# Bonn-Dwingeloo Neighbourhood VLBI Meeting

4 July 2017
MPIfR
Europe/Berlin timezone
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MPIfR - 0.02

# A Global Millimeter VLBI Array Survey of Compact Extra Galactic Radio Sources at 86 GHz

## Speakers

• Ms. Dhanya G. NAIR

## Content

Very Long Baseline Interferometry (VLBI) Observations at 86$\,$GHz reach a resolution of about 50 $\mu$as and sample the scales as small as 10$^3$--10$^4$ Schwarzschild radii of the central black hole in Active Galactic Nuclei (AGN), and uncover the jet regions where acceleration and collimation of the relativistic flow takes place. Synchrotron radiation becomes optically thin at millimetre wavelengths; making it possible to look deeper into the core and inner jets of AGN which are invisible at centimetre and longer wavelengths due to self-absorption or free-free absorption by the torus. We present the results from a large global VLBI survey of 162 ultra compact radio sources at 86 GHz conducted in 2010 -- 2011. This survey has contributed an increase of $\sim$ 2 on the total number of AGNs 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 ($T_\mathrm{b}$) of the VLBI bright core (base) of the jet and inner jet components of AGN, taking into account the resolution limits of the data at 3mm. We have applied a basic population model with a single value of intrinsic brightness temperature, $T_\mathrm{0}$, in order to reproduce the observed distribution of $T_\mathrm{b}$. In this talk, the analysis and the results of the basic population model will be presented. We also present the brightness temperature limits made directly from the visibility data.