1. Mahdi Khadem Ferdowsi University of Mashhad Supervisors: Dr S. Arbabi (INO) Dr J. Ghanbari (FUM)

2. Cosmology Cosmology is the science of studying the Universe in its totality. It attempts to make sense of the large-scale nature of the material world around us, by the method of the natural sciences.

3. Modern Cosmology Hubble's law describes the observation in physical cosmology that the velocity at which various galaxies are receding from the Earth is proportional to their distance from us. Reindl et al. APJ 624,532 (2005)

4. Modern Cosmology Hubble Constant WMAP5: WMAP5 + high-z SNe: (Riess A. G. et al., 2009 ApJ, 699: 539-563) Redshift

5. Modern Cosmology Redshift-distance relation

6. Modern Cosmology Redshift-distance relation

7. Redshift Photometric Redshift: Redshift estimating by using photometry technique with statndard filters. It was suggested by Baum in 1963: Multi-band photometry can be regarded as a very low resolution spectrum, and hence can be used to estimate the redshifts of galaxies and other extragalactic objects.

8. Redshift Photometric technique preferences: It is a low cost technique. It can estimate redshifts to the depth of 29 magnitude, much too faint for conventional spectroscopy. It can estimate redshift of more than 100 objects in just one observation. Photometric redshift techniques: SED fitting method Empirical Training Set Method

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

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

11. Structures Mapping Angular surveys Redshift surveys COSMOS: COSMOS is designed to probe the formation and evolution of galaxies as a function of redshift and large- scale structure. It covers 2 degree field. Over 2 million galaxies are detected, spanning 75% of the age of the Universe. It contains 304999 galaxies between zph=0.01 to zph=5.972 (fall 2008). COSMOS field:

12. Void Finding Process I selected all galaxies which have zph less than 3.00. One dimensional analysis: Pencil-Beam method in smoothed density field

13. Void Finding Process Smoothed density field

14. Void Finding Process Making cylindrical sample Making various cylindrical samples with 5, 10, 15 and 20 Mpc diameter. Calculating mean distance and galactic density as a function of redshift. Sample Diameter

15. Dividing cylindrical sample to cells Calculating galactic density in each cell in order to find voids Comparing cell density with density in that same redshift Void Finding Process Cells length: 5 Mpc

16. Evolution Analysis

18. Void distance (Mpc) zDia (Mpc) Void distance (Mpc) zDia (Mpc) Void distance (Mpc) zDia (Mpc) 1032.4972.56E-0110.006325067.5431.91803425.015795808.0112.4750035.003158 3806.7481.2180015.0031585327.7082.098035.0031585843.0332.5040015.003158 3831.7641.2290015.0031585352.7242.11702915.009475878.0552.5349995.003158 3999.3691.30900560.037895380.2412.13702810.006325898.0682.5519975.003158 4081.9211.3500075.0031585410.262.15902620.012635935.5912.58499510.00632 4191.9911.406015.0031585460.2922.19602310.006325973.1152.61899335.0221 4417.1331.52501525.015795482.8062.2130225.0031586010.6392.6529910.00632 4717.3221.6970235.0031585502.8182.2290215.0031586033.1532.6729895.003158 4749.8431.71702410.006325570.3612.28101710.006326053.1662.6919875.003158 4799.8751.74702610.006325645.4082.34001330.018956093.1912.72898515.00947 4912.4461.8170295.0031585680.432.36901110.006326150.7272.78398130.01895 4932.4581.8300295.0031585702.9442.3870095.0031586190.7522.82197820.01263 4979.9881.86103120.012635732.9632.41200815.009476250.7912.88097440.02526 5022.5151.8880325.0031585787.9982.4580045.0031586323.3362.95496875.04736

19. Evolution Analysis

21. Open Problems Comparing the results of this project with theoretical voids analysis projects. Using more accurate data from wide field surveys. …

22. Thanks For Attention