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A.P. Sluis, T.B. Williams (Rutgers, The State University of New Jersey)
The search for massive black holes in galactic nuclei has greatly improved our understanding of the inner regions of early type galaxies. However, the mass distribution far away from the nucleus remains poorly determined. The gas content of early type galaxies is usually low and does not extend far enough to be used as a tracer population. The stellar light drops off steeply outside one effective radius (typically a few kpc), making absorption line spectroscopy all but impossible. Planetary Nebulae (PNe) can circumvent these problems. As remnants of low mass stars we expect them to follow the stellar light distribution and be plentiful enough to be an effective tracer. Moreover, PNe emit most of their light in a few emission lines, primarily in the 5007 Å[OIII] line, allowing us to both detect them and measure their line of sight velocity. As a result PNe offer us the opportunity to build a kinematic, possibly even a dynamic, picture of the outer regions of early type galaxies.
We report studies of two early type galaxies, NGC 3379 and NGC 3384. We search for PNe using two methods: the first uses direct CCD imaging of a galaxy in two bands; a narrow (44 Å) band centered on the (redshifted) [OIII] line and a broad (240 Å) off band. By comparing the on and off band images we can detect PNe candidates and measure their emission line flux. The second method uses Fabry-Perot (FP) imaging, giving in essence a large set of images, each taken with a very narrow band (~2 Å) filter. With the FP data we can both detect the PNe and measure their line of sight velocities. We compare the results of our PNe searches using both methods, and present the extended kinematics of he two galaxies studied.