Megan Johnson (CASS)

Megan Johnson Colloquium -- The Three LITTLE Dwarfs: Evolutionary tales uncovered by stars

Abstract

Here I present the recent results from a kinematic study of three nearby dwarf irregular galaxies. We use longslit optical spectroscopy to obtain intrinsic stellar velocities and velocity dispersions of NGC 1569, DDO 168, and DDO 46, which are part of the LITTLE THINGS survey. We obtain a kinematic measure, V_max / sigma, the maximum rotational velocity divided by the stellar velocity dispersion, which is used to estimate the three dimensional shape of each system. We compare the stellar kinematics with the gas kinematics in all three galaxies and reveal the likely trigger for the most recent starburst activity currently observable in NGC 1569. The velocities of the stars and gas in DDO 168 show evidence for prolate rotation about an axis aligned close to the morphological minor axis. There may also be evidence for HI streaming motions in DDO 168. The lowest surface brightness galaxy DDO 46, has a V_max / sigma reminiscent of a kinematically cold system. The role of dwarf-dwarf galaxy interactions is explored as a mechanism that may drive dwarf galaxy evolution and create the observed kinematics. Evidence from single dish HI observations suggest that these kinds of interactions may be more prevalent that previously known.