Journal
ASTROPHYSICAL JOURNAL
Volume 565, Issue 1, Pages 238-243Publisher
IOP PUBLISHING LTD
DOI: 10.1086/324596
Keywords
dark matter; galaxies : dwarf; galaxies : halos; galaxies : individual (NGC 4605); galaxies : kinematics and dynamics; radio lines : galaxies
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We have obtained similar to100 pc resolution CO and similar to60 pc resolution Halpha observations of the dwarf spiral galaxy NGC 4605. We use them to derive a high-resolution rotation curve and study the central density profile of NGC 4605's dark matter halo. We find that these observations do not agree with the predictions of most high-resolution cold dark matter calculations. We investigate two extreme cases : (1) NGC 4605 has a maximal exponential disk, which we model using K-band observations and remove to study the structure of its dark matter halo, and (2) NGC 4605 is dark matter-dominated, and its disk is dynamically negligible. Because the mass-to-light ratio of the maximal disk is already very low, we favor the first solution, which indicates the halo has one component with a density profile rho proportional to r(-0.65) out to R similar to 2.8 kpc. In the second case, the rotation curve requires the presence of two components: a small (similar to600 pc) core surrounded by a much steeper rho proportional to r(-1.1) halo. Removal of intermediate (submaximal) disks does not ameliorate the discrepancy between the predictions and the observations.
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