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Session 6 - Evolution, Survey and Clusters of Galaxies.
Display session, Monday, June 10
Tripp Commons,

[6.01] A Photometric and Spectroscopic Survey of Galaxies Within Prominent Voids of the CfA2 Redshift Survey

N. Grogin, M. Geller (Harvard-Smithsonian Center for Astrophysics)

Galaxy redshift surveys reveal that the local universe is permeated with so-called voids, vast (10^5-6 Mpc^3) and well-defined regions where galaxies are largely absent. These voids are of great interest because they inform the current debates on galaxy formation and interaction, and on the evolution of large-scale structure in the universe. Current understanding of the voids is still rudimentary, and their existence poses a number of questions that merit further observations and analysis. For instance, galaxies residing in the voids are sufficiently sparse that many may never have interacted closely with other galaxies. Thus void galaxies represent a population which may enable the evaluation of the roles played by galaxy formation and interaction in the determination of the observed galaxy luminosity function (LF) and morphology-density relation (MDR).

Theories predict that galaxies which formed and evolved in globally underdense regions might be systematically different in their MDR and LF from galaxies in denser regions. It has been suggested, for example, that local mass concentrations in voids might become giant, low surface-brightness galaxies with unevolved disks, similar to Malin I. Recent observational studies of void galaxies, however, suggest that the fraction of absorption-line galaxies is typical of regions outside the cores of rich clusters and that the local MDR appears to hold within the globally underdense voids. There has also been recent evidence that the voids are not filled with faint dwarf galaxies.

We describe an optical photometric and spectroscopic survey we are undertaking of \sim\!150 galaxies in prominent CfA survey voids. This survey will substantially improve the observational status of void galaxies, exceeding by an order of magnitude the sample sizes of previous studies and having less bias towards emission-line objects. We present preliminary results from the survey regarding the morphology-density relation of void galaxies.

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