A Radio Survey of the Galactic Plane at a Frequency of 408 Mc/s. I. The Discrete Sources

Large, M. I.; Mathewson, D. S.; Haslam, C. G. T.

doi:10.1093/mnras/123.2.113

Cited by 21 publications

(11 citation statements)

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“…These also used a thresholding step followed by integration of the flux density in peaks of emission above that threshold (e.g., Kenderdine, Ryle, & Pooley 1966). This in turn followed naturally from the earlier practice of defining a smooth curve through the minima of paper trace profiles to represent the background level (e.g., Large, Mathewson, & Haslam 1961).…”

Section: Introductionmentioning

confidence: 99%

The ASKAP/EMU Source Finding Data Challenge

Hopkins

Whiting

Seymour

et al. 2015

Publ. Astron. Soc. Aust.

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The Evolutionary Map of the Universe (EMU) is a proposed radio continuum survey of the Southern Hemisphere up to declination +30• , with the Australian Square Kilometre Array Pathfinder (ASKAP). EMU will use an automated source identification and measurement approach that is demonstrably optimal, to maximise the reliability and robustness of the resulting radio source catalogues. As a step toward this goal we conducted a "Data Challenge" to test a variety of source finders on simulated images. The aim is to quantify the accuracy and limitations of existing automated source finding and measurement approaches. The Challenge initiators also tested the current ASKAPsoft source-finding tool to establish how it could benefit from incorporating successful features of the other tools. As expected, most finders show completeness around 100% at ≈10 σ dropping to about 10% by ≈5 σ . Reliability is typically close to 100% at ≈10 σ , with performance to lower sensitivities varying between finders. All finders show the expected trade-off, where a high completeness at low signal-to-noise gives a corresponding reduction in reliability, and vice versa. We conclude with a series of recommendations for improving the performance of the ASKAPsoft source-finding tool.

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Section: Introductionmentioning

confidence: 99%

The ASKAP/EMU Source Finding Data Challenge

Hopkins

Whiting

Seymour

et al. 2015

Publ. Astron. Soc. Aust.

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“…• (Large et al 1961). This ratio corresponds to η ∼ 0.5 at ν1 = 2.3 GHz for the above spectral indices.…”

Section: Radio Continuum Mapmentioning

confidence: 99%

Optical thickness, spin temperature and correction factor for the density of Galactic H i gas

Sofue¹

2017

Monthly Notices of the Royal Astronomical Society

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A method to determine the spin temperature of the local (V LSR = 0 km s −1 ) HI gas using saturated brightness temperature of the 21-cm line in the radial-velocity degenerate regions (VDR) is presented. The spin temperatures is determined to be T S = 146.2±16.1 K by measuring saturated brightness in the VDR toward the Galactic Center, 146.8 ± 10.7 K by χ 2 fitting of expected brightness distribution to observation around the VDR, and 144.4 ± 6.8 K toward the local arm. Assuming T S = 146 K, a correction factor Γ for the HI density, defined by the ratio of the true HI density for finite optical thickness to that calculated by assuming optically thin HI, was obtained to be Γ ∼ 1.2 (optical depth τ ∼ 0.3) in the local HI gas, ∼ 1.8 (∼ 1.3) toward the arm and anti-center, and as high as ∼ 3.6 (∼ 2.7) in the Galactic Center direction. It is suggested that the HI density and mass in the local arm could be ∼ 2 times, and that in the inner Galaxy ∼ 3.6 times, greater than the currently estimated values.

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“…radio spectrum, surveys made with pencil beams in the frequency range 80 -4080 MHz are used (Baldwin, 1955a;Denisse et al, 1955;Kraus and Ko, 1955;Piddington and Trent, 1956;Hill et al, 1958;Westerhout, 1958;Seeger et al, 1960;Wilson and Bolton, 1960;Large et al, 1961;Mathewson et al, 1962;Braccesi and Vespigani, 1964;Moron, 1965;Komesaroff, 1966;Penzias and Wilson, 1966;Wielebinski et al, 1968). These flux values shown in Figure 5.6 are the mean values in the two directions b = 3.6 0 N and 3.6S in the case of R1 and 1 = 20* and 3400 for R 2 , except in surveys, in which data is available for only one.…”

Section: Observational Datamentioning

confidence: 99%