J/MNRAS/515/1736 Scattering Properties of the Milky Way (Koryukova+, 2022)
Tracing Milky Way scattering by compact extragalactic radio sources.
Koryukova T.A., Pushkarev A.B., Plavin A.V., Kovalev Y.Y.
<Mon. Not. R. Astron. Soc., 515, 1736-1750 (2022)>
=2022MNRAS.515.1736K 2022MNRAS.515.1736K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Interferometry ; VLBI ; Interstellar medium
Keywords: scattering - galaxies: active - galaxies: jets - Galaxy: ISM
Abstract:
We used archival very long baseline interferometry (VLBI) data of
active galactic nuclei (AGN) observed from 1.4GHz to 86GHz to
measure the angular size of VLBI radio cores in 8959 AGNs. We analysed
their sky distributions, frequency dependencies and created the most
densely sampled and complete to date distribution map of large-scale
scattering properties of the interstellar medium in our Galaxy.
Significant angular broadening of the measured AGN core sizes is
detected for the sources seen through the Galactic plane, and this
effect is especially strong at low frequencies (e.g., at 2GHz). The
scattering screens containing electron density fluctuations of hot
plasma are mainly concentrated in the Galactic plane and manifest
clumpy distribution. The region of the strongest scattering is the
Galactic centre, where the Galactic bar and the compact radio source
Sagittarius A* are located. We have also found the enhancement of
scattering strength in regions of the Cygnus constellation, supernova
remnants Taurus A, Vela, W78 and Cassiopeia A, and the Orion Nebula.
Using multi-frequency observational data of AGN core sizes, we
separated the contribution of the intrinsic and scattered sizes to the
measured angular diameter for 1411 sources. For the sources observed
through the Galactic plane, the contribution of the scattered size
component is systematically larger than for those seen outside the
Galactic plane. The derived power-law scattering indices are found to
be in good agreement with theoretical predictions for the
diffractive-dominated scattering of radio emission in a hot plasma
with Gaussian distribution of density inhomogeneities.
Description:
File table2.dat contains the name of the sources, central observing
frequencies, epochs, apparent angular size of the AGN VLBI cores,
formal model depended error of the core size fitting and the Galactic
coordinates of the sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 56 105357 Apparent angular sizes of the VLBI cores of AGN
measured at frequencies ranging from 1.4 to 86GHz
with separate records for every epoch
for 17474 sources
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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 --- Name Source name (J2000)
12- 16 F5.2 GHz Freq Central observing frequency
18- 27 A10 "date" Epoch Epoch
29- 34 F6.3 mas Sizecore FWHM angular size of VLBI core
36- 42 F7.3 mas e_Sizecore Error of FWHM angular size of VLBI core
44- 49 F6.2 deg GLAT Galactic latitude (1)
51- 56 F6.2 deg GLON Galactic longitude (1)
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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.
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Acknowledgements:
Tatiana Koryukova, tatyana.koryukova(at)gmail.com
(End) Tatiana Koryukova [LPI RAS, Russia], Patricia Vannier [CDS] 28-Sep-2022