scholarly journals Australian Journal of Physics Astrophysical Supplements

1977 ◽  
Vol 30 (6) ◽  
pp. 681
Author(s):  
C Hazard ◽  
HS Murdoch
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Spectral Sensitivity ◽  
Australian Journal ◽  
Magnitude Distribution ◽  
Sky Survey ◽  
Magnitude Scales

This paper presents the results of an examination of the fields around 350 sources in the Molonglo radio source catalogues MC2 and MC3 for the R.A. interval 11 h 28m to 17h oom. The 300 sources with a flux density ;;. 0�45 Jy form an essentially complete radio sample and of these 21 % are identified with BSOs (most of which have now been spectroscopically confirmed as QSOs) and 22 % with galaxies of Ism or brighter. The magnitude scales adopted are carefully defined and based on the spectral sensitivity of the Palomar Sky Survey plates. A brief discussion is given of the magnitude distribution of the BSO identifications and possible evidence for anisotropy in the QSO distribution is noted.

scholarly journals A 6-CM Deep Sky Survey

1983 ◽  
Vol 104 ◽  
pp. 81-81
Author(s):  
E. B. Fomalont ◽  
K. I. Kellermann ◽  
J. V. Wall
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Small Region ◽  
Sky Survey ◽  
Deep Survey

In order to extend radio source counts to lower flux density, we have used the VLA to survey a small region of sky at 4.885 GHz (6 cm) to a limiting flux density of 50 μJy. Details of this deep survey are given in the paper by Kellermann et al. (these proceedings). In addition, we have observed 10 other nearby fields to a limiting flux density of 350 μJy in order to provide better statistics on sources of intermediate flux density.

A Confusion Limited Radio Survey from the Molonglo Cross

1984 ◽  
Vol 5 (3) ◽  
pp. 290-340 ◽  
Author(s):  
Graeme L. White
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Radio Sources ◽  
Chronological Order ◽  
Extragalactic Radio Sources ◽  
Density Limit ◽  
Sky Survey ◽  
Radio Survey

Several catalogues of radio sources at 408 MHz have been prepared from observations made with the Molonglo cross telescope. These include (in chronological order) ‘The Molonglo Radio Source Catalogue 1’, the MC1, by Davies et al. (1973), the MC2 and MC3 by Sutton et al. (1974), MC4 by Clarke et al. (1976), ‘The Molonglo Deep Sky Survey of Radio Sources’ by Robertson (1977a,b,d) and ‘The Molonglo Reference Catalogue of Radio Sources’ (MRC) by Large et al. (1981). The catalogues MC1-4 cover selected areas of sky to a flux density limit of ~0.2 Jy to 0.3 Jy. The MRC includes extragalactic radio sources between δ = +18° and δ = −85° and is essentially complete at S408 = 1.00 Jy with raany sources to ˜0.7 Jy. The Wyllie (1969a,b) scale of flux density is used throughout.

scholarly journals Australian Journal of Physics Astrophysical Supplement

1973 ◽  
Vol 26 (1) ◽  
pp. 115
Author(s):  
OB Slee ◽  
CS Higgins
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Australian Journal ◽  
Radio Sources ◽  
Success Rates ◽  
Low Resolution ◽  
Upper Limits

The Culgoora radioheliograph operating at 80 MHz has been used to observe 999 radio sources selected from published catalogues and distributed over the declination range -48� to +35�. The Culgoora-l list contains measurements with 3' . 7 arc resolution of positions, flux densities, and angular sizes of 777 sources, while upper limits to the flux densities of 222 undetected sources are given in a separate list. Success rates for the detection of various classes of radio source at 80 MHz are listed and discussed. Comparisons are made between the Culgoora flux densities and those given in other catalogues, and it is shown that unresolved sources in the earlier low-resolution measurements near 80 MHz cause the flux density to be systematically overestimated.

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.

Studying the Flux Density of Bright Active Galaxies at Different Spectral Bands

2019 ◽  
Vol 16 (1(Suppl.)) ◽  
pp. 0230
Author(s):  
Rashed Et al.
Keyword(s):  
Flux Density ◽  
Galactic Nuclei ◽  
Absolute Magnitude ◽  
Active Galaxies ◽  
X Ray ◽  
Spectral Bands ◽  
Sky Survey ◽  
Multi Wavelength ◽  
Statistical Studies ◽  
Density Ratios

Statistical studies are reported in this article for an active galactic nuclei sample of different type of active galaxies Seyferts 1, Seyferts 2, and Quasars. These sources have been selected from a Catalogue for bright X-ray galaxies. The name of this index is ROSAT Bright Source Catalogue (RBSC) and the NRAO VLA Sky Survey (NVSS). In this research, multi-wavelength observational bands Radio at 1.4 GHz, Optical at 4400 A0, and X-ray at energy 0.1-2.4 KeV have been adopted in this study. The behavior of flux density ratios has been studied ,  with respect to the absolute magnitude . Furthermore, the Seyfert1 and Seyfert 2 objects are combined in one group and the QSOs are collectest in another group. Also, it has been found that the ratios , are increasing towards fainter optical absolute magnitude especially in Quasars.

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.

Broad-band flux density variations of the extragalactic radio source 1611+343

1979 ◽  
Vol 228 ◽  
pp. L63 ◽  
Author(s):  
W. D. Cotton ◽  
S. R. Spangler
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Broad Band ◽  
Extragalactic Radio Source

scholarly journals Searching for Pulsars in the WENSS

1996 ◽  
Vol 160 ◽  
pp. 15-16
Author(s):  
Marco Kouwenhoven ◽  
Michiel Berger ◽  
Will Deich ◽  
Ger de Bruyn
Keyword(s):  
High Resolution ◽  
Flux Density ◽  
Sky Survey

The Westerbork Northern Sky Survey is an imaging survey carried out at 325 MHz by the Westerbork Synthesis Array Telescope (de Bruyn, 1996). It covers the northern sky above declination 30° with a resolution of 54” and a limiting flux density (5σ) of circa 15 mJy/beam. The WENSS also provides polarization maps of this part of the sky. About one fourth of the WENSS-325 area will also be covered at 608 MHz to the same limiting flux density. Table 1 gives the parameters of these surveys. It also contains the parameters of the FIRST (Faint Images of the Radio Sky at Twenty-cm, Becker et al. 1995), which is a high resolution survey carried out at 1500 MHz.

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 A Comparison of the Structures of 3CR Quasars and Blank Field Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 435-436 ◽  
Author(s):  
F. N. Owen ◽  
J. J. Puschell ◽  
R. A. Laing
Keyword(s):  
Radio Source ◽  
Structural Properties ◽  
Low Frequency ◽  
Radio Sources ◽  
Blank Field ◽  
Sky Survey

The purpose of this communication is to update our knowledge of the radio structural properties of quasars and blank field radio sources (blank field ≡ any radio source without an identification on the Palomar Sky Survey prints). The quasar sample consists of all sources (25) with angular sizes greater than 10 arcsec in the list of Jodrell Bank quasars observed by Owen, Porcas and Neff (1978). The blank fields consist of 16 3CR sources also with structures >10 arcsec based on Cambridge 5 km telescope observations. The sources were selected in low-frequency surveys; their emission at ν < 1 GHz is dominated by extended components with steep spectra. Thus, both samples should be oriented randomly in space except for a slight bias to be in the plane of the sky.

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