Intrinsic profiles of strong diffuse interstellar bands

This paper presents a survey of the profiles of strong diffuse bands based on an extensive set of high-resolution spectra acquired with the echelle spectrograph installed at the Cassegrain focus of the 2.1 m telescope of the McDonald Observatory. Only targets characterized by narrow and symmetric lines of interstellar sodium, as well as by very high signal-to-noise ratio (S/N), have been selected. The surveyed diffuse interstellar bands are those at 5780, 5797, 5850, 6196, 6234, 6270, 6376, 6379, 6614, and 6660 Angstrom. The possible modifications caused by stellar and telluric lines, as well as by Doppler splitting, are discussed together with methods of getting rid of them. The presented profiles are as free of the aforementioned contaminations as possible. The very broad features such as lambda 5778 and lambda 6177 are not discussed, as their profiles extracted from the echelle spectra are very uncertain. The lambda 6203/lambda 6205 feature is also not considered, as it is a mixture of two unresolvable diffuse bands of different origin. The very broad 6284 Angstrom band is so contaminated with telluric features that its profile was also found to be too uncertain. The spectra are still not of high enough S/N to discuss the profiles of the numerous weak interstellar features discovered recently.