Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1B085

GROWTH OF DUST GRAINS IN A LOW-METALLICITY GAS AND ITS EFFECT ON THE CLOUD FRAGMENTATION

Chiaki, Gen (U-Tokyo)
Schneider, Raffaella (INAF)
Nozawa, Takaya (K-IPMU)
Yoshida, Naoki (U-Tokyo, K-IPMU)
Omukai, Kazuyuki (U-Tohoku)
Limongi, Marco (INAF)
Chieffi, Alessandro (INAF)
Bianchi, Simone (INAF)

Abstract:
We study formation of low-mass star (< Msun) in an extremely metal-poor gas (Z ~ 10^-5 Zsun) in the early universe. Our study is motivated by the recent discovery of a low-mass (M* < 0.8 Msun) and extremely metal-poor (Z < 4.5x10^-5 Zsun) star in the Galactic halo by Caffau et al. In such a low-metallicity gas, dust cooling is considered to trigger instability even in an extremely low-metallicity cloud (Z < 10^-4 Zsun). However, in the early universe, the sites where grains are formed are limited and thus dust abundance is smaller than present-day. We propose a model that the accretion of heavy elements onto grain surfaces (grain growth) can induce dust cooling. We calculate cloud evolution and grain growth self-consistently. As a result, grain growth in a gas cloud can eventually enhance dust amount and induce dust cooling for the metallicity 4.5x10^-5 Zsun.

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