Survey of Very Broad Diffuse Interstellar Bands

Abstract

This paper considers a very special set of a few interstellar features—broad diffuse interstellar bands (DIBs) at 4430, 4882, 5450, 5779, and 6175 ÅÅ. The set is small, and measurements of equivalent widths of these DIBs are challenging because of severe stellar, interstellar, and sometimes, also telluric contaminations inside their broad profiles. Nevertheless, we demonstrate that they do correlate pretty tightly (DIBs 4882 and 5450 to a lesser extent though) with other narrower diffuse bands, as well as with the color excess E ( B − V ). The studied broad DIBs correlate well with both interstellar molecule CH and interstellar K i , i.e., it is hardly possible to verify whether the environments, facilitating the formation of very broad DIB carriers, are dominated by either molecular or atomic gas as both these species likely occupy the same volume.