| 18 | | There are elongated dense structures in Taurus that seem to run perpendicular to the field lines (Onishi '96, '02, Goldsmith '08). These are thought to have formed from along-field contraction (Heyer, Tamura '87). Star formation has been occuring there, so across field contraction has to have begun happening as well. Palla and Stahler ('02) have found Taurus has an accelerating star formation rate |
| | 18 | There are elongated dense structures in Taurus that seem to run perpendicular to the field lines (Onishi '96, '02, Goldsmith '08). These are thought to have formed from along-field contraction (Heyer, Tamura '87). Star formation has been occuring there, so across field contraction has to have begun happening as well. Palla and Stahler ('02) have found Taurus has an accelerating star formation rate - SF has begun ~10 Myr, but most has been happening in the last ~3 Myr. This is conducive with a 2 stage collapse -- along field lines and then across them once enough material has collected to make you critical/supercritical. The star formation rate in the last 3 Myr in the dense gas is ~ M-dot ~ 5x10^-5^ solar masses/year -- ~2 orders below free fall rate in the dense gas (Goldsmith '2008). Krumholz and Tan '07 have found this holds for a wide variety of objects. This can be explained by turbulent support, people have found marginallly supersonic motions in Taurus (~M=2). However, marginal magnetic criticality also explains it quite naturally (Basu & Ciolek '04) - stars form locally on short timescales, but the gas overall is magnetically supported. The authors have demonstrated this is possible in 2D sheet-geometry sims. The pipe nebula might be an earlier phase of evolution for a magnetically dominated cloud (Lada '08, Alves '08). |
