CI and CO in the nearby spiral galaxies IC 342 and Maffei 2

¹ Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
² Joint Astronomy Centre, 660 N. A'ohoku Pl., Hilo, Hawaii, 96720, USA

Corresponding author: F. P. Israel, israel@strw.leidenuniv.nl

Received: 19 February 2003
Accepted: 27 March 2003

Abstract

We present , , and 492 GHz [CI] maps as well as and measurements of the central regions in the nearby Sc galaxies IC 342 and Maffei 2. In both galaxies, the distribution of CO and [CI] is strongly concentrated towards the center. These centers harbour modest starbursts. Both galaxies have nearly identical transitional ratios but the relative intensities of their and [CI] emission lines differ significantly. The observed sets of line intensities require modelling with a multi-component molecular gas. In both galaxies, a dense component must be present () with kinetic temperatures  K (IC 342) or  K (Maffei 2), as well as a less dense (IC 342: a few hundred at most; Maffei 2: ) and hotter ( K) component. In both galaxies, neutral and ionized atomic carbon amounts are between 1.5 and 2.5 times those of CO. In both starburst centers about half to two thirds of the molecular gas mass is associated with the hot PDR phase. The center of IC 342 contains within  kpc an (atomic and molecular) gas mass of 1 and a peak face-on gas mass density of about 70   pc^-2. For Maffei 2 these numbers are less clearly defined, mainly because of uncertainties in its distance and carbon abundance. We find a gass mass , and a peak face-on gas mass density of about 35   pc^-2.