Speaker
Description
The recent progress in HI, CO, dust, and gamma-ray observations provides excellent opportunities to probe the properties of the interstellar medium (ISM) at a resolution of a few parsecs inside nearby clouds and to search for biases in the different gas tracers.
The nearby clouds in Galactic anti-center and Chamaleon regions have been studied using jointly the gamma-ray observations of Fermi Large Area Telescope, and the dust optical depth inferred from Planck and IRAS observations.
We have quantified the potential variations in cosmic-ray density and dust properties per gas nucleon across the different gas phases and different clouds, and we have measured the CO-to-H2 conversion factor, XCO, in different environments. We also mapped the gas not seen, or poorly traced, by HI, free-free, and 12CO emissions, namely (i) the opaque HI and diffuse H2 present in the Dark Neutral Medium at the atomic-molecular transition, and (ii) the dense H2 to be added where 12CO lines saturate.
We will present these results and show how the precise modelling of the ISM we have performed helps to improve the modelling of diffuse Galactic gamma-ray emission.
