High dynamic range VLBI observations of NGC 6251

Jones, Dayton L.; Unwin, S. C.; Readhead, A. C. S.; Sargent, W. L. W.; Seielstad, G. A.; Simon, R. S.; Walker, R. C.; Benson, John M.; Perley, R. A.; Bridle, A. H.; Pauliny-Toth, I. I. K.; Romney, J. D.; Witzel, A.; Wilkinson, P. N.; Bååth, Lars B.; Booth, R. S.; Fort, D.; Galt, John; Mutel, R. L.; Linfield, R. P.

doi:10.1086/164283

Cited by 40 publications

(57 citation statements)

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“…We assume the nucleus to be centered at the origin of the reference frame, with the dust disk lying in the (X, Y )-plane, the major axis along the X-axis, the rotation axis along the Z-axis, and the dust disk inclined relative to the line of sight by an angle i. The dust disk major axis and the jet are projected onto the sky plane, and the difference Feretti et al 1990; (11) Fanti et al 1982;(12) Fanti et al 1986;(13) Ferrarese & Ford 1999;(14) Jones et al 1986;(15) Capetti et al 2000;(16) de Juan, Colina, & Golombek 1996;(17) Fanti et al 1987. between their position angles is . The angle between the jet and the galaxy rotation axis is .…”

Section: Resultsmentioning

confidence: 99%

The Orientation of Jets Relative to Dust Disks in Radio Galaxies

Schmitt¹,

Pringle²,

Clarke³

et al. 2002

ApJ

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We use Hubble Space Telescope broadband images and VLA and VLBI continuum data to study the threedimensional orientation of jets relative to nuclear dust disks in 20 radio galaxies. The comparison between the position angles of the jets and those of the dust disk major axes shows a wide distribution, suggesting that they are not aligned preferentially perpendicular to each other. We use a statistical technique to determine the three-dimensional distribution of angles between jets and dust disk rotation axes. This analysis shows that the observations are consistent with jets homogeneously distributed over a large region, extending over polar caps of 55 -77 but seeming to avoid lying close to the plane of the dust disks. We argue that the lack of close alignment between jets and dust disks axes is not likely to be caused by feeding the nucleus with gas from mergers originated from random directions. We suggest that the misalignment can be due to a warping mechanism in the accretion disk, such as self-irradiation instability or the Bardeen-Petterson effect, or that the gravitational potential in the inner regions of the galaxy is misaligned with respect to that of the dust disk.

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Section: Resultsmentioning

confidence: 99%

The Orientation of Jets Relative to Dust Disks in Radio Galaxies

Schmitt¹,

Pringle²,

Clarke³

et al. 2002

ApJ

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“…Blazars detected by EGRET are compact radio sources, with radio spectral indices !À0.5. The kpc-scale jet of NGC 6251 has a slightly smaller spectral index (À0.64; Saunders et al 1981), but it could account for relativistic electrons and inverse Compton emission in this source (Jones et al 1986). Figure 5 shows the spectral energy distribution of NGC 6251, assuming that it is the counterpart to 3EG J1621+8203.…”

Section: Discussionmentioning

confidence: 97%

“…NGC 6251 is the parent galaxy of an exceptional radio jet from pc to Mpc scale, which makes an angle of $45 to our line of sight (Sudou & Taniguchi 2000). High dynamic range observations of NGC 6251 with the VLBI show the presence of a bright core and an asymmetric jet, which implies relativistic beaming in this source (Jones et al 1986). The VLBI observations are described further in x 6.…”

Section: Notes On Individual Sourcesmentioning

confidence: 89%

“…High dynamic range VLBI and VLA maps are available for NGC 6251 at 6, 13, and 18 cm, showing a bright core, a jet/counterjet brightness ratio of $80 to 1 (Jones et al 1986). The fact that the source has a nuclear structure and a large-scale radio morphology implies relativistic beaming.…”

Section: Discussionmentioning

confidence: 99%

“…X-ray sources 7 and 10 are coincident with weak radio sources listed in Table 1. previously. We have also included VLBI and VLA data at 2.22, 6, and 18 cm (Jones et al 1986). Similar to Cen A, the high-energy gamma-ray emission from 3EG J1621+8203 represents a lower luminosity (3 Â 10 43 ergs s À1 ) than that of other EGRET blazars (typically 10 45 to 10 48 ergs s À1 ).…”

Section: Discussionmentioning

confidence: 99%

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Is the EGRET Source 3EG J1621+8203 the Radio Galaxy NGC 6251?

Mukherjee

Halpern

Mirabal

et al. 2002

ApJ

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We discuss the nature of the unidentified EGRET source 3EG J1621+8203. In an effort to identify the gamma-ray source, we have examined X-ray images of the field from ROSAT PSPC, ROSAT HRI, and ASCA GIS. Of the several faint X-ray point sources in the error circle of 3EG J1621+8203, most are stars or faint radio sources, unlikely to be counterparts to the EGRET source. The most notable object in the gamma-ray error box is the bright FR I radio galaxy NGC 6251. If 3EG J1621+8203 corresponds to NGC 6251, then it would be the second radio galaxy to be detected in high-energy gamma rays after Cen A, which provided the first clear evidence of the detection above 100 MeV of an active galactic nucleus (AGN) with a large-inclination jet. If the detection of more radio galaxies by EGRET has been limited by its threshold sensitivity, there exists the exciting possibility that new high-energy gamma-ray instruments, with much higher sensitivity, will detect a larger number of radio galaxies in the future.

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