PROFESSOR CHANDA J. JOG

A galactic disk is believed to be embedded in an extended dark matter halo, which dominates its dynamics in the outer parts. However, the shape of the halo is not known. We show that the dark matter halo in the Milky Way is prolate with the vertical-to-planar axis ratio monotonically increasing to 2.0 at 24 kpc. This is obtained by modeling the observed steeply flaring atomic hydrogen gas layer in the outer Galaxy, where the gas is supported by pressure against the net gravitational field of the disk and the halo (Banerjee & Jog 2011). We next calculate the potential of a prolate spheroidal halo with a radially varying eccentricity, and show that this does not result in a long-lived Galactic warp - contrary to what has been proposed in the literature (Rathulnath & Jog 2012).