1. Mahdi Khadem Ferdowsi University of Mashhad

2. Large-scale structures There are various structures in the Universe: Groups and Clusters Walls and filaments Voids SDSS data and the CfA2 catalog →

3. Voids There is not a standard definition for “void” in cosmology. Weygaret and Kampen (1993): Irregular low-density regions in the density field El-Ad and Piran (1997) Continues volumes that do not contain any wall galaxies. …

4. Our definition: Irregular regions in the density field that their density is less than 20% of average density in each redshift. Voids

5. COSMOS Data Base COMOS released latest galactic data in fall 2008. It contains 304999 galaxies between zph=0.01 to zph=5.00. I selected all galaxies which have zph less than 3.00. This release has accuracy of 0.001 in redshift.

6. Void Finding Process Calculating comoving distance and galactic longitude and latitude for all galaxies. Making cylindrical sample I made various cylindrical samples with 5, 10, 15 and 20 Mpc diameter. Sample Diameter

7. Dividing cylindrical sample to cells Calculating galactic number density in each cell in order to find voids Void Finding Process Cells length: 5 Mpc

8. Void Finding Process Calculating mean distance and galactic number density by redshift D= 10 Mpc

9. Void Finding Process D=5 Mpc Calculating mean distance and galactic number density by redshift

11. Thanks For Attention