Transcript Significant age range in massive star cluster excluded by tight sub

Significant age range in massive star cluster
excluded by tight sub-giant-branch morphology
Chengyuan Li
Richard de Grijs
Licai Deng
Science lead the way.
以化成天下。
Multiple stellar populations in Magellanic Cloud clusters,
an ordinary feature for intermediate age globulars in the LMC?
--- Milone et al.2009
~300 Myr age spread
Multiple stellar populations in Magellanic Cloud clusters,
an ordinary feature for intermediate age globulars in the LMC?
--- Milone et al.2009
NGC 1868: 320 Myr age spread
Li et al. 2014
How to detect multiple stellar populations in
Galactic Globular Clusters?
•
•
•
•
•
Multiple or Broadened
Main Sequence(s),
Sub-giant branch(es),
Red-giant branch(es)
Horizontal-branch(es)
Omega-Centauri:
Villanova et al.2007
Extended Main-Sequence Turn-Off should link to
a broadened Sub-giant-branch, but where is it?
NGC 1651: Li et al. 2014, Nature, accepted
Extended Main-Sequence Turn-Off should link to
a broadened Sub-giant-branch, but where is it?
Age spread: 450 Myr (eMSTO), SSP (SGB)
NGC 1651: Li et al. 2014, Nature, accepted
Is this feature unique for NGC 1651?
NGC 2155
SL 674
Piatta et al. 2014
Multiple stellar populations in Magellanic Cloud clusters,
an ordinary feature for intermediate age globulars in the LMC?
--- Milone et al.2009
Single stellar population suggested by tight sub-giant-branch,
an ordinary feature for intermediate age globulars in the LMC?
--- Li et al.2014
Questions:
Why sub-giant-branch is ideal?
1, It direct link to turn-off region.
2, It easy to learn, do not experience significant mass loss.
3, It ideally get rid of the effect from fast rotating.
Narrow sub-giant-branch  ideal single stellar population
Why there is no one found this feature for a long time? (set by Luis)
1, Not every clusters show clear sub-giant-branch.
2, Bias.
3, People already began action (Nate Bastian group, 2014, prepare to submit)
The Significance:
1, Single stellar population still hold for
intermediate-age star clusters.
2, No additional physics is needed to prevent
gas from collapsing into star forming.
3, No need for us to expect a tremendous
massive origin.
4, Stellar rotating seems important for
intermediate-age star clusters.
Thanks!
Science lead the way.
以化成天下。