ARE (PSEUDO)BULGES IN ISOLATED GALAXIES ACTUALLY PRIMORDIAL RELICS?
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 (n{sub b} > 2.5) and pseudobulges (n{sub b} < 2.5), resulting in a dominant pseudobulge population (94%) with only 12 classical bulges. In the (μ {sub e})-R {sub e} plane, pseudobulges are distributed below the elliptical relation (smaller R {sub e} and fainter μ {sub e}), 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) {sub b} ∼ 1.06, while their associated disks are much bluer, (g – i) {sub 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.
- OSTI ID:
- 22365764
- Journal Information:
- Astrophysical Journal Letters, Vol. 788, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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