Milky Way scattering properties and intrinsic sizes of active galactic nuclei cores probed by very long baseline interferometry surveys of compact extragalactic radio sources

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, $\nu$, from 2 to 43 GHz 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 ($|b|\lesssim 10^{\circ }$) at 2, 5 and 8 GHz, 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 $220^{\circ }\lesssim l\lesssim 260^{\circ }$ (the Fitzgerald window). The strength of interstellar scattering of the AGNs is found to correlate with the Galactic H$\alpha$ 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${}^{\ast }$ 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 ${\nu }^{-1}$ confirming predictions of a conical synchrotron jet model with equipartition.

9 pages, 7 figures, 5 tables, published by MNRAS; full electronic table 2 (redshifts updated) is available from ftp://cdsarc.u-strasbg.fr/pub/cats/J/MNRAS/452/4274/

References in corpus (16)

• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei III. Kinematics of Parsec-Scale Radio Jets
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. V. Multi-epoch VLBA Images
• RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
• The VLBA Imaging and Polarimetry Survey at 5 GHz
• Opacity in compact extragalactic radio sources and its effect on astrophysical and astrometric studies
• The Sixth VLBA Calibrator Survey: VCS6
• The Fifth VLBA Calibrator Survey: VCS5
• Spiral structure in the outer Galactic disk. I. The Third Galactic Quadrant
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• Discovery of Substructure in the Scatter-Broadened Image of Sgr A*
• VERA 22 GHz fringe search survey
• Angular Broadening of Intraday Variable AGN. II. Interstellar and Intergalactic Scattering
• The intra-hour variable quasar J1819$+$3845: 13-year evolution, jet polarization structure and interstellar scattering screen properties
• Early science with Korean VLBI network: the QCAL-1 43GHz calibrator survey
• Why Do Compact Active Galactic Nuclei at High Redshift Scintillate Less?
• Scatter broadening of compact radio sources by the ionized intergalactic medium: Prospects for detection with Space VLBI and the SKA

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