THE BAR PATTERN SPEED OF DWARF GALAXY NGC 44311

Abstract

We present surface photometry and stellar kinematics of NGC 4431, a barred dwarf galaxy in the Virgo Cluster undergoing a tidal interaction with one of its neighbors, NGC 4436. We measured its bar pattern speed using the Tremaine-Weinberg method and derived the ratio of the corotation radius, DL, to the bar semimajor axis, a . We found D /a p 0.6+1.2 at 99% confidence level. Albeit with large uncertainty, the probability that the bar ends close to its corotation radius (i.e., 1.0 ≤ DL/aB ≤ 1.4) is about twice as likely as that the bar is much shorter than the corotation radius (i.e., DL/aB 1 1.4).