NGC 6946: kinematics of the starburst in the circum-nuclear zone.

Abstract

Using spectroscopic observations at relatively high resolution (Δλ ≡ 0.35 Å) in the region within 30 arcseconds of the nucleus of NGC 6946 the authors have found clear evidence of a strong expansion, with velocities of order 100 km s^-1. By comparison with intensity maps in H I (21 cm) H₂ (CO 2.6 mm) and Hα taken from the literature the authors derive a picture of a starburst which contains ⪆10⁴ O V stars. The gas in the most neutral region has been largely used in star formation, while a placental molecular cloud remains around the starburst. The authors propose a mechanism for maintaining the starburst, and using the molecular mass for progressive star formation.