2008A&A...483..759K


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.19CEST20:24:06

2008A&A...483..759K - Astronomy and Astrophysics, volume 483, 759-768 (2008/6-1)

Opacity in compact extragalactic radio sources and its effect on astrophysical and astrometric studies.

KOVALEV Y.Y., LOBANOV A.P., PUSHKAREV A.B. and ZENSUS J.A.

Abstract (from CDS):

The apparent position of the ``core'' in a parsec-scale radio jet (a compact, bright emitting region at the narrow end of the jet) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. While providing a tool probing physical conditions in the vicinity of the core, this dependency poses problems for astrometric studies using compact radio sources. We investigated the frequency-dependent shift in the positions of the cores (core shift) observed with very long baseline interferometry (VLBI) in parsec-scale jets. We discuss related physics, as well as its effect on radio astrometry and the connection between radio and optical positions of astrometric reference objects. We searched for the core shift in a sample of 277 radio sources imaged at 2.3GHz (13cm) and 8.6GHz (4cm) frequency bands using VLBI observations made in 2002 and 2003. The core shift was measured by referencing the core position to optically thin jet features whose positions are not expected to change with frequency. We present here results for 29 selected active galactic nuclei (AGN) with bright distinct VLBI jet features that can be used in differential measurements and that allow robust measurements of the shift to be made. In these AGN, the magnitude of the measured core shift between 2.3 and 8.6GHz reaches 1.4mas, with a median value for the sample of 0.44mas. Nuclear flares result in temporal variability of the shift. An average shift between the radio (4 cm) and optical (6000Å) bands is estimated to be approximately 0.1mas, and it should be taken into account in order to provide the required accuracy of the radio-optical reference frame connection. This can be accomplished with multi-frequency VLBI measurements yielding estimates of the core shift in the sources used for the radio reference frame and radio-optical position alignment.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: jets - radio continuum: galaxies - astrometry - reference systems

Simbad objects: 32

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Number of rows : 32

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 QSO B0003-066 BLL 00 06 13.89288849 -06 23 35.3353162   19.1   17.14   ~ 251 1
2 QSO B0118-272 BLL 01 20 31.6632705443 -27 01 24.643168036   15.89 15.56 15.49   ~ 234 1
3 [VV98] J015127.1+274442 QSO 01 51 27.14618081 +27 44 41.7936492   20.6   20.42   ~ 40 0
4 4C 15.05 Bla 02 04 50.41389571 +15 14 11.0436591   21.9 22.1 21.00   ~ 356 1
5 QSO B0239+108 QSO 02 42 29.17085456 +11 01 00.7279554   20.0   19.66   ~ 97 1
6 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3460 3
7 ICRF J034506.4+145349 QSO 03 45 06.41654424 +14 53 49.5582021       20.00   ~ 37 1
8 QSO J0427+0457 QSO 04 27 47.57053172 +04 57 08.3256492   20.0       ~ 49 1
9 Mrk 1506 Sy1 04 33 11.0958197353 +05 21 15.617543663   15.72 15.05 10.08   ~ 1805 2
10 QSO B0507+179 QSO 05 10 02.36912982 +18 00 41.5816534   20.0 19.0 19.09   ~ 276 1
11 QSO B0607-157 QSO 06 09 40.9477650070 -15 42 40.649794982   18.47 18.0 19.90   ~ 282 1
12 3C 154.0 QSO 06 13 50.13917401 +26 04 36.7198424           ~ 144 0
13 QSO B0736+01 QSO 07 39 18.03389693 +01 37 04.6178588   16.90 16.47 16.19   ~ 613 1
14 QSO B0839+187 QSO 08 42 05.09417058 +18 35 40.9905528   16.63 16.36 16.56   ~ 159 2
15 4C 58.17 QSO 08 54 41.99641123 +57 57 29.9390674   18.56 18.18 17.43   ~ 204 1
16 QSO B0952+179 QSO 09 54 56.82361250 +17 43 31.2222114   17.31 17.23     ~ 188 1
17 QSO J1007+1356 QSO 10 07 41.49808563 +13 56 29.6008672     19.0 18.59   ~ 101 1
18 4C 21.28 QSO 10 51 48.78907490 +21 19 52.3138145     18.5 17.72   ~ 121 1
19 7C 1147+2434 BLL 11 50 19.2119754161 +24 17 53.834754764   16.26 15.74 15.80   ~ 238 1
20 7C 1219+2830 BLL 12 21 31.6902446545 +28 13 58.500383827   16.81 16.11 14.24   ~ 763 1
21 6C 164218+690201 QSO 16 42 07.84850549 +68 56 39.7564973   19.723   19.219   ~ 278 1
22 QSO J1658+0741 QSO 16 58 09.01146700 +07 41 27.5405227   19.993 19.5 19.598   ~ 150 1
23 QSO J1658+0515 QSO 16 58 33.4475275967 +05 15 16.444287791   17.00 16.54 16.21   ~ 201 1
24 8C 1803+784 BLL 18 00 45.6831135718 +78 28 04.017792333   16.4 16.4 15.46   ~ 651 1
25 4C 28.45 QSO 18 32 50.18562512 +28 33 35.9552936   16.91 17.16     ~ 119 1
26 ICRF J184208.9+794617 Sy1 18 42 08.9910523393 +79 46 17.129210139   16.06 15.38     ~ 1186 0
27 IERS B1926+087 Rad 19 28 40.85549 +08 48 48.4133           ~ 12 0
28 4C 31.56 QSO 20 23 19.01734280 +31 53 02.3061150           ~ 93 1
29 ICRF J214622.9-152543 Sy1 21 46 22.97933395 -15 25 43.8856129   17.70 17.27 17.20   ~ 106 1
30 QSO B2155-152 QSO 21 58 06.28190211 -15 01 09.3278616   18.63 17.5 17.79   ~ 283 1
31 4C 31.63 BLL 22 03 14.9758020 +31 45 38.269707   15.85 15.58 14.33   ~ 453 1
32 ICRF J232225.9+505751 QSO 23 22 25.98218320 +50 57 51.9636985       18.6   ~ 52 1

    Equat.    Gal    SGal    Ecl

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2019.10.19-20:24:06

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