The relative DIB strengths as well as those of the simple radicals seem to be related to the shapes of interstellar extinction curves. Details of the profiles of narrow DIBs, documenting their molecular origin, are presented. In the latter (prototype HD149757), narrow DIBs, as well as bands of simple radicals, are strong while the broad DIBs are weak (in relation to E(B−V)).
In the former (prototype HD147165), broad DIBs are very strong, while the narrow ones and molecular features are weak. Certain DIB strength ratios seem to be related to intensities of the known features of simple molecular species this led to the introduction of the so-called σ and ζ type interstellar clouds. It was found that the strength ratio of the major DIBs, 57, is heavily variable at the same E(B−V), the DIB intensities may vary by as much as a factor of three or more. The mutual correlations of different DIBs, aiming at finding “families” of common origin, are briefly discussed. It demonstrates why the bands are commonly considered as having originated in many still unknown carriers. The paper presents and documents the most important observational results concerning the enigmatic diffuse interstellar bands (DIBs) that have remained unidentified since 1922. Here we show the gradual growths of the widths of DIBs, confirmed in spectra from different instruments. The extreme peculiarity of the DIB profiles was detected in Herschel 36. However, objects that demonstrate extremely broadened profiles of DIBs are scarce. Moreover, DIBs are broader in clouds with abundantly populated vibrationally excited states of hydrogen molecules that is, the broadening of DIBs correlates with the rotational temperature estimated on the H2ν= 2 vibrational level. The profile broadening in the studied DIBs moves the profile’s centres towards longer wavelengths, probably due to the excitation of higher levels of the P branch of the unknown molecular carrier. Despite the high magnitude of the effect, our current analysis is restricted to the strongest DIBs because the weaker ones require a much higher signal-to-noise ratio.
FLEURY MANICO FULL
The full width at half-maximum of four studied DIBs (5780, 5797, 61 Å) demonstrates strong variability, sometimes doubling the widths of the features. The paper describes profile broadening and peak wavelength variation of diffuse interstellar bands (DIBs) measured for 46 lines of sight, probably caused by the physical properties of intervening clouds.
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