AAS 201st Meeting, January, 2003
Session 13. Galaxy - Structure
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

## [13.11] The Kinematics of M33's Disk Planetary Nebulae

P.R. Durrell, R. Ciardullo, M.B. Laychak (PSU), G.H. Jacoby (WIYN), J.J. Feldmeier (CWRU), K. Moody (PSU)

We have performed a photometric and spectroscopic survey of planetary nebulae (PNe) throughout the disk of the Local Group spiral galaxy M33. Using the [O~III] \lambda 5007 and H\alpha MOSAIC images from the Massey et al. 4-m survey of Local Group galaxies (http://www.lowell.edu/users/massey/lgsurvey.html), we have identified 172 PN candidates over 5 disk scale lengths (~9 kpc) in the galaxy, and have obtained radial velocities for ~160 of them. We use these data to improve the PNLF distance to the galaxy, probe its stellar populations, and measure the z-component velocities of its old disk stars. We find that the PN-based distance to the galaxy is ~ 0.15~mag further than previously reported (Magrini et al. 2000), and in excellent agreement with the Cepheid distances, if a common reddening value is assumed. We also find that the shape of the [O~III] \lambda 5007 planetary nebula luminosity function is similar to that of the SMC, in that it has a pronounced dip'' ~1~mag from the bright-end cutoff. We use our radial velocities to derive an independent measurement of the galaxy's disk mass-to-light ratio and disk-mass distribution. We discuss the implications of our results for the maximal-disk hypothesis and cold-dark-matter scenarios.