| 1. |
- Bååth, L.B. 1948-, et al.
(författare)
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High Resolution Observations of the QSO 3C 345 at 1.3 centimeters
- 1981
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Ingår i: Astrophysical Journal. - Philadelphia, PA : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 243, s. L123-L126
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution VLBI observations made at a frequency of 22.235 GHz of the quasar 3C 345 are discussed. Antennas located at the Crimean Astrophysical Observatory, USSR; Onsala, Sweden; Effelsberg, West Germany; and the Haystack Observatory, Massachusetts were employed at 4-min integration times to provide baselines ranging up to 5.5 x 10 to the 8th wavelengths. About 40% of the total flux density of 7.85 Jy, observed in November 1977, and 8.05 Jy, observed in October 1978, is found to originate in an unresolved component of the quasar core in a region less than 0.1 milliarcsec in diameter. The elongated jet-like component of the quasar is observed to contain several peaks of emission extending up to 6 milliarsec from the core which decreased in extent between the two observations.
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| 2. |
- Giuffrida, T.S., et al.
(författare)
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VLBI Studies of the W3OH Water Maser
- 1977
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Ingår i: Bulletin of the American Astronomical Society. - New York, NY : American Institute of Physics (AIP). - 0002-7537 .- 2330-9458. ; 9, s. 576-576
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Bååth, L.B. 1948-, et al.
(författare)
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The microarcsecond structure of 3C 273 at 3 MM
- 1991
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 241:1, s. L1-L4
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Tidskriftsartikel (refereegranskat)abstract
- Recent improvements in data analysis and receiver techniques have allowed us to produce a map of the 100GHz emission from the compact radio source 3C273 with the unsurpassed resolution of 50-mu-as (microarcseconds). Our map shows that the structure within 300-mu-as (approximately 1.5.10(18).h-1 cm) has a position angle significantly different from the position angle of the jet observed at lower frequencies. There are also indications in our map that the inner structure has a more pronounced wiggling structure than has been observed on larger scales. The observations were made about 60 days from the start of the outburst of 1988. Most of the flux from the outburst is concentrated in a component which is elongated approximately (56 x 5).10(16).h-1 cm perpendicular to the overall jet-axis. The distance between this component and the core is approximately 128-mu-as, which corresponds to the distance expected from an apparent velocity of approximately 800-mu-as year-1.
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| 4. |
- Bååth, L.B. 1948-, et al.
(författare)
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VLBI observations of active galactic nuclei at 3 MM
- 1992
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 257:1, s. 31-46
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Tidskriftsartikel (refereegranskat)abstract
- Recent improvements in data analysis and receiver techniques have allowed us to produce maps of the 100 GHz emission from the compact cores of active galactic nuclei with the unsurpassed resolution of 50-mu-as (microarcseconds). We present here hybrid maps of a set of compact radio sources observed at two epochs with a global VLBI array. The high resolution enables us to show details of active galactic nuclei on size scales of 10(16)-10(17) cm. Jets are shown to be more curved in these inner parts than further out in the areas mapped with VLBI at lower frequencies. Our maps of the quasar 3C345 show that the curvature seen with lower resolution instruments continues very close to the core. New components are seen separating from the cores of 3C84 and BL Lac. We observe a component in 3C84 separating from the core with an apparent speed approximately 21000 km sec-1. The radio source OJ287 is still unresolved with our array, having a core size of less-than-or-similar-to 10(17) cm. There is no indication of any compact component in 3C279 which would be associated with the outburst in integrated flux density which happened some months before our observation. The flux density of the most compact component we observe in 3C279 agrees well with that of the quiet core as extrapolated from its radio spectrum at lower frequencies. The inner part of the radio jet of the giant elliptical galaxy M87 also shows a continuation of the structure on a larger size scale, with a structure we interpret as parts of a helical pattern. No fringes were found for 4C39.25 or Sgr A.
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| 5. |
- Tang, G., et al.
(författare)
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Radio source structure from geodetic VLBI observations : evolution of the quasar 3C 345 at 8 GHz
- 1989
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 216:1-2, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- Eight VLBI maps of 3C 345 were obtained at 8.3 GHz between 1980 and 1986. During this period, the two jet components C4 and C5 were shown to emerge from the core in succession and to move superluminally toward the west with angular velocities of 0.17 + or - 0.5 and 0.11 + or - 0.02 mas/yr, respectively. An emission detected between D and C5 after 1985.46 suggests that a new component emerged from the core, moving at an angular velocity of 0.2 mas/yr. The C3 component retained a velocity of about 0.44 mas/yr, and its proper motion was found to accelerate in the y-direction and decelerate in the x-direction.
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| 6. |
- Tang, Guoquiang, et al.
(författare)
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Radio source structure from geodetic VLBI observations : 8 GHz multi-epoch maps of the quasar 4C 39.25
- 1987
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 185:1-2, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- Techniques for estimating and/or eliminating the effects of structure variations in the extragalactic radio sources used as fiducial points in 8.3-GHz geodetic VLBI observations are described and demonstrated. Particular attention is given to the data base statistics, the calibration of visibility data, the production of hybrid maps with AIPS, and the implementation of these steps in a software package. A set of X-band maps of 4C 39.25, obtained with the receivers of the Mark III dual-frequency VLBI network at six epochs during 1980-1985, is presented. Such maps are shown to be of value (1) for maintaining submarcsec accuracy in the extragalactic reference frame and (2) for qualitative astronomical monitoring of the sources. In 4C 39.25, for example, apparent superluminal motions, complex internal kinematics, and a double western component are observed.
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| 7. |
- Tang, G., et al.
(författare)
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Recent Evolution of Jet Components in 3C345 at 3.6 cm
- 1990
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Ingår i: Parsec-Scale radio jets. - Cambridge : Cambridge University Press. - 0521392268 ; , s. 32-37
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Bokkapitel (refereegranskat)abstract
- A series of 3.6 cm VLBI maps of 3C345 (1980.79 to 1988.38) is presented. The evolution of the jet components in this quasar is briefly discussed. Recent behavior of component C5 is described and the presence of a new component, tentatively labeled C6, is suggested.
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