The low-mass end of the baryonic Tully-Fisher relation

NAVARRO JULIO F; FERRERO ISMAEL; SALES LAURA V; AZADEH FATTAHI; OMAN KYLE; ABADI MARIO GABRIEL

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 464 p. 2419 - 2428

0035-8711

The scaling of disk galaxy rotation velocity with baryonic mass (the ?Baryonic Tully-Fisher?relation; BTF) has long confounded galaxy formation models. It is steeper than the M ∝ V3scaling relating halo virial masses and circular velocities and its zero point implies that galaxiescomprise a very small fraction of available baryons. Such low galaxy formation efficienciesmay in principle be explained by winds driven by evolving stars, but the tightness ofthe BTF relation argues against the substantial scatter expected from such vigorous feedbackmechanism. We use the APOSTLE/EAGLE simulations to show that the BTF relation is wellreproduced in ΛCDM simulations that match the size and number of galaxies as a function ofstellar mass. In such models, galaxy rotation velocities are proportional to halo virial velocityand the steep velocity-mass dependence results from the decline in galaxy formation effi-ciency with decreasing halo mass needed to reconcile the CDM halo mass function with thegalaxy luminosity function. Despite the strong feedback, the scatter in the simulated BTF issmaller than observed, even when considering all simulated galaxies and not just rotationallysupportedones. The simulations predict that the BTF should become increasingly steep at thefaint end, although the velocity scatter at fixed mass should remain small. Observed galaxieswith rotation speeds below ∼ 40 km s−1seem to deviate from this prediction. We discussobservational biases and modeling uncertainties that may help to explain this disagreement inthe context of ΛCDM models of dwarf galaxy formation.