2,249 research outputs found
Helical motions in the jet of blazar 1156+295
The blazar 1156+295 was observed by VLBA and EVN + MERLIN at 5 GHz in June
1996 and February 1997 respectively. The results show that the jet of the
source has structural oscillations on the milliarcsecond scale and turns
through a large angle to the direction of the arcsecond-scale extension. A
helical jet model can explain most of the observed properties of the radio
structure in 1156+295.Comment: 6 pages, 2 figures, to appear in New Astronomy Reviews (EVN/JIVE
Symposium No. 4, special issue
Morphological Dependence of MIR Properties of SDSS Galaxies in the Spitzer SWIRE Survey
We explore the correlation between morphological types and mid-infrared (MIR)
properties of an optically flux-limited sample of 154 galaxies from the Forth
Data Release (DR4) of Sloan Digital Sky Survey (SDSS), cross-correlated with
Spitzer SWIRE (Spitzer Wide-Area InfraRed Extragalactic Survey) fields of
ELAIS-N1, ELAIS-N2 and Lockman Hole. Aperture photometry is performed on the
SDSS and Spitzer images to obtain optical and MIR properties. The morphological
classifications are given based on both visual inspection and bulge-disk
decomposition on SDSS g- and r-band images. The average bulge-to-total ratio
(B/T) is a smooth function over different morphological types. Both the
8um(dust) and 24um(dust) luminosities and their relative luminosity ratios to
3.6um (MIR dust-to-star ratios) present obvious correlations with both the
Hubble T-type and B/T. The early-type galaxies notably differ from the
late-types in the MIR properties, especially in the MIR dust-to-star ratios. It
is suggested that the MIR dust-to-star ratio is an effective way to separate
the early-type galaxies from the late-type ones. Based on the tight correlation
between the stellar mass and the 3.6um luminosity, we have derived a formula to
calculate the stellar mass from the latter. We have also investigated the MIR
properties of both edge-on galaxies and barred galaxies in our sample. Since
they present similar MIR properties to the other sample galaxies, they do not
influence the MIR properties obtained for the entire sample.Comment: Accepted for publication by AJ. 18 pages, 14 figures, and 4 table
A relativistic helical jet in the gamma-ray AGN 1156+295
We present the results of a number of high resolution radio observations of
the AGN 1156+295. These include multi-epoch and multi-frequency VLBI, VSOP,
MERLIN and VLA observations made over a period of 50 months. The 5 GHz MERLIN
images trace a straight jet extending to 2 arcsec at P.A. -18 degrees. Extended
low brightness emission was detected in the MERLIN observation at 1.6 GHz and
the VLA observation at 8.5 GHz with a bend of about 90 degrees at the end of
the 2 arcsecond jet. A region of similar diffuse emission is also seen about 2
arcseconds south of the radio core. The VLBI images of the blazar reveal a
core-jet structure with an oscillating jet on a milli-arcsecond (mas) scale
which aligns with the arcsecond jet at a distance of several tens of
milli-arcseconds from the core. This probably indicates that the orientation of
the jet structure is close to the line of sight, with the northern jet being
relativistically beamed toward us. In this scenario the diffuse emission to the
north and south is not beamed and appears symmetrical. For the northern jet at
the mas scale, proper motions of 13.7 +/-3.5, 10.6 +/- 2.8, and 11.8 +/- 2.8 c
are measured in three distinct components of the jet (q_0=0.5, H_0=65 km /s
/Mpc are used through out this paper). Highly polarised emission is detected on
VLBI scales in the region in which the jet bends sharply to the north-west. The
spectral index distribution of the source shows that the strongest compact
component has a flat spectrum, and the extended jet has a steep spectrum. A
helical trajectory along the surface of a cone was proposed based on the
conservation laws for kinetic energy and momentum to explain the observed
phenomena, which is in a good agreement with the observed results on scales of
1 mas to 1 arcsec.Comment: 19 pages with 18 figures. Accepted for publication in the A&
Multipole analysis of spin observables in vector meson photoproduction
A multipole analysis of vector meson photoproduction is formulated as a
generalization of the pseudoscalar meson case. Expansion of spin observables in
the multipole basis and behavior of these observables near threshold and
resonances are examined.Comment: 15 pages, latex, 2 figure
Determination of the HQET Parameters from the Decay
We combine the resummations for radiative corrections and for the heavy quark
expansion to study the inclusive radiative decay . The
infrared renormalon ambiguity is also taken into account. Including both
theoretical and experimental uncertainties, we determine the allowed domain for
the HQET parameters and centered at GeV and GeV.Comment: IR renormalon ambiguity is include
Quelques remarques sur La Chatte de Colette
Résumé de l\u27éditeur
Quatrième de couverture
