ALMA reveals thermal and non-thermal desorption of methanol ice in the HD 100546 protoplanetary disk

Abstract

There is growing evidence that planet formation is already underway during the protoplanetary disk stage, making the chemical study of such objects imperative when considering the planet-forming environment. This talk presents ALMA observations which study the chemistry of two Herbig disks: HD100546 and IRS48. I will present briefly the resultant chemical inventory of these two objects which enables the first detailed characterisation of the complex organic reservoir. The main topic of the talk will focus on multiple detected lines of methanol and formaldehyde, towards HD100546, which likely hosts two giant planets. Methyl formate is also detected, revealing another level of chemical complexity. Previous research has suggested that methanol has an inherited origin in HD100546 as it could not form efficiently in situ. As the simplest complex organic molecule (COM), methanol is fundamental within the context of astrochemical origins, representing a bridge between simple molecules and more complex compounds vital to life. Multiple lines of methanol and formaldehyde are detected towards the hot inner and cold outer disk, suggesting that the outer dust grains are icy. Through rotational diagram analysis, we constrain for the first time the temperature and column density of these two organic molecules in both spatial components. This enables a thorough investigation into the organic chemical history of this disk, including methanol inheritance and thermal vs non-thermal desorption.