- #1
bakerjay
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- TL;DR Summary
- I'm confused by some galaxies from the SPARC dataset which seem to have velocities which are lower than expected from observed matter, instead of higher
I've been looking through the SPARC dataset (in particular, this part: http://astroweb.case.edu/SPARC/MassModels_Lelli2016c.mrt), and looking at the observed velocities vs velocities expected from baryonic matter.
While in some cases I see the sort of rotation curves I'd expect, with observed velocities higher than expected due to DM:
In lots of other cases I see the opposite - observed velocities far lower than expected from the baryonic matter:
What is going on here? I assume I'm missing something obvious/doing something wrong, but I can't figure out what...
(graphed here is the Vobs column, and (Vgas + Vdisk + Vbulge) as V(baryonic))
While in some cases I see the sort of rotation curves I'd expect, with observed velocities higher than expected due to DM:
In lots of other cases I see the opposite - observed velocities far lower than expected from the baryonic matter:
What is going on here? I assume I'm missing something obvious/doing something wrong, but I can't figure out what...
(graphed here is the Vobs column, and (Vgas + Vdisk + Vbulge) as V(baryonic))