Astrophysics II: Galactic Dynamics (2/18/2008-3/14/2008)

Instructor: Gu, Pin-Gao (
Meeting place & time: RM 618, 15:30-17:20 (Mondays) & 10:20-12:10 (Fridays)
Reference books (reserved in the IAA library: RM 720): "Galactic Dynamics" by Binney & Tremaine (BT), "Gas Dynamics" by F. Shu

2/18 (ref: Chap1 in BT): galaxy morphology (Hubble's tuning fork, gas content, ellipticity, bulge to disk luminosity ratio), surface brightness (de Vaucouleurs' law for ellipticals, Freeman's law for disk galaxies), structure of the Milky Way, local standard of rest, solar motion, galactic coordinates, Oort constants, rotation curve

2/22 (ref: Chap4 & Page490-491 in BT): relaxation time, evaporation time, Boltzmann equation, moment equations, asymmmetric drift

2/25 (ref: Chap3 in BT; Page98-99 & Chap2 in Shu): epicyclic motion, Rayleigh stability criterion, Maxwellian distribution, fluid equations, homework set I distributed

2/29 (ref: Chap 5 in BT): gravitational instability (free-fall collapse time, sound-speed crossing time, WKBJ approximation, Jeans' criterion, Toomre Q value)

3/3 (ref: Chap11 in Shu; Chap6 in BT): equation for spiral patterns, winding problem

3/7 (ref: Chap11 in Shu; Chap6 in BT): Lin-Shu dispersion relation (relation between co-rotation wave frequency, disk natural frequency, and free-fall rate)

3/10 (ref: Chap11 in Shu; Chap6 in BT): gravitational instability (revisit Toomre Q value), density wave propagation (Q>1, co-rotation, outer Lindblad and inner Lindblad resonances, Q-barriers, long & short waves, group velocities), homework set II distributed

3/14: (ref: Page47, Page148-149, Chap12 in Shu; Balbus' paper) driving waves at Lindblad resonances (kr=0), angular momentum flux carried by waves (Reynolds and gravitational stresses)