Multi-frequency VLBI imaging of two compact symmetric radio galaxies

Multi-frequency VLBI imaging of two compact symmetric radio galaxies

Physics and Astronomy

Perry, Thomas Mastrianni

Marr, Jonathan

6/1/2009

Compact symmetric radio galaxies (known as compact symmetric objects, or CSOs) are believed to be the very young versions of the classical double-lobed radio galaxies, and are known to have radio spectra which peak at GHz frequencies. The downturn in their spectra at lower frequencies must be due to some absorption mechanism – either by free-free (f-f) absorption by line-of-sight electrons in the host galaxy, or synchrotron self-absorption (SSA) by electrons within their jets. We present the results of our analysis of high resolution observations made with Very Long Baseline Interferometry at six frequencies of two CSOs, 0026+346 and 1321+410, including models of their absorption spectra at high spatial resolution. An extrapolation of the optically-thin high-frequency images are compared with the low-frequency images to obtain maps of optical depth, and the spectral shape of the absorption regions are fit to models of f-f absorption versus SSA. For 1321+410 we find that the observed spectral shape does fit well with a simple single-component f-f absorption model while the spectrum of 0026+346 does not. Assuming SSA is the primary absorption mechanism in 0026+346, we determine an upper limit on the strength of the magnetic field in the core of this galaxy at a radius of 0.02±0.01 parsecs (6±3×1011 km) to be Gauss.

thesis

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