Today we step back and Hans runs The Big Questions past us.
It is always good to think about the Big Picture.
- Most likely scenario for cluster formation:
- a) compressed/triggered initial conditions: cloud collisions or intersecting shells, or
- b) did globular clusters form as nuclei in dwarf galaxies that got accreted by our MW (dE,N hypothesis), or
- c) scaled-up version of open cluster formation in mol. clouds? (Pudritz papers, Krumholz talk); the role of high pressure?
- Relation of halo stars and globular cluster destruction ... (are Pop II stars dissolved globular clusters or something else?) How much of their original mass do globular clusters retain?
- Why are there no globular clusters with metallicity [Fe/H] = -3 but halo stars with [Fe/H] = -5. Top-heavy IMF for lower [Fe/H]? Why are globular cluster populations so extremely well mixed?
- Did globular clusters have an ordinary IMF (ratio low/high m) like open clusters today? IMF of multiple populations the same? How did stellar dynamics and cluster evolution change the IMF?
- Did the binary properties at birth differ in globular clusters from those of current open clusters and if so why? mass-dep.? What are the observed binary properties of Pop II halo stars?
- How to explain the origin of the multiple stellar populations? (Piotto, d'Antona, etc), is high-He pop. due to AGB enrichment? How much gas and dust has been shed and lost causing expansion?
- Are young high-z globular clusters sites for GRB? observable? Is there enough time for O-stars to collide in protoglobulars? Are runaway collisions possible in a mass-segregated cluster?
- How many stellar mass BHs should a typical GC contain today? what about an intermediate mass BH in the very dense center?
- Is 30 Doradus or Westerlund 1 a protoglobular cluster? mass? core radius, surface brightness profile, binary fraction?
- Globular cluster systems, specific frequency (number/lum.); what are the most important trends with their host galaxies?
Hans Zinnecker Feb. 10, 2009, KITP, Santa Barbara
We don't get to go home until we have answered these.
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