The Central Region of NGC 1365. SEST and VLA Observations of CO and the Radio Continuum

Abstract

The barred spiral Seyfert galaxy NGC 1365 has been observed in the radio continuum at wavelengths of 2, 6 and 20 cm, using scaled arrays of the VLA, and complete maps have been made in the J = 1–0 and J = 2–1 CO emission lines using the SEST. MEM maps of the 6 and 20 cm emission, as well as a spectral index map, have been produced with a resolution of 2″.3 × 0″.9, and the 2-cm map has a resolution of 0″.25 ×0″.10. The dominant continuum features are a number of unresolved sources with relatively flat non-thermal spectral indices (−0.3 to −0.5), immersed in an incomplete circumnuclear ring, which is superimposed upon a background that extends into the bar along the prominent dust lanes. The ring has angular dimensions of 8″ × 20″, which corresponds to a linear dimension of the order of 1 kpc. There is clear evidence of a jet, about 5″ long, originating at the position of the Seyfert nucleus and extending in a southeastern direction, closely along the minor axis of the galaxy. The jet has a steep non-thermal spectral index (–1.0) and is aligned along the axis of a conical shell of [OIII] emission. The CO molecular gas peaks at the nucleus and is strongly concentrated to the nucleus and bar regions with a certain enhancement along the bar. The total molecular hydrogen gas mass in the observed region is 2 × 10¹⁰ M _⊙, with 6 × 10⁹ M _⊙ lying within 2.2 kpc of the nucleus. A full presentation of the results will be published in Astronomy and Astrophysics in 1994.