Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array

Hurley‐Walker, N.; Johnston‐Hollitt, M.; Ekers, R. D.; Hunstead, R. W.; Sadler, E. M.; Hindson, L.; Hancock, P. J.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, Jacqueline N.; Kaplan, David L.; Kasper, J. C.; Kratzenberg, E.; Lonsdale, Colin J.; Lynch, M. J.; Mitchell, D. A.; McWhirter, R.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Shankar, U.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

doi:10.1093/mnras/stu2570

Cited by 36 publications

(52 citation statements)

References 54 publications

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“…GLEAM will be unparalleled in its ability to image large, low surface brightness structures, both Galactic and extragalactic, in full polarisation. The strengths of MWA's surface brightness sensitivity have already been made evident by the serendipitous discovery of a relic radio galaxy in early MWA data (Hurley-Walker et al, 2015).…”

Section: Comparison To Other Southern Hemisphere Surveysmentioning

confidence: 94%

GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey

Wayth

Lenc

Bell

et al. 2015

Publ. Astron. Soc. Aust.

320

225

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GLEAM, the GaLactic and Extragalactic All-sky MWA survey, is a survey of the entire radio sky south of declination +25• at frequencies between 72 and 231 MHz, made with the MWA using a drift scan method that makes efficient use of the MWA's very large field-of-view. We present the observation details, imaging strategies, and theoretical sensitivity for GLEAM. The survey ran for two years, the first year using 40-kHz frequency resolution and 0.5-s time resolution; the second year using 10-kHz frequency resolution and 2 s time resolution. The resulting image resolution and sensitivity depends on observing frequency, sky pointing, and image weighting scheme. At 154 MHz, the image resolution is approximately 2.5 × 2.2/ cos(δ + 26.7• ) arcmin with sensitivity to structures up to ∼10 • in angular size. We provide tables to calculate the expected thermal noise for GLEAM mosaics depending on pointing and frequency and discuss limitations to achieving theoretical noise in Stokes I images. We discuss challenges, and their solutions, that arise for GLEAM including ionospheric effects on source positions and linearly polarised emission, and the instrumental polarisation effects inherent to the MWA's primary beam.

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Section: Comparison To Other Southern Hemisphere Surveysmentioning

confidence: 94%

GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey

Wayth

Lenc

Bell

et al. 2015

Publ. Astron. Soc. Aust.

320

225

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“…Murgia et al 2011). To date, very few other remnant sources outside clusters have been detected and studied: 0924+30 (Jamrozy et al 2004), NGC 5580 (de Gasperin et al 2014), and NGC 1534(Hurley-Walker et al 2015.…”

Section: Spectral Comparison With Other Remnant Radio Galaxies and Immentioning

confidence: 99%

“…Visual inspection of radio sources has already provided a number of detections in addition to the source presented here (e.g. de Gasperin et al 2014;Harris et al 1993;Hurley-Walker et al 2015;Giovannini et al 1991), but it still has not been applied in a systematic way. Tentative searches based on morphological characteristics have only been performed by Saripalli et al (2012) in the context of the Australia Telescope Low Brightness Survey and by Jones & Preston (2001) using the VLSS.…”

Section: Implications For Selection Of Remnant Radio Galaxiesmentioning

confidence: 99%

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LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift

Brienza

Godfrey

Morganti

et al. 2015

A&A

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Context. Remnant radio galaxies represent the final dying phase of radio galaxy evolution in which the jets are no longer active. Remnants are rare in flux-limited samples, comprising at most a few percent. As a result of their rarity and because they are difficult to identify, this dying phase remains poorly understood and the luminosity evolution is largely unconstrained. Aims. Here we present the discovery and detailed analysis of a large (700 kpc) remnant radio galaxy with a low surface brightness that has been identified in LOFAR images at 150 MHz. Methods. By combining LOFAR data with new follow-up Westerbork observations and archival data at higher frequencies, we investigated the source morphology and spectral properties from 116 to 4850 MHz. By modelling the radio spectrum, we probed characteristic timescales of the radio activity. Results. The source has a relatively smooth, diffuse, amorphous appearance together with a very weak central compact core that is associated with the host galaxy located at z = 0.051. From our ageing and morphological analysis it is clear that the nuclear engine is currently switched off or, at most, active at a very low power state. We find that the source has remained visible in the remnant phase for about 60 Myr, significantly longer than its active phase of 15 Myr, despite being located outside a cluster. The host galaxy is currently interacting with another galaxy located at a projected separation of 15 kpc and a radial velocity offset of ∼300 km s −1 . This interaction may have played a role in the triggering and/or shut-down of the radio jets. Conclusions. The spectral shape of this remnant radio galaxy differs from most of the previously identified remnant sources, which show steep or curved spectra at low to intermediate frequencies. Our results demonstrate that remnant radio galaxies can show a wide range of evolutionary paths and spectral properties. In light of this finding and in preparation for new-generation deep low-frequency surveys, we discuss the selection criteria to be used to select representative samples of these sources.

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“…Obenberger et al 2014). Propagation phenomena in the magneto-ionized medium of our galaxy are stronger (Stovall et al 2015), galaxy clusters show extended relics and halos (Feretti et al 2012), and both AGN and radio galaxies show evidence of earlier phases of activity through steep spectrum, extended emission (Hurley-Walker et al 2015;Brienza et al 2016). Despite these science opportunities, there are special challenges with the processing of high-resolution, low-frequency radio observations.…”

Section: Introductionmentioning

confidence: 99%

The GMRT 150 MHz all-sky radio survey

Intema

Jagannathan

Mooley

et al. 2017

A&A

857

767

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We present the first full release of a survey of the 150 MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000 h of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. Our data release covers 36 900 deg 2 (or 3.6 π steradians) of the sky between −53• and +90• declination (Dec), which is 90 percent of the total sky. The majority of pointing images have a noise level below 5 mJy beamwith an approximate resolution of 25 × 25 (or 25 × 25 /cos (Dec − 19 • ) for pointings south of 19 • declination). We have produced a catalog of 0.62 Million radio sources derived from an initial, high reliability source extraction at the seven sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than two arcseconds in right ascension and declination, while the flux density accuracy is estimated at approximately ten percent. Within the scope of the TGSS alternative data release (TGSS ADR) project, the source catalog, as well as 5336 mosaic images (5• × 5 • ) and an image cutout service, are made publicly available at the CDS as a service to the astronomical community. Next to enabling a wide range of different scientific investigations, we anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionisation (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data.

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Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array

Cited by 36 publications

References 54 publications

GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey

GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey

LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift

The GMRT 150 MHz all-sky radio survey

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