VLBI Observations of Southern EGRET Identifications. I. PKS 0208-512, PKS 0521-365, and PKS 0537-441

Tingay, S. J.; Edwards, Philip; Costa, M. E.; Lovell, J. E. J.; McCulloch, P. M.; Jauncey, D. L.; Reynolds, John E.; Tzioumis, A. K.; Migenes, V.; Gough, R. G.; King, E. A.; Jones, D. L.; Preston, R. A.; Murphy, D. W.; Meier, D. L.; Ommen, T. D. van; John, M. St.; Hoard, D. W.; Nicolson, G. D.; Wan, Tao; Shen, Zhi-Qiang

doi:10.1086/177309

Cited by 29 publications

(33 citation statements)

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“…Interestingly, the source has a prominent radio, optical, and X-ray jet (Danziger 1979;Keel 1986;Falomo 1994;Macchetto et al 1991;Scarpa et al 1999;Birkinshaw et al 2002), which resembles that of the nearby radio galaxy M 87 (Sparks et al 1994). Tingay et al (1996Tingay et al ( , 1998, Tingay & Edwards (2002) and Giroletti et al (2004) studied the structure of this source on sub-pc scales in the radio. The optical jet was observed with HST by Macchetto et al (1991) and by Scarpa et al (1999), who found a structure consisting of a bright knot close to the nucleus and a diffuse and knotty structure that extends out to ∼6 arcsec from the nucleus.…”

Section: Pks 0521-365mentioning

confidence: 99%

The jet of the BL Lacertae object PKS 0521-365 in the near-IR: MAD adaptive optics observations

Falomo¹,

Pian

Treves

et al. 2009

A&A

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Context. BL Lac objects are low-power active nuclei exhibiting a variety of peculiar properties caused by the presence of a relativistic jet and orientation effects. Aims. We present adaptive optics near-IR images at high spatial resolution of the nearby BL Lac object PKS 0521-365, which is known to display a prominent jet both at radio and optical frequencies. Methods. The observations were obtained in Ks-band using the ESO multi-conjugated adaptive optics demonstrator at the Very Large Telescope. This allowed us to obtain images with 0.1 arcsec effective resolution. We performed a detailed analysis of the jet and its related features from the near-IR images, and combined them with images previously obtained with HST in the R band and by a re-analysis of VLA radio maps. Results. We find a remarkable similarity in the structure of the jet at radio, near-IR, and optical wavelengths. The broad-band emission of the jet knots is dominated by synchrotron radiation, while the nucleus also exhibits a significant inverse Compton component. We discovered the near-IR counterpart of the radio hotspot and found that the near-IR flux is consistent with being a synchrotron emission from radio to X-ray wavelengths. The bright red object (red-tip), detached but well aligned with the jet, is well resolved in the near-IR and has a linear light profile. Since it has no radio counterpart, we propose that it is a background galaxy not associated with the jet. Conclusions. The new adaptive optics near-IR images and previous observations at other frequencies allow us to study the complex environment around the remarkable BL Lac object PKS 0521-365. These data exemplify the capabilities of multi conjugate adaptive optics observations of extragalactic extended sources.

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Section: Pks 0521-365mentioning

confidence: 99%

The jet of the BL Lacertae object PKS 0521-365 in the near-IR: MAD adaptive optics observations

Falomo¹,

Pian

Treves

et al. 2009

A&A

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“…PKS 0537-441 (z = 0.896) is one of the most luminous and variable blazars at all frequencies, and has been the target of monitoring from radio to X-rays at many epochs (Cruz-Gonzalez & Huchra 1984;Maraschi et al 1985;Tanzi et al 1986;O'Brien et al 1988;Bersanelli et al 1992;Edelson et al 1992;Falomo et al 1993a;Treves et al 1993;Falomo et al 1994;Romero et al 1994;Heidt & Wagner 1996;Tingay et al 1996;Sefako et al 2000;Tornikoski et al 2001;Romero et al 2002). The source was detected by EGRET for the first time in 1991 (Michelson et al 1992; Thompson et al 1993), and then re-observed at many successive epochs.…”

Section: Introductionmentioning

confidence: 99%

Broad-band continuum and line emission of theγ-ray blazar PKS 0537–441

Pian

Falomo

Hartman

et al. 2002

A&A

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Abstract. PKS 0537-441, a bright γ-ray emitting blazar, was observed at radio, optical, UV and X-ray frequencies during various EGRET pointings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies, allow us to characterize precisely the spectral shape of the high energy blazar component, which we attribute to inverse Compton scattering. The optical-to-γ-ray spectral energy distributions at the different epochs show that the γ-ray luminosity dominates the bolometric output. This, together with the presence of optical and UV line emission, suggests that, besides the synchrotron self-Compton mechanism, the Compton upscattering of photons external to the jet (e.g., in the broad line region) may have a significant role in the production of high energy radiation. The multiwavelength variability can be reproduced by changes of the plasma bulk Lorentz factor. The spectrum secured by IUE in 1995 appears to be partially absorbed shortward of ∼1700 Å. However, this signature is not detected in the HST spectrum taken during a lower state of the source. The presence of intervening absorbers is not supported by optical imaging and spectroscopy of the field.

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“…Keel 1986; Macchetto et al 1991). No motion of the core components was detected in very long baseline interferometry (VLBI) observations ( Tingay et al 1996) and this, together with the comparatively low ratios of nuclear to host‐galaxy optical emission ( Falomo et al 1994) and radio core to extended radio flux ( Antonucci & Ulvestad 1985), suggests a source that is only moderately relativistically boosted along the line of sight compared with the most extreme BL Lacs. It was for this reason that we selected it as a suitable candidate for an X‐ray search for extended emission with the ROSAT High Resolution Imager (HRI).…”

Section: Introductionmentioning

confidence: 99%

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

Hardcastle

Worrall

Birkinshaw

1999

Monthly Notices of the Royal Astronomical Society

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The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-8711.1999.02353.xModels that seek to unify BL Lacs and low-power radio galaxies predict that the two types of object should show similar isotropically emitted X-ray emission. Testing this is usually limited by difficulties in separating strong X-ray emission from a BL Lac nucleus and surrounding low-surface brightness emission. In this paper we report ROSAT HRI observations of the z = 0.055 BL Lac object PKS 0521???365.We are able to separate a luminous extended X-ray component from the bright nucleus. Using a new radio map, we show that it is unlikely that the extended emission is due to inverse- Compton scattering of photons from the active nucleus, and instead interpret it as thermal emission from dense, rapidly cooling gas. This is a more extreme environment than is found in typical FRI radio galaxies, and may pose a problem for unified models

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VLBI Observations of Southern EGRET Identifications. I. PKS 0208-512, PKS 0521-365, and PKS 0537-441

Cited by 29 publications

References 0 publications

The jet of the BL Lacertae object PKS 0521-365 in the near-IR: MAD adaptive optics observations

The jet of the BL Lacertae object PKS 0521-365 in the near-IR: MAD adaptive optics observations

Broad-band continuum and line emission of theγ-ray blazar PKS 0537–441

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

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