scholarly journals Complete Samples of Flat Spectrum Radio Sources from the Parkes 2.7 GHz Survey

1988 ◽  
Vol 129 ◽  
pp. 77-78
Author(s):  
David L. Jauncey ◽  
G. L. White ◽  
B. R. Harvey ◽  
M. J. Batty ◽  
A. E. Wright ◽  
...  
Keyword(s):  
Size Distribution ◽  
Reference Frame ◽  
Southern Hemisphere ◽  
Luminosity Function ◽  
Space Distribution ◽  
Radio Sources ◽  
Spectrum Radio ◽  
The Individual ◽  
Galactic Radio

We are investigating complete samples of southern hemisphere flat spectrum extra-galactic radio sources drawn from the Parkes 2.7 GHz Survey (see Bolton et al. 1979 and references therein). These samples are being used for a variety of investigations, including a determination of the space distribution and luminosity function of radio QSOs, their radio size distribution, as well as the structures of the individual sources. Accurate positions are being determined, as well, in order to establish an extra-galactic position reference frame in the southern hemisphere.

scholarly journals Mapping The Radio Sky: Compact Radio Quasars From The Parkes 2.7 GHz Survey

1988 ◽  
Vol 133 ◽  
pp. 487-490
Author(s):  
David L. Jauncey ◽  
Graeme L. White ◽  
Bruce R. Harvey ◽  
Michael J. Batty ◽  
Alan E. Wright ◽  
...  
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Luminosity Function ◽  
Space Distribution ◽  
Complete Sample ◽  
Selection Of

We are investigating a complete sample of flat-spectrum extragalactic radio quasars drawn from the Parkes 2.7 GHz survey. The sample is being used to map the space distribution of radio quasars and to determine their luminosity function. Accurate positions are being measured for a selection of the brighter quasars in order to establish an extragalactic position reference frame in the Southern Hemisphere.

scholarly journals Statistical Effects of Doppler Beaming and Malmquist Bias on Flux-Limited Samples of Compact Radio Sources

1998 ◽  
Vol 164 ◽  
pp. 137-138
Author(s):  
Matthew L. Lister ◽  
Alan P. Marscher
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Radio Sources ◽  
Apparent Velocity ◽  
Parent Population ◽  
Relativistic Jet ◽  
Spectrum Radio ◽  
Statistical Effects

AbstractWe examine the effects of Doppler beaming on flux-limited samples of compact extragalactic radio sources using Monte Carlo simulations. We incorporate a luminosity function and z-distribution for the parent population, and investigate models in which the unbeamed synchrotron luminosity L of a relativistic jet is related to its bulk Lorentz factor Γ. The predicted flux density, redshift, monochromatic luminosity, and apparent velocity distributions of our simulated flux-limited samples are compared to the Caltech-Jodrell Bank (CJF) sample of flat-spectrum, radio core-dominated active galactic nuclei (AGNs).We find that a relation between L and Γ is not needed to reproduce the characteristics of the CJF sample. Introducing a positive correlation between these quantities results in an underabundance of objects with high viewing angles, while a negative correlation gives generally poor fits to the data.

scholarly journals OPTICAL SPECTRA OF CANDIDATE SOUTHERN HEMISPHERE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) RADIO SOURCES

2011 ◽  
Vol 142 (5) ◽  
pp. 165 ◽  
Author(s):  
O. Titov ◽  
D. L. Jauncey ◽  
H. M. Johnston ◽  
R. W. Hunstead ◽  
L. Christensen
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Optical Spectra ◽  
Radio Sources ◽  
Celestial Reference Frame

The determination of the size distribution of soil clods and crumbs

1940 ◽  
Vol 30 (2) ◽  
pp. 210-234 ◽  
Author(s):  
E. W. Russell ◽  
R. V. Tamhane
Keyword(s):  
Size Distribution ◽  
Maximum Amount ◽  
Moist Soil ◽  
Personal Factor ◽  
Water Stable Aggregates ◽  
Dry Soil ◽  
Pre Treatment ◽  
The Individual ◽  
And Training

1. It is possible to determine the size distribution of clods in the field by simple sieving of the soil without any pre-treatment provided the soil is not too wet. There is a personal factor involved in the sieving, but with care and training this will not affect comparisons of results obtained by that person. If the soil is too wet the individual clods smaller than 3 mm. stick together on the 3 mm. sieve. This sticking together is first apparent on the 3 mm. sieve but may become appreciable on the ¼ in. (6 mm.) sieve. No certain way was found for overcoming this difficulty.2. There appears to be no best method for determining the size distribution of the soil crumbs, i.e. of the water-stable aggregates in the soil. The method and the technique must be chosen so as to give the maximum amount of useful information. If an appreciable proportion of the crumbs are larger than ½ mm., a water-sieving method is practically essential.3. The method of wetting to be used can only be chosen from a consideration of what information is wanted. If possible it would be desirable for general purposes to use a very slow or a vacuum wetting technique and a very rapid wetting technique such as wetting the soil by immersion in water.4. The decision whether air-dry or field-moist soil should be used depends entirely on the information needed. For general purposes the use of air-dry soil is recommended.

