The cusp/core problem in galactic halos: long-slit spectra for a large dwarf galaxy sample.
SPEKKENS K., GIOVANELLI R. and HAYNES M.P.
Abstract (from CDS):
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 ρ(r)∼r–α near the galaxy center, we measure median inner slopes ranging from αm=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 (αint∼1) predicted by simulations of halo assembly in cold dark matter (CDM) cosmologies. To elucidate the relationship between αmand αintin our data, we simulate long-slit observations of model galaxies with halo shapes broadly consistent with the CDM paradigm. Simulations with αint=1/2 and 1 recover both the observed distribution of αmand correlations between αmand primary observational parameters such as distance and disk inclination, whereas those with αint=5/4 are marginally consistent with the data. Conversely, the hypothesis that low-mass galaxies have αint=3/2 is rejected. While the simulations do not imply that the data favor intrinsic cusps over cores, they demonstrate that the discrepancy between αmand αint∼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.
Cosmology: Dark Matter - Galaxies: Dwarf - Galaxies: Halos - Galaxies: Kinematics and Dynamics - Galaxies: Structure
VizieR on-line data:
<Available at CDS (J/AJ/129/2119): table1.dat>