AAS 207th Meeting, 8-12 January 2006
Session 188 Galaxy Anatomy: from Bars to Halos
Poster, Thursday, 9:20am-4:00pm, January 11, 2006, Exhibit Hall

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[188.12] Star Formation and Dark Matter in NGC 157

L. E. Davis, S. T. Gottesman (University of Florida)

We have made high-resolution images of the atomic hydrogen in NGC 157 using the B array of the Very Large Array. When combined with the radio observations of Ryder et al. (1998), these allow a more detailed look at the structure of the extended HI disk of NGC 157. In the inner part of the HI disk we found an association between large HI density and the presence of ionized hydrogen regions. The rotation curve of the galaxy falls significantly from its peak value of ~ 190 km/s, suggesting a less massive dark matter halo. The determinations of the rotation curve and HI flux distribution allow the calculation of total mass, HI mass, and mass-to-light ratios. We have detected a tail in the atomic hydrogen on the northern edge of the galaxy and a satellite; the more diffuse outer region of the galaxy appears strongly disturbed by interaction with the satellite. The absence of a corresponding optical source for the satellite galaxy suggests a high mass-to-light ratio.

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