scholarly journals Accurate Optical Positions for Radio Source Identifications

1994 ◽  
Vol 47 (5) ◽  
pp. 657 ◽  
Author(s):  
Richard W Hunstead
Keyword(s):  
Radio Source ◽  
Southern Hemisphere ◽  
Radio Sources ◽  
Position Measurement ◽  
Optical Identification ◽  
Optical Position ◽  
Optical Identifications

The optical identification of strong radio sources was a key step in establishing a grid of southern hemisphere calibrators, both for Parkes and for Molonglo. However, the measurement of precise positions for these optical counterparts presented some special astrometric problems and led to some novel solutions. This paper summarises the progress of optical position measurement from a radio astronomer's viewpoint and examines the role of the COSMOS database against this background. The source 0007-44, from the first Parkes catalogue, is used as a case study to illustrate the present-day approach to optical identifications.

Optical Identification of the Strong Radio Source PKS 0511-48

1981 ◽  
Vol 4 (2) ◽  
pp. 187-189 ◽  
Author(s):  
J. G. Robertson ◽  
R. M. Smith
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Optical Identification ◽  
Low Frequencies ◽  
Complex Source ◽  
Optical Identifications

The radio source PKS 0511-48 is among the hundred strongest southern sources at low frequencies. It was catalogued in the Parkes survey (Ekers 1969) and mapped with the Molonglo Cross at 408 MHz by Schilizzi and McAdam (1975) with a resolution of 2′ .6 arc. It appeared in that work as a complex source, with an integrated flux density of 8.8 Jy. A search for optical identifications was made by Tritton and Schilizzi (1973), but none were found to a level of B ~ 19. We have inspected the field on the ESO B survey film, and find a group of ~ 20 faint galaxies (approximately 19-20 mag).

Accurate Radio Positions with the Tidbinbilla Interferometer

1979 ◽  
Vol 3 (6) ◽  
pp. 400-402 ◽  
Author(s):  
M. J. Batty ◽  
David L. Jauncey ◽  
P. T. Rayner ◽  
S. Gulkis
Keyword(s):  
Absorption Spectra ◽  
High Redshift ◽  
Optical Emission ◽  
Radio Sources ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Optical Position ◽  
Bl Lac ◽  
Compact Galaxies ◽  
Optical Identifications

Radio position measurements with an error of <2” arc rms allow reliable optical identifications of compact radio sources to be made solely on the basis of radio-optical position coincidence. In this way neutral or red stellar objects, faint compact galaxies and faint QSOs can be reliably identified. Such identifications are of particular interest because they are rich in BL Lac objects, high-redshift QSOs, QSOs with unusual optical emission or absorption spectra and galaxies with active nuclei (see Jauncey et al. 1978).

scholarly journals Radio-optical Identification of Very-Steep Spectrum Radio Sources from the UTR-2 Catalogue

2002 ◽  
Vol 199 ◽  
pp. 217-218 ◽  
Author(s):  
H. Andernach ◽  
O.V. Verkhodanov ◽  
N.V. Verkhodanova
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Radio Galaxies ◽  
Image Databases ◽  
Radio Continuum ◽  
Radio Sources ◽  
Optical Identification ◽  
X Ray ◽  
Spectrum Radio

We used radio source catalogues accessible from the CATS database to establish radio continuum spectra for decametric radio sources in the UTR-2 catalogue. In an attempt to find further candidates for high-redshift radio galaxies, we searched the FIRST and NVSS surveys for counterparts of a sample of UTR sources with ultra-steep radio spectra (USS, α ≤ −1.2, S ∼ vα). We derived accurate positions and sizes for 23 of these USS sources. The search for optical counterparts from the APM (object) and DSS (image) databases, as well as infrared and X—ray identifications of these UTR sources are in progress.

