Growth of dust grains in a low-metallicity gas and its effect on the cloud fragmentation

Gen Chiaki, Takaya Nozawa, Naoki Yoshida

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

In a low-metallicity gas, rapid cooling by dust thermal emission is considered to induce cloud fragmentation and play a vital role in the formation of low-mass stars (≲ 1 M) in metal-poor environments. We investigate how the growth of dust grains through accretion of heavy elements in the gas phase onto grain surfaces alters the thermal evolution and fragmentation properties of a collapsing gas cloud. We directly calculate grain growth and dust emission cooling in a self-consistent manner. We show that MgSiO3 grains grow sufficiently at gas densities n H = 1010, 1012, and 1014 cm-3 for metallicities Z = 10-4, 10-5, and 10-6 Z , respectively, where the cooling of the collapsing gas cloud is enhanced. The condition for efficient dust cooling is insensitive to the initial condensation factor of pre-existing grains within the realistic range of 0.001-0.1, but sensitive to metallicity. The critical metallicity is Z crit ∼ 10-5.5 Z for the initial grain radius and Zcrit ∼ 10-4.5 Z for . The formation of a recently discovered low-mass star with extremely low metallicity (≤4.5 × 10-5 Z ) could have been triggered by grain growth.

Original languageEnglish
Article numberL3
JournalAstrophysical Journal Letters
Volume765
Issue number1
DOIs
Publication statusPublished - 2013 Mar 1
Externally publishedYes

Keywords

  • ISM: abundances
  • dust, extinction
  • galaxies: evolution
  • stars: Population II
  • stars: formation
  • stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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