![]() |
|
Diffuse
Interstellar Bands |
Diffuse Interstellar Bands (DIBs) are
a (ever increasing) set of about 300 absorption features superposed
on the interstellar extinction curve. They fall in the range from 400
to 1000 nm, and exhibit a full width at half maximum ranging from less
than 1 up to 30 angstroms. Since Merrill (1934), DIBs were seen towards
more than a hundred sight lines, showing differences in profile shapes
and varying relative strengths from one environment to another. This
hinted an origin due to a variety of carriers, and many hypotheses have
been formulated, ranging from dust grains to several gas-phase free
molecules. Nowadays, high resolution observations show partially resolved
components inside the profile of some DIBs; this fact, combined with
their nearly constant rest wavelength irrespective of the direction
of observation, suggests that gas-phase polyatomic molecules are very
likely to be responsible for their production. In particular, complex carbon based molecules, such asPAHs, fullerenes and linear carbon chains, which are thought to be ubiquitous in the ISM, have been proposed as attractive candidates. However, no definitive match between any DIB and any individual such molecules exists to date. The AstroC-Hemistry Group did collect a rather large number of high resolution and high signal-to-noise ratio spectra, most of which were published in a number of papers. The observational activity still continues, in effort to match the laboratory and theoretical suggestions. |
|