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)
Abstract:
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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