J/MNRAS/452/4274 Angular sizes of AGN cores at 2-43GHz (Pushkarev+, 2015)
Milky Way scattering properties and intrinsic sizes of active galactic nuclei
cores probed by very long baseline interferometry surveys of compact
extragalactic radio sources.
Pushkarev A.B., Kovalev Y.Y.
<Mon. Not. R. Astron. Soc. 452, 4274 (2015)>
=2015MNRAS.452.4274P 2015MNRAS.452.4274P
ADC_Keywords: Galaxies, radio ; Interferometry ; VLBI ; Interstellar medium
Keywords: scattering - Galaxy: centre - galaxies: active - ISM: general: Sgr A -
galaxies: jets
Abstract:
We have measured the angular sizes of radio cores of active galactic
nuclei (AGN) and analyzed their sky distributions and frequency
dependencies to study synchrotron opacity in AGN jets and the strength
of angular broadening in the interstellar medium. We have used
archival very long baseline interferometry (VLBI) data of more than
3000 compact extragalactic radio sources observed at frequencies,
ν, from 2 to 43GHz to measure the observed angular size of VLBI
cores. We have found a significant increase in the angular sizes of
the extragalactic sources seen through the Galactic plane
(|b|<10°) at 2, 5 and 8GHz, about 1/3 of which show significant
scattering. These sources are mainly detected in directions to the
Galactic bar, the Cygnus region, and a region with galactic longitudes
220°<l<260° (the Fitzgerald window). The strength of
interstellar scattering of the AGNs is found to correlate with the
Galactic Hα intensity, free-electron density, and Galactic
rotation measure. The dependence of scattering strengths on source
redshift is insignificant, suggesting that the dominant scattering
screens are located in our Galaxy. The observed angular size of Sgr-A*
is found to be the largest among thousands of AGN observed over the
sky; we discuss possible reasons of this strange result. Excluding
extragalactic radio sources with significant scattering, we find that
angular size of opaque cores in AGN scales typically as ν-1
confirming predictions of a conical synchrotron jet model with
equipartition.
Description:
File table2 contains the name of the sources and their Galactic
coordinates, redshift, apparent angular size of the VLBI cores.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 4963 Apparent angular sizes of the VLBI cores of AGN
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Source Source name (J2000)
12- 18 F7.3 deg GLAT Galactic latitude (1)
20- 26 F7.3 deg GLON Galactic longitude (1)
28- 32 F5.3 --- z [0.001/5.3]? Redshift (2)
34- 38 F5.2 mas theta2 ? FWHM angular size of VLBI core at 2GHz (3)
40- 44 F5.2 mas theta5 ? FWHM angular size of VLBI core at 5GHz (3)
46- 50 F5.2 mas theta8 ? FWHM angular size of VLBI core at 8GHz (3)
52- 56 F5.2 mas theta15 ? FWHM angular size of VLBI core at 15GHz (3)
58- 62 F5.2 mas theta24 ? FWHM angular size of VLBI core at 24GHz (3)
64- 68 F5.2 mas theta43 ? FWHM angular size of VLBI core at 43GHz (3)
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Note (1): The Galactic coordinates were calculated from coordinate positions
taken from the Radio Fundamental Catalog (http://astrogeo.org/rfc) as derived
from analysis of all VLBI observations made in absolute astrometry and
geodesy mode.
Note (2): Redshifts taken from
http://www.gao.spb.ru/english/as/ac_vlbi/ocars.txt
Note on (3): If a source was observed over multiple epochs, the median of the
observed angular size is given.
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Acknowledgements:
Alexander Pushkarev, pushkarev.alexander(at)gmail.com
History:
* 21-Aug-2015: on-line version
* 03-Feb-2017: corrected version for GLON (from author)
* 31-May-2017: redshifts corrected or added (from author)
(End) Alexander Pushkarev [CrAO, Russia], Patricia Vannier [CDS] 19-Aug-2015