The baryonic TullyFisher relation for different velocity definitions and implications for galaxy angular momentum
Abstract
We study the baryonic TullyFisher relation (BTFR) at z ≃ 0 using 153 galaxies from the Spitzer Photometry and Accurate Rotation Curve sample. We consider different definitions of the characteristic velocity from H I and H α rotation curves, as well as H I linewidths from singledish observations. We reach the following results: (1) The tightest BTFR is given by the mean velocity along the flat part of the rotation curve. The orthogonal intrinsic scatter is extremely small (∼ 6 per cent) and the bestfitting slope is 3.85 ± 0.09, but systematic uncertainties may drive the slope from 3.5 to 4.0. Other velocity definitions lead to BTFRs with systematically higher scatters and shallower slopes. (2) We provide statistical relations to infer the flat rotation velocity from H I linewidths or less extended rotation curves (like H α and CO data). These can be useful to study the BTFR from large H I surveys or the BTFR at high redshifts. (3) The BTFR is more fundamental than the relation between angular momentum and galaxy mass (the Fall relation). The Fall relation has about seven times more scatter than the BTFR, which is merely driven by the scatter in the masssize relation of galaxies. The BTFR is already the `Fundamental Plane' of galaxy discs: no value is added with a radial variable as a third parameter.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 April 2019
 DOI:
 10.1093/mnras/stz205
 arXiv:
 arXiv:1901.05966
 Bibcode:
 2019MNRAS.484.3267L
 Keywords:

 galaxies: dwarf;
 galaxies: kinematics and dynamics;
 galaxies: spiral;
 dark matter;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 12 pages, 6 figures, accepted for publication in MNRAS