Infrared Diffuse Interstellar Bands in the Galactic Centre Region
  The spectrum of any star viewed through a sufficient quantity of diffuse
interstellar material reveals a number of absorption features collectively
called diffuse interstellar bands (DIBs). The first DIBs were reported 90 years
ago, and currently well over 500 are known. None of them has been convincingly
identified with any specific element or molecule, although recent studies
suggest that the DIB carriers are polyatomic molecules containing carbon. Most
of the DIBs currently known are at visible and very near-infrared wavelengths,
with only two previously known at wavelengths beyond one micron (10,000
Angstroms), the longer of which is at 1.318 microns. Here we report the
discovery of thirteen diffuse interstellar bands in the 1.5-1.8 micron interval
on high extinction sightlines toward stars in the Galactic centre. We argue
that they originate almost entirely in the Galactic Centre region, a
considerably warmer and harsher environment than where DIBs have been observed
previously. The relative strengths of these DIBs toward the Galactic Centre and
the Cygnus OB2 diffuse cloud are consistent with their strengths scaling mainly
with extinction by diffuse material.
