X-ray photoevaporation’s limited success in the formation of planetesimals by the streaming instability

X-ray photoevaporation’s limited success in the formation of planetesimals by the streaming instability

Authors:

Ercolano et al

Abstract:

The streaming instability is often invoked as solution to the fragmentation and drift barriers in planetesimal formation, catalysing the aggregation of dust on kyr time-scales to grow km-sized cores. However, there remains a lack of consensus on the physical mechanism(s) responsible for initiating it. One potential avenue is disc photoevaporation, wherein the preferential removal of relatively dust-free gas increases the disc metallicity. Late in the disc lifetime, photoevaporation dominates viscous accretion, creating a gradient in the depleted gas surface density near the location of the gap. This induces a local pressure maximum that collects drifting dust particles, which may then become susceptible to the streaming instability. Using a one-dimensional viscous evolution model of a disc subject to internal X-ray photoevaporation, we explore the efficacy of this process to build planetesimals. Over a range of parameters, we find that the amount of dust mass converted into planetesimals is often <1 a="" across="" an="" and="" are="" at="" au.="" be="" best="" common="" conclude="" considered="" contrast="" cores.="" debris="" discs="" driven="" far-ultra-violet="" few="" for="" formation="" in="" investigation="" large="" m="" may="" mechanism="" model="" most="" of="" our="" photoevaporation="" planetary="" rather="" recent="" relevant="" reported="" results="" similar="" spread="" tens="" than="" that="" the="" to="" we="">100 au) disc radii. The discrepancies are primarily a consequence of the different photoevaporation profiles assumed. Until observations more tightly constrain photoevaporation models, the relevance of this process to the formation of planets remains uncertain.