Discussion Overview
The discussion revolves around the Faber-Jackson relation, its implications regarding luminosity and velocity dispersion in elliptical galaxies, and comparisons with the Tully-Fisher relation, which pertains to spiral galaxies. Participants seek clarification on the derivation of the Faber-Jackson equation and inquire about models applicable to irregular galaxies.
Discussion Character
- Exploratory, Technical explanation, Conceptual clarification, Debate/contested
Main Points Raised
- Some participants question whether the Faber-Jackson relation indicates a directly proportional relationship between luminosity and velocity dispersion.
- There is a request for an explanation of the derivation of the equation L sigma times gamma.
- Participants inquire if the Tully-Fisher relation is used to calculate the relationship between luminosity and velocity dispersion in spiral galaxies.
- Some participants suggest that the Tully-Fisher and Faber-Jackson relations are similar, differing primarily in their application to spiral and elliptical galaxies, respectively.
- There is a question about what model is used to calculate properties of irregular galaxies.
Areas of Agreement / Disagreement
The discussion contains multiple competing views regarding the relationships and models mentioned, and it remains unresolved whether the Faber-Jackson and Tully-Fisher relations are fundamentally the same or different.
Contextual Notes
Participants have not yet established consensus on the definitions or implications of the relations discussed, and there are unresolved questions regarding the derivation and applicability of the models to different types of galaxies.