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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20120126T000000
DTEND;TZID=Atlantic/Canary:20120126T010000
UID:iactalks-365
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/365
CREATED:2012-01-26T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:The Star Formation & Chemical Evolution timescales of two nearby dw
 arf spheroidal galaxies 
DESCRIPTION:The Star Formation & Chemical Evolution timescales of two nearb
 y dwarf spheroidal galaxies \nMr. Thomas de Boer\n\nWe present the detaile
 d Star Formation History of the nearby  Sculptor and Fornax dwarf spheroid
 al galaxies, from wide-field  photometry of resolved stars, going down to 
 the oldest Main Sequence  Turn-Off. The accurately flux calibrated, wide-f
 ield Colour-Magnitude  Diagrams are used directly in combination with spec
 troscopic  metallicities of individual RGB stars to constrain the ages of 
 different  stellar populations, and derive the Star Formation History with
   particular accuracy. The detailed Star Formation History shows the star 
 formation at  different ages and metallicities, at different positions in 
 the galaxy,  and shows that the known metallicity gradients are well match
 ed to an  age gradient. The obtained SFH is used to determine accurate age
   estimates for individual RGB stars, for which spectroscopic abundances  
 (alpha-elements, r- and s-process elements) are known. In this way, we  ob
 tain the accurate age-metallicity relation of each galaxy, as well as  the
  temporal evolution of alpha-element abundances. This allows us to study, 
 for the first time, the timescale of chemical  evolution in these two dwar
 f galaxies, and determine an accurate age of  the "knee" in the alpha-elem
 ent distribution. Finally, we compare the  timescale of chemical evolution
  in both dwarf galaxies, and determine  whether the chemical abundance pat
 terns seen in galaxies with recent  episodes of star formation are a direc
 t continuation of those with only  old populations.
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