Analysis of Voids in the Large-Scale Structure of the Universe Mahdi Khadem

Analysis of Voids in Analysis of Voids in the Large-Scale the Large-Scale

StructureStructure of the Universe of the Universe

Mahdi KhademMahdi Khadem

CosmologyCosmology

Cosmology is the science of studying Cosmology is the science of studying the Universe in its totality.the Universe in its totality.

It attempts to make sense of the It attempts to make sense of the large-scale nature of the material large-scale nature of the material world around us, by the method of world around us, by the method of the natural sciences.the natural sciences.

Structure FormationStructure Formation

Cosmic Microwave Background Cosmic Microwave Background radiation (CMB) gives us an radiation (CMB) gives us an exceedingly important probe of the exceedingly important probe of the history of structure formation in the history of structure formation in the evolving universe.evolving universe.

Large-scale structure of the Large-scale structure of the UniverseUniverse There are various structures in the There are various structures in the

Universe:Universe: Groups and ClustersGroups and Clusters Walls and filamentsWalls and filaments VoidsVoids

SDSS data and the CfA2 catalog

Voids

There is not a standard definition for There is not a standard definition for “void” in cosmology.“void” in cosmology. Weygaret and Kampen (1993):Weygaret and Kampen (1993):

Irregular low-density regions in the density Irregular low-density regions in the density fieldfield

El-Ad and Piran (1997)El-Ad and Piran (1997)Continues volumes that do not contain any Continues volumes that do not contain any

wall galaxies.wall galaxies. ……

Void Finding Process

We should have spatial coordinates for galaxies. We used the COSMOS data catalogue for 433065 galaxies:

Spatial constraints: 82684.15041145.149 RA 91275.249882.1 Dec

00.301.0 Zphoto

Converting RA and Dec to galactic longitude (l ) and galactic latitude (b) [6]:


25.1924912 mhNGP

4.27NGP

1230


Converting Zphoto to comoving distance:

Hubble’s law:

rVDtHCZV

rV cZ H t D V

CMBLGLGGSRGSRLSRLSRsunCMBsunr VVVVVV

118306 skmV LGsun 4.025.48,1.085.265 bl

122627 skmV CMBLG

329,3273 bl [3]


0H

cdH

. cos cos . cos sin . sinCMB helZ Z 50 3201 b l 251 621 b l 248 5953 b

Converting Zphoto to comoving distance:

z

km

H

zz

zddd

0 23 11

Einstein-de Sitter Universe:7.0,.0,3.0 km

LengthsHubbledH '

[5]

[7]

[7]

Mpc

skmH

1

0

.70



Making volume-limited samples:


Void finder algorithms: Void Finder (Piran 1997, Hoyle &

Vogeley 2002) CELL Void Finder (Patiri et al. 2005) HB Void Finder (Patiri et al. 2005)


Primary Results Mean Distance

3

1

n

V

Primary Results

Redshift accuracy:

ΔZ=0.01

Z=0.1 : Δd ≈ 40 Mpc

Z=2.5 : Δd ≈ 11 Mpc

Open Problems

Making algorithms to find voids in a narrow samples.

Analysis of voids in high-redshift Universe.

Time evolution of voids. …

References:عنبرانی، امیر؛ پایان نامه کارشناسی ارشد؛ دانشگاه فردوسی مشهد؛ 1.

13852. Cosmological evolution survey (COSMOS):

http://cosmos.astro.caltech.edu/index.html3. Courteau S., Van den Bergh S.; Thr Astronomical

Journal, 118:337-345, 19994. El-Ad H., Piran T.; Voids in the large-scale structure; The

astrophysical journal; 491:421-435, 19975. Erdogdu P. et al.; Mon. Not. Roy. Astron. Soc.; 368:1515-

1526; 20066. Johnson D. R. H., Soderblom D.; The Astronomical

Journal; 93: 864-867; 19877. Peebles P.J.E; Principles of Physical Cosmology;

Princeton University Press; 19938. Weygaret & Kampen; Voids in gravitational instability

scenarios; Mon. Not. Roy. Astron. Soc. 263: 481-526; 1993

Thanks for Your Attention

Documents

Analysis of Voids in the Large-Scale Structure of the Universe Mahdi Khadem