Observations and Models of the Sacred Mushroom: AM 1724-622
Abstract
Results of multiband (UBVRI) surface photometry of the collisional ring galaxy AM 1724-622 (ESO 138-IG 29/30), nicknamed the "Sacred Mushroom," are presented. The reddish ring colors and the apparent lack of gas in the ring both support the hypothesis that the ring consists primarily of old stars. The theory of collisional ring formation also leads us to expect that only a stellar ring will be as broad as that in AM 1724 - 622. The theory predicts that the ring should be. bounded by sharp, caustic edges. In order to test the theory several types of models of the ring galaxy were constructed, including an analytic models for the form and location of caustics, semianalytic calculations in a kinematic approximation to the stellar orbits following an impulsive disturbance, and an extensive series of restricted three-body model simulations. We find good agreement between the results of all these techniques, and between the models and observation. This agreement confirms the applicability of our analytic models and the approximations they are based on. The restricted three- body simulations also successfully model the morphology of the companion galaxy in AM 1724 - 622, and suggest that an apparent second bulge may be a tidal tail seen at a rather special viewing angle. Although no kinematical data are available yet, the best-fitting models have a rising rotation curve, suggesting the importance of the bulge component in AM 1724 - 622. Thus, several lines of evidence suggest that the precursor to the ring was an S0-type galaxy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1994
- DOI:
- 10.1086/174672
- Bibcode:
- 1994ApJ...433..631W
- Keywords:
-
- Astronomical Models;
- Computerized Simulation;
- Galactic Structure;
- Interacting Galaxies;
- Kinematics;
- Ring Galaxies;
- Three Body Problem;
- Astronomical Photography;
- Astronomical Photometry;
- Caustic Lines;
- Galactic Bulge;
- Interstellar Gas;
- Morphology;
- Astrophysics;
- GALAXIES: INTERACTIONS;
- GALAXIES: INDIVIDUAL ALPHANUMERIC: AM 1724-622;
- GALAXIES: KINEMATICS AND DYNAMICS;
- GALAXIES: PHOTOMETRY;
- GALAXIES: STELLAR CONTENT