A Catalogue of ‘Southern’ Radio Sources with Accurate Positions

1992 ◽  
Vol 10 (2) ◽  
pp. 140-167 ◽  
Author(s):  
Graeme L. White
Keyword(s):  
Radio Source ◽  
Total Power ◽  
Radio Sources ◽  
Power Flux ◽  
Optical Identifications ◽  
Better Than ◽  
Compact Array

AbstractA list of 901 radio sources with positional accuracies better than 0.5 arcseconds has been prepared from seventeen lists of radio source positions found in the literature. This compilation includes all such sources south of declination + 48° (the northern declination limit of the Compact Array of the Australia Telescope National Facility). Where available, optical identifications, optical magnitudes and redshifts are given as well as total-power flux densities.

scholarly journals Spectra for 107 Radio Sources Selected at 408 MHz

1973 ◽  
Vol 26 (6) ◽  
pp. 867 ◽  
Author(s):  
HS Murdoch ◽  
DG Hoskins
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Optical Identification ◽  
Density Measurements ◽  
Identification Rate ◽  
Significant Difference ◽  
Index Distribution ◽  
Optical Identifications ◽  
The Relationship ◽  
Very High

Radio spectra are presented for 107 sources which have previously been examined for optical identifications based on 408 MHz positions obtained with the Molonglo cross. Flux density measurements are given at five frequencies from 318 to 2695 MHz. The relationship between spectrum and optical identification is discussed. For sources with peaked, flat, or complex spectra the identification rate with QSO candidates is very high. For the remaining sources, no significant difference between the spectral index distribution of QSOs and galaxies is found.

scholarly journals Optical Identification Strategies for the Molonglo Cluster Survey

1997 ◽  
Vol 14 (3) ◽  
pp. 221-229 ◽  
Author(s):  
A. J. Haigh ◽  
J. G. Robertson ◽  
R. W. Hunstead
Keyword(s):  
Production Rate ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Optical Identification ◽  
Strong Concentration ◽  
Sky Survey ◽  
Extended Sources ◽  
Abell Cluster ◽  
Absolute Magnitudes ◽  
Optical Identifications

AbstractWe describe a newly refined procedure for making optical identifications of radio sources in Abell cluster fields observed with the Molonglo Observatory Synthesis Telescope (MOST). The method is based on past experience but uses a range of new tools to improve the reliability and production rate of identification lists. The COSMOS/UKST Southern Sky Object Catalogue was used to make preliminary identifications which were then inspected visually with the assistance of computer generated overlays of the MOST images and the Digitized Sky Survey (DSS). The overlaid images were essential for securing identifications for the extended sources prevalent among nearby clusters.We find 21±1·5% of the radio sources are identified with galaxies and 4·6±0·7% with QSO candidates in a sample of 927 radio sources in 27 cluster fields. We make a preliminary attempt to separate cluster radio galaxies from interlopers on the basis of absolute magnitudes. A strong concentration of radio galaxies was found at projected distances less than 100 kpc from the cluster centres and a weaker concentration for projected distances of 100–500 kpc.

An ‘X-Banded’ Tidbinbilla Interferometer

1986 ◽  
Vol 6 (3) ◽  
pp. 351-353
Author(s):  
Michael J. Batty ◽  
R. G. Gardyne ◽  
G.J. Gay ◽  
S. Gulkis ◽  
David L. Jauncey ◽  
...  
Keyword(s):  
Radio Source ◽  
Southern Hemisphere ◽  
Band System ◽  
Radio Sources ◽  
Fringe Spacing ◽  
X Ray ◽  
Measurement Capability ◽  
X Band ◽  
Astronomical Facility ◽  
Radio Stars

AbstractThe recent upgrading of the Tidbinbilla two-element interferometer to simultaneous S-band (2.3 GHz) and X-band (8.4 GHz) operation has provided a powerful new astronomical facility for weak radio source measurement in the Southern Hemisphere. The new X-band system has a minimum fringe spacing of 38 arcsec, and about the same positional measurement capability (approximately 2 arcsec) and sensitivity (1 s rms noise of 10 mJy) as the previous S-band system. However, the far lower confusion limit will allow detection and accurate positional measurements for sources as weak as a few millijanskys. This capability will be invaluable for observations of radio stars, X-ray sources and other weak, compact radio sources.

