Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-05-07
Astrophys.J.664:640-649,2007
Astronomy and Astrophysics
Astrophysics
10 pages, 4 figures, ApJ in press (August 20, 2007, v665n 2)
Scientific paper
10.1086/519441
The global colors of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a ``red sequence'', populated prototypically by early-type galaxies, and a ``blue cloud'', whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: ``classical bulges'' that are dynamically hot systems resembling (little) ellipticals, and ``pseudobulges'', dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Therefore thee question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio, $B/T$, or, whether it separates galaxies of different bulge type, irrespective of their $B/T$. We identify classical bulges and pseudobulges morphologically with HST images in a sample of nearby galaxies. Detailed surface photometry reveals that: (1) The red -- blue dichotomy is a function of bulge type: at the same $B/T$, pseudobulges are in globally blue galaxies and classical bulges are in globally red galaxies. (2) Bulge type also predicts where the galaxy lies in other (bimodal) global structural parameters. (3) Hence, the red -- blue dichotomy is not due to decreasing bulge prominence alone, and the bulge type of a galaxy carries significance for the galaxy's evolutionary history ... (Abridged)
Drory Niv
Fisher David B.
No associations
LandOfFree
A Connection Between Bulge Properties and the Bimodality of Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Connection Between Bulge Properties and the Bimodality of Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Connection Between Bulge Properties and the Bimodality of Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-152565