Digital Universe Guide - Hayden Planetarium

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162 4. THE EXTRAGALACTIC ATLAS color prox2 Both of these show dense regions in red, then, as the density decreases, the colors change to orange, yellow, green, and aqua. Luminosity Settings Normally, the 2MASS galaxies are given a constant luminosity, which is to say all points are given an equal intrinsic brightness. Of course, the actual brightness you see in Partiview is a function of the galaxy’s intrinsic brightness plus your distance from that galaxy. If you want to highlight the structure a little, you can assign luminosity as a function of the proximity value, so higher values of prox5 will have a higher intrinsic luminosity. We have preset such a scenario which you can see by typing lum prox5 After issuing this command, you may see the galaxies go dim or bright; just adjust the Slum Slider (remember, each lum setting has its own slum value). This lum setting pumps up the brightness just a tad on the clusters and filaments so that they stand out a little. Return to the default constant luminosity with lum const so that all galaxies have equal intrinsic brightness. The 2MASS galaxies have given us a comprehensive look at the structure of the nearby <strong>Universe</strong>. Next, we’ll explore galaxy clusters more closely and take a look at the nearest superclusters. 4.2.6 Tutorial: Galaxy Clusters and Superclusters Goals: Observe the distribution of galaxy clusters and superclusters Before starting, turn on: galaxy, Tully You will be using: Abell, see command, censize command, 1Gly Let’s begin this tutorial by looking at the entire Tully galaxy catalog. Fly outside the Tully data set so you can see the entire cube; you may need to brighten up the data set. Now, type the command
4.2. EXTRAGALACTIC ATLAS TUTORIAL 163 see abell to remove all the Tully galaxies except those inside dense clusters. These clusters are called Abell clusters after George Abell (1927–1983), who first cataloged them. Now you are left with a few dozen galaxy clusters that contain red-colored galaxies. Turn up the center size using the Censize Slider so that we know where the Milky Way is. Turn on the Abell data group. Each point in this data group represents a cluster of galaxies. Some points may represent tens of galaxies, others may stand in for hundreds or even thousands of galaxies. The first thing you should do is turn off the labels, you won’t need them yet. Notice that those red clusters from Tully now are accompanied by a single point in Abell. Pull out to see the entire data set and turn on the 1Gly group for scale. As you orbit the Milky Way, you will see immediately that, unlike Tully, the Abell clusters do not readily show large-scale structure. In fact, the galaxy clusters do not appear to cluster or form connecting filaments with one another. However, some of the Abell clusters are grouped, and these groupings are indicated by the various non-gray points and the labels (turn on the labels now). The color of the points represents their membership in superclusters. A supercluster is a cluster of galaxy clusters. By now, you know that the Virgo Cluster is the nearest galaxy cluster to the Milky Way. It’s about 60 million light-years away, 15 million light-years in diameter, and contains over 1,000 galaxies. A supercluster contains many galaxy clusters and is on the order of 300 million light-years across. Those galaxy clusters with a color other than gray are considered to be members of a supercluster. Let’s filter the data set to see these clusters on their own. Abell has a data variable attached to it called notable (that’s “notable”, not “no table”). If notable = 1, then the galaxy cluster is part of a supercluster. So, use the only= command to see these notable galaxy clusters by typing only= notable 1 (note: there is no space between the word “only” and the equal sign.) Now you see the largest superclusters around our Local Supercluster, which is also called the Virgo Supercluster. Most of these superclusters are named for the constellations they appear in. Our supercluster contains the mighty Virgo Cluster and many other smaller groups such as the Ursa Major Group, the M51 Group, the M81 Group, and our group, the Local Group, among others. Now you see similar systems in the <strong>Universe</strong>, representing at least hundreds of thousands of galaxies.
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The Digital Universe Guide Brian Ab
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Contents Contents 3 List of Tables
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List of Tables 2.1 Log and Linear F
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1.2. GETTING HELP 7 1.2 Getting Hel
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1.5. ACKNOWLEDGMENTS 9 1.5 Acknowle
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2.2. LAUNCHING THE MILKY WAY ATLAS
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2.3. LEARNING TO FLY PARTIVIEW 13 T
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2.3. LEARNING TO FLY PARTIVIEW 15 M
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2.4. PARTIVIEW’S USER INTERFACE 1
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2.5. DIGITAL UNIVERSE FILES 23 File
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3.1. MILKY WAY ATLAS OVERVIEW 25 3.
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3.2. MILKY WAY ATLAS TUTORIAL 27 3.
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3.2. MILKY WAY ATLAS TUTORIAL 29 Wi
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3.2. MILKY WAY ATLAS TUTORIAL 47 No
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3.2. MILKY WAY ATLAS TUTORIAL 51 to
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3.2. MILKY WAY ATLAS TUTORIAL 63 mo
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3.2. MILKY WAY ATLAS TUTORIAL 65 fa
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3.3. MILKY WAY DATA GROUPS 67 Earth
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3.3. MILKY WAY DATA GROUPS 69 Data
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3.3. MILKY WAY DATA GROUPS 71 The l
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3.3. MILKY WAY DATA GROUPS 73 3.3.3
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3.3. MILKY WAY DATA GROUPS 77 If yo
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3.3. MILKY WAY DATA GROUPS 79 lumin
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3.3. MILKY WAY DATA GROUPS 81 not p
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3.3. MILKY WAY DATA GROUPS 83 Two p
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3.3. MILKY WAY DATA GROUPS 87 marke
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3.3. MILKY WAY DATA GROUPS 89 brigh
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3.3. MILKY WAY DATA GROUPS 93 inclu
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3.3. MILKY WAY DATA GROUPS 97 centi
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3.3. MILKY WAY DATA GROUPS 101 3.3.
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3.3. MILKY WAY DATA GROUPS 103 heat
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3.3. MILKY WAY DATA GROUPS 105 3.3.
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3.3. MILKY WAY DATA GROUPS 107 righ
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3.3. MILKY WAY DATA GROUPS 109 beyo
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Page 145 and 146: 4 The Extragalactic Atlas The word
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discovered that there was a linear
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Appendix D Electromagnetic Spectrum
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Appendix E Constants and Units In a
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Metric Prefixes These prefixes are
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INDEX 221 center command, 50, 61 cl
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INDEX 223 Earth’s radio signals,
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INDEX 225 irregular galaxy, 147, 17
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INDEX 227 entering, 21 every, 206 j
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INDEX 229 stellar distance uncertai
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Digital Universe Guide - Hayden Planetarium

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