Accountability and Sleaze

Pilkington, Colin

doi:10.1007/978-1-349-05368-1_11

Cited by 2 publications

(2 citation statements)

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“…The flux density at 327 MHz was measured on the VLA-C array image 0.20 ± 0.02 (9) 10700 0.11 ± 0.01 (13) References. -(1) Viner & Erickson (1975); (2) VLSS image, Cohen et al (2007); (3) 4C; Pilkington & Scott (1965), Gower et al (1967); (4) VLA archival data (Obs. Id.…”

Section: Spectral Analysismentioning

confidence: 99%

A Giant Metrewave Radio Telescope Multifrequency Radio Study of the Isothermal Core of the Poor Galaxy Cluster AWM 4

Giacintucci

Vrtilek

Murgia

et al. 2008

ApJ

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We present a detailed radio morphological study and spectral analysis of the wide-angle-tail radio source 4C +24.36 associated with the dominant galaxy in the relaxed galaxy cluster AWM 4. Our study is based on new high sensitivity GMRT observations at 235 MHz, 327 MHz and 610 MHz, and on literature and archival data at other frequencies. We find that the source major axis is likely oriented at a small angle with respect to the plane of the sky. The wide-angle-tail morphology can be reasonably explained by adopting a simple hydrodynamical model in which both ram pressure (driven by the motion of the host galaxy) and buoyancy forces contribute to bend the radio structure. The spectral index progressively steepens along the source major axis from α ∼0.3 in the region close to the radio nucleus to beyond 1.5 in the lobes. The results of the analysis of the spectral index image allow us to derive an estimate of the radiative age of the source of ∼ 160 Myr. The cluster X-ray emitting gas has a relaxed morphology and short cooling time, but its temperature profile is isothermal out to at least 160 kpc from the centre. Therefore we seek evidence of energy ejection from the central AGN to prevent catastrophic cooling. We find that the energy injected by 4C +24.36 in the form of synchrotron luminosity during its lifetime is far less than the energy required to maintain the high gas temperature in the core. We also find that it is not possible for the central source to eject the requisite energy in the intracluster gas in terms of the enthalpy of buoyant bubbles of relativistic fluid, without creating discernible large cavities in the existing X-ray XMM-Newton observations.

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Section: Spectral Analysismentioning

confidence: 99%

A Giant Metrewave Radio Telescope Multifrequency Radio Study of the Isothermal Core of the Poor Galaxy Cluster AWM 4

Giacintucci

Vrtilek

Murgia

et al. 2008

ApJ

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“…Best et al 2005;Baldi & Capetti 2010;Baldi et al 2018a): this implies that they have typical sizes of less than ∼10 kpc. In contrast, radio galaxies selected by high-flux limited lowfrequency surveys such as the 3C (Edge et al 1959), the 3CR (Bennett 1962), the 4C (Pilkington et al 1965) and the B2 (Colla et al 1975;Fanti et al 1978) often extend E-mail: torresi@iasfbo.inaf.it 1 Sloan Digital Sky Survey (York et al 2000) 2 Faint Images of the Radio Sky at Twenty centimetres survey (Becker et al 1995;Helfand et al 2015) to hundreds of kpc (FRI/FRII) and appear resolved at the angular resolution provided by FIRST. Baldi et al (2010Baldi et al ( , 2018a showed that the radio galaxies selected in the local Universe at 1.4 GHz, with similar bolometric luminosities, span in a broad distribution of radio luminosities and sizes, from compact to resolved with clear extended radio emission.…”

Section: Introductionmentioning

confidence: 99%

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

Torresi

Grandi²,

Capetti

et al. 2018

Monthly Notices of the Royal Astronomical Society

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FR0s are compact radio sources that represent the bulk of the Radio-Loud (RL) AGN population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first Xray study of a sample of 19 FR0 radio galaxies selected from the SDSS/NVSS/FIRST sample of Best & Heckman (2012), with redshift ≤ 0.15, radio size ≤ 10 kpc and optically classified as low-excitation galaxies (LEG). The X-ray spectra are modeled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to FRIs. The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low luminosity BL Lacs, rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. GPS/CSS sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

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Accountability and Sleaze

Cited by 2 publications

References 0 publications

A Giant Metrewave Radio Telescope Multifrequency Radio Study of the Isothermal Core of the Poor Galaxy Cluster AWM 4

A Giant Metrewave Radio Telescope Multifrequency Radio Study of the Isothermal Core of the Poor Galaxy Cluster AWM 4

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

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