The Structure and Dynamics of Ringed Galaxies. III. Surface Photometry and Kinematics of the Ringed Nonbarred Spiral NGC 7531
Abstract
The photometric and kinematic properties of the southern galaxy NGC 7531, a large example of a nonbarred spiral possessing a very bright inner ring, are explored via UVBRI surface photometry and emission-line spectroscopy. The galaxy is a global, two-armed spiral galaxy possessing a bright inner ring with a radius of 2.3 kpc. The ring has an average surface brightness in blue light of four to six times higher than in NGC 1433, and is 2.5 times smaller in size. The ring is a zone of active star formation and H II region concentration. The light distribution within NGC 7531 cannot be modelled in terms of a simple combination of an r exp 1/4 spheroid, exponential disk, and ring. A Fourier analysis suggests that the 'intermediate zone' between the inner ring and the outer arms is intrinsically oval with a phase of about 100 deg with respect to the line of nodes in the galaxy plane.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- May 1987
- DOI:
- 10.1086/191190
- Bibcode:
- 1987ApJS...64....1B
- Keywords:
-
- Astronomical Photometry;
- Celestial Mechanics;
- Galactic Structure;
- Spiral Galaxies;
- Astronomical Models;
- Astronomical Spectroscopy;
- H Ii Regions;
- Kinematic Equations;
- Luminosity;
- Astrophysics;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 7531;
- GALAXIES: INTERNAL MOTIONS;
- GALAXIES: STELLAR CONTENT;
- GALAXIES: STRUCTURE;
- NEBULAE: H II REGIONS