2013A&A...550A.108V

The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614Å and - in a smaller region near the central cluster R136 - neutral sodium (the Na iD doublet); we also measured the DIBs at 5780 and 5797Å. The maps show strong 4428 and 6614Å DIBs in the quiescent cloud complex to the south of 30Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R136, and small-scale structure in the Milky Way. The strengths of the 4428, 5780, 5797 and 6614Å DIBs are correlated, also with Na absorption and visual extinction. The strong 4428Å DIB is present already at low Na column density but the 6614, 5780 and 5797Å DIBs start to be detectable at subsequently larger Na column densities. The carriers of the 4428, 6614, 5780 and 5797Å DIBs are increasingly prone to removal from irradiated gas. The relative strength of the 5780 and 5797Å DIBs clearly confirm the Tarantula Nebula as well as Galactic high-latitude gas to represent a harsh radiation environment. The resilience of the 4428Å DIB suggests its carrier is large, compact and neutral. Structure is detected in the distribution of cool-warm gas on scales between one and >100pc in the LMC and as little as 0.01pc in the Sun's vicinity. Stellar winds from the central cluster R136 have created an expanding shell; some infalling gas is also detected, reminiscent of a galactic ``fountain''.