2019A&A...629A..59P

In ΛCDM cosmology, to first order, galaxies form out of the cooling of baryons within the virial radius of their dark matter halo. The fractions of mass and angular momentum retained in the baryonic and stellar components of disc galaxies put strong constraints on our understanding of galaxy formation. In this work, we derive the fraction of angular momentum retained in the stellar component of spirals, f_j, the global star formation efficiency f_M, and the ratio of the asymptotic circular velocity (V_flat) to the virial velocity f_V, and their scatter, by fitting simultaneously the observed stellar mass-velocity (Tully-Fisher), size-mass, and mass-angular momentum (Fall) relations. We compare the goodness of fit of three models: (i) where the logarithm of f_j, f_M, and f_V vary linearly with the logarithm of the observable V_flat; (ii) where these values vary as a double power law; and (iii) where these values also vary as a double power law but with a prior imposed on f_M such that it follows the expectations from widely used abundance matching models. We conclude that the scatter in these fractions is particularly small (∼0.07dex) and that the linear model is by far statistically preferred to that with abundance matching priors. This indicates that the fundamental galaxy formation parameters are small-scatter single-slope monotonic functions of mass, instead of being complicated non-monotonic functions. This incidentally confirms that the most massive spiral galaxies should have turned nearly all the baryons associated with their haloes into stars. We call this the failed feedback problem.