Infrared Diffuse Interstellar Bands in the Galactic Centre Region

TL;DR

This paper reports the discovery of thirteen new diffuse interstellar bands in the 1.5-1.8 micron range toward stars in the Galactic Centre, suggesting these features originate in a harsher environment and scale with diffuse material extinction.

Contribution

It presents the first detection of DIBs beyond 1.3 microns in the Galactic Centre, expanding the known spectral range of these features and their environmental dependence.

Findings

Thirteen new DIBs discovered in the 1.5-1.8 micron range.

DIB strengths scale mainly with diffuse material extinction.

DIBs originate predominantly in the Galactic Centre region.

Abstract

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.