摘要：We use a sample of 97 galaxies selected from the Arecibo legacy fast ALFA (ALFALFA) 21 cm
survey to make an accurate measurement of the baryonic Tully-Fisher relation (BTFR). These
galaxies are specifically selected to be heavily gas-dominated (Mgas/M∗ ≳
2.7) and to be oriented edge-on. The former property ensures that the
error on the galactic baryonic mass is small, despite the large systematic uncertainty
involved in galactic stellar mass estimates. The latter property means that rotational
velocities can be derived directly from the width of the 21 cm emission line, without any
need for inclination corrections. We measure a slope for the linewidth-based BTFR of
α = 3.75 ±
0.11, a value that is somewhat steeper than (but in broad agreement
with) previous literature results. The relation is remarkably tight, with almost all
galaxies being located within a perpendicular distance of ± 0.1 dex from the best fit line. The low
observational error budget for our sample enables us to establish that, despite its
tightness, the measured linewidth-based BTFR has some small (i.e., non-zero) intrinsic
scatter. We furthermore find a systematic difference in the BTFR of galaxies with
“double-horned” 21 cm line profiles – suggestive of flat outer galactic rotation curves –
and those with “peaked” profiles – suggestive of rising rotation curves. When we restrict
our sample of galaxies to objects in the former category, we measure a slightly steeper
slope of α = 4.13 ±
0.15. Overall, the high-accuracy measurement of the BTFR presented in
this article is intended as a reliable observational benchmark against which to test
theoretical expectations. Here we consider a representative set of semi-analytic models
and hydrodynamic simulations in the lambda cold dark matter (ΛCDM) context, as well as modified Newtonian
dynamics (MOND). In the near future, interferometric follow-up observations of several
sample members will enable us to further refine the BTFR measurement, and make sharper
comparisons with theoretical models.
关键词：galaxies: fundamental parameters;galaxies: kinematics and dynamics;galaxies: formation;radio lines: galaxies
