THE HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). II. DUST AND GAS IN ANDROMEDA**Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

We present an analysis of the dust and gas in Andromeda, using Herschel images sampling the entire far-infrared peak. We fit a modified-blackbody model to ∼4000 quasi-independent pixels with spatial resolution of ∼140 pc and find that a variable dust-emissivity index (β) is required to fit the data. We find no significant long-wavelength excess above this model, suggesting there is no cold dust component. We show that the gas-to-dust ratio …