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PhD Defense: Karthik Reddy Solipuram


Physics : 401

Date & Time

June 1, 2022, 1:00 pm3:00 pm


ADVISORS: Dr. Markos Georganopoulos and Dr. Eileen Meyer

TITLE: Morphological Clues to the X-ray Emission from Extragalactic Jets

ABSTRACT: Since its launch in 1999, the Chandra X-ray observatory has detected about 200 large-scale extragalactic jets. Surprisingly, for many of the powerful jets, the detected X-ray emission is spectrally too powerful and/or too hard to be part of the radio (and optical, when observations exist) spectral component. This strongly suggests a second, high-energy, spectral component.

These X-rays, the working model argues, can be produced by low energy electrons in the jet that inverse-Compton (IC) scatter photons of the cosmic microwave background (CMB) to X-ray energies. In the simplest scenario, this IC/CMB model predicts the X-ray jet to extend past its radio counterpart. However, observations reveal that X-rays decay before the radio in many jets, thereby producing offsets that contradict the IC/CMB model. Alternatively, a second-electron population with energies up to a hundred TeV can produce the X-rays. However, such alternative models also do not offer any explanation for these offsets. Despite both models reproducing the observed X-rays, they imply contrasting jet energetics and, in turn, contrasting environmental impacts that have important implications for the evolution of structure in the universe. In this thesis, I will present a detailed observational and statistical analysis of X-ray/radio offsets and spectral properties of a large sample of X-ray jets, which collectively rule out one-zone IC/CMB interpretations. I will also present the possibility that knots and offsets in powerful jets are produced when slow-moving portions of the jet plasma act as obstacles to a faster outer flow, and discuss the implications of this setup for the energy budget of jets.