The baryonic Tully-Fisher relation for different velocity definitions and implications for galaxy angular momentum. (arXiv:1901.05966v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Lelli_F/0/1/0/all/0/1">Federico Lelli</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+McGaugh_S/0/1/0/all/0/1">Stacy S. McGaugh</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Schombert_J/0/1/0/all/0/1">James M. Schombert</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Desmond_H/0/1/0/all/0/1">Harry Desmond</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Katz_H/0/1/0/all/0/1">Harley Katz</a> (4) ((1) European Southern Observatory, (2) Case Western Reserve University, (3) University of Oregon, (4) University of Oxford)
We study the baryonic Tully-Fisher relation (BTFR) at z=0 using 153 galaxies
from the SPARC sample. We consider different definitions of the characteristic
velocity from HI and H-alpha rotation curves, as well as HI line-widths from
single-dish 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%) and the best-fit 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 HI line-widths or less extended rotation curves (like
H-alpha and CO data). These can be useful to study the BTFR from large HI
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 7 times more scatter than the BTFR, which is merely
driven by the scatter in the mass-size 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.
We study the baryonic Tully-Fisher relation (BTFR) at z=0 using 153 galaxies
from the SPARC sample. We consider different definitions of the characteristic
velocity from HI and H-alpha rotation curves, as well as HI line-widths from
single-dish 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%) and the best-fit 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 HI line-widths or less extended rotation curves (like
H-alpha and CO data). These can be useful to study the BTFR from large HI
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 7 times more scatter than the BTFR, which is merely
driven by the scatter in the mass-size 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.
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