2004-2005 Colloquium Series

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NAU Physical Sciences (Bldg 19, Rm 321), Monday, 28 February 2005, 4:00 PM
(Refreshments at 3:35pm)

Voids and Void Galaxies in Redshift Surveys

Fiona Hoyle
Widener University

Abstract

One of the most striking features in galaxy redshift surveys is the ubiquitous presence of voids. However, voids have not been extensively studied due to observational limitations. Until recently, galaxy redshift surveys included only a few voids of diameter >30 Mpc.

The first step in studying voids is the identification process. We outline a method for detecting voids. We apply it to the 2dF Galaxy Redshift Survey and We find that voids have typical diameters of 25Mpc and are very underdense regions with less than 5% of the mean density of the Universe. Up to 40% of volume of the Universe is occupied by voids.

We also study the few galaxies that lie inside the voids, the so called void galaxies. We compare their photometric and spectroscopic properties to galaxies at higher density and find that void galaxies are blue, form stars at a high rate for their mass and have profiles that look like spiral galaxies.

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