Professor Thomas W. Hartquist

Profile

Angular Momentum in Star Formation

Molecular Astrophysics

Research interests

My research primarily concerns diffuse astrophysical media, including the interstellar medium of the Milky Way. Physical and chemical processes operating in the interstellar medium govern star formation.

Feedback influences star formation. Positive feedback occurs when the winds and radiation fields of newly born stars cause the star formation rate in ambient matter to increase. Feedback can also be negative. During the formation of a galaxy, the nature of star formation feedback affected the final ratio of the spheroidal and disc components. Shocks play a central role in feedback. I continue to conduct research on a wide variety of interstellar shocks. In the last several years I have: a) used shock modeling together with observational results to infer how a supernova driven shock is modified by cosmic rays; b) calculated the rates at which shocks with various Mach numbers destroy inhomogeneities in which stars might otherwise form; c) determined how the inhomogeneous structure of a medium affects the large-scale properties of shock propagation; d) conducted the first investigating of the destruction of grains in oblique shocks in dusty star forming regions based on self-consistent multifluid hydromagnetic models of C-type shocks.

Around half of the interstellar matter is molecular, and stars and planets form in molecular regions. I model the chemistry of interstellar regions in order to develop diagnostics of the physical conditions and of the dynamics of star and planet formation. Recently, I have used models and molecular observations of the central galaxy of the Perseus cluster of galaxies to infer that the ionization rate and heating due to cosmic rays are hundreds of time higher than throughout most of the Milky Way. I have also modeled the chemistry of a protoplanetary accretion disc in which the contribution of the disc to the gravity is important for the dynamics and planet formation.

I have worked on molecular diagnostics of the collapse of objects called dense cores, which are the progenitors of stars. My current interests include the role of dust particles in the non-ideal magnetohydrodynamics controlling the collapse dynamics, including the angular momentum loss. I have dabbled in dusty plasma physics research more generally and have co-authored papers on dusty plasmas in Saturn’s rings and in the terrestrial mesosphere.