The Demographics of Galactic Bulges in the SDSS Database
Abstract
We present a new database of our two-dimensional bulge-disk decompositions for 14,233 galaxies drawn from Sloan Digital Sky Survey DR12 in order to examine the properties of bulges residing in the local universe (0.005 < z < 0.05). We performed decompositions in the g and r bands by utilizing the galfit software. The bulge colors and bulge-to-total ratios are found to be sensitive to the details in the decomposition technique, and hence we hereby provide full details of our method. The g - r colors of bulges derived are almost constantly red regardless of bulge size, except for the bulges in the low bulge-to-total ratio galaxies (B/T r ≲ 0.3). Bulges exhibit similar scaling relations to those followed by elliptical galaxies, but the bulges in galaxies with lower bulge-to-total ratios clearly show a gradually larger departure in slope from the elliptical galaxy sequence. The scatters around the scaling relations are also larger for the bulges in galaxies with lower bulge-to-total ratios. Both the departure in slopes and larger scatters likely originate from the presence of young stars. The bulges in galaxies with low bulge-to-total ratios show signs of a frosting of young stars so substantial that their luminosity-weighted Balmer-line ages are as small as 1 Gyr in some cases. While bulges seem largely similar in optical properties to elliptical galaxies, they do show clear and systematic departures as a function of bulge-to-total ratio. The stellar properties and perhaps associated formation processes of bulges seem much more diverse than those of elliptical galaxies.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- July 2016
- DOI:
- 10.3847/0067-0049/225/1/6
- arXiv:
- arXiv:1604.06814
- Bibcode:
- 2016ApJS..225....6K
- Keywords:
-
- galaxies: bulges;
- galaxies: elliptical and lenticular;
- cD;
- galaxies: formation;
- galaxies: spiral;
- galaxies: stellar content;
- galaxies: structure;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in ApJS. 16 pages, 12 figures. The bulge-disk decomposition catalog will be provided