Cosmological Origin of the Lowest Metallicity Halo Stars

Abstract

We explore the predictions of the standard hierarchical clustering scenario of galaxy formation, regarding the numbers and metallicities of PopIII stars likely to be found within our Galaxy today. By PopIII we shall be referring to stars formed at large redshift ($z>4$), with low metallicities ($[Z/Z_{\odot }]<-2.5$) and in small systems (total mass $\simlt$ $2\times 10^8{M}_{\odot }$) that are extremely sensitive to stellar feedback, and which through a prescribed merging history (Lacey & Cole 1993) end up becoming part of the Milky Way today. An analytic, extended Press-Schechter formalism is used to get the mass functions of halos which will host PopIII stars at a given redshift, and which will end up in Milky Way sized systems today. Each of these is modeled as a mini galaxy, with a detailed treatment of the dark halo structure, angular momentum distribution, final gas temperature and disk instabilities, all of which determine the fraction of the baryons which are subject to star formation. Use of new primordial metallicity stellar evolutionary models allows us to trace the history of the stars formed, give accurate estimates of their expected numbers today, and their location in $L/L_{\odot }$ vs. $T/K$ HR diagrams. A first comparison with observational data suggests that the IMF of the first stars was increasingly high mass weighted towards high redshifts, levelling off at $z\simgt 9$ at a characteristic stellar mass scale $m_s=10-15M_{\odot }$.

7 pages including figures, MNRAS in press. Replaced with final version, minnor changes suggested by the referee

References in corpus (10)

• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Forming the First Stars in the Universe: The Fragmentation of Primordial Gas
• Simulations of Pregalactic Structure Formation with Radiative Feedback
• On the Initial Mass Function of Population III Stars
• Non-parametric star formation histories for 5 dwarf spheroidal galaxies of the local group
• Evidence of self-interacting cold dark matter from galactic to galaxy cluster scales
• Simulation of primordial object formation
• Where are the First Stars now?
• Gravitational Waves Signals from the Collapse of the First Stars
• Formation of Primordial Galaxies under UV background Radiation

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