2003A&A...397...87I

We present maps of the first-ranked HII region complex Hubble V in the metal-poor Local Group dwarf galaxy NGC 6822 in the first four transitions of ¹²CO, the 158µm transition of C⁺, the 21-cm line of HI, the Paβ line of HII, and the continuum at 21cm and 2.2µm wavelengths. We have also determined various integrated intensities, notably of HCO⁺ and near-IR h₅₀^–12 emission. Although the second-ranked HII region Hubble X is located in a region of relatively strong HI emission, our mapping failed to reveal any significant CO emission from it. The relatively small CO cloud complex associated with Hubble V is comparable in size to the ionized HII region. The CO clouds are hot (T_kin=150K) and have high molecular gas densities (n(h₅₀^–12)≃10⁴cm^–3). Molecular hydrogen probably extends well beyond the CO boundaries. C⁺ column densities are more than an order of magnitude higher than those of CO. The total mass of the complex is about 10⁶M_☉ and molecular gas accounts for more than half of this. The complex is excited by luminous stars reddened or obscured at visual, but apparent at near-infrared wavelengths. The total embedded stellar mass may account for about 10% of the total mass, and the mass of ionized gas for half of that. Hubble V illustrates that modest star formation efficiencies may be associated with high CO destruction efficiencies in low-metallicity objects. The analysis of the Hubble V photon-dominated region (PDR) confirms in an independent manner the high value of the CO-to-h₅₀^–12 conversion factor X found earlier, characteristic of starforming low-metallicity regions.