Probing the Local Bubble with Diffuse Interstellar Bands (DIBs)
  The Sun lies in the middle of an enormous cavity of a million degree gas,
known as the Local Bubble. The Local Bubble is surrounded by a wall of denser
neutral and ionized gas. The Local Bubble extends around 100 pc in the plane of
Galaxy and hundreds of parsecs vertically, but absorption-line surveys of
neutral sodium and singly-ionized calcium have revealed a highly irregular
structure and the presence of neutral clouds within an otherwise tenuous and
hot gas. We have undertaken an all-sky, European-Iranian survey of the Local
Bubble in the absorption of a number of diffuse interstellar bands (DIBs) to
offer a novel view of our neighbourhood. Our dedicated campaigns with ESO's New
Technology Telescope and the ING's Isaac Newton Telescope comprise high
signal-to-noise, medium-resolution spectra, concentrating on the 5780 and 5797
\AA\ bands which trace ionized/irradiated and neutral/shielded environments,
respectively; their carriers are unknown but likely to be large carbonaceous
molecules. With about 660 sightlines towards early-type stars distributed over
distances up to about 200 pc, our data allow us to reconstruct the first ever
3D DIB map of the Local Bubble, which we present here. While we confirm our
expectations that the 5780 \AA\ DIB is relatively strong compared to the 5797
\AA\ DIB in hot/irradiated regions such as which prevail within the Local
Bubble and its walls, and the opposite is true for cooler/shielded regions
beyond the confines of the Local Bubble, we unexpectedly also detect DIB
cloudlets inside of the Local Bubble. These results reveal new insight into the
structure of the Local Bubble, as well as helping constrain our understanding
of the carriers of the DIBs.
