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SUMMARY:The dawn of star formation:  a local perspective - Piercarlo Bonif
 acio (Observatoire de Paris\, France)
DTSTART:20160209T140000Z
DTEND:20160209T150000Z
UID:TALK63876@talks.cam.ac.uk
CONTACT:Greg Willatt
DESCRIPTION:At the end of the Dark Ages gravity began to make matter colla
 pse around over-densities\, resulting in the formation of the first stars\
 , the Pop III.  These stars are very important in the cosmological context
 \, the most massive ones contributed ionising photons that played a role i
 n the reionisation of the Universe and synthetized the first metals.  We k
 now that the formation mode of these first stars was different than the on
 e operating today.  The lack of metals implies it is difficult to cool a c
 ontracting cloud\, which would argue for a preferential formation of massi
 ve or very massive stars.  However from the theoretical point of view it i
 s not yet possible to determine the initial mass function of the first sta
 rs. Simulations show that\, even in the absence of metals\, a collapsing c
 loud may fragment into smaller clouds giving rise to stars that span a ran
 ge of masses\, even sub-solar.  Once the first metals begin to be shed in 
 the clouds cooling becomes possible\, either through atomic lines or throu
 gh dust.  It is likely that there is a transition from Pop III to ‘norma
 l’ Pop II star formation at some critical metallicity\, however the prec
 ise value of this critical metallicity cannot be presently determined theo
 retically.\n   In this seminar I will describe the observational efforts t
 hat our group is conducting in the local Universe in order to derive as ma
 ny constraints as possible on the nature of the Pop III stars.  These incl
 ude searches of the most metal-poor stars\, and their chemical characteris
 ation.  Both the metallicity distribution function and the chemical patter
 n of the most metal-poor stars contain precious information of the first s
 tars.\n
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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