Evidence against cuspy dark matter haloes in large galaxies

We develop and apply new techniques to uncover systematic effects in galaxy rotation curves (RCs). Considering that an ideal dark matter (DM) profile should yield RCs that have no bias towards any particular radius, we find that the Burkert DM profile satisfies the test, while the Navarro-Frenk-While (NFW) profile is better at fitting the region between one and two disc scale lengths than the inner disc scale length region. Our sample indicates that this behaviour happens to more than 75 per cent of the galaxies fitted with an NFW halo. Also, this tendency is not weakened by considering large galaxies, for instance those with M* greater than or similar to 10(10) M-circle dot. Besides the tests on the homogeneity of the fits, we also use a sample of 62 galaxies of diverse types to test the quality of the overall fit of each galaxy, and to search for correlations with stellar mass, gas mass and the disc scale length. In particular, we find that only 13 galaxies are better fitted by the NFW halo, and that even for the galaxies with M* greater than or similar to 10(10) M-circle dot, the Burkert profile either fits as well as, or better than, the NFW profile. This result is relevant since different baryonic effects important for the smaller galaxies, like supernova feedback and dynamical friction from baryonic clumps, indicate that at such large stellar masses the NFW profile should be preferred over the Burkert profile. Hence, our results suggest either there is a new baryonic effect or a change to the DM physics is required.