The evolution of the angular momentum of galaxies
in the EAGLE simulations
by Claudia Lagos (ICRAR/UWA)
Abstract. We use the EAGLE cosmological
hydrodynamic simulation suite to study the specific angular momentum of
galaxies, j, in the redshift range 0 < z < 3. Our aims are (i) to investigate
the physical causes behind the wide range of j in galaxies at fixed mass at z=0
and (ii) examine whether simple, theoretical models can explain the seemingly
complex and non-linear nature of the evolution of j in EAGLE. We find that j
of the stars and baryons are strongly correlated with stellar and baryon mass,
respectively, and that the dispersion of the relation is highly correlated with
morphological proxies such as gas fraction, stellar concentration, (u-r)
intrinsic colour, stellar age and the ratio of circular velocity to velocity
dispersion. We present the most comprehensive comparison with available
observations at z = 0 to date and find excellent agreement. Our findings in
EAGLE suggest that in the case of all baryons and stars, j follows the
theoretical expectation of an isothermal collapsing halo under conservation
of specific angular momentum to within ~50%. When we focus on galaxies that
are rotation-supported, the strong dependence of the baryon j on the neutral
gas fraction is well described (at least at z < 2) by a simple model in which
the disk angular momentum is just enough to maintain marginally stable disks.
I will also show the main evolutionary tracks of the stellar j extracted from
EAGLE and describe the catastrophic effect galaxy mergers have on it.
