Investigating the Origin of Gamma-ray Emission in Non-blazar AGN with the Fermi Large Area Telescope

Abstract

The Fermi Large Area Telescope (Fermi-LAT) has detected a small sample of

gamma-ray loud non-blazar Active Galactic Nuclei (AGN), including the so-called misaligned

AGN, whose radio jets are believed to be pointed off-axis with respect to

the observer's line of sight, in contrast to the far more populous gamma-ray loud blazars,

whose jets are pointed directly toward the line of sight of the observer. The origin

of the gamma-ray emission in these misaligned sources has been widely attributed

to the so-called "blazar zone" under the pretense of AGN unification, in which the

misaligned Fanaroff-Riley type I and II objects are purported to make up the parent

population of the BL Lac and FSRQ blazars, respectively. For a number of

misaligned sources, the observations prove to be consistent under this scenario, in

that the sources demonstrate short timescale gamma-ray variability, thus confining the

emission region to a size scale consistent with the inner parsec-scale regions of the

jet.

Representing an even smaller percentage of non-blazar sources are those that

exhibit no evidence of variable gamma-ray emission over timescales of > 3 years. Steady

high energy (HE) emission over these timescales, if proven to be statistically significant,

relaxes the constraint that would place the gamma-ray emission within a < 1 parsec

region consistent with the size scale of the blazar zone. Three sources in particular

that have demonstrated no evidence of variability in the LAT range are 4C+55.17,

Fornax A, and M87. Each of these objects further demonstrates a unique set of

multiwavelength properties that could potentially give rise to gamma-ray emission that is

produced outside of the blazar zone. In this thesis, I conduct a detailed investigation

into the origin of gamma-rays from each of these objects, and I discuss the multiwavelength

properties that could give rise to a steady gamma-ray component consistent with

non-blazar emission. Further improvements in LAT analysis techniques are also

briefly discussed.