= Hierarchical galaxy formation
{title2=$\sigma(M)\text{ increases as }M\text{ decreases}$}
In <hierarchical galaxy formation>, low-mass dark-matter structures typically collapse before larger structures because the smoothed linear density <variance> is larger on smaller <mass> scales. Accretion and mergers assemble increasingly massive haloes. Cooling, feedback and <angular momentum> determine how baryons form <galaxies> within that halo hierarchy; the ordering is statistical rather than an absolute rule for every object.
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