Key points are not available for this paper at this time.
lar mass in spirals has been formed and this can happen through gas compression occurring during the different phases of major, gas-rich mergers (Hammer et al. 2005). In this theory, the disk angular momentum mostly results from the orbital angular momentum of the last major collision (Puech et al. 2007a; Hammer et al. 2007; Hopkins et al. 2009a). A more recent epoch for disk formation is indeed supported by the large decrease with redshift of the fraction of rotationally supported disks. Neichel et al. (2008) (hereafter IMAGES-II) found that rotational disks were two times less abundant at zmedian=0.65, a result that is based on a study combining detailed-morphology and spatially-resolved kinematics. How can mergers be related to the regular local galaxies, of which our Milky Way has been so often taken as typical? Deep observations attest the rather tumultuous history of several nearby galaxies that is imprinted in their inner halo (e.g. M31, see Brown et al. 2008; Ibata et al. 2005; see also Davidge 2008 for M81). The Milky Way appears to be quite exceptional (Hammer et al. 2007), possibly related to its quiescent merger history. Particularly, its halo is the most primordial within galaxies with similar masses (Mouhcine 2006) and it shows an angular momentum two times smaller than that of typical spirals. Galaxy simulations can help to test various galaxy formation scenarios. Assuming large accretions of cold gas flows may reproduce several correlations, mostly those linking the gas conarXiv:0903.3962v4
Hammer et al. (Thu,) studied this question.