Time Coordinate: 3:30 pm 28th April 2017 (Friday)

Space Coordinate: NTHU General Building II, R521

Speaker: Dr. Kevin Jun-Yi Koay (ASIAA)

Title: Interstellar scintillation as micro-arcsecond scale probes of compact radio AGNs

Abstract:

The variability of compact AGNs on timescales of hours and days observed at cm-wavelengths is predominantly caused by scattering in the ionized interstellar medium (ISM) of our Galaxy. With the ISM as an AU-scale interferometer, interstellar scintillation (ISS) provides an exquisite probe of the micro-arcsecond scale structure of AGNs. I present results from the Micro-arcsecond Scintillation-Induced Variability (MASIV) Survey of ~500 compact AGNs and its follow-up observations.

I will discuss the dependence of ISS on intrinsic AGN properties, including their gamma-ray loudness, radio spectral indices, optical spectral classification, redshift, and intrinsic variability. I will show how we have used ISS to probe the source size-redshift relation of compact AGNs, and place strong constraints on the turbulent properties of the intervening intergalactic medium.

Future surveys of ISS with highly-sensitive instruments such as the SKA will potentially probe the micro-arcsecond structure of faint (~100 muJy to 10 mJy) AGNs, thereby complementing studies at comparable angular resolutions with Space-VLBI and mm-VLBI which are limited only to the brightest AGNs.