Master's Thesis

Spectral Variations of Radio Galaxies

by Kari M. Treichel

Under the supervision of Professor Lawrence Rudnick


One major source of confusion when studying radio galaxies is separating overlapping structures. Spectral tomography is a new method that can be used to unravel these structures. This thesis gives a summary of the current scientific issues in radio galaxies and a short tutorial on the method of spectral tomography. Eight radio galaxies are then examined for spectral variation. We found that the lobes of these galaxies contained a mixture of regions of steep and flat spectra. We also found a steep structure that ran parallel to the jet in 3C438 which may be a sheath surrounding the jet. We found that the hot spots had a spectral index gradient - going from steep to flat at the outer edges. We also used spectral tomography to study the spectral indices along several jets. The spectral index of the jet in 3C401 stayed fairly constant along its length, while the spectral indices of the jets in 3C438 varied. Their spectral indices seemed to correlate with the width of the jet - as the jet widened, its spectrum steepened. While taking a close look at the properties of several jets, we noticed that the jet intensity changed upon entering the lobe. In most cases, the jet brightened after entering the lobe, but in one case the jet darkened. In conclusion, we make some suggestions for future work.