scholarly journals Diffuse Cluster Radio Sources

1996 ◽  
Vol 175 ◽  
pp. 333-338 ◽  
Author(s):  
L. Feretti ◽  
G. Giovannini
Keyword(s):  
Surface Brightness ◽  
Radio Galaxy ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Rare Phenomenon ◽  
Low Surface Brightness ◽  
Extended Sources ◽  
Formation And Evolution

Diffuse radio sources in clusters remain a poorly understood phenomenon. They are very extended sources (0.4-0.6 Mpc), of low surface brightness and steep spectrum, which cannot be identified with any active radio galaxy. They are a rare phenomenon, as they have been found so far in few clusters of galaxies. This paper reviews the current findings about this kind of sources, and the suggestions about their formation and evolution.

scholarly journals The Ghosts of Galaxies: Tidal Debris in Clusters

2004 ◽  
Vol 217 ◽  
pp. 70-76
Author(s):  
Michael D. Gregg ◽  
Michael J. West
Keyword(s):  
Globular Clusters ◽  
Surface Brightness ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Cluster Formation ◽  
X Ray ◽  
Cluster Evolution ◽  
Low Surface Brightness ◽  
Intergalactic Space ◽  
Formation And Evolution

Gravitational interactions in rich clusters can strip material from the outer parts of galaxies or even completely disrupt entire systems, giving rise to large scale, low surface brightness ghostly features stretching across intergalactic space. The nearby Coma and Centaurus clusters both have striking examples of galaxy ghosts, in the form of 100 kpc-long plumes of intergalactic debris. By searching HST archival images, we have found numerous other examples of galaxy ghosts in rich clusters at low redshift, evidence that galaxy destruction and recycling are ubiquitous, important in cluster formation and evolution, and continue to mold clusters at the present epoch. Many ghosts appear in X-ray bright clusters, perhaps signaling a connection with energetic subcluster mergers.The fate of such material has important ramifications for cluster evolution. Our new HST WFPC2 V & I images of a portion of the Centaurus plume reveal that it contains an excess of discrete objects with −12 < MV < −6, consistent with being globular clusters or smaller dwarf galaxies. This tidally liberated material is being recycled directly into the intracluster population of stars, dwarf galaxies, globular clusters, and gas, which may have been built largely from a multitude of similar events over the life of the cluster.

scholarly journals LOFAR view of NGC 3998, a sputtering AGN

2020 ◽  
Vol 634 ◽  
pp. A108 ◽  
Author(s):  
Sarrvesh S. Sridhar ◽  
Raffaella Morganti ◽  
Kristina Nyland ◽  
Bradley S. Frank ◽  
Jeremy Harwood ◽  
...  
Keyword(s):  
Low Power ◽  
Galaxy Evolution ◽  
Spectral Index ◽  
Surface Brightness ◽  
Large Scale ◽  
Radio Sources ◽  
The Core ◽  
Low Surface Brightness ◽  
High Turbulence ◽  
The Rich

Low-power radio sources dominate the radio sky. They tend to be small in size and dominated by their cores, but the origin of their properties and the evolution of their radio plasma are not well constrained. Interestingly, there is mounting evidence that low-power radio sources can significantly affect their surrounding gaseous medium and may therefore be more relevant for galaxy evolution than previously thought. In this paper, we present low radio frequency observations obtained with LOFAR at 147 MHz of the radio source hosted by NGC 3998. This is a rare example of a low-power source that is extremely dominated by its core, but that has two large-scale lobes of low surface brightness. We combine the new 147 MHz image with available 1400 MHz data to derive the spectral index over the source. Despite the low surface brightness, reminiscent of remnant structures, the lobes show an optically thin synchrotron spectral index (∼0.6). We interpret this as being due to rapid decollimation of the jets close to the core, to high turbulence of the plasma flow, and to entrainment of thermal gas. This could be the result of intermittent activity of the central active galactic nucleus, or, more likely, temporary disruption of the jet due to the interaction of the jet with the rich circumnuclear interstellar matter. Both would result in sputtering energy injection from the core, which would keep the lobes fed, albeit at a low rate. We discuss these results in connection with the properties of low-power radio sources in general. Our findings show that amorphous low surface brightness lobes should not be interpreted by default as remnant structures. Large deep surveys (in particular the LOFAR 150 MHz LoTSS and the recently started 1400 MHz Apertif survey) will identify a growing number of objects similar to NGC 3998 where these ideas can be further tested.

scholarly journals Revisiting the Fanaroff–Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)

