CfA Colloquium: April 10, 2003

Speaker: Naomi McClure-Griffiths (ATNF)

Title: HI Structure in the Milky Way: The Big and the Small

Abstract: Neutral hydrogen (HI) structure exists in the Galaxy on all sizes from sub-parsec (even AU!) scales up to kiloparsec scales. On the smallest scales most of the structure is stochastic, whereas on the larger scales we see deterministic structures in the form of spiral arms, bubbles and chimneys. Despite the close proximity of the Milky Way, we seem to know very little about how it works. In particular, we don't fully understand how large scale deterministic structures are formed, how they die and how they relate to the small-scale structure. Over the past 5 years there has been renewed interest in these questions, fuelled mainly by the International Galactic Plane Survey (IGPS). This survey, made up of the Canadian, VLA, and Southern Galactic Plane Surveys, is in the process of imaging the HI throughout the Galactic Plane with sensitivity to angular scales between 2 arcminutes and several degrees. In this talk I will focus on some recent and on-going work with the Southern portion of the IGPS on a wide range of questions such as: what role do large scale deterministic structures have in forming small scale structure? what dynamical processes are observed in the rotation curve of the Galaxy? and how does the HI scale height vary across the disk?