AAS 204th Meeting, June 2004
Session 40 Galaxies
Poster, Tuesday, June 1, 2004, 10:00am-7:00pm, Ballroom

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[40.02] Nuclear Stellar Populations in Bright Spiral Galaxies: an Infrared Spectroscopic Perspective

G. J. Bendo (Steward Observatory), R. D. Joseph (Institute for Astronomy)

We have used H- and K-band spectroscopy to investigate the nuclear stellar populations and star formation histories of a subsample of 41 bright spiral galaxies from an optically-selected sample (the ISO Atlas of Bright Spiral Galaxies). ~80% of the sample have spectra that are essentially identical and that exhibit only absorption features characteristic of the atmospheres of late-type stars. We present a composite near-infrared spectrum that characterizes these "quiescent" galaxies. In the other ~20% of the sample, we detect both this quiescent continuum and emission lines from HI (Brackett \gamma), H2, and [FeII] that are indicative of recent bursts of star formation. The starbursts were detected only in Sbc and later-type galaxies, and most are barred or show evidence of recent interactions. The stellar populations are most consistent with instantaneous starbursts. While only ~2% of the total nuclear stellar mass in these galaxies is due to these starbursts, we show how the nuclear stellar populations of normal spiral galaxies can be built up through a series of these bursts.

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