Compact continuum source finding for next generation radio surveys

Hancock, P. J.; Murphy, Tara; Gaensler, B. M.; Hopkins, A. M.; Curran, James

doi:10.1111/j.1365-2966.2012.20768.x

Cited by 248 publications

(313 citation statements)

References 20 publications

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“…The GLEAM survey will allow us to explore the low-frequency radio environment of already detected radio haloes and relics in the southern sky. We will also be able to search for a new sample of radio haloes and relics using new detection algorithms such as the circle Hough transform , Latent Dirichelet Allocation (Frean et al 2014;) and other diffuse source detection methods such as localized kernel transforms (Starck, Donoho & Candès 2003;Finoguenov et al 2006) or possibly appropriately filtered segmentation methods (Hancock et al 2012;Whiting 2012) and spatial scale filtering (Rudnick & Lemmerman 2009). For further details and discussion of the limitations of these algorithms for diffuse source detection, see section 4.5.2 of Norris et al (2013).…”

Section: Future Prospectsmentioning

confidence: 99%

The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Hindson¹,

Johnston‐Hollitt²,

Hurley‐Walker³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origin of radio haloes, relics and bridges is still unclear, however galaxy cluster merger seems to be an important factor. We clearly detect the north-west (NW) and south-east radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 ± 1.7 and 2.4 ± 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of −0.9 ± 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. However, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features.

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Section: Future Prospectsmentioning

confidence: 99%

The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Hindson¹,

Johnston‐Hollitt²,

Hurley‐Walker³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…There are many radio source extraction tools available, including AIPS and MIRIAD Gaussian fitting routines sad, vsad and imsad, the false discovery rate algorithm sfind (Hopkins et al 2002), and newer codes such as Duchamp (Whiting 2012), BLOBCAT (Hales et al 2012), and AEGEAN (Hancock et al 2012). Most of these source finding algorithms use a simple S/N thresholding technique whereby a source is deemed a true source if it has a peak flux density, or pixel value, above a set threshold.…”

Section: Source Extractionmentioning

confidence: 99%

The ATLAS 5.5 GHz survey of the extendedChandraDeep Field South: the second data release

Huynh¹,

Bell²,

Hopkins³

et al. 2015

Mon. Not. R. Astron. Soc.

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We present a new image of the 5.5 GHz radio emission from the extended Chandra Deep Field South. Deep radio observations at 5.5 GHz were obtained in 2010 and presented in the first data release. A further 76 hours of integration has since been obtained, nearly doubling the integration time. This paper presents a new analysis of all the data. The new image reaches 8.6 µJy rms, an improvement of about 40% in sensitivity. We present a new catalogue of 5.5 GHz sources, identifying 212 source components, roughly 50% more than were detected in the first data release. Source counts derived from this sample are consistent with those reported in the literature for S 5.5GHz > 0.1 mJy but significantly lower than published values in the lowest flux density bins (S 5.5GHz < 0.1 mJy), where we have more detected sources and improved statistical reliability. The 5.5 GHz radio sources were matched to 1.4 GHz sources in the literature and we find a mean spectral index of −0.35 ± 0.10 for S 5.5GHz > 0.5 mJy, consistent with the flattening of the spectral index observed in 5 GHz sub-mJy samples. The median spectral index of the whole sample is α med = −0.58, indicating that these observations may be starting to probe the star forming population. However, even at the faintest levels (0.05 < S 5.5GHz < 0.1 mJy), 39% of the 5.5 GHz sources have flat or inverted radio spectra. Four flux density measurements from our data, across the full 4.5 to 6.5 GHz bandwidth, are combined with those from literature and we find 10% of sources (S 5.5GHz 0.1 mJy) show significant curvature in their radio spectral energy distribution spanning 1.4 to 9 GHz.

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“…Hancock et al 2012;Hales et al 2012) that aim to determine the correct number of components within an island, and to generate an initial parameter set for the fitting of multiple Gaussian components. Hancock et al (2012) use a Laplace transform, to identify regions of negative curvature in the pixel intensity profiles, combined with the map defined from the islands of pixels above a threshold, to automate the process of identifying the numbers of components in each island, and their initial position and peak flux density estimates.…”

Section: Compact Source Extractionmentioning

confidence: 99%