scholarly journals Radio Source Counts at 408 MHz

1973 ◽  
Vol 26 (3) ◽  
pp. 417 ◽  
Author(s):  
BY Mills ◽  
IM Davies ◽  
JG Robertson
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
High Exponent ◽  
Density Relation

Radio source counts at 408 MHz are investigated using the data from the first Molonglo catalogue (MC1) and an all-sky catalogue of strong sources. Earlier results are qualitatively confirmed. Possible explanations of the high exponent of the numberflux density relation between sources of strong and intermediate flux density are discussed briefly, but no firm conclusions seem possible.

scholarly journals The Angular Size - Flux Density Relation

1977 ◽  
Vol 74 ◽  
pp. 119-123
Author(s):  
Vijay K. Kapahi
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Angular Size ◽  
World Model ◽  
The World ◽  
Density Relation

The relation between angular size and flux density depends on the world model and more strongly on evolution in radio source properties with epoch. I shall consider here the simplest forms of evolution that explain the observed θ-S relations (Swarup 1975; Kapahi 1975a,b; Ekers, this symposium).

scholarly journals VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

2018 ◽  
Vol 616 ◽  
pp. A128 ◽  
Author(s):  
N. Herrera Ruiz ◽  
E. Middelberg ◽  
A. Deller ◽  
V. Smolčić ◽  
R. P. Norris ◽  
...  
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Lower Limit ◽  
High Sensitivity ◽  
Host Galaxy ◽  
Radio Sources ◽  
Source Population ◽  
Star Forming ◽  
Brightness Temperatures ◽  
Long Baseline

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of μJy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, meaning that it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z ≥ 0.1). On the other hand, this technique only allows us to positively identify when a radio-active AGN is present, in other words, we cannot affirm that there is no AGN when the source is not detected. For this reason, the number of identified AGN using VLBI should be always treated as a lower limit. We present a catalogue containing the 35 radio sources detected with the VLBA+GBT, ten of which were not previously detected using only the VLBA. We have constructed the radio source counts at 1.4 GHz using the samples of the VLBA and VLBA+GBT detected sources of the COSMOS field to determine a lower limit for the AGN contribution to the faint radio source population. We found an AGN contribution of >40−75% at flux density levels between 150 μJy and 1 mJy. This flux density range is characterised by the upturn of the Euclidean-normalised radio source counts, which implies a contribution of a new population. This result supports the idea that the sub-mJy radio population is composed of a significant fraction of radio-emitting AGN, rather than solely by star-forming galaxies, in agreement with previous studies.

scholarly journals Long-Term Variations of the Compact Radio Source Sgr A∗ at the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 535-541 ◽  
Author(s):  
Jun-Hui Zhao ◽  
R. D. Ekers ◽  
W. M. Goss ◽  
K. Y. Lo ◽  
Ramesh Narayan
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
High Velocity ◽  
Galactic Center ◽  
Light Curves ◽  
Radio Flux ◽  
Compact Radio Source ◽  
Sgr A ◽  
Long Term Variations

We investigate the long-term flux density variations of the compact radio source Sgr A∗ at the galactic center by combining recent VLA observations with previous Green Bank interferometer data. We present radio flux density light-curves for Sgr A∗ at 20, 11, 6 and 3.7 cm from 1974 to 1987. Long-term variability with a timescale of at least 5 years is seen at 20 cm and there is evidence for more rapid variations at the shorter wavelengths. The variability timescales at 20, 11 and 6 cm fit the λ2 scaling predicted by the theory of refractive scintillation suggesting that the variability could be due to this cause. However, the timescales are relatively short, implying an unusually high velocity in the scattering screen. The modulation index of the variability is large and relatively independent of wavelength.

On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources

2003 ◽  
Vol 3 (4) ◽  
pp. 347-358 ◽  
Author(s):  
Xi-Zhen Zhang ◽  
W. Reich ◽  
P. Reich ◽  
R. Wielebinski
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Radio Sources ◽  
Large Samples ◽  
Density Relation

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).

scholarly journals Flux Density Variations Of PKS 1830–211

1996 ◽  
Vol 173 ◽  
pp. 347-348
Author(s):  
J.E.J. Lovell ◽  
P.M. McCulloch ◽  
E.A. King ◽  
D.L. Jauncey
Keyword(s):  
Time Series ◽  
Radio Source ◽  
Flux Density ◽  
Monitoring Program ◽  
Gravitational Lens ◽  
Total Flux ◽  
Initial Value ◽  
Mount Pleasant

We have been observing the strong radio source and Einstein ring gravitational lens PKS 1830–211 as part of a flux density monitoring program at 2.3 and 8.4 GHz using the 26 m antenna at the Mt Pleasant Observatory. As can be seen from Figure 1 this source is variable at both frequencies. The 2.3 GHz flux density decreased from 10 Jy in 1990 November to a minimum of 9 Jy during 1992, and has since steadily increased to its present ∼12 Jy. Over the same interval, the flux density at 8.4 GHz has exhibited greater variability, more than doubling from an initial value of 5 Jy in late 1990 to a peak of ∼11 Jy early in 1992, before decreasing to a level of ∼7.5 Jy. VLA observations by van Ommen et al. (1995) show that the 15 GHz total flux density increased before the 8.4 GHz brightening seen at Mount Pleasant. Although the 15 GHz time series is not well sampled, it is clear from these data that the 15 GHz outburst precedes the 8.4 GHz feature by ∼400 days.

scholarly journals New Limits to the Small Scale Fluctuations in the Cosmic Background Radiation

1983 ◽  
Vol 104 ◽  
pp. 125-126
Author(s):  
K. I. Kellermann ◽  
E. B. Fomalont ◽  
J. V. Wall
Keyword(s):  
Cosmic Microwave Background ◽  
Radio Source ◽  
Flux Density ◽  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Small Region ◽  
Small Scale ◽  
Microwave Background ◽  
Cosmic Background ◽  
Microwave Background Radiation

The VLA has been used at 4.9 GHz to observe a small region of sky in order to extend the radio source count to low flux density (Fomalont et al., these proceedings) and to look for small scale fluctuations in the 2.7 K cosmic microwave background radiation.

Secular Variation of the Flux Density of the Radio Source Cassiopeia A

Nature ◽  
1961 ◽  
Vol 190 (4777) ◽  
pp. 705-706 ◽  
Author(s):  
D. S. HEESCHEN ◽  
B. L. MEREDITH
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Secular Variation ◽  
Cassiopeia A
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