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 Cepheïds and/or TRGB stars. 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-light ratio (ϒ *) on the statistical properties of the BTFr. Stellar masses of our sample galaxies are derived 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, we use high-quality, resolved HI kinematics to study the BTFr based on three kinematic measures: W₅₀ⁱ from the global HI profile, and V_max and V_flat from the rotation curve. We find the intrinsic perpendicular scatter, or tightness, of our BTFr to be σ⊥ = 0.026 ± 0.013 dex, consistent with the 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-based TFr at 3.6 μm. We use our BTFr to place important observational constraints on theoretical models of galaxy formation and evolution by making comparisons with theoretical predictions based on either the Λ cold dark matter framework or modified Newtonian dynamics.