Martin Gostisha University of Wisconsin-Whitewater Summer 2011 REU Program Univ. of Wisconsin - Madison Madison, WI 53706 e-mail: gostishamc27 at uww dot edu

Research of Fellow 2011 REU students My 2010 REU Webpage Useful links Conclusions

Introduction

The field of galactic structure gained in popularity during the 1950's, but came to a relative halt in the 80's, as there wasn't enough computing power to dig through the heaps of data necessary to look at large-scale structure. Now, with computing where it's at now, the field is once again rising in popularity.

Throughout the site, I'll show some of the ways that we're looking at data to research the Milky Way's large-scale structure using the Wisconsin H-Alpha Mapper (WHAM).

Fig. 1: This "artist's conception" image of the Milky Way Galaxy by Robert Hurt (Spitzer Science Center/IPAC/JPL) shows most of the claimed structures in the Galaxy, where the Sun, located at the center of the polar grid, is assumed to be Ro=8 kpc from Galactic center. Superimposed is the line-of-sight velocity that would be measured from gas at a given position, assuming the rotation curve obtained by McClure-Griffiths and Dickey (2007, ApJ 671, 427). Rotation curve overlaid by Bob Benjamin.

There's one major problem when studying galactic structure. Astronomers measure distances by redshifts, or how fast the gas is moving towards or away from us. Knowing this redshift allows us to figure out a kinematic distance to an object. However, as can be seen in the following picture, velocities inside the solar circle are double-valued, meaning that gas is moving at the same velocity at two different distances, making it near impossible for us to determine whether the gas is at the nearer distance or the farther one.