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Investigacion Dirigida II AS4108 January 23, 2012

Final Report, Investigacion Dirigida II

Voids in the local Universe, based on the VOCLUDET sample of galaxy clustersand groups

Carlos Hervas C.1

Prof. in charge: Luis Campusano1

Departamento de Astronoma, FCFM, U. de Chile

January 23, 2012

Resumen. Voids in the north galactic pole of the VOCLUDET sample of galaxy clusters and groups are found using the

algorithm of?

1. Introduction

In recent years, the redshift surveys have been able to provide a

much better picture of the structure of the Universe in the large

scale. It seems to be organized in a hierarchical model, with

galaxies making clusters and superclusters, this tracing a sortof filament structure with immense voids in-between, creating

the so called cosmic web. As an example of this, the 2 Degree

Field Galaxy Redshift Survey (2dFGRS) is shown in fig. 1. The

structures and voids are clearly discernible.

The objective of this investigation is to quantify the voids in the

local universe, based on a sample of galaxy clusters and groups

found using a Voronoi based algorithm in the 2dFGRS. Also, a

brief section about the luminosity function of the rich clusters

found is included.

Fig. 1. The 2 Degree Field Galaxy Redshift Survey

2. 2dFGRS y VOCLUDET

The data consists of a sample of galaxy clusters found auto-

matically via a Voronoi tessellation based algorithm in the 2dF-

GRS.

2.1. 2 Degree Field Galaxy Redshift Survey (2dFGRS)

For full description, see ?. The 2dFGRS is a redshift survey

that measured nearly 250000 galaxies in 2 thin strips near the

equator:

Fig. 2. The southern and northern strips in the 2dFGRS. The strips are

in black.

1. One in the Southern Galactic Hemisphere, spanning 80 15. The limits are 21h40m < R.A. < 03h40m and

37.5