The impact of the initial core temperature on protostellar disc fragmentation. Issue 2 (16th December 2022)

• Record Type: Journal Article
• Authors: Sigalotti, L Di G; Cruz, F; Hareter, M; Gabbasov, R; Klapp, J; Fierro-Santillán, C R; Ramírez-Velásquez, J M; Zsargó, J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 2(2023)
• Page Start: 2578
• Page End: 2589
• Publication Date: 2022-12-16
• Subjects: stars: formation -- hydrodynamics -- methods: numerical -- stars: protostars -- binaries: general -- accretion, accretion discs -- stars: low-mass; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3694
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Ground-based and satellite observations have revealed dust temperatures as low as ∼5−7 K in the centre of low-mass, pre-stellar cloud cores, where star formation takes place. However, external heating may rise the outer core temperatures up to ∼15−20 K. Such low temperatures at the centre of pre-stellar cores are a key factor to constrain the conditions that lead to the formation of gravitationally bound protostellar systems as was recently captured by highly-resolved Atacama large millimeter/submillimeter array observations. Here, we report consistent smoothed particle hydrodynamics collapse calculations of cold cores that demonstrate the formation of close protobinary systems via small-scale fragmentation of a gravitationally unstable protostellar disc. The results indicate that mean binary separations, of tens of astronomical units, are a consequence of disc fragmentation in cold pre-stellar cores. Cloud cores initially with temperatures ≤6 K and a low amplitude ( a = 0.1), m = 2 density perturbation formed close protobinaries that were followed deep into the non-isothermal collapse for several orbital periods and appeared to survive as independent stellar entities. At temperatures ≥7 K disc fragmentation is no longer observed and the calculations terminate with the formation of a wide protobinary, which may occasionally be accompanied by small substellar objects emerging by fragmentation of the circumbinary disc. When the perturbation amplitude is raised to a = 0.25, disc fragmentation occurs again only in cores with initial temperatures ≤6 K. Therefore, increasing the perturbation amplitude does not necessarily imply that there will be disc fragmentation at higher core temperatures.