scholarly journals Celestial Reference Frames

1980 ◽  
Vol 56 ◽  
pp. 77-86 ◽  
Author(s):  
J. Kovalevsky
Keyword(s):  
Reference Frames ◽  
Present Situation ◽  
Radio Sources ◽  
Star Catalogue ◽  
Kinematic Approximation ◽  
Lunar Laser ◽  
Absolute Coordinate System ◽  
Celestial Reference Frame ◽  
Galactic Radio

AbstractA celestial reference frame is based on some dynamical or kinematic approximation of an absolute coordinate system and is materialized by a fundamental catalogue of stars. It is characterized by the accuracy of the system and the precision of its stellar realization.The present situation, marked by the construction of the FK5 system and catalogue, is briefly described. It will be an hybrid system based on the discussion of all existing observations. The prospects for improvement in accuracy are good using lunar laser observations or VLBI determination of the positions of extra-galactic radio-sources. Three procedures that may be used to link such a system to a star catalogue are given. A major improvement in precision is expected from the Hipparcos programme and further extensions include essentially the densification of catalogues with stars of magnitudes 10 to 14 using photoelectric automatic meridian instruments.

scholarly journals Research on the Errors in Determination of Precise Optical Positions of Radio Sources

1990 ◽  
Vol 141 ◽  
pp. 499-500
Author(s):  
Lu Chun-Lin ◽  
Li Dong-Ming
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Optical Reference ◽  
Observation Program ◽  
Radio Stars

To link the optical reference frame to extragalactic radio frame, an observation program is in progress in Purple Mountain Observatory (PMO) and Shanghai Observatory. In this program, 70 extragalactic sources will be observed with the 1.56 m astrometric reflector in Shanghai. The secondary reference stars are determined with the twin astrograph (D = 40 cm, f = 300 cm) in PMO, and about 50 radio stars and some bright extragalactic sources will be observed with the twin astrograph.

scholarly journals The determination of the spectral turnover in faint Compact Steep-Spectrum radio sources using the VLA at 74 MHz

2003 ◽  
Vol 402 (1) ◽  
pp. 171-179 ◽  
Author(s):  
W. Tschager ◽  
R. T. Schilizzi ◽  
H. J. A. Röttgering ◽  
I. A. G. Snellen ◽  
G. K. Miley ◽  
...  
Keyword(s):  
Radio Sources ◽  
Spectrum Radio

scholarly journals Optical Reference Frame Defined by Carlsberg Meridian Catalogue La Palma Number 4

1990 ◽  
Vol 141 ◽  
pp. 391-401
Author(s):  
LV Morrison ◽  
RW Argyle ◽  
L Helmer ◽  
C Fabricius ◽  
OH Einicke ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Reference Frames ◽  
Radio Sources ◽  
Present Epoch ◽  
Extragalactic Radio Sources ◽  
La Palma ◽  
Average Accuracy ◽  
Optical Reference

The contribution of the Carlsberg Meridian Catalogue La Palma Number 4 to the determination of the optical reference frame is discussed. This catalogue of almost 51000 stars provides one of the most accurate optical reference frames at the present epoch, having a density of 1 star per square degree, and an average accuracy of 0.″12 in position and 0.″003 per year in proper motion for stars with V<9. The catalogue also contains positions of reference stars with V>11 in the fields of benchmark extragalactic radio sources which can be used in linking the optical reference frame defined by the FK5 to the extragalactic frame.

scholarly journals Nearly Microarcsecond Precision Differential Astrometry

1984 ◽  
Vol 110 ◽  
pp. 361-362
Author(s):  
J. Marcaide ◽  
I. Shapiro ◽  
J. Ball ◽  
N. Bartel ◽  
T. Clark ◽  
...  
Keyword(s):  
Small Angle ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Propagation Medium ◽  
The Individual

In studies of extragalactic radio sources with multiple compact components the determination of which components, if any, are stationary and which moving is of importance. In order to learn about the radio properties of the individual components it is also relevant to be able to register maps made at several wavelengths. Both tasks are usually not possible with VLBI because of the irrecoverable corruption of the fringe phase introduced by the propagation medium and the instrumentation. However, when two or more compact radio sources are separated by only a small angle from each other difference techniques can be used to help tackle both questions.

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