Circumnuclear Rings and Lindblad Resonances in Spiral Galaxies

Abstract

In order to study the location of circumnuclear rings (CNR) and their possible relation with the inner Lindblad res- onances (ILR), we investigate a sample of spiral galaxies. For this purpose, we have obtained and analyzed medium resolution spectra of 5 spiral galaxies in the range 6200 Å to 6900 Å. Through the Hα emission line, we constructed the radial velocity curves, and then the rotation curves. By fitting them, considering two or three components of an axisy- metric Miyamoto−Nagai gravitational potential, we constructed the angular velocity and Lindblad curves. In addition, we determined the CNR radius by using the 2D spectra and generating the Hα spatial emission radial profiles.We determined the position of the resonances and we calculated the angular velocity pattern, which are in the range of 26 − 47 km s−1 kpc−1 for the galaxies of the sample. According to our results, the CNRs are located between the inner ILR (iILR) and the outer ILR (oILR), or between the center of the galaxy and the ILR, when the object has only one of such resonance; in agreement with previous results. In addition, we calculated the dimensionless parameter defined as R = RCR / Rbar, being in the range 1.1 − 1.6, in agreement with previous results found in the literature.