We investigate whether the spectral-type of a locally dominant (most luminous) galaxy can be used to select sets of galaxies that are physically associated (groups). We assume that passive dominants trace a group-like potential, and SF-dominants a field-like environment. The group sample includes 988 groups selected in the 2dFGRS applying a maximum magnitude difference criterion. We find that the average number of passive galaxies associated to a dominant is larger when the dominant is passive, a result supporting our assumption that galaxy associations around a passive dominant are reliable groups. Finally we show that, to reduce the contamination by unbound galaxy associations (SF-dominant), ${rm a}geq 3$ passive-members criterion is more efficient than ${rm a}geq 6$ all-members criterion.

Dominant galaxies in 2dF groups

KELM, BIRGIT;FOCARDI, PAOLA
2004

Abstract

We investigate whether the spectral-type of a locally dominant (most luminous) galaxy can be used to select sets of galaxies that are physically associated (groups). We assume that passive dominants trace a group-like potential, and SF-dominants a field-like environment. The group sample includes 988 groups selected in the 2dFGRS applying a maximum magnitude difference criterion. We find that the average number of passive galaxies associated to a dominant is larger when the dominant is passive, a result supporting our assumption that galaxy associations around a passive dominant are reliable groups. Finally we show that, to reduce the contamination by unbound galaxy associations (SF-dominant), ${rm a}geq 3$ passive-members criterion is more efficient than ${rm a}geq 6$ all-members criterion.
Outskirts of Galaxy Clusters: Intense Life in the Suburbs, IAU Coll. 195
456
458
B. Kelm; P. Focardi
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/9798
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