Rotation Curve vs. Central Spiral-Bar Structure in Nearby Galaxies
Abstract
Most of the nearby galaxies are found to have a central gas-dust disk. Their structures, however, are often obscured by the background luminous star lights. These hidden structures, however, can be extracted from observations by using wavelet methods, after the broad contributions of the Population II stars in the center are removed. The atrous wavelet method proves to be extremely useful for such a purpose. We have analyzed the NICMOS and WFPC (WFPC2) data from HST for some 15 nearby disk galaxies without a major bar, for which rotation curves, either by HI or by Hα, are available. We divide our sample galaxies into two groups: one with rapidly rising rotation curves and the other, slowly rising rotation curves. According to the theory developed by Yuan and Kuo (1997, ApJ, 486, 750), the former tends to host a fast nuclear bar (or oval distortion) capable of exciting tightly wound central spirals and the latter tends to give rise to open central spirals which are excited resonantly by a slowly rotating nuclear bar. We use the wavelet methods to search for the central spirals and their morphology in our sample galaxies and test the theory. We find for most of them, the central regions are characterized by spiral or/and bar structures. The majority supports the theoretical prediction. Removing from our list those galaxies which have conflicting data on their rotation curves, or those for which the central structure cannot be discerned by the present method, we present the results for 10 galaxies in this paper.
- Publication:
-
Coevolution of Black Holes and Galaxies
- Pub Date:
- 2004
- Bibcode:
- 2004cbhg.sympE..68Y