Astronomy and Astrophysics, volume 625A, 55-55 (2019/5-1)
The relation between 5780 and 5797 diffuse interstellar bands, CH/CH+molecules, and atomic or molecular hydrogen.
Abstract (from CDS):
Correlations between column densities of neutral and molecular hydrogen and strengths of major 5780 and 5797Å diffuse interstellar bands (DIBs) based on spectra of 66 OB stars were analyzed. We confirm that the 5797Å DIB is more tightly correlated with column density of molecular hydrogen while the 5780 DIB - with that of atomic hydrogen. This leads to a reasonably tight relation between the molecular fraction of H2 and equivalent width ratio of the 5797 and 5780 major diffuse bands with correlation coefficient equal to 0.77±0.05. Column densities of CH and CH+ molecules were used to analyze correlations between abundances of CH/CH+ molecules and strengths of the major 5780 and 5797 DIBs. The 5780 DIB is better correlated with the column density of methydyline cation than the 5797 DIB. A relation with correlation coefficient equal to 0.95±0.02 based on precise column densities, between column densities of CH and H2 molecules, is also presented; in other words, the column densitiy ratio in the case of H2 and CH molecules in the ISM is equal to (2.01±0.09)x107.