Determination of the gas-to-dust ratio in nearby dense clouds using X-ray absorption measurements

We present a comparison of the gas and dust properties of the dense interstellar matter in six nearby star forming regions (d 2) than the galactic value, derived using the standard extinction curve (RV = 3:1). This result is consistent with the recent downwards revision of the metallicity of the Sun and stars in the solar vicinity. We find that the Oph dense cloud has the same metallicity than the local ISM when assuming that the galactic gas-to-dust ratio remains unchanged. The dierence between galactic and local values of the gas-to-dust ratio can thus be attributed entirely to a dierence in metallicity.