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

Poster 1K086

Rewriting the Star-Formation History of the Nearest OB Association

Mamajek, Eric E. (University of Rochester)
Pecaut, Mark J. (University of Rochester, Rockhurst University)
Nguyen, Duy C. (University of Rochester, University of Toronto)
Bubar, Eric J. (University of Rochester, Marymount University)

The Sco-Cen (Sco OB2) OB association is the nearest region of recent massive star formation to the Sun. Sco-Cen is important for understanding the star-formation history of giant molecular cloud complexes, constraining circumstellar disk evolution, and providing samples of age-dated substellar objects and imaged planetary companions. Here we summarize some recent results on the classic Sco-Cen subgroups Upper Sco (US), Upper Cen-Lup (UCL), and Lower Cen-Cru (LCC): (1) isochronal analysis of the >1 Msun stars in the Upper Scorpius subgroup shows it to be twice as old as previously thought (∼11 Myr vs. ∼5 Myr), (2) analysis of high resolution optical spectra of FGK-type Sco-Cen members are consistent with the subgroups having solar metallicity, (3) we briefly describe a new subgroup dubbed ”Lower Sco”. Lastly, we find that the disk census of Sco-Cen members taken together are consistent with a protoplanetary disk fraction e-folding decay timescale of ∼4.5 Myr. This e-folding timescale is nearly twice that inferred previously for a large sample of nearby young stellar groups (~2.5 Myr ; see review of Mamajek 2009, AIPC, 1158, 3), but is consistent with the recent findings of Bell et al. (2013, MNRAS, in press; arxiv/1306.3237), which revised the ages of several benchmark clusters older by roughly a factor of two. The near doubling of the protoplanetary disk decay timescale may have important implications for inferring the lifetimes of early evolutionary stages of protostars, as well the efficiency of formation and subsequent migrational evolution of young gas giant planets.

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