We have obtained deep HST NICMOS images of the edge-on spiral NGC 5907 to determine the composition of its stellar halo. Ground-based observations find very extended faint halo light, which roughly traces the isothermal profile required to reproduce this galaxy's notorious flat rotation curve. For a normal stellar population, we should have resolved many bright giant stars in our images, but we did not. Combined with previous ground-based measurements of the integrated optical/IR color of the halo, these results raise many puzzles about the nature and origin of the faint extended emission. We address the resulting constraints on the stellar metallicity and initial mass function and their implications for the baryon fraction of NGC 5907's dark matter halo.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1998