A Study on the Effect of Galactic Atmospheres on Shock Induced Disruption of Extragalactic Jets (Clusters, Galaxies, Winds, Cooling)
Sumi, Dean Matthew
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https://hdl.handle.net/2142/70666
Description
Title
A Study on the Effect of Galactic Atmospheres on Shock Induced Disruption of Extragalactic Jets (Clusters, Galaxies, Winds, Cooling)
Author(s)
Sumi, Dean Matthew
Issue Date
1986
Department of Study
Astronomy
Discipline
Astronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Astronomy and Astrophysics
Abstract
This dissertation studies the interaction of collimated outflows of gas, or beams, from the nuclei of elliptical galaxies with the gas medium surrounding these galaxies. In particular, the distribution of the gas medium around galaxies at rest with respect to this gas medium is explored. In this case, the density and temperature of the gas varies spatially and their relationship will be determined by the energy balance of the gas in the gravitational potential defined by the galaxy. One finds that the gas environment or "atmosphere" around a galaxy can be described either as an outflowing "wind", in the case where heating dominates, or a "cooling" inflow, in the case where cooling dominates.
The response of a beam progagating through a cooling inflow atmosphere is found to be very different from the response of a beam in a wind atmosphere. In the case of a cooling inflow, the beam can make a transition from a regime where the beam is dominated by biconical shocks into a regime where the beam is dominated by planar shocks. A beam initially in the biconical shock regime propagating in a wind atmosphere does not make this transition. The transition is caused by inversion of the temperature and pressure distributions found in cooling inflows and the beam length before this transition occurs is dependent on the Mach number and the ratio of the beam density to the external medium.
The planar shocks cause a laminar, supersonic beam to disrupt, becoming subsonic and turbulent. The observed manifestations of this change in the beam is believed to be responsible for the radio morphology associated with galaxies at the centers of cooling inflows. Conversely, the nontransition behavior of beams in winds is believed to be responsible for the radio morphology associated with isolated elliptical galaxies, where winds are most likely to form.
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