From light to baryonic mass: The effect of the stellar mass-to-light ratio on the Baryonic Tully-Fisher relation

In this paper, we investigate the statistical properties of the Baryonic Tully–Fisher relation(BTFr) for a sample of 32 galaxies with accurate distances based on Cephe¨ıds and/or TRGBstars. We make use of homogeneously analysed photometry in 18 bands ranging from the farultraviolet to 160 μm, allowing us to investigate the effect of the inferred stellar mass-to-lightratio (ϒ) on the statistical properties of the BTFr. Stellar masses of our sample galaxies arederived with four different methods based on full SED fitting, studies of stellar dynamics,near-infrared colours, and the assumption of the same ϒ[3.6] for all galaxies. In addition, weuse high-quality, resolved H I kinematics to study the BTFr based on three kinematic measures:Wi50 from the global H I profile, and Vmax and Vflat from the rotation curve. We find the intrinsicperpendicular scatter, or tightness, of our BTFr to be σ ⊥ = 0.026 ± 0.013 dex, consistent withthe intrinsic tightness of the 3.6 μm luminosity-based Tully–Fisher relation (TFr). However,we find the slope of the BTFr to be 2.99 ± 0.2 instead of 3.7 ± 0.1 for the luminosity-basedTFr at 3.6 μm. We use our BTFr to place important observational constraints on theoreticalmodels of galaxy formation and evolution by making comparisons with theoretical predictionsbased on either the Λ cold dark matter framework or modified Newtonian dynamics.