The hot and dusty interstellar medium through X-ray spectroscopy

The interstellar medium fills the space between the stars in our Galaxy. Depending on the thermodynamic state, it is possible to distinguish between three phases: a cold and dense phase consisting of clouds of atomic and molecular hydrogen; a warm inter-cloud phase comprising tenuous ionised and neutral gas; a dynamic hot phase represented by highly ionised gas, shock-heated by supernova explosions. The cold phase includes the cosmic dust, which represents only a small fraction of the mass of the interstellar medium, but it fulfils an important role in the Galaxy, especially in star and planet formation. This thesis studies the extinction of X-rays by dust grains in our Galaxy. In particular, this work investigates the physical and chemical characteristics of all phases of the interstellar medium, especially of interstellar dust. This is carried out by combining high-resolution spectroscopy of bright X-ray sources and with new extinction models, based on synchrotron measurements.