arXiv subjects

Precious K. Sejake

Publications and source records attributed to Precious K. Sejake.

4 recordsLinked to original sources

arXiv2026

The GLEAM 4-Jy (G4Jy) Sample: IV. Multiwavelength data and analysis

We provide an updated 'multiwavelength' version of the G4Jy catalogue (available at https://github.com/svw26/G4Jy, https://zenodo.org/communities/g4jy/records, and through VizieR), which has 127 new host-galaxy identifications, as described in Paper III of this paper series. We also supplement the redshift information (0.0 < z < 3.6), gathered in Paper III, with $griz$ photometry available through DR10 of the DESI Legacy Surveys. Together, this legacy dataset allows us to investigate the multiwavelength properties of these southern radio-bright galaxies, which includes an initial analysis of radio spectral-curvature for this complete sample (S_151MHz > 4 Jy). For example, we present (for the first time in the literature) the radio-power--size diagram as a function of radio spectral-curvature, [P--D](SCI), noting that the spectral-curvature index (SCI) can act as a proxy for the spectral age of the radio source. This radio-power--size--age diagram shows a predominance of radio galaxies with SCI > 0.15 and D < 200 kpc, which are candidates for both remnant radio-galaxies and young radio sources, and a vast range of linear sizes for candidate restarted radio-galaxies (having SCI < -0.15). We also show that (i) G4Jy sources populate the entirety of WISE colour-colour space, (ii) optically point-like sources (i.e. candidate quasars) are brighter than the well-studied K--z relation (as expected), and (iii) there is no relation between the SCI of the radio source and its host-galaxy properties.

astro-ph.GA↗

arXiv2026

The GLEAM 4-Jy (G4Jy) Sample: III. Further host-galaxy identification, and redshift assessment

In this paper we present 127 new host-galaxy identifications for G4Jy sources (S_151MHz > 4 Jy), based on radio images from MeerKAT, the Very Large Array Sky Survey (VLASS), and the Rapid ASKAP (Australian Square Kilometre Array Pathfinder) Continuum Survey (RACS). This includes identifications that result from visual inspection of radio contours on K_s-band images, as opposed to the AllWISE-W1 images that were used for the original set of overlays when defining the G4Jy Sample (Papers I and II). Our aim is to achieve 100 per cent spectroscopic completeness for the sample, where all of the spectroscopy is available in digital form online. For now, we have gathered (i) digital optical spectroscopy for 34 per cent of the sample, (ii) photometric redshifts for an additional 21 per cent of the sample, and (iii) further redshifts found through the NASA/IPAC Extragalactic Database (but not recently verified). Our assessment of the redshifts includes visual inspection of all of the digital spectroscopy, and re-fitting redshift templates where necessary. The resulting redshift range is (currently) 0.0 < z < 3.6. We also present 151-MHz luminosities and linear sizes for the G4Jy Sample, based on initial analysis.

astro-ph.GA↗

arXiv2025

SALT spectroscopic follow-up of the G4Jy Sample

The GLEAM 4-Jy (G4Jy) Sample is a thorough compilation of the 'brightest' radio sources in the southern sky (Declination < 30 deg), as measured at 151 MHz (S > 4.0 Jy) with the Murchison Widefield Array (MWA), through the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey. In addition to flux-density measurements, the G4Jy catalogue provides host-galaxy identifications (through careful visual-inspection) and four sets of spectral indices. Despite their brightness in the radio, many of these sources are poorly-studied, with the vast majority lacking a spectroscopic redshift in published work. This is crucial for studying the intrinsic properties of the sources, and so we conduct a multi-semester observing campaign on the Southern African Large Telescope (SALT), with optical spectroscopy enabling us to provide new redshifts to the astronomical community. Initial results show that not all of the host galaxies exhibit emission-line spectra in the optical (~4500-7500 Ang), which illustrates the importance of radio-frequency selection (rather than optical selection) for creating an unbiased sample of active galactic nuclei. By combining SALT redshifts with those from the 6-degree Field Galaxy Survey (6dFGS) and the Sloan Digital Sky Survey (SDSS), we calculate radio luminosities and linear sizes for 299 G4Jy sources (which includes one newly-discovered giant radio-galaxy, G4Jy 604). Furthermore, with the highest redshift acquired (so far) being z ~ 2.2 from SDSS, we look forward to evolution studies of this complete sample, as well as breaking degeneracies in radio properties with respect to, for example, the galaxy environment.

astro-ph.GA↗

arXiv2023

MeerKAT follow-up of enigmatic GLEAM 4-Jy (G4Jy) sources

We present the results from studying 140 radio sources in the GLEAM (GaLactic and Extragalactic All-sky MWA [Murchison Widefield Array]) 4-Jy (G4Jy) Sample. These sources were followed-up with MeerKAT to assess their radio morphology and enable host-galaxy identification, as existing radio images of 25 to 45-arcsec resolution do not provide sufficient information. We refer to these sources as the MeerKAT-2019 subset. The aim is to identify the host galaxy of these sources by visually inspecting the overlays comprising radio data from four surveys (at 150, 200, 843/1400, and 1300 MHz). Our morphological classification and host-galaxy identification relies upon the ~7-arcsec resolution images from MeerKAT (1300 MHz). Through the visual inspection of the overlays, 14 radio sources in the MeerKAT-2019 subset have wide-angle tail (WAT) morphology, 10 are head-tail, and 5 have X-, S-/Z-shaped morphology. Most of the remaining sources have the radio morphology of typical symmetric lobes. Of 140 sources, we find host galaxies for 98 sources, leaving 42 with no identified host galaxy. These 42 sources still have ambiguous identification even with higher resolution images from MeerKAT.

astro-ph.GA↗