The second PhD student of the Department of Space and Aeronautics successfully defended his PhD thesis


On 28/03/2018, Le Ngoc Tram defended his PhD thesis on the topic of "Bow shock chemistry in the interstellar medium”. Tram was the second student to receive a PhD after graduating from the first intake of the Master Space program of the Department of Space and Aeronautics, Hanoi University of Science and Technology - USTH (Vietnam-France University) in 2014.

The author develops a 3D magnetized axisymmetric bow shock model by a statistical distribution of 1D planar shocks computed with the Paris-Durham model. For the first time, he examines systematically the effect of the geometry, age, and various other parameters on the H2 excitation diagram and emission line profiles. Then, he shows that this 3D bow shock model unprecedentedly improves interpretations of the H2 observations in Orion BN-KL and BHR71, and shows how spectrally resolved H2 line emission profiles on the Herbig-Haro object HH54 can be used to extract a wealth of dynamical information.

The author also develops a 1D steady stellar winds model from AGB stars, which trigger the termination shock, by including relevant physical and chemical ingredients in the Paris-Durham code. For the first time, he examines the time-dependent conversion of atomic to molecular hydrogen along the wind trajectories of “hot” and “cold” AGB stars. He suggests that the low abundance of HI inferred from observations is due to hydrogen locked in its molecular form. Then, he tries to reproduce HI 21-cm line profile in a “hot” AGB (called Y Cvn) and a “cold” AGB (called CW Leo).

Photo: Le Ngoc Tram and his supervisors (Sylvie Cabrit and Pierre Lesaffre) and Pierre Encrenaz (LERMA - Observatoire de Paris) - former and first director of the Space and Aeronautics USTH department
Photo: Le Ngoc Tram and his friends