CAN THE GROWTH OF DUST GRAINS IN LOW-METALLICITY STAR-FORMING CLOUDS AFFECT THE FORMATION OF METAL-POOR LOW-MASS STARS?
- Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)
- Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)
The discovery of a low-mass star with such a low metallicity as {<=}4.5 Multiplication-Sign 10{sup -5} Z{sub Sun} reveals the critical role of dust in the formation of extremely metal-poor stars. In this Letter, we explore the effect of the growth of dust grains through accretion of gaseous refractory elements in very low metallicity pre-stellar cores on cloud fragmentation induced by dust emission cooling. Employing a simple model of grain growth in a gravitationally collapsing gas, we show that Fe and Si grains can grow efficiently at hydrogen densities of {approx_equal} 10{sup 10}-10{sup 14} cm{sup -3} in the clouds with metal abundances of -5 {approx}< [Fe, Si/H] {approx}< -3. The critical metal number abundances, above which the grain growth could induce the fragmentation of the gas clouds, are estimated to be A{sub crit} {approx_equal} 10{sup -9}-10{sup -8}, unless the initial grain radius is too large ({approx}>1 {mu}m) or the sticking probability is too small ({approx}<0.01). We find that even if the initial dust-to-gas mass ratio is well below the minimum value required for the dust-induced fragmentation, the grain growth increases the dust mass high enough to cause the gas to fragment into sub-solar mass clumps. We suggest that as long as the critical metal abundance is satisfied, grain growth could play an important role in the formation of low-mass stars with metallicity as low as 10{sup -5} Z{sub Sun }.
- OSTI ID:
- 22078549
- Journal Information:
- Astrophysical Journal Letters, Vol. 756, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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