AAS 203rd Meeting, January 2004
Session 115 Dwarf, Irregular and Starburst Galaxies
Poster, Thursday, January 8, 2004, 9:20am-4:00pm, Grand Hall

## [115.02] Neutral Hydrogen in the Interacting Magellanic Spirals NGC 4618/4625

S. Bush (Case Western Reserve University), E. Wilcots (University of Wisconsin-Madison)

Asymmetry is a common trait in spiral galaxies. However, it is particularly frequent among Magellanic spirals. To explore how morphological and kinematic asymmetry are affected by companion galaxies, we analyze neutral hydrogen observations of the interacting Magellanic spirals NGC 4618 and 4625. Through calculations based on derived H~I profiles, we show that NGC 4618 and 4625 are no more asymmetric than non-interacting Magellanic spirals analyzed by Wilcots & Prescott (2003). We also derive rotation curves for the approaching and receding sides of each galaxy. By fitting the mean curves with an isothermal halo model, we calculate dynamical masses of 4.7 \times 109 M\odot and 9.8 \times 109 M\odot out to 230 arcseconds for NGC 4618 and 4625, respectively. While the rotation curves have systematically higher velocities on the receding side of each galaxy, the effect is no more pronounced than in studies of non-interacting spirals (Swaters et. al. 1999). Therefore, we find no compelling evidence that interactions have caused the asymmetry in NGC 4618/4625. This work was supported by a NSF-REU site grant (AST-0139563) to the University of Wisconsin-Madison.