Nuclear Starbursts in Barred Spiral Galaxies

Summary

ABSTRACT

The nuclear star formation rates have been measured for a complete sample of 156 spiral galaxies. The nuclear star formation rates of barred and unbarred galaxies are compared separately for early and late Hubble types. Significant differences are observed and critically evaluated within the context of a possible causal relationship between stellar bars and nuclear starbursts.

INTRODUCTION

Considerable interest surrounds the possible association between nuclear activity and galaxy morphology (Sersic and Pastoriza 1967; Heckman 1978; Simkin, Su, and Schwarz 1980). Indeed, the unambiguous association with a morphological feature, such as a stellar bar for example, may provide an important clue as to the origin of the activity. A number of studies have demonstrated the frequency of nuclear star formation to be enhanced in the nuclei of barred spiral galaxies. Heckman (1980) demonstrated a higher incidence of HII regions in the nuclei of barred spirals and Balzano (1983) noted an excess of barred spirals in an optically selected sample of starburst galaxies. The results discussed in this contribution, however, I believe are the first to demonstrate that the high mass star formation rate is enhanced in the nuclei of barred spirals when compared to unbarred spirals.

THE SAMPLE

A complete sample of 227 nearby (15 ≤ D)[Mpc] ≤ 40), infrared luminous, L(40 – 120 μm) ≥ 3 × 10⁹ L_⊙ spiral galaxies were selected upon comparison of the Infrared Astronomical Satellite (IRAS) Point Source Catalog with the Nearby Galaxies Catalog (Tully 1988).