The rotation period distribution of pre-main-sequence stars in and around the Orion Nebula

We report rotation periods for 254 stars in an area 40' x 80' centered on t he Orion Nebula. We show that these stars are likely members of the young ( similar to 10(6) yr) Orion OBIc/d association. The rotation period distribu tion we determine, which is sensitive to periods 0.1 < P < 8 days, shows a sharp cutoff for periods P < 0.5 days, corresponding to breakup velocity fo r these stars. Above 0.5 days the distribution is consistent with a uniform distribution; we do not find evidence for a "gap" of periods at 4-5 days. We find signatures of active accretion among stars at all periods; active a ccretion does not occur preferentially among slow rotators in our sample. W e find no correlation between rotation period and near-IR signatures of cir cumstellar disks. In addition, we show that the distribution of nu sin i am ong stars in our sample bears striking resemblance to that of low-mass Plei ades stars. We discuss the implications of our findings for the evolution o f stellar angular momentum during the pre-main-sequence phase. We argue tha t all stars in our sample must still deplete angular momentum by factors of roughly 5-10, if they are to preserve their nu sin i distribution over app roximately the next 100 Myr. We consider in detail whether our findings are consistent with disk-regulated stellar rotation. We do not find observatio nal evidence that magnetic disk-locking is the dominant mechanism in angula r momentum evolution during the pre-main-sequence phase.