Optical Identifications and Radio Spectra of Sources Found by the Michigan 8-GHZ Survey

Brandie, G. W.; Bridle, A. H.

doi:10.1086/111627

Cited by 7 publications

(4 citation statements)

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“…B. Dependence Upon Spectral Index Figure 3 locates the sources in the complete sample for which adequate spectral data 4 exist on a radio "twocolor" diagram (following Brandie and Bridle 1974). If we define spectra as steep when a < -0.5 and as flat otherwise, we note that 66% of the nonvariable sources and only 6% of the variable sources have steep spectra over both frequency regimes.…”

Section: Discussionmentioning

confidence: 99%

10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

Seielstad¹,

Pearson²,

Readhead³

1983

PASP

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We have measured the 10.8-GHz flux densities of 285 radio sources at 14 epochs between January 1979 and November 1982. For the subset of 258 objects constituting a complex flux-density-limited sample selected at 5 GHz, we find that (a) at least 45% vary within ten years, (b) about nine-tenths of the steep spectrum (a < -0.5) sources do not vary, whereas about two-thirds of the flat spectrum sources do, (c) the amplitude of the variations, considering variable sources only, is least for sources having negative spectral indices from 2.7 to 10.7 GHz and is greatest for sources whose spectra invert from negative to positive between these two frequency extremes, (d) quasars are much more likely to vary than either galaxies or empty field sources, (e) the variable components of quasars are, as a class, slightly greater fractions of the mean flux densities than for either galaxies or empty field sources, and (f) most objects from the S4 catalog identified with empty fields are galaxies beyond the plate limit.

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Section: Discussionmentioning

confidence: 99%

10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

Seielstad¹,

Pearson²,

Readhead³

1983

PASP

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“…These sources were found to be different from those detected in low‐frequency surveys, with 70 per cent having flat or inverted spectra. More than 80 per cent had optical counterparts on the Palomar Sky Survey, most of them quasi‐stellar objects (QSOs) (Brandie & Bridle 1974; Brandie, Bridle & Kesteven 1974).…”

Section: Introductionmentioning

confidence: 99%

First results from the Australia Telescope Compact Array 18-GHz pilot survey

Ricci

Sadler

Ekers

et al. 2004

Monthly Notices of the Royal Astronomical Society

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As a pilot study for the first all‐sky radio survey at short wavelengths, we have observed 1216 deg2 of the southern sky at 18 GHz (16 mm) using a novel wide‐band (3.4‐GHz bandwidth) analogue correlator on one baseline of the Australia Telescope Compact Array. We scanned a region of sky between declination −71° and −59° with an rms noise level of 15 mJy. Follow‐up radio imaging of candidate sources above a 4σ detection limit of 60 mJy resulted in 221 confirmed detections, for which we have measured accurate positions and flux densities. For extragalactic sources, the survey is roughly 70 per cent complete at a flux density of 126 mJy and 95 per cent complete above 300 mJy. Almost half the detected sources lie within a few degrees of the Galactic plane, but there are 123 sources with |b| > 5°, which can be assumed to be extragalactic. The differential source counts for extragalactic sources in the range 0.1 Jy ≤S18 GHz≤ 3 Jy are well fitted by a relation of the form n(S) = 57 (S/Jy)−2.2±0.2 Jy−1 sr−1, in good agreement with the 15‐GHz counts published by Taylor et al. and Waldram et al. Over 70 per cent of the extragalactic sources have a flat radio spectrum (α180.843 > −0.5, Sν∝να), and 29 per cent have inverted radio spectra (α180.843 > 0). The optical identification rate is high: 51 per cent of the extragalactic sources are identified with stellar objects (candidate quasi‐stellar objects), 22 per cent with galaxies and only 27 per cent with faint optical objects or blank fields.

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“…The addition of substantial numbers of flat-spectrum sources from the high-frequency NRAO survey has now resulted in a V/V of sufficient precision to establish the effect. max Qualitative confirmation of the low V/V for flat-spectrum max quasars can be obtained from high-frequency source counts, since a very large fraction of the flat-spectrum objects among these are identified with quasars according to Brandie and Bridle (1974) and Peterson and Bolton (Wall 1975)• Condon and Jauncey (1974) derived a slope of -0o85 for the integral counts of flat-spectrum sources in the Parkes 2700 MHz surveyo I find from a list of 8 GHz sources by Brandie and Bridle (1974) a slope of -1.1 for the flat-spectrum sources. Such a low slope is consistent with a uniform space distribution (V/V = 0.5) if the redshift distribution of these quasars is similar to that maX of the NRAO 6-cm quasarso Finally, we consider in Table 4 the optically selected quasars, regardless of their radio flux density.…”

Section: Results Of the V/v Wav Methods Maxmentioning

confidence: 97%

Cosmological Interpretation of Redshift Data on Quasars through the V/V_MaxTest

Schmidt

1977

Symp. - Int. Astron. Union

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The ultimate aim of statistical studies of redshift, magnitudes and flux densities of quasars is to derive the general luminosity function Φ(z, Fopt, Frad, α, …) which describes the space density as a function of redshift, intrinsic optical luminosity, intrinsic radio luminosity, spectral index, etc. We assume throughout that the emission-line redshifts z of quasars are cosmological. The function Φ contains information that will be pertinent for any theory of the formation and evolution of quasars.

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Optical Identifications and Radio Spectra of Sources Found by the Michigan 8-GHZ Survey

Cited by 7 publications

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10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

First results from the Australia Telescope Compact Array 18-GHz pilot survey

Cosmological Interpretation of Redshift Data on Quasars through the V/V_MaxTest

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Optical Identifications and Radio Spectra of Sources Found by the Michigan 8-GHZ Survey

Cited by 7 publications

References 0 publications

10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

10.8-GHz flux density variations among a complete sample of sources from the NRAO-Bonn 84 survey

First results from the Australia Telescope Compact Array 18-GHz pilot survey

Cosmological Interpretation of Redshift Data on Quasars through the V/VMaxTest

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Product

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Cosmological Interpretation of Redshift Data on Quasars through the V/V_MaxTest