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2000AJ....119...32G - Astron. J., 119, 32-43 (2000/January-0)
An imaging and spectroscopic survey of galaxies within prominent nearby voids. II. Morphologies, star formation, and faint companions.
GROGIN N.A. and GELLER M.J.
Abstract (from CDS):
The redshift survey of projected companions, 80% complete to mR=16.13, demonstrates that the incidence of a close companion in redshift space is insensitive to global density over the range we investigate (0.16<n/n{d1}≤2). However, the typical velocity separation of close pairs drops significantly (>3 σ) from Δcz≳200 km.s–1 at 0.5<n/n{d1}≤2 down to Δcz=103±20 km.s–1 at n≤0.5n{d1}. In the lowest density environments, galaxies with companions clearly (∼4 σ) have stronger star formation than comparable galaxies at larger global density (0.5<n/n{d1}≤2). On the other hand, the distribution of EW(Hα) for galaxies without nearby companions (closer than ~150 h–1 kpc and 1000 km.s–1) varies little over the entire density range. These results, combined with the luminosity- and color-density relations of this sample (Paper I), suggest that the formation and evolution of field galaxies are insensitive to large-scale underdensity down to a threshold of roughly half the mean density. The differences in galaxy properties at the lowest global densities we can explore (n≤0.5n{d1}) may be explained by (1) a relative scarcity of the small-scale primordial density enhancements needed to form massive early-type/absorption-line galaxies and (2) present-day galaxy encounters that are relatively more effective because of the lower velocity dispersion on small scales (≲200 h–1 kpc) we observe in these regions. In the voids, where the luminous galaxies presumably formed more recently, there should be more gas and dust present for active star formation triggered by nearby companions.
Abstract Copyright: ∼
Journal keyword(s): Galaxies: Distances and Redshifts - Galaxies: Fundamental Parameters - Galaxies: Photometry - Galaxies: Statistics - Cosmology: Large-Scale Structure of Universe
VizieR on-line data: <Available at CDS (J/AJ/119/32): table1.dat table2.dat>
Nomenclature: Table 2: [GG2000] HHMMSS.ss+DDMMSS.s N=211.
Simbad objects: 462