tokens: owned by the most massive passive galaxies (Correa et al. 2017 ; Lagos et al. 2018 ). But we note that simulated passive galaxies with are more dispersion dominated than the observed ones. It is revealing to compare our Figs 1 and 7 with the left-hand panel of fig. 1 of Wuyts et al. ( 2011 ), which visualizes the distribution of the Sersic ( 1968 ) index on the diagram. That diagram is often presented to demonstrate the connection between galaxy structure and SFR, with the passive galaxies having a index close to the de Vaucouleurs ( 1948 ) profile ( n = 4) while the star forming ones having exponential profiles ( n = 1) typical for discs. This is interpreted as galaxies generally becoming ellipticals when they quench and become passive. Our diagrams show a similar feature. However there is a crucial difference. In fact, while in the Wuyts et al. ( 2011 ) figure the region of ‘ellipticals’ span the entire mass range from just above up to the largest masses of nearly , in our diagrams there is a clear transition at a significantly larger mass of . Only above that mass being passive is associated to being slow-rotator ‘ellipticals’, while for lower masses quenching produces no more than a minor structural transformation (increasing bulges but retaining significant level of rotation). This is the key novelty we want to emphasize with this work. A transition around is not unexpected, given that only above that critical mass are slow-rotator ETGs starting to dominate, while below that mass one only finds spiral galaxies and fast rotator ETGs (e.g. Cappellari 2016 ). However, in this paper we first illustrate this fact specifically in the context of the diagram, where this fact is not yet universally appreciated. Beyond fitting the light distribution with single Sersic profiles, efforts have been made to decompose galaxies into multiple components including bulges and discs. A relevant result in Morselli et al. ( 2017 ) illustrating bulge to total ratio as a function of stellar mass and SFR shows overall consistency with what we found using the spin parameter. The same difference appears in the passive population for which the spin reveals a sharp transition among massive galaxies whereas fig. 5 of Morselli et al. ( 2017 ) by contrast indicates very close bulge to total ratio over a large range of mass. In the following section, we discuss the implications of our results in the context of a ΛCDM universe in order to understand the trend of with stellar mass and star formation level. 5.1 Understanding in the context of galaxy formation and evolution within a ΛCDM universe 5.1.1 Early/late star formation and in/ex situ mass assembly To understand the current kinematics of galaxies, we need to know what factors are key to determining their kinematic state. In principle, whether a galaxy is mainly in ordered rotation or random motion (that is disc-dominated or spheroid-dominated) will depend on (1) the angular momentum of gas used as raw material for
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