Jeff Hodgson

PhD Thesis: Ultra-high resolution observations of selected blazars

March 20, 2015

Supervisor: Dr. Thomas P. Krichbaum

I recently completed my doctorate working on global VLBI at mm frequencies within the VLBI group at the MPIfR. The aim of the project was to reduce and analyse a sample of 26 Gamma-ray bright blazars that had been observed approximately every six months since 2008. The use of mm-VLBI with the Global mm-VLBI Array (GMVA) allowed for tracking micro-arcsecond scale structural changes and investigating a connection, if any, with radio and Gamma-ray flaring. The data could be combined with VLBI at lower frequencies to perform spectral decompositions, that would indirectly allow us to determine the magnetic field strengths both within the observable blazar and also closer to the central super-massive black hole (SMBH).

My results suggest that in at least some cases, structural changes at the micro-arcsecond scale coincide with Gamma-ray flaring activity. However, the morphology in GMVA images, suggests that the internal structure is very complex with many quasi-stationary features exhibiting flaring events at similar times. An example is shown here in the famous blazar BL Lac. These complex structures make the conclusive identification of the location of the Gamma-ray flaring difficult. The spectral decomposition of the blazars shows that the magnetic field strengths within the blazar are ~1 Gauss, which in turn suggests that the magnetic field strength near the base of the jet is of the order of thousands of Gauss.

About me  BSc (Hons) in Physics, Curtin University of Technology (2004-2010), manager at Domino's pizza (2004-2011) researcher in astrophysics at CSIRO (November 2010-February 2011), research Coordinator in Downing Teal (February-September 2011), and PhD Student at the MPIfR (November 2011-January 2015).  See profile.

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