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
Picture of Washburn Observatory

Spiral Structure of the Milky Way Galaxy

Home | The Perseus Arm | First LV Plots | Scale Height | Results


The structure of our own galaxy sounds like it would be an easy task; we're placed right in it! However, this is the same reason that constructing a picture of our galaxy is so hard. When looking at other galaxies, some are edge-on with respect to us (making it easy to measure their thickness), while others are face-on with respect to us (making their diameter measurable), and yet others are at some different, intermediate pitch to these extreme cases.

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.

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Useful links

The following links are very useful for looking up info on UNIX, web page making, and astrophysical data and journals.

SIMBAD (Stellar/Galactic database)

NED (Extragalactic database)

UNIX tutorial

Web page basics

NASA Astrophysics Data Service