Thursday

Since early models of galaxy formation, it became clear that mass and angular momentum are two fundamental parameters controlling the evolution of galaxies. While the relation between stellar mass and stellar specific angular momentum has been broadly studied in the literature, its baryonic counterpart remains relatively unexplored. The main reason for this is that the relation between gas mass and gas specific angular momentum has not been well characterized for large galaxy samples. Yet, with the large-volume HI surveys coming soon, it is important to start taking this into account.

In this talk, I will present results regarding the baryonic specific angular momentum of disc galaxies, which we have recently derived using a large sample of galaxies with the highest available quality in their stellar surface brightness profiles and gas kinematics. We find that the relation between the baryonic mass (M_bar) and the baryonic specific angular momentum (j_bar) of disc galaxies is a well defined, unbroken power law across four orders of magnitude in M_bar and j_bar, with spiral and dwarf galaxies lying along the same sequence, opposite to previous claims. The shape of this relation also implies that our sample of galaxies has a j_bar which is about 60% the value of the specific angular momentum of their dark-matter haloes.
Besides this, we find that the gas fraction (f_gas = M_gas/M_bar) correlates very well with M_bar and j_bar. The three parameters define an extremely tight plane with zero intrinsic scatter, making the M_bar-j_bar-f_gas relation one of the tightest empirical scaling relations of galaxies. Even extreme galaxies like "super-spiral", "super-thin", or "ultra-diffuse" galaxies follow this relation rather closely, highlighting the fundamental nature of this law. I will briefly discuss the possible physical mechanisms that give rise (or not) to such relation.