4.6 Article

A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass

Journal

ASTROPHYSICAL JOURNAL LETTERS
Volume 884, Issue 1, Pages -

Publisher

IOP PUBLISHING LTD
DOI: 10.3847/2041-8213/ab459e

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Funding

  1. National Aeronautics and Space Administration

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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) x 10(12) M-circle dot. Super spirals with mass in stars log M-stars/M-circle dot > 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 similar to 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-circle dot < 11.8. Most giant elliptical galaxies also obey this fundamental limit, which corresponds to a critical dark halo mass of log M-halo/M-circle dot similar or equal to 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-circle dot similar or equal to 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.

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