Flows, fragmentation, and star formation. I. Low-mass stars in Taurus

The remarkably filamentary spatial distribution of young stars in the Taurus molecular cloud has significant implications for understanding low-mass star formation in relatively quiescent conditions. The large scale and regular spacing of the laments suggests that small-scale turbulence is of limited importance, which could be consistent with the driving on large scales by flows that produced the cloud. The small spatial dispersion of stars from gaseous laments indicates that the low-mass stars are generally born with small velocity dispersions relative to their natal gas, of the order of the sound speed or less. The spatial distribution of the stars exhibits a mean separation of about 0.25 pc, comparable to the estimated Jeans length in the densest gaseous laments, and is consistent with roughly uniform density along the laments. The efficiency of star formation in laments is much higher than elsewhere, with an associated higher frequency of protostars and accreting T Tauri stars. The protostellar cores are generally aligned with the laments, suggesting that they are produced by gravitational fragmentation, resulting in initially quasi-prolate cores. Given the absence of massive stars that could strongly dominate cloud dynamics, Taurus provides important tests of theories of dispersed low-mass star formation and numerical simulations of molecular cloud structure and evolution.