not uniform in the sky and that there exists a special direction in the
universe in our neighborhood. The data is consistent with the assumption that
the tidal force due to the mass distribution around the universe center causes
the deformation of galactic shapes depending on its orientation and location
relative to the center and our galaxy. Moreover, the cmb dipole data can also
be associated with the center of the universe expansion, if the cmb dipole at
the center of our supercluster is assumed to be due to Hubble flow. The
location of the center is estimated from the cmb dipole data. The direction to
the center from both sets of data is consistent and the distance to the center
is computed from the cmb dipole data.Comment: 9 pages, 3 figures (10 figure captions), 1 tabl
Improving liquid chromatography efficiency: channels structured with micro-pillars
Band dispersion has been measured in micromachined separation channels structured with orderly disposed cylindrical micropillars. It was found that with an optimal channel design the band broadening could be lower by a factor of 3 than in packed columns with a comparable particle size. The positioning of the row of pillars closest to the side wall was a decisive factor in influencing band broadening
Modeling Non-Circular Motions in Disk Galaxies: Application to NGC 2976
We present a new procedure to fit non-axisymmetric flow patterns to 2-D
velocity maps of spiral galaxies. We concentrate on flows caused by bar-like or
oval distortions to the total potential that may arise either from a
non-axially symmetric halo or a bar in the luminous disk. We apply our method
to high-quality CO and Halpha data for the nearby, low-mass spiral NGC 2976
previously obtained by Simon et al., and find that a bar-like model fits the
data at least as well as their model with large radial flows. We find
supporting evidence for the existence of a bar in the baryonic disk. Our model
suggests that the azimuthally averaged central attraction in the inner part of
this galaxy is larger than estimated by these authors. It is likely that the
disk is also more massive, which will limit the increase to the allowed dark
halo density. Allowance for bar-like distortions in other galaxies may either
increase or decrease the estimated central attraction.Comment: 12 pages, 6 figures, accepted for publication in ApJ. v2: minor
changes to match proofs. For version with high-resolution figures, see
http://www.physics.rutgers.edu/~spekkens/papers/noncirc.pd
Self-Consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential
We calculate the self-consistent response of an axisymmetric galactic disk
perturbed by an elliptical halo potential of harmonic number m = 2, and obtain
the net disk ellipticity. Such a potential is commonly expected to arise due to
a galactic tidal encounter and also during the galaxy formation process. The
self-gravitational potential corresponding to the self-consistent,
non-axisymmetric density response of the disk is obtained by inversion of
Poisson equation for a thin disk. This response potential is shown to oppose
the perturbation potential, because physically the disk self-gravity resists
the imposed potential. This results in a reduction in the net ellipticity of
the perturbation halo potential in the disk plane. The reduction factor
denoting this decrease is independent of the strength of the perturbation
potential, and has a typical minimum value of 0.75 - 0.9 for a wide range of
galaxy parameters. The reduction is negligible at all radii for higher
harmonics (m > or = 3) of the halo potential. (abridged).Comment: 26 pages (LaTex- aastex style), 3 .eps figures. To appear in the
Astrophysical Journal, Vol. 542, Oct. 20, 200
The radio source B 1834+620: A double-double radio galaxy with interesting properties
We present a study of the peculiar radio galaxy B 1834+620. It is
characterised by the presence of a 420-kpc large edge-brightened radio source
which is situated within, and well aligned with, a larger (1.66 Mpc) radio
source. Both sources apparently originate in the same host galaxy, which has a
R_s-magnitude of 19.7 and a redshift of 0.5194, as determined from the strong
emission-lines in the spectrum. We have determined the rotation measures
towards this source, as well as the radio spectral energy distribution of its
components. The radio spectrum of the large outer source is steeper than that
of the smaller inner source. The radio core has a spectrum that peaks at a
frequency of a few GHz. The rotation measures towards the four main components
are quite similar, within rad m of 58 rad m. They are
probably largely galactic in origin. We have used the presence of a bright
hotspot in the northern outer lobe to constrain the advance velocity of the
inner radio lobes to the range between 0.19c and 0.29c, depending on the
orientation of the source. This corresponds to an age of this structure in the
range between 2.6 and 5.8 Myr. We estimate a density of the ambient medium of
the inner lobes of \la 1.6 \times 10^{-30} gr\,cm (particle density
\la 8 \times 10^{-7} cm). A low ambient density is further supported
by the discrepancy between the large optical emission-line luminosity of the
host galaxy and the relatively low radio power of the inner lobes.Comment: Accepted for publication in MNRA
Spectral ageing analysis of the double-double radio galaxy J1453+3308
We present new radio observations at frequencies ranging from 240 to 4860 MHz
of the well-known, double-double radio galaxy (DDRG), J1453+3308, using both
the Giant Metrewave Radio Telescope (GMRT) and the Very Large Array (VLA).
These observations enable us to determine the spectra of the inner and outer
lobes over a large frequency range and demonstrate that while the spectrum of
the outer lobes exhibits significant curvature, that of the inner lobes appears
practically straight. The break frequency, and hence the inferred synchrotron
age of the outer structure, determined from 16arcsec strips transverse to
the source axis, increases with distance from the heads of the lobes. The
maximum spectral ages for the northern and southern lobes are 47 and 58
Myr respectively. Because of the difference in the lengths of the lobes these
ages imply a mean separation velocity of the heads of the lobes from the
emitting plasma of 0.036c for both the northern and southern lobes. The
synchrotron age of the inner double is about 2 Myr which implies an advance
velocity of 0.1c, but these values have large uncertainties because the
spectrum is practically straight.Comment: 10 pages, 10 figures, 5 tables, accepted for publication in MNRA
Topicality and anaphoricity in Dutch scrambling
Direct objects in Dutch can precede or follow adverbs, a phenomenon commonly referred to as scrambling. The linguistic literature agrees in its assumption that scrambling is regulated by the topicality and anaphoricity status of definite objects, but theories vary as to what kinds of objects exactly are predicted to scramble. This study reports experimental data from a sentence completion experiment with adult native speakers of Dutch, showing that topics are scrambled more often than foci, and that anaphoric objects are scrambled more often than non-anaphoric objects. However, while the data provide support for the assumption that topicality and anaphoricity play an important role in scrambling, they also indicate that the discourse status of the object in and of itself cannot explain the full scrambling variation
Quantum secret sharing with qudit graph states
We present a unified formalism for threshold quantum secret sharing using
graph states of systems with prime dimension. We construct protocols for three
varieties of secret sharing: with classical and quantum secrets shared between
parties over both classical and quantum channels.Comment: 13 pages, 12 figures. v2: Corrected to reflect imperfections of (n,n)
QQ protocol. Also changed notation from to , corrected typos,
updated references, shortened introduction. v3: Updated acknowledgement
- …