  While galaxy rotation curves provide one of the most powerful methods for
measuring dark matter profiles in the inner regions of rotation-supported
galaxies, at the dwarf scale there are factors that can complicate this
analysis. Given the expectation of a universal profile in dark matter-only
simulations, the diversity of observed rotation curves has become an
often-discussed issue in Lambda Cold Dark Matter cosmology on galactic scales.
We analyze a suite of Feedback in Realistic Environments (FIRE) simulations of
$10^{10}-10^{12}$ $M_\odot$ halos with standard cold dark matter, and compare
the true circular velocity to rotation curve reconstructions. We find that, for
galaxies with well-ordered gaseous disks, the measured rotation curve may
deviate from true circular velocity by at most 10% within the radius of the
disk. However, non-equilibrium behavior, non-circular motions, and non-thermal
and non-kinetic stresses may cause much larger discrepancies of 50% or more.
Most rotation curve reconstructions underestimate the true circular velocity,
while some reconstructions transiently over-estimate it in the central few
kiloparsecs due to dynamical phenomena. We further demonstrate that the
features that contribute to these failures are not always visibly obvious in HI
observations. If such dwarf galaxies are included in galaxy catalogs, they may
give rise to the appearance of "artificial" rotation curve diversity that does
not reflect the true variation in underlying dark matter profiles.
