scholarly journals The Molonglo Deep Sky Survey of Radio Sources. II. Declination Zone -62°

1977 ◽  
Vol 30 (2) ◽  
pp. 231 ◽  
Author(s):  
JG Robertson
Keyword(s):  
Flux Density ◽  
Lower Limit ◽  
Solid Angle ◽  
Radio Sources ◽  
Upper Limit ◽  
Sky Survey ◽  
Deep Survey ◽  
The Right

Results are given for the second zone of a deep survey made at 408 MHz with the Molonglo cross. The catalogue lists positions and flux densities for 95 sources, none of which has been previously catalogued, in a solid angle of 5�51 x 10-3 sr. The right ascensions covered (with some excluded areas) are 18h 26m-OOh 06m, with a range in declination of 45'. The lower limit of flux density is 84 inJy. An upper limit of 1000 mJy has also been imposed. The position uncertainties are typically 12''at 100 mJy and 6# at 250 mJy.

scholarly journals The Molonglo Deep Sky Survey of Radio Sources. I. Declination Zone -20°

1977 ◽  
Vol 30 (2) ◽  
pp. 209 ◽  
Author(s):  
JG Robertson
Keyword(s):  
Error Analysis ◽  
Flux Density ◽  
Lower Limit ◽  
Solid Angle ◽  
Radio Sources ◽  
Contour Maps ◽  
Upper Limit ◽  
Sky Survey ◽  
Deep Survey

Results of a deep survey made at 408 MHz with the Molonglo cross are given. The catalogue lists positions and flux densities for a total of 373 radio sources, most of which have not previously been catalogued, in a solid angle of 0�0201 Sf. This covers (with some excluded areas) right ascensions 0l h oom-06h 44m and 13h 45m-17h 19m, with a range in declination of 41'. Eighteen contour maps are given of sources that are extended or have very close companions. A thorough error analysis is given, as well as new operational definitions of completeness and reliability. The lower limit of flux density is 88 mJy, which is five times the r.m.s. error. An upper limit of 1000 mJy has also been imposed. Typical errors in positions are 15" at 100 mJy and 6" at 250 mJy.

scholarly journals Limits on long-timescale radio transients at 150 MHz using the TGSS ADR1 and LoTSS DR2 catalogues

2021 ◽  
Author(s):  
Iris de Ruiter ◽  
Guillaume Leseigneur ◽  
Antonia Rowlinson ◽  
Ralph A M J Wijers ◽  
Alexander Drabent ◽  
...  
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Compactness Criterion ◽  
Compact Source ◽  
Upper Limit ◽  
Sky Survey ◽  
Data Release ◽  
Transient Sources ◽  
Radio Transients ◽  
Compact Sources

Abstract We present a search for transient radio sources on timescales of 2-9 years at 150 MHz. This search is conducted by comparing the first Alternative Data Release of the TIFR GMRT Sky Survey (TGSS ADR1) and the second data release of the LOFAR Two-metre Sky Survey (LoTSS DR2). The overlapping survey area covers 5570 $\rm {deg}^2$ on the sky, or 14 per cent of the total sky. We introduce a method to compare the source catalogues that involves a pair match of sources, a flux density cutoff to meet the survey completeness limit and a newly developed compactness criterion. This method is used to identify both transient candidates in the TGSS source catalogue that have no counterpart in the LoTSS catalogue and transient candidates in LoTSS without a counterpart in TGSS. We find that imaging artefacts and uncertainties and variations in the flux density scales complicate the transient search. Our method to search for transients by comparing two different surveys, while taking into account imaging artefacts around bright sources and misaligned flux scales between surveys, is universally applicable to future radio transient searches. No transient sources were identified, but we are able to place an upper limit on the transient surface density of <5.4 · 10−4 deg−2 at 150 MHz for compact sources with an integrated flux density over 100 mJy. Here we define a transient as a compact source with flux density greater than 100 mJy that appears in the catalogue of one survey without a counterpart in the other survey.

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.

The Over-estimation of the Flux Density of Weak Radio Sources

1969 ◽  
Vol 1 (5) ◽  
pp. 233-234
Author(s):  
H. S. Murdoch
Keyword(s):  
Monte Carlo ◽  
Flux Density ◽  
Lower Limit ◽  
Error Distribution ◽  
Radio Sources ◽  
Systematic Bias ◽  
Digital Recording ◽  
Analysis Techniques ◽  
Monte Carlo Techniques ◽  
The Past

The over-estimation of the flux density of radio sources near the lower limit of a survey has often been considered in the past. The use of digital recording and analysis techniques now enables a quantitative approach to the problem. Monte Carlo techniques may be used to determine the error distribution, including any systematic bias.

scholarly journals The Murchison Widefield Array Commissioning Survey: A Low-Frequency Catalogue of 14 110 Compact Radio Sources over 6 100 Square Degrees

2014 ◽  
Vol 31 ◽  
Author(s):  
Natasha Hurley-Walker ◽  
John Morgan ◽  
Randall B. Wayth ◽  
Paul J. Hancock ◽  
Martin E. Bell ◽  
...  
Keyword(s):  
Flux Density ◽  
Noise Level ◽  
Angular Resolution ◽  
Low Frequency ◽  
Radio Sources ◽  
Reduction Strategy ◽  
Sky Survey ◽  
Field Boundaries ◽  
Murchison Widefield Array ◽  
Finding Method

