The cusp/core problem in galactic halos: Long-slit spectra for a large dwarf galaxy sample

We derive inner dark matter halo density profiles for a sample of 165 low-mass galaxies using rotation curves obtained from high-quality, long-slit optical spectra assuming minimal disks and spherical symmetry. For rho( r) similar to r(-alpha) near the galaxy center, we measure median inner slopes ranging from alpha(m) = 0.22 +/- 0.08 to 0.28 +/- 0.06 for various subsamples of the data. This is similar to values found by other authors and in stark contrast to the intrinsic cusps (alpha(int) similar to 1) predicted by simulations of halo assembly in cold dark matter (CDM) cosmologies. To elucidate the relationship between alpha(m) and alpha(int) in our data, we simulate long-slit observations of model galaxies with halo shapes broadly consistent with the CDM paradigm. Simulations with alpha(int) = 1/2 and 1 recover both the observed distribution of alpha(m) and correlations between alpha(m) and primary observational parameters such as distance and disk inclination, whereas those with alpha(int) = 5/4 are marginally consistent with the data. Conversely, the hypothesis that low-mass galaxies have alpha(int) = 3/2 is rejected. While the simulations do not imply that the data favor intrinsic cusps over cores, they demonstrate that the discrepancy between alpha(m) and alpha(int) similar to 1 for our sample does not necessarily imply a genuine conflict between our results and CDM predictions; rather, the apparent cusp/core problem may be reconciled by considering the impact of observing and data-processing techniques on rotation curves derived from long-slit spectra.