TW Hya as a chemical Rosetta stone: the case of H2CO

We present ALMA observations of several formaldehyde transitions of the planet forming disk around TW Hya, obtained as part of the project 'TW Hya as a chemical Rosetta stone'. Formaldehyde (H2CO) is a precursor of the simplest complex organic molecule methanol (CH3OH) and thus understanding its formation history and the link to the physical structure is of great importance. Formation of H2CO is possible in the gas-phase at increased temperatures but also in the solid-state in the midplane and outer regions where the temperature drops below 30K. To investigate this, several lines with different excitation temperatures have been measured and analyzed. The channel maps, moment-zero map, and radial profiles give an insight into the distribution and origin of the gas-phase H2CO abundances in the protoplanetary disk. Comparison to detailed model calculations provides further constraints on which formation routes dominate H2CO, and its relation to CH3OH.