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SUMMARY:Star Formation at Very Low Metallicity - Anne-Katharina Jappsen\, 
 Cardiff
DTSTART:20100204T163000Z
DTEND:20100204T173000Z
UID:TALK20944@talks.cam.ac.uk
CONTACT:scott chapman
DESCRIPTION:In cold dark matter cosmological models\, the first stars to f
 orm are believed to do\nso within small\nprotogalaxies. We wish to underst
 and how the evolution of these early protogalaxies\nchanges once the\ngas 
 forming them has been enriched with small quantities of heavy elements\, w
 hich\nare produced and\ndispersed into the intergalactic medium by the fir
 st supernovae. We use\nhigh-resolution hydrodynamic\nsimulations that inco
 rporate the effects of the appropriate chemical and thermal\nprocesses. \n
 Our initial conditions represent protogalaxies forming within a fossil HII
  region\, a\npreviously\nionized region that has not yet had time to cool 
 and recombine. We study the\ninfluence of low levels\nof metal enrichment 
 on the cooling and collapse of ionized gas in small\nprotogalactic halos u
 sing\nthree-dimensional\, smoothed particle hydrodynamics simulations with
  particle\nsplitting. \nIn the centrally condensed potential that we study
  here\, a wide variety of initial\nconditions for\nthe gas yield a monolit
 hic central collapse. Our models show no fragmentation during\ncollapse to
 \nnumber densities as high as 10^5 cm^â^È^Ò3 for metallicities reaching
  as high as\n10^â^È^Ò1 Z_sun\, far above\nthe threshold suggested by pr
 evious work. We therefore argue that fragmentation at\nmoderate density\nd
 epends on the initial conditions for star formation more than on the metal
 \nabundances present.\n\n
LOCATION:Sackler Lecture Theatre\, IoA (tea at 4:00 pm)
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