Kinematic Signatures of Bulges Correlate with Bulge Morphologies and Sérsic Index
Abstract
We use the Marcario Low Resolution Spectrograph at the Hobby-Eberly Telescope to study the kinematics of pseudobulges and classical bulges in the nearby universe. We present major axis rotational velocities, velocity dispersions, and h 3 and h 4 moments derived from high-resolution (σinst ≈ 39 km s-1) spectra for 45 S0 to Sc galaxies; for 27 of the galaxies we also present minor axis data. We combine our kinematics with bulge-to-disk decompositions. We demonstrate for the first time that purely kinematic diagnostics of the bulge dichotomy agree systematically with those based on Sérsic index. Low Sérsic index bulges have both increased rotational support (higher v/σ values) and on average lower central velocity dispersions. Furthermore, we confirm that the same correlation also holds when visual morphologies are used to diagnose bulge type. The previously noted trend of photometrically flattened bulges to have shallower velocity dispersion profiles turns out to be significant and systematic if the Sérsic index is used to distinguish between pseudobulges and classical bulges. The anti-correlation between h 3 and v/σ observed in elliptical galaxies is also observed in intermediate-type galaxies, irrespective of bulge type. Finally, we present evidence for formerly undetected counter-rotation in the two systems NGC 3945 and NGC 4736.
This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2012
- DOI:
- 10.1088/0004-637X/754/1/67
- arXiv:
- arXiv:1204.5188
- Bibcode:
- 2012ApJ...754...67F
- Keywords:
-
- galaxies: bulges;
- galaxies: formation;
- galaxies: general;
- galaxies: kinematics and dynamics;
- galaxies: photometry;
- galaxies: spiral;
- galaxies: structure;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 49 pages, 16 figures. Accepted for publication in ApJ