Extended X-ray emission from the BL Lac object PKS 0521-365

Hardcastle, M. J.; Worrall, D. M.; Birkinshaw, Mark

doi:10.1046/j.1365-8711.1999.02353.x

Cited by 10 publications

(11 citation statements)

References 42 publications

(62 reference statements)

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“…), but still worse than the broken power law model. The broken power law model absorbed by the Galactic column provides the best fit to the present data, consistent with the results obtained by Einstein, EXOSAT (Pian et al 1996), ROSAT (Pian et al 1996;Hardcastle et al 1999), BeppoSAX .…”

Section: Eg J0530-3626 (Pks 0521-365)supporting

confidence: 91%

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XMM–Newton observations of a sample of γ-ray loud active galactic nuclei

Foschini

Ghisellini

Raiteri

et al. 2006

A&A

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Aims. To understand the nature of γ-ray loud active galactic nuclei (AGN) and the mechanisms for the generation of high-energy γ-rays. Methods. We performed a homogeneous and systematic analysis of simultaneous X-ray and optical/UV properties of a group of 15 γ-ray loud AGN, using observations performed with XMM-Newton. The sample is composed of 13 blazars (6 BL Lac and 7 FlatSpectrum Radio Quasar) and 2 radio galaxies that are associated with detections at energies >100 MeV. The data for 7 of them are analyzed here for the first time, including the first X-ray observation of PKS 1406 − 706. The spectral characteristics of the sources in the present sample were compared with those in previous catalogs of blazars and other AGN, to search for difference or long term changes.Results. All the selected sources appear to follow the classic "blazar sequence" and the spectral energy distributions (SED) built with the present X-ray and optical/UV data and completed with historical data, confirm the findings of previous studies on this type of source. Some sources display interesting features: four of them, namely AO 0235 + 164, PKS 1127 − 145, S5 0836 + 710 and PKS 1830 − 211 show the presence of an intervening absorption system along the line of sight, but only the last is known to be gravitationally lensed. AO 0235 + 164 was detected during an outburst and its SED shows a clear shift of the synchrotron peak. 3C 273 shows a change in state with respect to the previous BeppoSAX observations that can be interpreted as an increase of the Seyfert-like component and a corresponding decline of the jet emission. This is consistent with the monitoring at radio wavelengths performed during the same period. PKS 1406− 706 is detected with a flux higher than in the past, but with a corresponding low optical flux. Although it is classified as FSRQ, the SED can be modelled with a simple synchrotron self-Compton model.

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Section: Eg J0530-3626 (Pks 0521-365)supporting

confidence: 91%

“…Hardcastle et al (1999) and Birkinshaw et al (2002) reported also the presence of extended emission that can be fitted with thermal plasma model with kT = 1.6 keV and Z = 0.05. Given the size of the PSF of EPIC camera on board XMM-Newton (12 −15 HEW, see Jansen et al 2001), the above mentioned structures are not resolved.…”

Section: Eg J0530-3626 (Pks 0521-365)mentioning

confidence: 87%

XMM–Newton observations of a sample of γ-ray loud active galactic nuclei

Foschini

Ghisellini

Raiteri

et al. 2006

A&A

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“…4). The best‐fitting spectrum has a spectral index α= 0.34 ± 0.03 (corresponding to a photon index Γ=α+ 1 = 1.34), consistent with the spectral index found by Garilli & Maccagni (1990) using EXOSAT , but flatter than the value α= 0.93 ± 0.03 reported by Hardcastle et al (1999) based on the ROSAT Position Sensitive Proportional Counter (PSPC) data. The effects of pileup and inadequate calibration of the response matrix may cause a systematic error of about 0.1 on the measured power‐law index.…”