"Bien des contes, récits animaliers, romans, poèmes, encyclopédies ou histoires naturelles accordent une place de choix aux animaux. Les bestiaires, plus que tout autre genre, leur donnent un statut privilégié. Les bestiaires médiévaux, par leurs pratiques diversifiées, posent la question suivante : comment faire entrer l\u27animal dans l\u27organisation et le pouvoir de signification du livre ? Premier élément de réponse, la structure : le genre du bestiaire reflète l\u27instabilité des classifications du vivant et les incertitudes du savoir sur le monde qu\u27il soit philosophique, scientifique ou artistique. Deuxième élément : la valeur originelle de l\u27animal, à travers les codes du récit mythique et de la poésie, permet de dire l\u27origine de la littérature et de creuser la profondeur des sentiments les plus intimes. Le bestiaire individuel des écrivains renoue avec la dimension interprétative des premiers bestiaires et ouvre la voie à trois discours, sur l\u27homme, sur le monde qui l\u27entoure, comme sur la possibilité d\u27un autre monde. La complexité des liens entre animal et homme est autant affaire de relations, entre l\u27animal domestique et son maître, que de reflet, voire de caricature. Les bestiaires d\u27écrivains déploient idées et croyances, dans une perspective politique, sociale ou spirituelle qui va du grave à l\u27excentrique. Ils peuvent, à l\u27inverse, surtout à l\u27époque contemporaine, réactiver l\u27énergie de la description et traduire la fascination d\u27une rupture avec le réel, inscrite dans l\u27altérité de l\u27animal. Les contributions de ce recueil réuni en hommage à Arlette Bouloumié tentent de saisir comment le bestiaire a forgé un imaginaire inscrit tant dans son personnel animalier que dans ses codes génériques. Les écrivains, privilégiant tantôt la description des formes ou des comportements, tantôt la quête des significations, n\u27ont cessé de diversifier ce dosage.
Clusters, phason elasticity, and entropic stabilisation: a theory perspective
Personal comments are made about the title subjects, including: the relation
of Friedel oscillations to Hume-Rothery stabilisation; how calculations may
resolve the random-tiling versus ideal pictures of quasicrystals; and the role
of entropies apart from tile-configurational.Comment: IOP macros; 8pp, 1 figure. In press, Phil. Mag. A (Proc. Intl. Conf.
on Quasicrystals 9, Ames Iowa, May 2005
The potential use of service-oriented infrastructure framework to enable transparent vertical scalability of cloud computing infrastructure
Cloud computing technology has become familiar to most Internet users. Subsequently, there has been an increased growth in the use of cloud computing, including Infrastructure as a Service (IaaS). To ensure that IaaS can easily meet the growing demand, IaaS providers usually increase the capacity of their facilities in a vertical IaaS increase capability and the capacity for local IaaS amenities such as increasing the number of servers, storage and network bandwidth. However, at the same time, horizontal scalability is sometimes not enough and requires additional strategies to ensure that the large number of IaaS service requests can be met. Therefore, strategies requiring horizontal scalability are more complex than the vertical scalability strategies because they involve the interaction of more than one facility at different service centers. To reduce the complexity of the implementation of the horizontal scalability of the IaaS infrastructures, the use of a technology service oriented infrastructure is recommended to ensure that the interaction between two or more different service centers can be done more simply and easily even though it is likely to involve a wide range of communication technologies and different cloud computing management. This is because the service oriented infrastructure acts as a middle man that translates and processes interactions and protocols of different cloud computing infrastructures without the modification of the complex to ensure horizontal scalability can be run easily and smoothly. This paper presents the potential of using a service-oriented infrastructure framework to enable transparent vertical scalability of cloud computing infrastructures by adapting three projects in this research: SLA@SOI consortium, Open Cloud Computing Interface (OCCI), and OpenStack
Effects of the littlest Higgs model with T-parity on Higgs boson production at high energy colliders
The Higgs boson production processes , , and
are very important for studying Higgs boson
properties and further testing new physics beyond the standard model() in
the high energy linear
collider(). We estimate the contributions of the littlest
Higgs model with T-parity( model) to these processes and find that the
model can generate significantly corrections to the production cross
sections of these processes.
We expect the possible signals of the model can be detected via these
processes in the future experiments.Comment: 9 pages, 2 figures, references adde
GMRT detection of HI 21 cm associated absorption towards the z=1.2 red quasar 3C 190
We report the GMRT detection of associated HI 21 cm-line absorption in the
z=1.1946 red quasar 3C 190. Most of the absorption is blue-shifted with respect
to the systemic redshift. The absorption, at 647.7 MHz, is broad and
complex, spanning a velocity width of 600 \kms. Since the core is
self-absorbed at this frequency, the absorption is most likely towards the
hotspots. Comparison of the radio and deep optical images reveal linear
filaments in the optical which overlap with the brighter radio jet towards the
south-west. We therefore suggest that most of the HI 21 cm-line absorption
could be occurring in the atomic gas shocked by the south-west jet.Comment: 8 pages, 1 fugure. To appear in Journal of Astrophysics and Astronom
- …