A census of the Carina Nebula - I. Cumulative energy input from massive stars

The Carina Nebula (NGC 3372) is our richest nearby laboratory in which to study feedback through ultraviolet radiation and stellar winds from very massive stars during the formation of an OB association, at an early phase in the evolution of the surrounding proto-superbubble before supernova explosions have influenced the environment. This feedback is triggering successive generations of new star formation around the periphery of the nebula, while simultaneously evaporating the gas and dust reservoirs out of which young stars are trying to accrete material. This paper takes inventory of the combined effect from all the known massive stars that power the Carina Nebula through their total ionizing flux and integrated mechanical energy from their stellar winds. Carina is close enough and accessible enough that spectral types for individual stars are available, and many close binary and multiple systems have recently been spatially resolved, so that one can simply add them. Adopting values from the literature for corresponding spectral types, the present-day total ionizing photon luminosity produced by the 65 O stars and three WNL stars in Carina is Q_H~= 10⁵¹s^-1, the total bolometric luminosity of all stars earlier than B2 is 2.5 × 10⁷L_solar, and the total mechanical luminosity of stellar winds is L_SW~= 10⁵L_solar. The total Q_H was about 25 per cent higher when η Carinae was on the main sequence, before it and its companion were surrounded by its obscuring dust shell; for the first 3Myr, the net ionizing flux of the 70 O stars in Carina was about 150 times greater than in the Orion Nebula. About 400-500M_solar has been contributed to the HII region by stellar wind mass-loss during the past 3Myr. Values for Q_H and L_SW are also given for the individual clusters Tr14, 15 and 16, and Bo10 and 11, which are more relevant on smaller spatial scales than the total values for the whole nebula.