A New 1.4 GHz Radio Continuum Map of the Sky South of Declination +25°

Calabretta, M. R.; Staveley‐Smith, L.; Barnes, David G.

doi:10.1017/pasa.2013.36

Cited by 89 publications

(81 citation statements)

References 31 publications

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“…This emission is accounted for by Carretti et al (2013) who estimate a contribution from Galactic emission of 8 and 2 mJy at 2.3 and 3.3 GHz, respectively. Inspection of the publicly available continuum H I Parkes All Sky Survey (Calabretta, Staveley-Smith & Barnes 2014) at 1.4 GHz reveals that A3667 is associated with significant Galactic emission. It is difficult to disentangle this Galactic emission from the emission associated with a putative radio bridge and halo.…”

Section: Radio Halo and Bridge: Discussionmentioning

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: Radio Halo and Bridge: Discussionmentioning

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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“…3. Large-scale fluctuations correspond to Galactic structure in that their position is constant with frequency and they correspond to increased flux density in the Continuum HI Parkes All Sky Survey map (Calabretta, Staveley-Smith & Barnes 2014). The mean background within the half-power beamwidth is -2.7 mJy/beam.…”

Section: Determining the 15mhz Source Countsmentioning

confidence: 96%

The 154 MHz radio sky observed by the Murchison Widefield Array: noise, confusion, and first source count analyses

Franzen

Jackson

Offringa

et al. 2016

Mon. Not. R. Astron. Soc.

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We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg 2 , a resolution of 2.3 arcmin and contains 13,458 sources above 5σ. The rms noise in the centre of the image is 4 − 5 mJy/beam. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the sky area covered. Using the deepest available source count data, we find that the MWA image is affected by sidelobe confusion noise at the ≈ 3.5 mJy/beam level, due to incompletely-peeled and out-of-image sources, and classical confusion becomes apparent at ≈ 1.7 mJy/beam. This work highlights that (i) further improvements in ionospheric calibration and deconvolution imaging techniques would be required to probe to the classical confusion limit and (ii) the shape of low-frequency source counts, including any flattening towards lower flux densities, must be determined from deeper ≈ 150 MHz surveys as it cannot be directly inferred from higher frequency data.

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“…These sources include those listed in Table 3 of Calabretta et al (2014) in addition RCW74, RCW145, and RCW146 from Table 2 of Rodgers et al (1960) and HIPASS J1324-42 from the HIPASS Bright Galaxies Catalog (Koribalski et al 2004). …”

Section: Excluding Complete Dumpsmentioning

confidence: 99%

GASS: The Parkes Galactic All-Sky Survey

Kalberla

Haud

2015

A&A

139

148

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Context. The Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (H i) emission in the southern sky observed with the Parkes 64-m Radio Telescope. The first data release (GASS I) concerned survey goals and observing techniques, the second release (GASS II) focused on stray radiation and instrumental corrections. Aims. We seek to remove the remaining instrumental effects and present a third data release. Methods. We use the HEALPix tessellation concept to grid the data on the sphere. Individual telescope records are compared with averages on the nearest grid position for significant deviations. All averages are also decomposed into Gaussian components with the aim of segregating unacceptable solutions. Improved priors are used for an iterative baseline fitting and cleaning. In the last step we generate 3D FITS data cubes and examine them for remaining problems. Results. We have removed weak, but systematic baseline offsets with an improved baseline fitting algorithm. We have unraveled correlator failures that cause time dependent oscillations; errors cause stripes in the scanning direction. The remaining problems from radio frequency interference (RFI) are spotted. Classifying the severeness of instrumental errors for each individual telescope record (dump) allows us to exclude bad data from averages. We derive parameters that allow us to discard dumps without compromising the noise of the resulting data products too much. All steps are reiterated several times: in each case, we check the Gaussian parameters for remaining problems and inspect 3D FITS data cubes visually. We find that in total ∼1.5% of the telescope dumps need to be discarded in addition to ∼0.5% of the spectral channels that were excluded in GASS II. Conclusions. The new data release (GASS III) facilitates data products with improved quality. A new web interface, compatible with the previous version, is available for download of GASS III FITS cubes and spectra.

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A New 1.4 GHz Radio Continuum Map of the Sky South of Declination +25°

Cited by 89 publications

References 31 publications

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

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

The 154 MHz radio sky observed by the Murchison Widefield Array: noise, confusion, and first source count analyses

GASS: The Parkes Galactic All-Sky Survey

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