The Bo÷tes Superclusters

There are two superclusters in Bootes within one billion light years. The nearest one is about 830 million light years away - the second one lies directly behind it at a distance of about 1 billion light years. This map shows all of the galaxies brighter than magnitude 17 (from the HyperLeda database) in this part of the sky. The locations of the major clusters of galaxies are marked. On the right side of the map is the much closer Coma cluster (A1656), and on the left are some of the clusters in the Corona Borealis supercluster which is probably connected to the two Bootes superclusters by a wall of galaxies.

The Bootes Superclusters

Below is a list of the major clusters of galaxies in the two Bootes Superclusters. The exact distance to one of these clusters (A1861) is currently uncertain and it could be a background cluster.

   1           2       3        4         5       6      7               
 Abell         Equatorial    Redshift  Distance  Rich  Notes             
 Number       Coordinates       z        Mly                             
              RA       Dec                                               
 A1781      13 44.5  +29 51   .0606      820      0                      
 A1795      13 49.0  +26 35   .0619      840      2                      
 A1825      13 58.0  +20 39   .0583      790      0                      
 A1827      13 58.2  +21 42   .0642      870      1                      
 A1828      13 58.4  +18 23   .0611      840      1                      
 A1831      13 59.2  +27 59   .0603      815      1                      

 A1775      13 41.9  +26 22   .0705      950      2                      
 A1800      13 49.7  +28 04   .0743     1000      0                      
 A1861      14 07.5  +27 49      -        -       1    uncertain distance
 A1873      14 11.7  +28 09   .0764     1025      0                      
 A1898      14 20.6  +25 09   .0762     1025      1                      
Column 1: The name/number of the cluster.
Column 2: The Right Ascension for epoch 2000.
Column 3: The Declination for epoch 2000.
Column 4: The redshift of the cluster.
Column 5: The distance in millions of light years assuming H=70km/s/Mpc.
Column 6: The 'richness' class of the cluster.
Column 7: Additional names and notes.

References:
Abell G, Corwin H, Olowin R, (1989), A catalogue of Rich Clusters of Galaxies, 
          Astrophys J Supp, 70, 1.
Struble M, Rood H, (1999), A compilation of redshifts and velocity dispersions for 
          ACO clusters, Astrophys J, 125, 35.

Below - one of the clusters of galaxies in the Bootes supercluster. This is the A1795 cluster at a distance of 840 million light years. The massive elliptical galaxy in the middle is PGC 49005.

A1795 - from the Digitized Sky Survey

The Bo÷tes Void

The Bootes superclusters are famous mainly because they lie next to (and slightly behind) the Bootes void. This void is one of the most famous voids in the universe mainly because it was one of the first major voids discovered. It was discovered in 1981. The centre of the void is about 700 million light years from us (redshift 0.052) and it has a diameter of about 300 million light years.

This map below is a plot of all the galaxies brighter than magnitude 17 in this part of the sky. The location of the Bootes void is marked. The void contains very few galaxies, although there are a lot of foreground galaxies between us and the void. This map shows how the void is bordered to the south and west by several major superclusters, including the Bootes superclusters to the southeast.

A map of the Bootes Void
The discovery of the Bootes Void

Left - A newspaper article dating from 1983 announcing the discovery of the Bootes void. This was when it was officially confirmed that it existed.


A map of the Bootes Void

Right - a slice of the universe which shows the Bootes Void. This map is a plot of 3500 galaxies (from the HyperLeda Database) in the direction of the Bootes Void. Our galaxy is at the bottom and the top of the map is 1 billion light years away. The data is very incomplete beyond 500 million light years so the void is not very prominant, but its location is marked. Most of the galaxies located within the area of the void are galaxies which lie above and below the void.



The Scientific Study of the Bo÷tes Superclusters

There has been no scientific study of the superclusters in Bootes. Although these superclusters are much bigger than the Virgo supercluster, there are many closer superclusters which are considered to be more interesting.

The Bootes Void has received a lot of scientific research. The Bootes void was discovered by Robert Kirshner, Augustus Oemler Jr, Paul Schechter and Stephen Shectman in 1981. They surveyed galaxies in three small areas of the sky in this region and noticed that there was a large gap where there were no galaxies. They subsequently surveyed the entire region and in 1983 they confirmed the presence of the void. In a paper published in 1987 they produced a map of the void.

Other astronomers also began to study this void and soon discovered some galaxies within the void. J Moody, R Kirshner, G MacAlpine and S Gregory in a paper in 1987 listed eight galaxies which had been discovered in this void. Soon, it became a popular sport among some astronomers to find galaxies in the Bootes Void. M Strauss and J Huchra announced the discovery of a further three galaxies in 1988, and G Aldering, G Bothun, R Kirshner and R Marzke announced the discovery of fifteen galaxies in 1989.

By 1993, 27 galaxies were known in the Bootes Void. In this paper S Cruzen, D Weistrop and C Hoopes list these 27 galaxies. More galaxies continued to be discovered, by 1997 a total of 60 Bootes Void galaxies were known. This is still a very low number. A normal region of the universe of this size would usually contain many thousands of bright galaxies. Most of the galaxies discovered are usually located near the edges of the void.


Bootes Void galaxies from the Digitized Sky Survey
Some very lonely galaxies. These are all galaxies within the Bootes Void. On the left is the spiral galaxy PGC 84225, in the centre is PGC 54010 (Markarian 845) and on the right is the pair of colliding galaxies MCG+09-25-43 and MCG+09-25-44.
The nearest superclusters Back to the Neighbouring Superclusters page