Mahdi KhademFerdowsi University of Mashhad

Large-scale structuresThere are various structures in the

Universe:Groups and ClustersWalls and filamentsVoids

SDSS data and the CfA2 catalog →

VoidsThere is not a standard definition for “void”

in cosmology.Weygaret and Kampen (1993):

Irregular low-density regions in the density fieldEl-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.

Voids

COSMOS Data BaseCOMOS 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.

Void Finding ProcessCalculating 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

Dividing cylindrical sample to cells

Calculating galactic number density in each cell in order to find voids

Void Finding Process

Cells length: 5 Mpc

Void Finding ProcessCalculating mean distance and galactic

number density by redshift

D= 10 Mpc

Void Finding Process

D=5 Mpc

Calculating mean distance and galactic number density by redshift

Thanks For Attention