VLBA15A-177

Core structure in 3C273 and 3C279 at ultra-high resolution with RadioAstron

Abstract

We request seven short HSA runs at 5 and 22GHz to provide crucial ground support to the approved RadioAstron space-VLBI observations of two high brightness temperature quasars, 3C273 and 3C279. Our aim is to, for the first time, sample the (u,v)-track of a full orbit of RadioAstron in order to measure the fine-structure of the radio cores at a resolution of 10-60 microarcseconds. The proposed observations take advantage of RadioAstron's wideband K-band receiver to improve the (u,v)-coverage of the space baselines by "multi-frequency synthesis" style observations. The successful detection of both sources on >10 Earth diameter baselines at 5GHz and especially the record-breaking detection of 3C273 on a 8.1ED baseline at 22GHz during the RadioAstron Early Science Program make this source pair a prime target for detailed studies of the core. If successful, these observations will provide the highest-ever angular resolution measurements of the core structure in quasars. They will help us to distinguish between different theoretical models of the radio core, and to accurately estimate its brightness temperature. Early RadioAstron data already suggests brightness temperature of 10^14K for 3C273, but this may in fact be underestimated due to poorly constrained core structure. The proposed observations can remove this uncertainty.

Investigators

Name	Institution
Tuomas Savolainen *	Max-Planck-Institut für Radioastronomie; Aalto yliopisto
Mikhail Lisakov	Max-Planck-Institut für Radioastronomie; Lebedev Physical Institute
Nikolai Kardashev	Lebedev Physical Institute
Gabriele Bruni	Istituto Nazionale di Astrofisica
Andrei Lobanov	Max-Planck-Institut für Radioastronomie
Tony Zensus	National Radio Astronomy Observatory; Max-Planck-Institut für Radioastronomie
Yuri Kovalev	Max-Planck-Institut für Radioastronomie

* indicates the PI