3,493 research outputs found
Filling in the Gaps in the 4.85 GHz Sky
We describe a 4.85 GHz survey of bright, flat-spectrum radio sources
conducted with the Effelsberg 100 m telescope in an attempt to improve the
completeness of existing surveys, such as CRATES. We report the results of
these observations and of follow-up 8.4 GHz observations with the VLA of a
subset of the sample. We comment on the connection to the WMAP point source
catalog and on the survey's effectiveness at supplementing the CRATES sky
coverage.Comment: 13 pages, 3 figures, 2 tables. Accepted for publication in the
Astronomical Journal. Tables available in electronic form:
http://astro.stanford.edu/gaps
A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)
A detailed analysis of the evolution of the properties of core-jet systems
within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a
power-law relationship between jet intensity and width that suggests for the
typical jet, little if any energy is lost as it moves away from its core. Using
VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be
aligned with the the direction of emission on kiloparsec scales. We also found
that this alignment improves as the jets move farther from their cores on
projected scales as small as ~50-100 pc. This suggests that realignment of jets
on these projected scales is relatively common. We typically find a modest
amount of bending (a change in jet position angle of ~5 deg.) on these scales,
suggesting that this realignment may typically occur relatively gradually.Comment: Accepted to ApJ, 20 pages, 8 figure
J16021+3326: New Multi-Frequency Observations of a Complex Source
We present multifrequency Very Long Baseline Array (VLBA) observations of
J16021+3326. These observations, along with variability data obtained from the
Owens Valley Radio Observatory (OVRO) candidate gamma-ray blazar monitoring
program, clearly indicate this source is a blazar. The peculiar characteristic
of this blazar, which daunted previous classification attempts, is that we
appear to be observing down a precessing jet, the mean orientation of which is
aligned with us almost exactly.Comment: 16 pages, 7 Figures, 2 Tables, accepted to Ap
Recommended from our members
Evaluation of Non-photorealistic 3D Urban Models for Mobile Device Navigation.
An educational history of the Society for the Propagation of the Gospel in Newfoundland, 1703-1850
This thesis is entitled An Educational History of the Society for the Propagation of the Gospel in Newfoundland. 1703 - 1850. Its purpose is to provide - as far as possible - a detailed history of the educational work of the Society for the Propagation of the Gospel in Foreign Parts (S.P.G.) while it was active in Newfoundland throughout the eighteenth and nineteenth centuries. -- The S.P.G. was founded in London, England, in 1701 and served as the educational arm of the Church of England for many years, directing most of its efforts to missionary and pedagogical concerns throughout the British Empire. Its association with Newfoundland began in 1703 and continued well into the next century when, for all intents and purposes, it? educational endeavours ended around 1850 with a brief foray into Labrador. Since records indicate that the Society greatly reduced its operations after 1833 and eventually withdrew from the Newfoundland educational scene by the eighteen fifties, it seems appropriate to end this account of the Society's activities at the mid-nineteenth century. -- Largely through the use of primary sources, this thesis elaborates on the following topics: -- (i) the establishment and early history of the Society; -- (ii) the stated goals and objectives of the Society; -- (iii) social, economic and educational conditions in Newfoundland in the eighteenth and nineteenth centuries, as well as political events and their effects on the Society's operations; -- (iv) involvement of the Society in Newfoundland, including the assistance to and establishment of schools in several communities; -- (v) the work of specific missionaries and teachers as indicated in the primary sources; -- (vi) the gradual decline of the Society's operations in Newfoundland in the nineteenth century and factors pertaining to the decline; and -- (vii) an evaluation of the Society's work and effectiveness. -- This paper focuses on the pedagogical, as opposed to the spiritual, work of the S.P.G., although no description would be complete without some mention of the religious side of this organization, an aspect that, for the most part, is dealt with in the introductory chapters. -- The author hopes that, in the final analysis, this thesis will provide a concise, convenient record of a heretofore little-known era in Newfoundland's educational and cultural history
Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey
The radio properties of blazars detected by the Large Area Telescope (LAT) on
board the Fermi Gamma-ray Space Telescope have been observed as part of the
VLBA Imaging and Polarimetry Survey (VIPS). This large, flux-limited sample of
active galactic nuclei (AGN) provides insights into the mechanism that produces
strong gamma-ray emission. At lower flux levels, radio flux density does not
directly correlate with gamma-ray flux. We find that the LAT-detected BL Lacs
tend to be similar to the non-LAT BL Lacs, but that the LAT-detected FSRQs are
often significantly different from the non-LAT FSRQs. The differences between
the gamma-ray loud and quiet FSRQs can be explained by Doppler boosting; these
objects appear to require larger Doppler factors than those of the BL Lacs. It
is possible that the gamma-ray loud FSRQs are fundamentally different from the
gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be
a signature for gamma-ray loud AGN.Comment: 32 pages, 9 figures, accepted by Ap
Precise absolute astrometry from the VLBA imaging and polarimetry survey at 5 GHz
We present in this paper accurate positions of 857 sources derived from the
astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline
Array imaging and polarimetry survey at 5 GHz (VIPS). Among observed sources,
positions of 430 objects were not determined before at a milliarcsecond level
of accuracy. For 95% of the sources the uncertainty of their positions range
from 0.3 to 0.9 mas, with the median value of 0.5 mas. This estimate of
accuracy is substantiated by the comparison of positions of 386 sources that
were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz.
Surprisingly, the ionosphere contribution to group delay was adequately modeled
with the use of the total electron contents maps derived from GPS observations
and only marginally affected estimates of source coordinates.Comment: Accepted for publication by the Astronomical Journal. 7 pages, 2
tables, 4 figures. Submission contains an ascii file with the catalogue. You
can get the catalogue by downloading the source of this paper and extracting
file table2.tx
The Labour Government, the Treasury and the £6 pay policy of July 1975
The 1974-79 Labour Government was elected in a climate of opinion that was fiercely opposed to government intervention in the wage determination process, and was committed to the principles of free collective bargaining in its manifestoes. However, by December 1974 the Treasury was advocating a formal incomes policy, and by July 1975 the government had introduced a £6 flat rate pay norm. With reference to archival sources, the paper demonstrates that TUC and Labour Party opposition to incomes policy was reconciled with the Treasury's advocacy by limiting the Bank of England‟s intervention in the foreign exchange market when sterling came under pressure. This both helped to achieve the Treasury's objective of improving the competitiveness of British industry, and acted as a catalyst for the introduction of incomes policy because the slide could be attributed to a lack of market confidence in British counter-inflation policy
Mixed income housing (MIH)
Mixed Income Housing (MIH) is the outcome of a deliberate effort to build a mixed-income development, usually including a variety of housing typologies, sometime combined with the goal of creating a mixed-tenure development. International consensus on a more specific definition of MIH does not exist; instead, multiple expressions can be equally used, with similar meaning. The expression MIH is mainly used within the USA context where it is sometime replaced by mixed-income neighborhood. In Europe, MIH tend to fall within initiatives on (sustainable) urban regeneration, neighborhood restructuring, urban renewal, while the UK legislation often refers to “pepper-potting” with respect to different tenures in the same neighborhood aimed to achieve MIH. Non-English-speaking countries tend to use different terms.
The MIH policies are challenged by a specific connotation, i.e., in the United States it is the combination between urban poverty and black or Latinos ghettoes; hence, spatial segregation is combined with racial considerations which are less present in other countries, except for South Africa. In the USA, desegregation in public housing estates became a legal obligation following the famous 1969 Gautreaux case, because of the application of the 1964 Civil Rights Act prohibiting racial discrimination in federally funded activities
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