AbstractWe present the results of an approximately 6 100 deg2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h < RA < 8.5 h, − 58° < Dec < −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam− 1, with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.

scholarly journals One- and two-point source statistics from the LOFAR Two-metre Sky Survey first data release

2020 ◽  
Vol 643 ◽  
pp. A100
Author(s):  
T. M. Siewert ◽  
C. Hale ◽  
N. Bhardwaj ◽  
M. Biermann ◽  
D. J. Bacon ◽  
...  
Keyword(s):  
Point Source ◽  
Flux Density ◽  
Large Scale ◽  
Value Added ◽  
Radio Sources ◽  
Sky Survey ◽  
Point Correlation ◽  
Point Correlation Function ◽  
The Universe ◽  
Density Threshold

Context. The LOFAR Two-metre Sky Survey (LoTSS) will eventually map the complete Northern sky and provide an excellent opportunity to study the distribution and evolution of the large-scale structure of the Universe. Aims. We test the quality of LoTSS observations through a statistical comparison of the LoTSS first data release (DR1) catalogues to expectations from the established cosmological model of a statistically isotropic and homogeneous Universe. Methods. We study the point-source completeness and define several quality cuts, in order to determine the count-in-cell statistics and differential source count statistics, and measure the angular two-point correlation function. We use the photometric redshift estimates, which are available for about half of the LoTSS-DR1 radio sources, to compare the clustering throughout the history of the Universe. Results. For the masked LoTSS-DR1 value-added source catalogue, we find a point-source completeness of 99% above flux densities of 0.8 mJy. The counts-in-cell statistic reveals that the distribution of radio sources cannot be described by a spatial Poisson process. Instead, a good fit is provided by a compound Poisson distribution. The differential source counts are in good agreement with previous findings in deep fields at low radio frequencies and with simulated catalogues from the SKA Design Study and the Tiered Radio Extragalactic Continuum Simulation. Restricting the value added source catalogue to low-noise regions and applying a flux density threshold of 2 mJy provides our most reliable estimate of the angular two-point correlation. Based on the distribution of photometric redshifts and the Planck 2018 best-fit cosmological model, the theoretically predicted angular two-point correlation between 0.1 deg and 6 deg agrees reasonably well with the measured clustering for the sub-sample of radio sources with redshift information. Conclusions. The deviation from a Poissonian distribution might be a consequence of the multi-component nature of a large number of resolved radio sources and/or of uncertainties on the flux density calibration. The angular two-point correlation function is < 10−2 at angular scales > 1 deg and up to the largest scales probed. At a 2 mJy flux density threshold and at a pivot angle of 1 deg, we find a clustering amplitude of A = (5.1 ± 0.6) × 10−3 with a slope parameter of γ = 0.74 ± 0.16. For smaller flux density thresholds, systematic issues are identified, which are most likely related to the flux density calibration of the individual pointings. We conclude that we find agreement with the expectation of large-scale statistical isotropy of the radio sky at the per cent level. The angular two-point correlation agrees well with the expectation of the cosmological standard model.

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 The Parkes 2700 MHz Survey. Catalogue for 03h, 11h, 19h, and 23h Zone, Declinations ?33° to ?75°

1971 ◽  
Vol 24 (4) ◽  
pp. 933
Author(s):  
AJ Shimmins
Keyword(s):  
Flux Density ◽  
Galactic Plane ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Sky Survey

A catalogue of 618 extragalactic radio sources obtained from a sky survey at 2700 MHz is presented. The area of 0�42 sr covers four southern zones of R.A. 03h to 04h , II h to 12h , 19h to 20h , and 23h to 00h, between Dec. -330 and -75�, with a region omitted in the llh zone which is close to the galactic plane. The catalogue is complete to a limiting flux density of 0�32 f.u. at 2700 MHz and is thought to be 90% complete at a flux density of 0�20 f.u. The positions are accurate to 15" arc or slightly better in both coordinates for sources stronger than 0�32 f.u.; the flux densities of the weaker sources are accurate to 0�02 f.u., and for sources stronger than 1 f.u. the accuracy is 3%.

scholarly journals The Molonglo Deep Sky Survey of Radio Sources. III. Source Counts

1977 ◽  
Vol 30 (2) ◽  
pp. 241 ◽  
Author(s):  
JG Robertson
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Sky Survey ◽  
Lower Limits

Number-flux density counts of radio sources are given for the first two deep surveys made with the Molonglo Mills Cross at 408 MHz, extending to lower limits of 84 and 88 mJy. Practical techniques are developed for the calculation of corrections to the counts when confusion errors are significant. The resulting corrections due to noise, confusion and other effects are given. Counts are also given for the MC2 and MC3 catalogues in the range 2-10 Jy to reduce the statistical uncertainties there. Results are shown on a composite plot, using relevant Molonglo surveys and an all-sky catalogue of strong sources. The existence of a convergence in the number of weak sources is confirmed.

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