The GLEAM 4-Jy (G4Jy) Sample: I. Definition and the catalogue. (2020)
- Record Type:
- Journal Article
- Title:
- The GLEAM 4-Jy (G4Jy) Sample: I. Definition and the catalogue. (2020)
- Main Title:
- The GLEAM 4-Jy (G4Jy) Sample: I. Definition and the catalogue
- Authors:
- White, Sarah V.
Franzen, Thomas M. O
Riseley, Chris J.
Wong, O. Ivy
Kapińska, Anna D.
Hurley-Walker, Natasha
Callingham, Joseph R.
Thorat, Kshitij
Wu, Chen
Hancock, Paul
Hunstead, Richard W.
Seymour, Nick
Swan, Jesse
Wayth, Randall
Morgan, John
Chhetri, Rajan
Jackson, Carole
Weston, Stuart
Bell, Martin
For, Bi-Qing
Gaensler, B. M.
Johnston-Hollitt, Melanie
Offringa, André
Staveley-Smith, Lister - Abstract:
- Abstract: The Murchison Widefield Array (MWA) has observed the entire southern sky (Declination, $\delta< 30^{\circ}$ ) at low radio frequencies, over the range 72–231MHz. These observations constitute the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey, and we use the extragalactic catalogue (EGC) (Galactic latitude, $|b| >10^{\circ}$ ) to define the GLEAM 4-Jy (G4Jy) Sample. This is a complete sample of the 'brightest' radio sources ( $S_{\textrm{151\, MHz}}>4\, \text{Jy}$ ), the majority of which are active galactic nuclei with powerful radio jets. Crucially, low-frequency observations allow the selection of such sources in an orientation-independent way (i.e. minimising the bias caused by Doppler boosting, inherent in high-frequency surveys). We then use higher-resolution radio images, and information at other wavelengths, to morphologically classify the brightest components in GLEAM. We also conduct cross-checks against the literature and perform internal matching, in order to improve sample completeness (which is estimated to be $>95.5$ %). This results in a catalogue of 1863 sources, making the G4Jy Sample over 10 times larger than that of the revised Third Cambridge Catalogue of Radio Sources (3CRR; $S_{\textrm{178\, MHz}}>10.9\, \text{Jy}$ ). Of these G4Jy sources, 78 are resolved by the MWA (Phase-I) synthesised beam ( $\sim2$ arcmin at 200MHz), and we label 67% of the sample as 'single', 26% as 'double', 4% as 'triple', and 3% as having 'complex' morphologyAbstract: The Murchison Widefield Array (MWA) has observed the entire southern sky (Declination, $\delta< 30^{\circ}$ ) at low radio frequencies, over the range 72–231MHz. These observations constitute the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey, and we use the extragalactic catalogue (EGC) (Galactic latitude, $|b| >10^{\circ}$ ) to define the GLEAM 4-Jy (G4Jy) Sample. This is a complete sample of the 'brightest' radio sources ( $S_{\textrm{151\, MHz}}>4\, \text{Jy}$ ), the majority of which are active galactic nuclei with powerful radio jets. Crucially, low-frequency observations allow the selection of such sources in an orientation-independent way (i.e. minimising the bias caused by Doppler boosting, inherent in high-frequency surveys). We then use higher-resolution radio images, and information at other wavelengths, to morphologically classify the brightest components in GLEAM. We also conduct cross-checks against the literature and perform internal matching, in order to improve sample completeness (which is estimated to be $>95.5$ %). This results in a catalogue of 1863 sources, making the G4Jy Sample over 10 times larger than that of the revised Third Cambridge Catalogue of Radio Sources (3CRR; $S_{\textrm{178\, MHz}}>10.9\, \text{Jy}$ ). Of these G4Jy sources, 78 are resolved by the MWA (Phase-I) synthesised beam ( $\sim2$ arcmin at 200MHz), and we label 67% of the sample as 'single', 26% as 'double', 4% as 'triple', and 3% as having 'complex' morphology at $\sim1\, \text{GHz}$ (45 arcsec resolution). We characterise the spectral behaviour of these objects in the radio and find that the median spectral index is $\alpha=-0.740 \pm 0.012$ between 151 and 843MHz, and $\alpha=-0.786 \pm 0.006$ between 151MHz and 1400MHz (assuming a power-law description, $S_{\nu} \propto \nu^{\alpha}$ ), compared to $\alpha=-0.829 \pm 0.006$ within the GLEAM band. Alongside this, our value-added catalogue provides mid-infrared source associations (subject to 6" resolution at 3.4 $\mu$ m) for the radio emission, as identified through visual inspection and thorough checks against the literature. As such, the G4Jy Sample can be used as a reliable training set for cross-identification via machine-learning algorithms. We also estimate the angular size of the sources, based on their associated components at $\sim1\, \text{GHz}$, and perform a flux density comparison for 67 G4Jy sources that overlap with 3CRR. Analysis of multi-wavelength data, and spectral curvature between 72MHz and 20GHz, will be presented in subsequent papers, and details for accessing all G4Jy overlays are provided at https://github.com/svw26/G4Jy . … (more)
- Is Part Of:
- Publications of the Astronomical Society of Australia. Volume 37(2020)
- Journal:
- Publications of the Astronomical Society of Australia
- Issue:
- Volume 37(2020)
- Issue Display:
- Volume 37, Issue 2020 (2020)
- Year:
- 2020
- Volume:
- 37
- Issue:
- 2020
- Issue Sort Value:
- 2020-0037-2020-0000
- Page Start:
- Page End:
- Publication Date:
- 2020
- Subjects:
- catalogues, -- galaxies: active, -- galaxies: evolution, -- radio continuum: galaxies
Astronomy -- Periodicals
Southern sky (Astronomy) -- Periodicals
Astrophysics -- Periodicals
Periodicals
520.5 - Journal URLs:
- http://journals.cambridge.org/action/displayJournal?jid=pas ↗
http://www.publish.csiro.au/?nid=138 ↗ - DOI:
- 10.1017/pasa.2020.9 ↗
- Languages:
- English
- ISSNs:
- 1323-3580
- Deposit Type:
- Legaldeposit
- View Content:
- Available online (eLD content is only available in our Reading Rooms) ↗
- Physical Locations:
- British Library HMNTS - ELD Digital store
- Ingest File:
- 14699.xml