Remnant radio galaxies discovered in a multi-frequency survey

Quici, Benjamin; Hurley‐Walker, N.; Seymour, N.; Turner, Ross J.; Shabala, Stanislav; Huynh, Minh; Andernach, H.; Kapińska, A. D.; Collier, Jordan D.; Johnston‐Hollitt, M.; White, Sarah V.; Prandoni, I.; Galvin, T. J.; Franzen, T. M. O.; Ishwara‐Chandra, C. H.; Bellstedt, Sabine; Tingay, S. J.; Gaensler, B. M.; O’Brien, Andrew; Rogers, Johnathan; Chow, Kate; Driver, Simon P.; Robotham, Aaron S. G.

doi:10.1017/pasa.2020.49

Cited by 31 publications

(34 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Brienza et al 2017;Mahatma et al 2018;Saripalli et al 2012), but these new observations probe a lower level of surface brightness than earlier studies. Another remnant radio galaxy imaged by ASKAP has also been recently reported (Quici et al 2021). However, none of the previously reported remnant radio galaxies has a circular lobe resembling that in Figure 23.…”

Section: Figure 22mentioning

confidence: 77%

The Evolutionary Map of the Universe pilot survey

Norris

Marvil

Collier

et al. 2021

Publ. Astron. Soc. Aust.

Self Cite

114

View full text Add to dashboard Cite

We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers $270 \,\mathrm{deg}^2$ of an area covered by the Dark Energy Survey, reaching a depth of 25–30 $\mu\mathrm{Jy\ beam}^{-1}$ rms at a spatial resolution of $\sim$ 11–18 arcsec, resulting in a catalogue of $\sim$ 220 000 sources, of which $\sim$ 180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.

show abstract

Section: Figure 22mentioning

confidence: 77%

The Evolutionary Map of the Universe pilot survey

Norris

Marvil

Collier

et al. 2021

Publ. Astron. Soc. Aust.

Self Cite

114

View full text Add to dashboard Cite

show abstract

“…The FIRST image at 1.4 GHz and VLASS 1.2 image at 3 GHz (c,d) reveal a pair of smaller-scale (∼30 kpc) inner lobes that are roughly co-linear with the outer lobes and embedded (at least in projection) within the galaxy's optical envelope. The SDSS 9 image in (d) suggests the presence of two nuclei at the galaxy center, which are also seen in infrared images from the UKIDSS 10 Galactic Center Survey (GCS; a J-band image is shown in Figure 2 with VLASS contours overlaid). Their approximate location is marked by blue crosses in Figure 1d and their projected separation is ∼2 (∼4.4 kpc).…”

Section: Radio Imagesmentioning

confidence: 69%

“…Eventually, radiative and adiabatic expansion losses will cause the remnant emission to fade out of the observable radio band and disappear completely. The remnant phase is expected to be relatively short (a few times 10 7 years), which may explain the rarity of dying and restarted radio sources among the general population of extended radio galaxies (e.g., [5,[7][8][9][10]). However, our current knowledge of the properties, occurrence and environment of dying/restarted radio galaxies is mostly based on studies of individual objects or small collections (e.g., [4,[11][12][13][14]), and only a few investigations have been conducted using samples selected from radio surveys (e.g., [5,8,10]) or literature [15].…”

Section: Introductionmentioning

confidence: 99%

“…An improved understanding of the statistical properties of remnant sources, and of radio galaxy evolution in general, requires larger and more representative samples of sources. These are now becoming available (e.g., [7,9,16]) thanks to new and upcoming high-resolution surveys (e.g., LoTSS 2 , MGCLS 3 , ASKAP 4 ) with the new generation of radio telescopes (e.g., LOFAR 5 , MWA 6 , uGMRT 7 , MeerKAT [23], ASKAP 8 . ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

et al. 2021

View full text Add to dashboard Cite

We present VLA Low-band Ionosphere and Transient Experiment (VLITE) 338 MHz observations of the galaxy cluster CL 0838+1948. We combine the VLITE data with Giant Metrewave Radio Telescope 610 MHz observations and survey data. The central galaxy hosts a 250 kpc source whose emission is dominated by two large lobes at low frequencies. At higher frequencies, a pair of smaller lobes (∼30 kpc) is detected within the galaxy optical envelope. The observed morphology is consistent with a restarted radio galaxy. The outer lobes have a spectral index αout=1.6, indicating that they are old, whereas the inner lobes have αinn=0.6, typical for an active source. Spectral modeling confirms that the outer emission is a dying source whose nuclear activity switched off not more than 110 Myr ago. Using archival Chandra X-ray data, we compare the radio and hot gas emission. We find that the active radio source is contained within the innermost and X-ray brightest region, possibly a galactic corona. Alternatively, it could be the remnant of a larger cool core whose outer layers have been heated by the former epoch of activity that has generated the outer lobes.

show abstract

“…The ultra-steep-spectrum AGN in our sample have a wide range of radio luminosities; the median value of P 200 MHz for the AGN with α low < −1.2 (10 24.41 W Hz −1 ) is slightly lower than the median value of P 200 MHz for all AGN (10 24.61 W Hz −1 ). Quici et al (2021) show that remnant radio galaxies can be reliably identified by their ultra-steep spectra at low frequency ( 400 MHz), although the technique fails to capture younger remnants with steeper spectra at high frequencies. The absence of a radio core at high frequency is needed to establish whether these are genuine remnant radio galaxies.…”

Section: Agnmentioning

confidence: 99%

The GLEAM 200-MHz local radio luminosity function for AGN and star-forming galaxies

Franzen

Seymour

Sadler

et al. 2021

Publ. Astron. Soc. Aust.

Self Cite

View full text Add to dashboard Cite

The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76–227 MHz of the entire southern sky (Declination $<\!{+}30^{\circ}$ ) with an angular resolution of ${\approx}2$ arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1 590 local (median $z \approx 0.064$ ) radio sources with $S_{200\,\mathrm{MHz}} > 55$ mJy across an area of ${\approx}16\,700\,\mathrm{deg}^{2}$ . From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73% are fuelled by an active galactic nucleus (AGN) and 27% by star formation. We present the local radio luminosity function for AGN and star-forming (SF) galaxies at 200 MHz and characterise the typical radio spectra of these two populations between 76 MHz and ${\sim}1$ GHz. For the AGN, the median spectral index between 200 MHz and ${\sim}1$ GHz, $\alpha_{\mathrm{high}}$ , is $-0.600 \pm 0.010$ (where $S \propto \nu^{\alpha}$ ) and the median spectral index within the GLEAM band, $\alpha_{\mathrm{low}}$ , is $-0.704 \pm 0.011$ . For the SF galaxies, the median value of $\alpha_{\mathrm{high}}$ is $-0.650 \pm 0.010$ and the median value of $\alpha_{\mathrm{low}}$ is $-0.596 \pm 0.015$ . Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4% of local radio AGN have ultra-steep radio spectra at low frequencies ( $\alpha_{\mathrm{low}} < -1.2$ ). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature.

show abstract

Remnant radio galaxies discovered in a multi-frequency survey

Cited by 31 publications

References 68 publications

The Evolutionary Map of the Universe pilot survey

The Evolutionary Map of the Universe pilot survey

Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

The GLEAM 200-MHz local radio luminosity function for AGN and star-forming galaxies

Contact Info

Product

Resources

About