A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass
Abstract
Super spirals are the most massive star-forming disk galaxies in the universe. We measured rotation curves for 23 massive spirals with the Southern African Large Telescope (SALT) and found a wide range of fast rotation speeds (240-570 km s-1), indicating enclosed dynamical masses of (0.6-4) ×ばつ 1012 M ⊙. Super spirals with mass in stars {log}{M}stars}/{M}⊙ > 11.5 break from the baryonic Tully-Fisher relation (BTFR) established for lower-mass galaxies. The BTFR power-law index breaks from 3.75 ± 0.11 to 0.25 ± 0.41 above a rotation speed of ∼340 km s-1. Super spirals also have very high specific angular momenta that break from the Fall relation. These results indicate that super spirals are undermassive for their dark matter halos, limited to a mass in stars of {log}{M}stars}/{M}⊙ < 11.8. Most giant elliptical galaxies also obey this fundamental limit, which corresponds to a critical dark halo mass of {log}{M}halo}/{M}⊙ ≃ 12.7. Once a halo reaches this mass, its gas can no longer cool and collapse in a dynamical time. Super spirals survive today in halos as massive as {log}{M}halo}/{M}⊙ ≃ 13.6, continuing to form stars from the cold baryons they captured before their halos reached critical mass. The observed high-mass break in the BTFR is inconsistent with the Modified Newtonian Dynamics theory.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2019
- DOI:
- arXiv:
- arXiv:1909.09080
- Bibcode:
- 2019ApJ...884L..11O
- Keywords:
-
- Spiral galaxies;
- Galaxy rotation curves;
- Dark matter;
- Galaxy evolution;
- 1560;
- 619;
- 353;
- 594;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in Astrophysical Journal Letters (7 pages, 3 figures, 1 table)