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VERSION:2.0
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METHOD:PUBLISH
BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20081027T000000
DTEND;TZID=Atlantic/Canary:20081027T010000
UID:iactalks-80
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/80
CREATED:2008-10-27T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Relative ages of Galactic globular clusters. Clues to the Milky Way
  formation time scales
DESCRIPTION:Relative ages of Galactic globular clusters. Clues to the Milky
  Way formation time scales\nDr. Antonio Marín-Franch\n\nBased on observat
 ions with the Advanced Camera for Surveys (ACS), I will present accurate r
 elative ages for a sample of 64 Galactic globular clusters. This Hubble Sp
 ace Telescope (HST) Treasury program has been designed to provide a new la
 rge, deep and homogeneous photometric database. Relative ages have been ob
 tained using a main sequence fitting procedure between clusters in the sam
 ple. Relative ages are determined with an accuracy from 2% to 7%. It has b
 een proved that derived ages are independent of the assumed theoretical mo
 dels. The existence of two well defined Galactic globular cluster groups i
 s found. A group of old globular clusters with an age dispersion of 6% and
  showing no age-metallicity relation, and, on the other hand, a younger gr
 oup showing a clear age-metallicity relation similar to that found in the 
 globular clusters associated to the Sagittarius dwarf galaxy. Roughly 1/3 
 of the clusters belong to the younger group. Considering these new results
 , it is very tempting to suggest a Milky Way's halo formation scenario in 
 which two differentiated phases took place. A very fast collapse, where th
 e old and coeval globular clusters where formed, followed by accretions of
  Milky Way's satellite galaxies.
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