86 GHz VLBI Survey of Ultra Compact Radio Emission in Active Galactic Nuclei
Transactions of IAA RAS, issue 40, 3–9 (2017)
Keywords: VLBI, Active Galaxies, Jets, Radio continuum, Millimetre surveys, Brightness temperature
About the paper Full textAbstract
Very Long Baseline Interferometry (VLBI) Observations at 86 GHz reach a resolution of about 50 µas and sample the scales as small as 10³ − 10⁴ Schwarzschild radii of the central black hole in Active Galactic Nuclei (AGN), uncovering the jet regions where acceleration and collimation of the relativistic flow takes place. We present the results from a large global VLBI survey of 162 ultra-compact radio sources at 86 GHz conducted in 2010–2011. All the sources were detected and imaged; increasing by a factor of ∼ 2 the total number of AGN so far imaged with VLBI at 86 GHz. The survey data attained a baseline sensitivity of 0.1 Jy and a typical image sensitivity of 5 mJy/beam. We have used Gaussian model fitting to represent the structure of the observed sources and to estimate the flux densities and sizes of the core and jet components. The model fitting yields estimates of the brightness temperature (Tb) of the compact VLBI (base) of the jet and inner jet components of AGN, taking into account the resolution limits of the data at 3 mm. We have applied a basic population model with a single value of intrinsic brightness temperature, T0, in order to reproduce the observed distribution of Tb. The modelling yields T₀ ∼ 1 − 7 × 10¹¹ K in the VLBI cores and T₀ ≤ 5 × 10¹⁰ K in the jets. This finding indicates that the VLBI cores reflect the inverse-Compton limit on brightness temperature, while the properties of the inner jets can be described by the equipartition between the particle and magnetic field energy. We also find a correlation between the brightness temperatures obtained from the model fits with estimates of the brightness temperature limits made directly from the visibility data. For objects with sufficient structural detail detected, we investigated the effect of adiabatic energy losses on the evolution of brightness temperature along the jet.
Citation
D. G. Nair, A. P. Lobanov, T. P. Krichbaum, E. Ros, J. A. Zensus. 86 GHz VLBI Survey of Ultra Compact Radio Emission in Active Galactic Nuclei // Transactions of IAA RAS. — 2017. — Issue 40. — P. 3–9.
@article{nair2017,
abstract = {Very Long Baseline Interferometry (VLBI) Observations at 86 GHz reach a resolution of about 50 µas and sample the scales as small as 10³ − 10⁴ Schwarzschild radii of the central black hole in Active Galactic Nuclei (AGN), uncovering the jet regions where acceleration and collimation of the relativistic flow takes place. We present the results from a large global VLBI survey of 162 ultra-compact radio sources at 86 GHz conducted in 2010–2011. All the sources were detected and imaged; increasing by a factor of ∼ 2 the total number of AGN so far imaged with VLBI at 86 GHz. The survey data attained a baseline sensitivity of 0.1 Jy and a typical image sensitivity of 5 mJy/beam.
We have used Gaussian model fitting to represent the structure of the observed sources and to estimate the flux densities and sizes of the core and jet components. The model fitting yields estimates of the brightness temperature (Tb) of the compact VLBI (base) of the jet and inner jet components of AGN, taking into account the resolution limits of the data at 3 mm. We have applied a basic population model with a single value of intrinsic brightness temperature, T0, in order to reproduce the observed distribution of Tb. The modelling yields T₀ ∼ 1 − 7 × 10¹¹ K in the VLBI cores and T₀ ≤ 5 × 10¹⁰ K in the jets. This finding indicates that the VLBI cores reflect the inverse-Compton limit on brightness temperature, while the properties of the inner jets can be described by the equipartition between the particle and magnetic field energy. We also find a correlation between the brightness temperatures obtained from the model fits with estimates of the brightness temperature limits made directly from the visibility data. For objects with sufficient structural detail detected, we investigated the effect of adiabatic energy losses on the evolution of brightness temperature along the jet.},
author = {D.~G. Nair and A.~P. Lobanov and T.~P. Krichbaum and E. Ros and J.~A. Zensus},
issue = {40},
journal = {Transactions of IAA RAS},
keyword = {VLBI, Active Galaxies, Jets, Radio continuum, Millimetre surveys, Brightness temperature},
pages = {3--9},
title = {86 GHz VLBI Survey of Ultra Compact Radio Emission in Active Galactic Nuclei},
url = {http://iaaras.ru/en/library/paper/1671/},
year = {2017}
}
TY - JOUR
TI - 86 GHz VLBI Survey of Ultra Compact Radio Emission in Active Galactic Nuclei
AU - Nair, D. G.
AU - Lobanov, A. P.
AU - Krichbaum, T. P.
AU - Ros, E.
AU - Zensus, J. A.
PY - 2017
T2 - Transactions of IAA RAS
IS - 40
SP - 3
AB - Very Long Baseline Interferometry (VLBI) Observations at 86 GHz
reach a resolution of about 50 µas and sample the scales as small
as 10³ − 10⁴ Schwarzschild radii of the central black hole in Active
Galactic Nuclei (AGN), uncovering the jet regions where acceleration
and collimation of the relativistic flow takes place. We present the
results from a large global VLBI survey of 162 ultra-compact radio
sources at 86 GHz conducted in 2010–2011. All the sources were
detected and imaged; increasing by a factor of ∼ 2 the total number
of AGN so far imaged with VLBI at 86 GHz. The survey data attained a
baseline sensitivity of 0.1 Jy and a typical image sensitivity of 5
mJy/beam. We have used Gaussian model fitting to represent the
structure of the observed sources and to estimate the flux densities
and sizes of the core and jet components. The model fitting yields
estimates of the brightness temperature (Tb) of the compact VLBI
(base) of the jet and inner jet components of AGN, taking into
account the resolution limits of the data at 3 mm. We have applied a
basic population model with a single value of intrinsic brightness
temperature, T0, in order to reproduce the observed distribution of
Tb. The modelling yields T₀ ∼ 1 − 7 × 10¹¹ K in the VLBI cores and
T₀ ≤ 5 × 10¹⁰ K in the jets. This finding indicates that the VLBI
cores reflect the inverse-Compton limit on brightness temperature,
while the properties of the inner jets can be described by the
equipartition between the particle and magnetic field energy. We also
find a correlation between the brightness temperatures obtained from
the model fits with estimates of the brightness temperature limits
made directly from the visibility data. For objects with sufficient
structural detail detected, we investigated the effect of adiabatic
energy losses on the evolution of brightness temperature along the
jet.
UR - http://iaaras.ru/en/library/paper/1671/
ER -