The Density Profile of the Dark Matter Halo of NGC 4605

We have obtained ~100 pc resolution CO and ~60 pc resolution Halphaobservations of the dwarf spiral galaxy NGC 4605. We use them to derive a highresolution rotation curve and study the central density profile of NGC 4605'sdark matter halo. We find that these observations do not agree with thepredictions of most high resolution Cold Dark Matter calculations. Weinvestigate two extreme cases: 1) NGC 4605 has a maximal exponential disk, thatwe model using K-band observations and remove to study the structure of itsdark matter halo, and 2) NGC 4605 is dark matter dominated and its disk isdynamically negligible. Because the mass-to-light ratio of the maximal disk isalready very low we favor the first solution, which indicates the halo has onecomponent with a density profile rho ~ r^{-0.6} out to R~2.8 kpc. In the secondcase, the rotation curve requires the presence of two components: a small (~600pc) core surrounded by a much steeper rho ~ r^{-1.1} halo. Removal ofintermediate (submaximal) disks does not ameliorate the discrepancy between thepredictions and the observations.