Section: Discussionsupporting

confidence: 80%

“…Wings on the point response function (PRF) of the X‐ray optics and detector used to observe a BL Lac are therefore likely to exceed the brightness of the extended emission. Nevertheless, Hardcastle, Worrall & Birkinshaw (1999), using the ROSAT High Resolution Imager (HRI), reported a halo of resolved emission around the AGN in the low‐redshift ( z = 0.055 34; Keel 1985) BL Lac PKS 0521−365. Although PKS 0521−365 had a low X‐ray flux during this observation, the halo was only detectable above the wings of the PRF of the HRI over a small range of angles.…”

Section: Introductionmentioning

confidence: 99%

The X-ray jet and halo of PKS 0521−365

Birkinshaw¹,

Worrall²,

Hardcastle³

2002

Monthly Notices of the Royal Astronomical Society

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Chandra ACIS observations of PKS 0521−365 find that the X-ray emission of this BL Lac object consists of emission from an unresolved core, a diffuse halo and a 2-arcsec jet feature coincident with the inner radio/optical jet. A comparison with a new ATCA 8.6-GHz map also finds X-ray emission from the bright hotspot south-east of the nucleus. The jet spectrum, from radio to X-ray, is probably synchrotron emission from an electron population with a broken power-law energy distribution, and resembles the spectra seen from the jets of low-power (FR I) radio galaxies. The hotspot X-ray flux is consistent with the expectations of synchrotron self-Compton emission from a plasma close to equipartition, as seen in studies of high-power (FR II) radio galaxies. While the angular structure of the halo is similar to that found by an analysis of the ROSAT High Resolution Imager image, its brightness is seen to be lower with Chandra, and the halo is best interpreted as thermal emission from an atmosphere of similar luminosity to the haloes around FR I radio galaxies. The X-ray properties of PKS 0521−365 are consistent with it being a foreshortened, beamed, radio galaxy.

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“… A straightforward cooling‐flow model with density and temperature within a cooling radius of (Hardcastle et al 1999), fitted in combination with a point‐source, is too spiked for the radial profile of the counts. Solid curves show the modelled point‐like emission (narrow curve), cooling‐flow model (broader curve) and their sum.…”

Section: X‐rays From the Cluster And Corementioning

confidence: 99%

Chandra measurements of the X-ray core and cluster of 3C 220.1

Worrall

Birkinshaw

Hardcastle

et al. 2001

Monthly Notices of the Royal Astronomical Society

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We report results of an 18‐ks exposure with the ACIS instrument on Chandra of the powerful z=0.62 radio galaxy 3C 220.1. The X‐ray emission separates into cluster gas of emission‐weighted kT∼5 keV, 0.7–12 keV luminosity (to a radius of 45 arcsec) of 5.6×1044 erg s−1 and unresolved emission (coincident with the radio core). While the extended X‐ray emission is clearly thermal in nature, a straightforward cooling‐flow model, even in conjunction with a point‐source component, is a poor fit to the radial profile of the X‐ray emission. This is despite the fact that the measured properties of the gas suggest a massive cooling flow of ∼130 M⊙ yr−1, and the data show weak evidence for a temperature gradient. The central unresolved X‐ray emission has a power‐law spectral energy index α∼0.7 and 0.7–12 keV luminosity of 1045 erg s−1, and any intrinsic absorption is relatively small. The two‐point spectrum of the core emission between radio and X‐ray energies has αrx=0.75. Since this is a flatter spectrum than seen in other sources where the X‐ray emission is presumed to be radio‐related, regions close to the active galactic nucleus (AGN) in this source may dominate the central X‐ray output, as is believed to be the case for lobe‐dominated quasars. Simple unification models would be challenged if this were found to be the case for a large fraction of high‐power radio galaxies.

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Extended X-ray emission from the BL Lac object PKS 0521-365

Cited by 10 publications

References 42 publications

XMM–Newton observations of a sample of γ-ray loud active galactic nuclei

XMM–Newton observations of a sample of γ-ray loud active galactic nuclei

The X-ray jet and halo of PKS 0521−365

Chandra measurements of the X-ray core and cluster of 3C 220.1

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