Rotational Desorption of Ice Mantles from Suprathermally Rotating Grains around Young Stellar Objects

Abstract

Abstract Ice mantles on dust grains play a central role in astrochemistry. Water and complex organic molecules (COMs) are thought to first form on the ice mantles and subsequently are released into the gas phase due to star-formation activity. However, the critical question is whether ice mantles can survive stellar radiation when grains are being heated from to ≳100 K. In this paper, we first study the effect of suprathermal grain rotation driven by the intense radiation of young stellar objects on the ice mantles. We find that the entire ice mantles can be disrupted into small fragments by centrifugal stress before the water ice and COMs desorb via thermal sublimation. We then study the consequence of resulting ice fragments and find that tiny fragments of radius a ≲ 10 Å exhibit a transient release of COMs due to thermal spikes, whereas larger fragments can facilitate thermal sublimation at much higher rates than from the original icy grain, or the same rate but with temperatures of ∼20–40 K lower. We find that rotational desorption is efficient for hot cores/corinos from the inner to outer regions where the temperature drops to and . We discuss the implications of this mechanism for desorption of COMs and water ice in various environments, including outflow cavity walls, photodissociation regions, and protoplanetary disks. Finally, we show that very large aggregate grains can be disrupted into individual icy grains via a rotational disruption mechanism, followed by rotational desorption of ice mantles.