AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 6. Interactions, Mergers and Starbursts
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[6.01] The Hubble Heritage Image of the Polar-Ring Galaxy NGC 4650A

A.L. Kinney (STScI), J. Gallagher (U. Wisconsin), L. Matthews (NRAO), L. Sparke (U. Wisconsin), H.E. Bond, C.A. Christian, J. English, L. Frattare, F. Hamilton, Z. Levay, K. Noll (STScI), Hubble Heritage Team

The Hubble Heritage Project has the aim of providing the public with pictorially striking images of celestial objects obtained with the Hubble Space Telescope. As part of the Heritage Project, we have used HST\/ to obtain a multi-color image of the peculiar galaxy NGC 4650A{}. This was the first Heritage observation for which the public joined in the target selection. NGC 4650A was chosen in the winter of 1998-99 from among several candidate objects by over 8,000 members of the public, who used the Heritage web site ({\tt heritage.stsci.edu}) to register their votes. The WFPC2 observations were obtained in April 1999, in the wide B (F450W), wide V (F606W), and I (F814W) bands. The resulting full-color image will be presented at the AAS meeting and on our web site, and the actual data frames are available publicly in the HST\/ archive for use by interested scientists.

NGC 4650A, located at a distance of about 40~Mpc, is the best-known and most spectacular example of the rare class of ``polar-ring'' galaxies. These objects are probably the remnants of collisions, in which the debris from a disrupted, gas-rich smaller galaxy has gone into orbit around a larger galaxy. The HST\/ image of NGC~4650A shows a rotating, almost edge-on inner disk of old red stars, around which orbits a younger ring of dust, gas, and stars, in a plane that is nearly perpendicular to that of the old disk. Numerous young blue star clusters reveal that active star formation is occurring within the polar ring, triggered by the collision process. Polar rings are particularly useful for probing the distribution of dark matter in galactic halos.

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