The gaseous environments of radio galaxies

Worrall, D. M.

doi:10.1016/s1387-6473(01)00167-1

Cited by 7 publications

(9 citation statements)

References 52 publications

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“…Depending on the jet and ambient medium parameters, most radio galaxies display sizes below 100 kpc (Begelman et al 1984). If this is the case, using standard Friedmann-Lemaître-Robertson-Walker formulae, the ∼4 ′ size of our extended source translates into a distance smaller than 80 Mpc, which yields radio luminosities of 1.1 × 10 23 W Hz −1 sr −1 at 4590 MHz and an X-ray flux at 3.1×10 16 W Hz −1 sr −1 at 2 keV, in agreement with Worrall (2002).…”

Section: Discussionsupporting

confidence: 83%

On the origin of two unidentified radio/X-ray sources discovered withXMM-Newton

García

Combi

Medina

et al. 2015

A&A

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Aims. We aim at clarifying the nature of the emission of two spatially related unidentified X-ray sources detected with XMM-Newton telescope at intermediate-low Galactic latitude Methods. We use the imaging and spectral capabilities of XMM-Newton to study the X-ray properties of these two sources. In addition, we complement our study with radio data obtained at different frequencies to analyze a possible physical association between the sources. Results. Observations reveal a point-like source aligned with elongated diffuse emission. The X-ray spectra of these sources is bestfitted by an absorbed power law with photon index Γ ∼ 1.7 for the point-like source and ∼2.0 for the extended source. Both sources show nonthermal radio-continuum counterparts that might indicate a physical association. In addition, from the available data, we did not detect variability on the point-like source in several timescales. Two possible scenarios are analyzed: one Galactic and one extra-Galactic. First, based on HI line absorption, assuming a Galactic origin, we infer a distance upper bound of 2 kpc, which poses a constraint on the height over the Galactic plane of < ∼ 200 pc and on the linear size of the system of < ∼ 2.3 pc. In this case, the X-ray luminosities are > ∼ 10 32 erg s −1 and > ∼ 7.5 × 10 32 erg s −1 , for the point-like and extended sources, respectively. Second, an extra-Galactic nature is discussed, where the point-like source might be the core of a radio galaxy and the extended source its lobe. In this case, we compare derived fluxes, spectral indices, and spatial correlation with those typical from the radio galaxy population, showing the feasibility of this alternative astrophysical scenario. Conclusions. From the available observational evidence, we suggest that the most promising scenario to explain the nature of these sources is a system consisting of a one-sided radio galaxy, where the point-like source is an active galactic nucleus and the extended source corresponds to the emission from its lobe. Other possibilities include a pulsar and its associated pulsar wind nebula, where the radio/X-ray emission originates from the synchrotron cooling of relativistic particles in the pulsar's magnetic field or a casual alignment between two unrelated sources, such as an active galactic nucleus and a Galactic X-ray blob. Deeper dedicated observations in both radio and X-ray bands are needed to fully understand the nature of these sources.

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Section: Discussionsupporting

confidence: 83%

On the origin of two unidentified radio/X-ray sources discovered withXMM-Newton

García

Combi

Medina

et al. 2015

A&A

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“…The count rate was converted into flux assuming a thermal Raymond-Smith spectrum with Galactic column density, temperature kT = 1 keV, and fixing abundances to 0.2 solar. The derived observed flux is F 0.4−5keV = 6.7 × 10 −14 erg cm −2 s −1 , corresponding to an absorption-corrected luminosity L 0.4−5keV = 1 × 10 42 erg s −1 , typical of FRIs halos (e.g., Worrall 2002).…”

