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Session 48 - Spiral & Field Galaxies.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[48.08] HST-WFPC2 Observations of the Nuclear Region of M51 ^(*)

N. Panagia (ESA/STScI), A. Capetti (STScI), S. Scuderi (ESA/STScI and Osservatorio Astrofisico di Catania), H. Lamers (STScI and Astronomical Inst., Univ. of Utrecht, Holland), R. P. Kirshner (Harvard-Smithsonian CfA)

>From an analysis of HST-WFPC2 images of M51, obtained in the B, V, R and I bands, we have determined the properties and the distribution of the dust present within the central 2 kpc region of the galaxy. We find that the bulk of the dust has properties similar to those of the dust of our Galaxy, and that dust obscuration is responsible for most of the apparent fine structure seen in the inner spiral arms.

We have also determined the bulk properties of the stellar population in the nucleus proper (an oval region of about 1.1^\prime\prime \times 1.6^\prime\prime) and the ones in the bulge (approximately 16^\prime\prime\times26^\prime\prime). We find that the bulge has colors which are characteristic of an old population (i.e. several Gyrs) whereas the intrinsic colors of the nucleus are at least as blue as those of magellanic irregulars, indicating the occurrence of active star formation less than 500 Myrs ago. The optical luminosity of the nucleus is about two magnitudes fainter than that of the SMC, suggesting that the total mass of stars in the nucleus be around 10^8 M_ødot or higher.

^(*) Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Program listing for Tuesday