2019 ◽  
Vol 488 (2) ◽  
pp. 2701-2721 ◽  
Author(s):  
B Mingo ◽  
J H Croston ◽  
M J Hardcastle ◽  
P N Best ◽  
K J Duncan ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Large Population ◽  
Automated Classification ◽  
Host Galaxies ◽  
Data Set ◽  
Extended Radio ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Extended Sources ◽  
Galaxy Population

Abstract The relative positions of the high and low surface brightness regions of radio-loud active galaxies in the 3CR sample were found by Fanaroff and Riley to be correlated with their luminosity. We revisit this canonical relationship with a sample of 5805 extended radio-loud active galactic nuclei (AGN) from the LOFAR Two-Metre Sky Survey (LoTSS), compiling the most complete data set of radio-galaxy morphological information obtained to date. We demonstrate that, for this sample, radio luminosity does not reliably predict whether a source is edge-brightened (FRII) or centre-brightened (FRI). We highlight a large population of low-luminosity FRIIs, extending three orders of magnitude below the traditional FR break, and demonstrate that their host galaxies are on average systematically fainter than those of high-luminosity FRIIs and of FRIs matched in luminosity. This result supports the jet power/environment paradigm for the FR break: low-power jets may remain undisrupted and form hotspots in lower mass hosts. We also find substantial populations that appear physically distinct from the traditional FR classes, including candidate restarting sources and ‘hybrids’. We identify 459 bent-tailed sources, which we find to have a significantly higher SDSS cluster association fraction (at z &lt; 0.4) than the general radio-galaxy population, similar to the results of previous work. The complexity of the LoTSS faint, extended radio sources not only demonstrates the need for caution in the automated classification and interpretation of extended sources in modern radio surveys, but also reveals the wealth of morphological information such surveys will provide and its value for advancing our physical understanding of radio-loud AGN.

Remnant radio galaxies discovered in a multi-frequency survey

2021 ◽  
Vol 38 ◽  
Author(s):  
Benjamin Quici ◽  
Natasha Hurley-Walker ◽  
Nicholas Seymour ◽  
Ross J. Turner ◽  
Stanislav S. Shabala ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Radio Galaxy ◽  
Radio Galaxies ◽  
Low Surface Brightness ◽  
Show Evidence ◽  
Frequency Survey ◽  
Square Kilometer Array ◽  
Murchison Widefield Array ◽  
Limiting Case ◽  
Compact Array

Abstract The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a $8.31$ deg $^2$ subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ( $\alpha<-1.2$ ) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to $4\%\lesssim f_{\mathrm{rem}} \lesssim 10\%$ ; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.

scholarly journals The quiescent fraction of isolated low surface brightness galaxies: observational constraints

2020 ◽  
Vol 500 (2) ◽  
pp. 2049-2062
Author(s):  
D J Prole ◽  
R F J van der Burg ◽  
M Hilker ◽  
L R Spitler
Keyword(s):  
Surface Brightness ◽  
Wide Field ◽  
Imaging Data ◽  
Distance Information ◽  
Spatially Correlated ◽  
Low Surface Brightness ◽  
Formation And Evolution ◽  
Strategic Program ◽  
Low Surface Brightness Galaxies ◽  
Lsb Galaxies

ABSTRACT Understanding the formation and evolution of low surface brightness galaxies (LSBGs) is critical for explaining their wide-ranging properties. However, studies of LSBGs in deep photometric surveys are often hindered by a lack of distance estimates. In this work, we present a new catalogue of 479 LSBGs, identified in deep optical imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). These galaxies are found across a range of environments, from the field to groups. Many are likely to be ultra-diffuse galaxies (UDGs). We see clear evidence for a bimodal population in colour–Sérsic index space, and split our sample into red and blue LSBG populations. We estimate environmental densities for a sub-sample of 215 sources by statistically associating them with nearby spectroscopic galaxies from the overlapping GAMA spectroscopic survey. We find that the blue LSBGs are statistically consistent with being spatially randomized with respect to local spectroscopic galaxies, implying they exist predominantly in low-density environments. However, the red LSBG population is significantly spatially correlated with local structure. We find that $26\pm 5{{\ \rm per\ cent}}$ of isolated, local LSBGs belong to the red population, which we interpret as quiescent. This indicates that high environmental density plays a dominant, but not exclusive, role in producing quiescent LSBGs. Our analysis method may prove to be very useful, given the large samples of LSB galaxies without distance information expected from e.g. the Vera C. Rubin observatory (aka LSST), especially in combination with upcoming comprehensive wide-field spectroscopic surveys.

