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