Digital Universe Guide - Hayden Planetarium
Digital Universe Guide - Hayden Planetarium
Digital Universe Guide - Hayden Planetarium
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164 4. THE EXTRAGALACTIC ATLAS<br />
Bring back all the Abell clusters by typing see all. The gray points, which are the majority of<br />
points, are not connected to any major supercluster, but remain as a nexus between the filaments and<br />
galaxies that must be present, but remain invisible in these data sets.<br />
Next, we explore two partial galaxy surveys, the Two Degree Field Survey and the Sloan <strong>Digital</strong> Sky<br />
Survey.<br />
4.2.7 Tutorial: Galaxy Surveys<br />
Goals: Understand the extragalactic data from Earth’s perspective; begin exploring the 2dF<br />
and Sloan galaxies.<br />
Before starting, turn on: galaxy, stars, constel, mwVis, galac<br />
You will be using: 2dFgals, SloanGals, 1Gly, 20Gly<br />
If you’re continuing from a previous tutorial, quit Partiview and restart the Extragalactic Atlas for a<br />
fresh start. Once the Atlas appears, turn off the local group. You should be left with the Point of<br />
Interest marker. Fly toward it until it disappears. Now you should see nothing.<br />
We’re first going to look at these surveys from Earth. Turn on the stars, constel, mwVis, and the<br />
galac groups so that you see the stars, constellations, visible all-sky image, and the constellations for<br />
reference.<br />
Viewing Galaxy Surveys from Earth Turn on the 2dF Galaxy Redshift Survey (2dFgals). As you<br />
pan around the sky, you will see one strip of yellow toward the northern Galactic latitudes and another<br />
strip surrounded by circular patches in the south Galactic polar region. Each of these patches of<br />
galaxies shows the actual telescope footprint on the sky. If you look at each closely, you will see they<br />
are two degrees wide and contain many galaxies.<br />
Now turn on the SloanGals group to see the Sloan <strong>Digital</strong> Sky Survey galaxies. You will see more<br />
coverage on the sky, particularly in the northern Galactic hemisphere. These are two major galaxy<br />
surveys that astronomers have completed. As you can see, they cover only a portion of the entire sky,<br />
often in narrow strips.<br />
Now turn off the Sloan galaxies so that you’re left with only the 2dF survey. Position yourself so<br />
you’re looking toward the random fields (circular patches) in the south Galactic pole. Begin flying away<br />
and, as you do, notice the random fields appear to be pulled in toward the Milky Way. You may also