Making giant planet cores: convergent migration and growth of planetary embryos in non-isothermal discs

Context. Rapid gas accretion onto gas giants requires the prior formation of ~ 10 M⊕ cores, and this presents a continuing challenge to planet formation models. Recent studies of oligarchic growth indicate that in the region around 5 AU growth stalls at ~ 2 M⊕. Earth-mass bodies are expected to undergo Type I migration directed either inward or outward depending on the thermodynamical state of the protoplanetary disc. Zones of convergent migration exist where the Type I torque cancels out. These “convergence zones” may represent ideal sites for the growth of giant planet cores by giant impacts between Earth-mass embryos.