[Ce II] emission from NGC 4038/9 (the "Antennae")

We present observations of NGC 4038/9 in the [C II] 158 mu m fine-structure line taken with the MPE/UCB Far-infrared Imaging Fabry-Perot Interferomete r (FIFI) on the Kuiper Airborne Observatory (KAO). A fully sampled map of t he galaxy pair (without the tidal tails) at 55 " resolution has been obtain ed. The [C II] emission line is detected from the entire galaxy pair and pe aks at the interaction zone. The total [C II] luminosity of the Antennae is L-[C II] = 3.7 x 10(8) L., which is about 1% of the far-infrared luminosit y observed with IRAS. The main part of the [C II] emission is probably prod uced by photodissociation regions (PDRs), and a minor fraction may be emitt ed from H II regions. A small part of the [C II] emission comes from a stan dard cold neutral medium (CNM); however, for high temperatures (T similar t o 100 K) and high densities (n(H) similar to 200 cm(-1)) of the CNM, up to about one third of the observed [C II] emission may originate from CNM. Fro m PDR models, we derive densities on the order of similar to 10(5) cm(-3) a nd far-UV (FUV) intensities of 460 chi(0), 500 chi(0), and 240 chi(0) for t he PDRs in the interaction zone, NGC 4038, and NGC 4039, respectively. Howe ver, PDRs with densities on the order of similar to 10(2) cm(-3) and FUV in tensities on the order of similar to 100 chi(0) could also explain the obse rved [C II] emission. The minimum masses in the [C II]-emitting regions in the interaction zone and the nuclei is a few x 10(7) M.. A comparison with single-dish CO observations of the Antennae shows a [C II] to CO intensity ratio at the interaction zone that is a factor of 2.6 lower than usually ob served in starburst galaxies, but still a factor of about 1.3 to 1.4 higher than at the nuclei of NGC 4038/9. Therefore, no global starburst is taking place in the Antennae. [C II] emission arising partly from confined starbu rst regions and partly from surrounding quiescent clouds could explain the observed [C II] radiation at the interaction zone and the nuclei. According ly, there are small confined regions with high star formation activity in t he interaction zone and with a lower star formation activity in the nuclei. This supports the high density and high FUV intensity of the PDRs in the i nteraction zone and the nuclei.