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We study the role of systematic effects in observational studies of thecusp-core problem under the minimum disc approximation using a suite ofhigh-resolution (25-pc softening length) hydrodynamical simulations of dwarfgalaxies. We mimic realistic kinematic observations and fit the mock rotationcurves with two analytic models commonly used to differentiate cores from cuspsin the dark matter distribution. We find that the cored pseudo-isothermalsphere (ISO) model is strongly favoured by the reduced $\chi^2_\nu$ of the fitsin spite of the fact that our simulations contain cuspy Navarro-Frenk-Whiteprofiles (NFW). We show that even idealized measurements of the gas circularmotions can lead to the incorrect answer if velocity underestimates induced bypressure support, with a typical size of order $\sim$5 km s$^{-1}$ in thecentral kiloparsec, are neglected. Increasing the spatial resolution of themock observations leads to more misleading results because the inner region,where the effect of pressure support is most significant, is better sampled.Fits to observations with a spatial resolution of 100 pc (2 arcsec at 10 Mpc)favour the ISO model in 78-90 per cent of the cases, while at 800-pcresolution, 40-78 per cent of the galaxies indicate the fictitious presence ofa dark matter core. The coefficients of our best-fit models agree well withthose reported in observational studies; therefore, we conclude that NFW haloescan not be ruled out reliably from this type of analysis.

Rotation curve fitting and its fatal attraction to cores in realistically simulated galaxy observations