THE CIRCUMNUCLEAR REGION IN NGC 4321 J.H. KNAPEN x AND J.E. BECKMAN Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife, Spain 1 Present Address: Universite de Montreal, Dept. de Physique, C.P. 6128, Succ. Centre Ville, Montreal, Quebec, H3C-3J7 Canada I. SHLOSMAN AND C.H. HELLER Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055, USA AND R.F. PELETIER AND R.S. DE JONG Kapteyn Astronomical Institute, Postbus 800, NL-9700 AV Groningen, The Netherlands Abstract. We present results from a recent study of the inner 1 kpc zone of the weakly barred spiral galaxy NGC 4321 (M100), which reveals a circumnu- clear starburst, organized in a pair of tightly-wound spiral arms. Combining high-resolution imaging in the optical and near-IR with a detailed dynami- cal model, we show that the morphology of this region can be explained by a resonance interaction between the disk and the stellar bar and its effects on the gas. NGC 4321 (M100) is a grand-design spiral in the Virgo cluster, which shows a remarkable circumnuclear star-forming structure when seen in Ha (Pogge 1989). The galaxy was classified as Sc by Sandage in the Hubble catalog of galaxies, and as "oval" (SABbc) by de Vaucouleurs et al. (1976), but from near-infrared (NIR) and Ha imaging and from the velocity struc- ture in Hi it is clear that NGC 4321 is barred, albeit weakly (Pierce 1986, Knapen et al. 1993). With a very modest L FIR , 1 _ 500fMm )/LB = 0.42 (Young 539 /. Appenzeller (ed.), Highlights of Astronomy, Vol. 10, 539-542. © 19951AU. Printed in the Netherlands. available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1539299600011989 Downloaded from https://www.cambridge.org/core. IP address: 3.81.87.58, on 12 Jul 2021 at 14:27:23, subject to the Cambridge Core terms of use,