scholarly journals Duty cycle of the radio galaxy B2 0258+35

2018 ◽  
Vol 618 ◽  
pp. A45 ◽  
Author(s):  
M. Brienza ◽  
R. Morganti ◽  
M. Murgia ◽  
N. Vilchez ◽  
B. Adebahr ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Duty Cycle ◽  
Spectral Properties ◽  
Surface Brightness ◽  
Large Scale ◽  
Radio Galaxy ◽  
Low Frequency ◽  
Evolutionary Stage ◽  
Low Surface Brightness ◽  
Frequency Coverage

Context. Radio loud active galactic nuclei (AGN) are episodic in nature, cycling through periods of activity and quiescence. The study of this duty cycle has recently gained new relevance because of the importance of AGN feedback for galaxy evolution. Aims. In this work we investigate the duty cycle of the radio galaxy B2 0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (∼240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. Methods. We have combined new LOFAR data at 145 MHz and new Sardinia Radio Telescope data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Results. Interestingly, the spectrum of both the outer northern and southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to α1451400 = 0.48 ± 0.11 and α14006600 = 0.69 ± 0.20 in the outer northern lobe, and α1451400 = 0.73 ± 0.07 in the outer southern lobe. Moreover, despite the wide frequency coverage available for the outer northern lobe (145–6600 MHz), we do not identify a significant spectral curvature (SPC ≃ 0.2 ± 0.2). Conclusions. While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age ≳ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago, allowing us to observe both the inner and outer structure simultaneously. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.

A full pipeline for modelling low surface brightness galaxies

2019 ◽  
Vol 14 (S353) ◽  
pp. 279-280
Author(s):  
Marius Peper ◽  
Boudewijn F. Roukema ◽  
Krzysztof Bolejko
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Surface Brightness ◽  
Dark Matter Halo ◽  
Cosmological Simulations ◽  
Galaxy Formation And Evolution ◽  
Low Surface Brightness ◽  
Formation And Evolution ◽  
Low Surface Brightness Galaxies

AbstractCosmological simulations are a powerful tool to test various cosmological and galaxy formation scenarios. The discovery of low surface brightness objects has been a challenge for both of these fields. Our work aims to create a fully reproducible pipeline to generate a realistic dark matter halo catalog with corresponding information on galaxy formation and evolution.

scholarly journals The 6C Survey

1977 ◽  
Vol 74 ◽  
pp. 3-7
Author(s):  
J. E. Baldwin
Keyword(s):  
Surface Brightness ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Aperture Synthesis ◽  
Radio Sources ◽  
Source Density ◽  
The North ◽  
Low Surface Brightness ◽  
Celestial Pole ◽  
Frequency Survey

A new survey of radio sources at 151 MHz, which has not been described previously, is in progress at Cambridge. There are several of us working on it including Warner, Kenderdine, Waggett, Masson and Mayer. The results of the first observations are at present in a preliminary state but we hope that in time they will form the first part of the 6C survey. The purpose of the survey is not to reach the faintest sources detected so far in aperture synthesis observations but to study moderately faint sources at a low observing frequency and to cover a large part of the northern sky rapidly. The deepest survey made so far at a low frequency is that of Ryle and Neville (1962) at 178 MHz over a region of 50 square degrees near the north celestial pole. The faintest sources detected had flux densities of 0.25 Jy, corresponding to a source density of 104 sr−1. It is already 15 years since that survey, which was the first trial of aperture synthesis using the earth's rotation, and much more is now technically possible. One of the most interesting features of a low frequency survey is its ability to detect preferentially sources with steep radio spectra and to be sensitive to sources of very low surface brightness. We know that in many cases these two properties go together and are associated with old radio sources, or at least with those parts of sources which are old. Many of the weak radio galaxies in nearby clusters are obvious examples of this type of source while the final, and so far unidentified, stages of the development of the most powerful double sources may be exciting candidates for discovery.

scholarly journals Historical Introduction

1999 ◽  
Vol 171 ◽  
pp. 3-8
Author(s):  
K.C. Freeman
Keyword(s):  
Angular Momentum ◽  
Surface Brightness ◽  
Brightness Distribution ◽  
Clusters Of Galaxies ◽  
Low Surface Brightness ◽  
The Subject ◽  
Potential Impact ◽  
Fisher Relation ◽  
Low Surface Brightness Galaxies ◽  
Present View

AbstractOur ideas about the surface brightness distribution of galaxies has changed greatly since 1970. I contrast the view at that time with our present view of the subject, and then briefly discuss some topics in the studies of Low Surface Brightness Galaxies (LSBG) that I think are particularly interesting: the Tully-Fisher relation, LSBG as systems of high angular momentum, LSBG in clusters of galaxies, and the potential impact of the HIPASS survey.

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