The skeleton connecting the cosmic web to galactic disc formation.

I will discuss the role of angular momentum in determining the shape of galaxies. 

The morphology of galaxies (elliptical versus spiral, bulge formation) is driven by the angular momentum budget at time of formation (and importantly during the so-called secondary infall phase). The spherical collapse picture (which has been the dominant framework for structure formation) is not able to properly account for morphology, as it basically ignores secondary infall of  angular momentum. 

This has proven recently to be more critical than anticipated because astronomers have  finally converged on the idea that the cosmic gas often behaves isothermally when shocking, and therefore follows closely the cosmic network of filaments and walls (as imposed by dark matter), bringing pristine gas right to the center of galaxies (the so-called cold flows arXiv:0803.4506). In turn these cold flows advect the angular momentum they acquired while they formed during the early phase of large scale structure formation. Indeed, generically the environment of a given protogalaxy is made of asymmetric voids which will expel gas towards their surrounding walls (where this gas shocks isothermally).  Thanks to this asymmetry, (some voids are larger than others) the resulting walls will have a net transverse motion relative to the protogalaxy. Since the gas has shocked, it has no option but to flow again along the walls, away from the least dense region within that wall.The same process occurs  once more when the  cold gas reaches the filaments. It will shock again  while keeping its  residual transverse component  (i.e. its angular momentum). It will now follow  the flow along the filament towards the central object, and advect a coherent (increasing) amount of angular momentum along specific directions (the cold flows connected to the galaxy). The increase arises because of a lever effect: later infall corresponds to similar transverse velocity but outer radii. This is precisely was is required to build up a disc (a steady aligned flow of cold gas with increasing momentum).

We argue that the infall of cold gas along the Large Scale structures and secondary advection of angular momentum leads to the following important conclusions:

i) disc orientation is statistically driven by the Large Scale Structures

ii) the relative faction of disc/spheroid depends on the connectivity of the cosmic web (the so called environment of forming galaxies); rare events (the larger nodes of the cosmic web) will be more connected and would therefore form more elliptical (or even feed directly supermassive BHs).

iii) lower mass galaxies will form during the process of cold gas winding up around filaments  and will have spins // to the direction of the filament. Larger, more massive galaxies form during the drift along these filaments or at the nodes, and will have lower momentum typically perpendicular to the dominant filament. This is a prediction of the Codis et al. paper (2012arXiv1201.5794C) which has been confirmed by SDSS observations ( 2012arXiv1207.0068T)

iv) in the most extreme environments, (very massives galaxies a large redshift) this process explains why cold gas makes it so efficiently to the very center of the galaxy to feed SMBHs.