Infrared view of the multiphase ISM in NGC 253

NGC 253 is the closest ($3.5\,\mathrm{Mpc}$) starburst galaxy and thus an ideal laboratory to study the various mechanisms of heating and cooling of the interstellar medium (ISM).

The impacts of an active galactic nucleus (AGN) or a nuclear starburst on the surrounding environment in general, but also in NGC 253 in particular are not completely understood.

Fine-structure lines in the mid-infrared and far-infrared spectral range, which are often only mildly affected by extinction and self-absorption, are perfect to study the ISM in very dusty sources such as starburst-galaxies.

In this study we present a combined data set from SOFIA, Spitzer, and Herschel observations of the nuclear region in NGC 253.

We use the line flux ratios OIII $52/88 \mu\mathrm{m}$, NII $122/205 \mu\mathrm{m}$, and SIII $19/33 \mu\mathrm{m}$ to determine the local electron density.

The line ratios are insenstive to the temperature, but depend strongly on the electron density.

Further, we use (NeII $13 \mu \mathrm{m}$ $+$ NeIII $16 \mu\mathrm{m}$) / H$\alpha$ line flux ratio to calculate the Ne/H abundance ratio, which serves as a measure for the metallicity in the nuclear region of NGC 253.

We also will show preliminary results from our ongoing, more sophisticated modelling approach with \verb|MULTIGRIS|.