Astrophys. J., 788, L39 (2014/June-3)
Are (pseudo)bulges in isolated galaxies actually primordial relics?
FERNANDEZ LORENZO M., SULENTIC J., VERDES-MONTENEGRO L., BLASCO-HERRERA J., ARGUDO-FERNANDEZ M., GARRIDO J., RAMIREZ-MORETA P., RUIZ J.E., SANCHEZ-EXPOSITO S. and SANTANDER-VELA J.D.
Abstract (from CDS):
We present structural parameters and (g - i) bulge/disk colors for a large sample (189) of isolated AMIGA galaxies. The structural parameters of bulges were derived from the two-dimensional bulge/disk/bar decomposition of Sloan Digital Sky Survey i-band images using GALFIT. Galaxies were separated between classical bulges (nb> 2.5) and pseudobulges (nb< 2.5), resulting in a dominant pseudobulge population (94%) with only 12 classical bulges. In the < µe > -Replane, pseudobulges are distributed below the elliptical relation (smaller Re and fainter µe), with the closest region to the Kormendy relation populated by those pseudobulges with larger values of B/T. We derived (g - i) bulge colors using aperture photometry and find that pseudobulges show median colors (g - i)b∼ 1.06, while their associated disks are much bluer, (g - i)d∼ 0.77. Moreover, 64% (113/177) of pseudobulges follow the red sequence of early-type galaxies. Bluer pseudobulges tend to be located in galaxies with the highest likelihood of tidal perturbation. The red bulge colors and low B/T values for AMIGA isolated galaxies are consistent with an early formation epoch and not much subsequent growth. Properties of bulges in isolated galaxies contrast with a picture where pseudobulges grow continuously via star formation. They also suggest that environment could be playing a role in rejuvenating the pseudobulges.
galaxies: fundamental parameters - galaxies: general - galaxies: interactions
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