Mahdi KhademFerdowsi University of Mashhad

Supervisors:Dr S. Arbabi (INO)Dr J. Ghanbari (FUM)

CosmologyCosmology 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.

Modern CosmologyHubble'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)

pvRHdtdR

0

Modern CosmologyHubble Constant

WMAP5:WMAP5 + high-z SNe:(Riess A. G. et al., 2009 ApJ, 699: 539-563)

Redshift

116.27.20 9.71

MpcskmH11

0 7.16.69 MpcskmH

11

0 z

cv

1

10

10 z

cv

dR

cv

RcH

z p

H

p

Modern CosmologyRedshift-distance relation

z

kM

H

zz

zddd0

21

23 11

10cHdH 3.0M 7.0 .0k

Modern CosmologyRedshift-distance relation

RedshiftPhotometric 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.

RedshiftPhotometric 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 methodEmpirical Training Set Method

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.

Structures Mapping Angular surveysRedshift 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:82684.15241143.149 RA

91273.249882.1 Dec

Void Finding ProcessI selected all galaxies which have zph less than

3.00.

One dimensional analysis: Pencil-Beam method in smoothed density field

Void Finding ProcessSmoothed density field

Void Finding ProcessMaking 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

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

Evolution Analysis

Evolution Analysis

Evolution AnalysisVoid distance

(Mpc)z Dia (Mpc)

Void distance (Mpc)

z Dia (Mpc)Void distance

(Mpc)z Dia (Mpc)

1032.497 2.56E-01 10.00632 5067.543 1.918034 25.01579 5808.011 2.475003 5.003158

3806.748 1.218001 5.003158 5327.708 2.09803 5.003158 5843.033 2.504001 5.003158

3831.764 1.229001 5.003158 5352.724 2.117029 15.00947 5878.055 2.534999 5.003158

3999.369 1.309005 60.03789 5380.241 2.137028 10.00632 5898.068 2.551997 5.003158

4081.921 1.350007 5.003158 5410.26 2.159026 20.01263 5935.591 2.584995 10.00632

4191.991 1.40601 5.003158 5460.292 2.196023 10.00632 5973.115 2.618993 35.0221

4417.133 1.525015 25.01579 5482.806 2.213022 5.003158 6010.639 2.65299 10.00632

4717.322 1.697023 5.003158 5502.818 2.229021 5.003158 6033.153 2.672989 5.003158

4749.843 1.717024 10.00632 5570.361 2.281017 10.00632 6053.166 2.691987 5.003158

4799.875 1.747026 10.00632 5645.408 2.340013 30.01895 6093.191 2.728985 15.00947

4912.446 1.817029 5.003158 5680.43 2.369011 10.00632 6150.727 2.783981 30.01895

4932.458 1.830029 5.003158 5702.944 2.387009 5.003158 6190.752 2.821978 20.01263

4979.988 1.861031 20.01263 5732.963 2.412008 15.00947 6250.791 2.880974 40.02526

5022.515 1.888032 5.003158 5787.998 2.458004 5.003158 6323.336 2.954968 75.04736

Evolution Analysis

Evolution Analysis

Open ProblemsComparing the results of this project with

theoretical voids analysis projects.Using more accurate data from wide field

surveys.…

Thanks For Attention