18 February 2020Diffuse interstellar bands in the Galaxy and beyond

Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features found in the spectra of stars viewed trough one or several clouds of interstellar medium (ISM). Identified for the first time by Heger (1922), their interstellar origin was not established until the 1930’s. Today, almost one century after their discovery the precise nature of their carriers (the agent originating these features) remains a mystery. DIBs display a link with other components of the ISM. Therefore, irrespective of the actual nature of carrier(s), they can be used as tools to infer properties of the 3D structure of the ISM. In this seminar we will see two experiments related with DIBs. In the first one, we will test our capability to extract the DIB’s parameters (i.e. strength, velocity and number of components) from the spectra of cool stars. Since they are much more numerous and prove less extreme conditions of the ISM in terms of radiation field than the traditionally used hot star spectra, they are a very appealing set of targets for studies aiming at tracing the structure of the Galactic ISM. In the second one, we will explore whether we are in a position to design experiments based on spatially resolved observations of DIBs beyond the Local Group. Carrying out such studies will permit studying the relationship between the DIBs and other components of the ISM in conditions different to those found in our Galaxy.