scholarly journals Optical identification of southern radio sources

1959 ◽  
Vol 9 ◽  
pp. 514-522 ◽  
Author(s):  
Jane Basinski ◽  
B. J. Bok ◽  
K. Gottlieb
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Radio Sources ◽  
Optical Identification ◽  
Collaborative Program ◽  
Challenging Tasks ◽  
The Subject ◽  
Discrete Radio Sources

The identification of discrete radio sources with optically observed celestial objects continues to be one of the most difficult and challenging tasks for the optical astronomer. Baade and Minkowski [1, 2] have done admirable work on the subject for the northern hemisphere and for the sections of the southern hemisphere accessible from the latitudes of Mount Wilson and Palomar Observatories. The zone south of declination −40 degrees, however, has not been studied to any great extent. As a part of our collaborative program of research with the C.S.I.R.O. Radiophysics Laboratory in Sydney, several members of the Mount Stromlo Observatory staff have initiated studies for the identification of sources with declinations south of −40 degrees.

scholarly journals Radio-Optical Correlations in Distant Radio Galaxies

1989 ◽  
Vol 134 ◽  
pp. 546-547
Author(s):  
Wil van Breugel ◽  
Patrick J. McCarthy
Keyword(s):  
Emission Line ◽  
Radio Source ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Optical Observations ◽  
Radio Sources ◽  
Systematic Comparison ◽  
New Radio ◽  
Optical Identifications

Optical identifications and redshifts are now available for nearly all 3CR radio galaxies (Spinrad et al. 1985; Djorgovski et al. 1988). Using new radio and optical observations, supplemented with data from the literature, we are conducting a systematic comparison of their radio and optical (emission-line and galaxy) properties, and their dependence on redshift. Here we present new results on the alignments of galaxies and their associated radio sources, and radio source asymmetries.

scholarly journals The Role of Nonquasigeostrophic Forcing in Southern Hemisphere Blocking Onsets

2015 ◽  
Vol 143 (4) ◽  
pp. 1455-1471 ◽  
Author(s):  
Li Dong ◽  
Stephen J. Colucci
Keyword(s):  
Southern Hemisphere ◽  
Zonal Wind ◽  
Geostrophic Wind ◽  
Relative Vorticity ◽  
Geostrophic Flow ◽  
Quasigeostrophic Model ◽  
Geostrophic Advection ◽  
Blocking Event

Abstract A generalized frictionless, adiabatic geostrophic zonal wind tendency equation is derived to diagnose the nonquasigeostrophic forcings to blocking onset in the Southern Hemisphere through case study and composite analysis. In general, the quasigeostrophic model is capable of representing the key physical processes associated with blocking onset in the troposphere reasonably well in most blocking cases. The consideration of nonquasigeostrophic forcings moderately improves the quasigeostrophic representation in a majority of the blocking events selected for this study, but not all events. This suggests that the nonquasigeostrophic terms could be important in a specific blocking event but not in a composite meaning. Furthermore, the nonquasigeostrophic forcing of geostrophic advection of ageostrophic relative vorticity term, , is extensively examined in this study. This forcing is found to be the leading nonquasigeostrophic forcing term among all nonquasigeostrophic forcings. In a composite sense, the forcing appears to have an alternative contribution that is dependent upon the curvature of the geostrophic flow within the blocking structure. In general, the southwesterly flow is likely associated with the -favoring effect to blocking onset whereas northwesterly flow is associated with the -opposing effect. Therefore, it is important to use the geostrophic flow pattern prior to blocking onset to foresee this ageostrophic-related nonquasigeostrophic forcing to blocking onset. Finally, a pronounced overestimation of geostrophic zonal wind tendency by the quasigeostrophic model is commonly found for selected blocking events within the stratosphere, in comparison to the nonquasigeostrophic model. This overestimation is essentially caused by geostrophic wind approximation.

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