Аннотация
Selecting disk galaxies from the cosmological, hydrodynamical simulation
Magneticum Pathfinder we show that almost half of our poster child disk
galaxies at $z=2$ show significantly declining rotation curves and low dark
matter fractions, very similar to recently reported observations. These
galaxies do not show any anomalous behavior, reside in standard dark matter
halos and typically grow significantly in mass until $z=0$, where they span all
morphological classes, including disk galaxies matching present day rotation
curves and observed dark matter fractions. Our findings demonstrate that
declining rotation curves and low dark matter fractions in rotation dominated
galaxies at $z=2$ appear naturally within the $Łambda$CDM paradigm and reflect
the complex baryonic physics, which plays a role at the peak epoch of
star-formation. In addition, we find that dispersion dominated galaxies at
$z=2$, which host a significant gas disk, exhibit similar shaped rotation
curves as the disk galaxy population, rendering it difficult to differentiate
between these two populations with currently available observation techniques.
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