Section: Spatial Analysismentioning

confidence: 91%

Chandraobservations of the X-ray environment of BL Lacs

Donato

Gliozzi

Sambruna

et al. 2003

A&A

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Abstract. We present Chandra observations of the X-ray environment of a sample of 6 BL Lacertae objects. The improved sensitivity of the ACIS experiment allows us to separate the core X-ray emission from the contribution of diffuse emission from the host galaxy/cluster scales. Within the short (2-6 ks) ACIS exposures, we find evidence for diffuse X-ray emission in 3 sources (BL Lac, PKS 0548-322, and PKS 2005-489). The diffuse emission can be modeled with a King profile with β ∼ 0.3−0.6, core radii r c ∼ 15−28 kpc, and 0.4-5 keV luminosities in the range 10 41 −10 42 erg s −1 . In the remaining 3 sources, one (3C 371) has a radial profile entirely consistent with an unresolved source, while two (1ES 2344+514 and 1ES 2321+419) show evidence for weak diffuse emission on kpc scales. These results support current models for radio-loud AGN unifying BL Lacs and FRI radio galaxies through the orientation of their jets. In PKS 0548-322 and PKS 2005-489, we also find evidence for diffuse emission on cluster scales, although the spatial properties of this emission are not constrained. The temperature (kT ∼ 3−5 keV) and luminosity (L 0.4−5 keV ∼ 10 42 erg s −1 ) of the cluster gas are typical of normal clusters. Interestingly, these are the two brightest sources of the sample, suggesting a link between environment and nuclear activity.

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“…The similar trends of L R,core and L X,tot with respect to γ are not unexpected, given that these two quantities correlate each other (Fabbiano et al 1989). The L-shape that they show with respect to cuspiness could then be produced in both cases by the hot gas, determining it directly L X,tot and being also essential for jet confinement and propagation (e.g., Worrall 2002, Kaiser 2009). In fact many of the core galaxies in fig.…”

Section: The Radio and X-ray Properties Of Nearby Nucleimentioning

confidence: 99%

The Nuclear X-Ray Emission of Nearby Early-Type Galaxies

Pellegrini

2010

ApJ

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Nuclear hard X-ray luminosities (L X,nuc ) for a sample of 112 early type galaxies within a distance of 67 Mpc are used to investigate their relationship with the central galactic black hole mass M BH (coming from direct dynamical studies or the M BH −σ relation), the inner galactic structure (using the parameters describing its cuspiness), the hot gas content and the core radio luminosity. For this sample, L X,nuc ranges from 10 38 to 10 42 erg s −1 , and the Eddington ratio L X,nuc /L Edd from 10 −9 to 10 −4 , with the largest values belonging to four Seyfert galaxies. Together with a trend for L X,nuc to increase on average with the galactic luminosity L B and M BH , there is a wide variation of L X,nuc (and L X,nuc /L Edd ), by up to 4 orders of magnitude, at any fixed L B > 6 × 10 9 L B,⊙ or M BH > 10 7 M ⊙ . This large observed range should reflect a large variation of the mass accretion rateṀ BH , and possible reasons for this difference are searched for. On the circumnuclear scale, in a scenario where accretion is (quasi) steady,Ṁ BH at fixed L B (or M BH ) could vary due to differences in the fuel production rate from stellar mass return linked to the inner galactic structure; a trend of L X,nuc with cuspiness is not observed, though, while a tendency for L X,nuc /L Edd to be larger in cuspier galaxies is present. In fact,Ṁ BH is predicted to vary with cuspiness by a factor exceeding a few only in hot gas poor galaxies and for large differences in the core radius; for a subsample with these characteristics the expected effect seems to be present in the observed L X,nuc values. L X,nuc does not show a dependence on the age of the stellar population in the central galactic region, for ages>3 Gyr; less luminous nuclei, though, are found among the youngest galaxies or galaxies with a younger stellar component. On the global galactic scale, L X,nuc shows a trend with the total galactic hot gas cooling rate (L X,ISM ): it is detected both in gas poor and gas rich galaxies, and on average increases with L X,ISM , but again with a large scatter. The observed lack of a tight relationship between L X,nuc and the circumnuclear and total gas content can be explained if accretion is regulated by factors overcoming the importance of fuel availability, as 1) the gas is heated by black hole feedback andṀ BH varies due to an activity cycle, and 2) the mass effectively accreted by the black hole can be largely reduced with respect to that entering the circumnuclear region, as in radiatively inefficient accretion with winds/outflows. Finally, differently from L X,nuc , the central 5 GHz VLA luminosity shows a clear trend with the inner galactic structure, that is similar to that shown by the total soft X-ray emission; therefore it is suggested that they could both be produced by the hot gas.

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The gaseous environments of radio galaxies

Cited by 7 publications

References 52 publications

On the origin of two unidentified radio/X-ray sources discovered withXMM-Newton

On the origin of two unidentified radio/X-ray sources discovered withXMM-Newton

Chandraobservations of the X-ray environment of BL Lacs

The Nuclear X-Ray Emission of Nearby Early-Type Galaxies

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