THE NEAR-INFRARED STRUCTURE OF M33

We present near-infrared mosaics of J, H, and K emission from the cent ral 15' x 30' in M33 which map the stellar distribution of its disk an d spheroidal components. Detailed examination of individual OB associa tions and population synthesis models show that recent massive star fo rmation contributes significantly to near infrared emission, which mus t be considered in deriving the stellar mass distribution. The scale l ength of the exponential disk is less than 6', shorter than optical sc ale lengths in part because of a radial gradient in extinction. We ide ntify two grand-design spiral arms with an underlying stellar componen t in the inner 9'; these terminate near the radius at which the rotati on curve begins to flatten. A weak, bar-shaped excess in the stellar m ass distribution is present in the inner 1'.5; it is unclear whether t his traces the inward extension of the spiral arms or a true bar. We f ind the spheroidal light is reasonably fitted by a single r1/4 distrib ution with a scale length much longer than previously reported for the central spheroidal component. Including a compact bulgelike component does not significantly improve the fit to the surface photometry indi cating that the contribution of a compact bulge component to the spher oidal light must be very low. In previous studies of M33, the ratio of the number of globular clusters to spheroid luminosity was anomalousl y high. Our more extended spheroid results in a ratio closer to that o btained for other spiral galaxies, although it is still high.