2026ApJ..1000..127S

While galaxy rotation curves (RCs) 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 the observed RCs has become an often-discussed issue in Lambda cold dark matter cosmology on galactic scales. We analyze a suite of Feedback in Realistic Environments simulations of 10¹⁰-10¹²M_⊙ halos with standard cold dark matter and compare the true circular velocity to RC reconstructions. We find that, for galaxies with well-ordered gaseous disks, the measured RC may deviate from the true circular velocity by at most ∼10% within the radius of the disk. However, nonequilibrium behaviors, noncircular motions, and nonthermal and nonkinetic stresses may cause much larger discrepancies, of ∼50% or more. Most RC reconstructions underestimate the true circular velocity, while some reconstructions transiently overestimate 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 H I observations. If such dwarf galaxies are included in galaxy catalogs, they may give rise to the appearance of “artificial” RC diversity that does not reflect the true variation in underlying dark matter profiles.