Density structure of the giant HII region NGC 2363

We perform a detailed measurement of the electron density along two slit position angles in the bright, low metallicity extragalactic HII region NGC 2363. A comparison of the density structures obtained with the two independent diagnostics given by [AIv]4711/4740 and [SII]6716/6731, show that they present both different absolute values and different radial dependencies, with the [AIV] densities reaching up to 1000 cm-3. We explore the implications for the computation of the He abundance.