Time-domain and spectral properties of pulsars at 154 MHz

Bell, M. E.; Murphy, Tara; Johnston, S.; Kaplan, David L.; Croft, Steve; Hancock, P. J.; Callingham, J. R.; Zic, Andrew; Dobie, Dougal; Swiggum, Joseph K.; Rowlinson, A.; Hurley‐Walker, N.; Offringa, A. R.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Gaensler, B. M.; Greenhill, L. J.; Hazelton, B. J.; Johnston‐Hollitt, M.; Lonsdale, Colin J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, Christopher

doi:10.1093/mnras/stw1293

Cited by 35 publications

(33 citation statements)

References 76 publications

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“…Once corrected for observational selection effects, the intrinsic average pulsar slope is α = −1.4±1.0 (Bates, Lorimer & Verbiest 2013). These values are in line with recent samples selected at low frequencies (∼ 100 − 200 MHz; Bilous et al 2016;Frail et al 2016;Bell et al 2016;Murphy et al 2017b). Polarisation can be another useful discriminant since pulsar profiles are often strongly polarised in linear and circular polarisation (Han et al 2009).…”

Section: An Excess Of Steep-spectrum Sources On the Galactic Planesupporting

confidence: 91%

A radio spectral index map and catalogue at 147–1400 MHz covering 80 per cent of the sky

Gasperin

Intema

Frail

2017

Monthly Notices of the Royal Astronomical Society

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The radio spectral index is a powerful probe for classifying cosmic radio sources and understanding the origin of the radio emission. Combining data at 147 MHz and 1.4 GHz from the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey (NVSS), we produced a large-area radio spectral index map of ∼ 80 per cent of the sky (Dec > −40 • ), as well as a radio spectral index catalogue containing 1 396 515 sources, of which 503 647 are not upper or lower limits. Almost every TGSS source has a detected counterpart, while this is true only for 36 per cent of NVSS sources. We released both the map and the catalogue to the astronomical community. The catalogue is analysed to discover systematic behaviours in the cosmic radio population. We find a differential spectral behaviour between faint and bright sources as well as between compact and extended sources. These trends are explained in terms of radio galaxy evolution. We also confirm earlier reports of an excess of steep-spectrum sources along the galactic plane. This corresponds to 86 compact and steep-spectrum source in excess compared to expectations. The properties of this excess are consistent with normal non-recycled pulsars, which may have been missed by pulsation searches due to larger than average scattering along the line of sight.

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Section: An Excess Of Steep-spectrum Sources On the Galactic Planesupporting

confidence: 91%

A radio spectral index map and catalogue at 147–1400 MHz covering 80 per cent of the sky

Gasperin

Intema

Frail

2017

Monthly Notices of the Royal Astronomical Society

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“…We refer the reader to Noutsos et al (2015) for further discussion of the physics behind the broad-band polarisation properties of pulsars. Previous observations with the MWA at 154 MHz found evidence of scintillation (Bell et al, 2016). However, this would not typically affect the fractional polarisation.…”

Section: Gleam J063049−283438mentioning

confidence: 81%

The POlarised GLEAM Survey (POGS) I: First results from a low-frequency radio linear polarisation survey of the southern sky

Riseley

Lenc

Eck

et al. 2018

Publ. Astron. Soc. Aust.

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The low-frequency polarisation properties of radio sources are poorly studied, particularly in statistical samples. However, the new generation of low-frequency telescopes, such as the Murchison Widefield Array (MWA; the precursor for the low-frequency component of the Square Kilometre Array) offers an opportunity to probe the physics of radio sources at very low radio frequencies. In this paper, we present a catalogue of linearly-polarised sources detected at 216 MHz, using data from the Galactic and Extragalactic All-sky MWA (GLEAM) survey. Our catalogue covers the Declination range −17 • to −37 • and 24 hours in Right Ascension, at a resolution of around 3 arcminutes. We detect 81 sources (including both a known pulsar and new pulsar candidate) with linearly-polarised flux densities in excess of 18 mJy across a survey area of approximately 6400 square degrees, corresponding to a surface density of 1 source per 79 square degrees. The level of Faraday rotation measured for our sources is broadly consistent with those recovered at higher frequencies, with typically more than an order of magnitude improvement in the uncertainty compared to higher-frequency measurements. However, our catalogue is likely incomplete at low Faraday rotation measures, due to our practice of excluding sources in the region where instrumental leakage appears. The majority of sources exhibit significant depolarisation compared to higher frequencies; however, a small sub-sample repolarise at 216 MHz. We also discuss the polarisation properties of four nearby, large-angular-scale radio galaxies, with a particular focus on the giant radio galaxy ESO 422−G028, in order to explain the striking differences in polarised morphology between 216 MHz and 1.4 GHz.

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“…The pulsar has also been detected as an MWA continuum source in GLEAM data by Murphy et al (2017a), who measured a flux density of 292 ± 14 mJy at 200 MHz, and appears in the GLEAM extragalactic catalogue as GLEAM J003408-072153. Bell et al (2016) found that this pulsar was a variable continuum source at 154 MHz and concluded that refractive scintillation was the most plausible cause of the variability they observed.…”

Section: The Pulsar Psr J0034-0721 and Pulsar Searchingmentioning

confidence: 93%

Interplanetary scintillation studies with the Murchison Widefield Array – II. Properties of sub-arcsecond compact sources at low radio frequencies

Chhetri

Morgan

Ekers

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report the first astrophysical application of the technique of wide-field Interplanetary Scintillation (IPS) with the Murchison Widefield Array (MWA). This powerful technique allows us to identify and measure sub-arcsecond compact components in lowfrequency radio sources across large areas of sky without the need for long-baseline interferometry or ionospheric calibration. We present the results of a five-minute observation of a 30×30 deg 2 MWA field at 162 MHz with 0.5 second time resolution. Of the 2550 continuum sources detected in this field, 302 (12 per cent) show rapid fluctuations caused by IPS. We find that at least 32% of bright low-frequency radio sources contain a sub-arcsec compact component that contributes over 40% of the total flux density. Perhaps surprisingly, peaked-spectrum radio sources are the dominant population among the strongly-scintillating, low-frequency sources in our sample. While gamma-ray AGN are generally compact, flat-spectrum radio sources at higher frequencies, the 162 MHz properties of many of the Fermi blazars in our field are consistent with a compact component embedded within more extended low-frequency emission. The detection of a known pulsar in our field shows that the wide-field IPS technique is at the threshold of sensitivity needed to detect new pulsars using image plane analysis, and scaling the current MWA sensitivity to that expected for SKA-low implies that large IPS-based pulsar searches will be feasible with SKA. Calibration strategies for the SKA require a better knowledge of the space density of compact sources at low radio frequencies, which IPS observations can now provide.

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Time-domain and spectral properties of pulsars at 154 MHz

Cited by 35 publications

References 76 publications

A radio spectral index map and catalogue at 147–1400 MHz covering 80 per cent of the sky

A radio spectral index map and catalogue at 147–1400 MHz covering 80 per cent of the sky

The POlarised GLEAM Survey (POGS) I: First results from a low-frequency radio linear polarisation survey of the southern sky

Interplanetary scintillation studies with the Murchison Widefield Array – II. Properties of sub-arcsecond compact sources at low radio frequencies

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