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A Slippery Slope: Systematic Uncertainties in the Baryonic Tully-Fisher Relation | | Jeremy D. Bradford
; Marla C. Geha
; Frank C. van den Bosch
; | | Date: |
8 Feb 2016 | | Abstract: | The baryonic Tully-Fisher relation (BTFR) is both a valuable observational
tool and a critical test of galaxy formation theory. We explore the systematic
uncertainty in the slope and the scatter of the observed BTFR utilizing a
homogeneously measured dataset of 930 isolated galaxies. We measure a fiducial
relation of log_10 M_baryon = 3.24 log_10 V_rot + 3.21 with a scatter of 0.25
dex over the baryonic mass range of 10^7.4 to 10^11.3 M_sun. We then
conservatively vary the definitions of M_baryon and V_rot, the sample
definition and the linear fitting algorithm used to fit the BTFR. We obtain
slopes ranging from 2.64 to 3.46 and scatter measurements ranging from 0.16 to
0.41 dex. We next compare our fiducial slope to literature measurements, where
reported slopes range from 3.0 to 4.3 and scatter is either unmeasured,
unmeasurable or as large as 0.4 dex. Measurements derived from unresolved HI
line-widths tend to produce slopes of 3.2, while measurements derived strictly
from resolved asymptotic rotation velocities produce slopes of 4.0. The largest
factor affecting the BTFR slope is the definition of rotation velocity. Sample
definition, mass range and linear fitting algorithm also significantly affect
the measured BTFR. Galaxies with V_rot < 100 km/s are consistent with the BTFR
of more massive galaxies, but these galaxies drive most of the scatter in the
BTFR. This is most likely due to the diversity in rotation curve shapes of
low-mass galaxies and underestimated systematic uncertainties. It is critical
when comparing predictions to an observed BTFR that the rotation velocity
definition, the sample selection and the fitting algorithm are similarly
defined. Fitting a power-law model to the BTFR is an oversimplification and we
recommend direct statistical comparisons between datasets with commensurable
properties. | | Source: | arXiv, 1602.2757 | | Services: | Forum | Review | PDF | Favorites | |
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