Department of Astronomy & Physics
Time: September 21, 2018 - 3:00 PM
Location: Atrium 101
In the heart of many galaxies lie supermassive black holes responsible for launching extremely powerful relativistic plasma outflows that emit radiation strongly from radio to TeV gamma-rays. Because of the effects of special relativity, these jets from active galactic nuclei (AGN) can easily outshine their entire host galaxy if they are pointed
nearly directly at us. As a result, they dominate the sky away from our galactic plane, as catalogued by large surveys in gamma-rays and at short radio wavelengths. The properties of AGN jets have been studied extensively with the Very Long Baseline Array, which provides sufficiently high angular resolution that their sub-light year scale
evolution can be studied via time-lapse imaging. I will present results from the largest such study, MOJAVE, which has monitored over 400 AGN jets to date, and has revealed apparent superluminal motion, standing features, and slow precession-like behavior of energized channels within the flows. MOJAVE has also found strong correlations with AGN gamma-ray emission detected by NASA's Fermi observatory, which has found distinct sub-divisions within the AGN jet population, based on the peak frequency of their synchrotron radiation output. I will discuss current controversies regarding the high-peaked jet population, whose slow apparent speeds and lower synchrotron output appear to be inconsistent with the high Lorentz factors inferred from emission modeling of rapid variability seen at gamma-ray energies.