Multiwavelength Modeling of the Blazar 1ES 0647+250 and the Impact of Cosmic Voids on the High-Energy Detection of Active Galactic Nuclei
Abstract
Multiwavelength spectra of active galactic nuclei (AGN) are affected by intrinsic AGN emission mechanisms fueled by the source environment and cosmic propagation along our line of sight (LoS), neither of which is fully understood. This thesis explores the former through multiwavelength data analysis and modeling of a particular blazar using a synchrotron-self-Compton model, and the latter specifically LoS effects due to photon-induced electromagnetic cascades developing in and out of cosmic voids through simulations of energetic (E> 100 MeV) photon propagation over cosmological distances.Three very high-energy (E > 100 GeV) states of the distant (20.45±0.10) blazar 1ES 0647+250 observed by the Very Energetic Radiation Imaging Telescope Array System are identified, and the emission zone is modeled using a leptonic synchrotron-self-Compton and blob-in-jet framework. It is found that one of the simplest scenarios that can describe the multiwavelength properties of the three states is a change in both the magnetic field strength of the emitting region's environment and the spectral index (below the break energy) of the electron energy distribution.2 Simulations of gamma-ray-emitting AGN at three redshifts (2 = 0.1, 0.4, and 0.7) and in four cosmic void configurations are conducted, where a void is parameterized by a region with magnetic field strength Bvoid = 0 and a non-void is defined by BIGMF 10-13 G; these are extreme assumptions about the magnetic field strength both in and out of voids. The spectral energy distributions of the detected photons show that the location of the void has a dramatic impact on the (detected) cascade flux under the extreme conditions considered in this thesis. An AGN in a void can result in a flux that is more than an order of magnitude greater than when the AGN is in a high-magnetic field BIGMF 10-13 G environment. The cascade emission appears as an enhanced MeV to GeV spectrum, which can increase the number of AGN that are detected by the Fermi Large Area Telescope when compared to other AGN catalogs, provided the AGN lie along lines of sight that intersect a high void fraction.