The origin of the most iron - poor star Stefania Marassi in collaboration with G. Chiaki, R. Schneider, M. Limongi, K. Omukai, T. Nozawa, A. Chieffi, N. Yoshida David Meeting Pisa october 2014

carbon-enhanced metal poor stars CEMP – r/s: mass transfer from an AGB companion in binary systems CEMP – no: metal yields from faint Pop III SNe with mixing/fallback ~ 20 % of stars with [Fe/H] 0.7 Yong et al. 2013; Norris et al [C/Fe] > 0.7 C-normal: metal yields from ordinary Pop III core- collapse SNe

the most iron-poor stars in the Galactic halo HE [Fe/H] = -5.4 Christlieb et al 02,04,08 HE [Fe/H] = -5.7 Frebel et al 05 HE [Fe/H] = SDSS J [Fe/H] = Caffau et al 11 Z ≈ Z sun Z ≈ Z sun Z ≈ Z sun Z < Z sun Norris et al. (2008) CEMP: C-enhanced metal poor stars C-normal SMSS J [Fe/H] < -7.1 Keller et al 14 Z≈ Z sun

C-normal and C-rich stars: different formation pathways? stars with [Fe/H] < -3.5 can not form through metal line-cooling The different composition in the material out of which these low-mass stars form suggest that their formation relies on two different cooling channels : fine-structure-line cooling and dust cooling Ji et al.2013 D trans = Log(10 [C/H] [O/H] ) Schneider et al dust formed in M  Pop III SN ejecta is enough to activate Dust-driven fragmentation if the D > D cr = (4.4 ± 2.0) x Both dust-cooling and fine structure cooling are relevant for low mass star formation and there is a tentative evidence that fine structure cooling and dust-cooling are mutually exclusive

D trans = Log(10 [C/H] [O/H] ) C-normal and C-rich stars: different formation pathways? Frebel et al. (2009) C-normal stars with [Fe/H] < -3.5 can not form through metal line-cooling Dust-driven fragmentation if the D > D cr = (4.4 ± 2.0) x Norris+07 forbidden zone for CII and OI cooling Caffau+11 Schneider & Omukai (2010) Schneider et al. (2012)

A single low-energy, iron-poor SN as the source of metals in SMSS J Keller et al.2014 [Fe/H]< is 30 times lower than the iron abundance in HE (Frebel star) It is the first time that the abundance patterns could be interpreted requiring a single SN event Best fit of the observed abundances in Keller et al.2014 SN explosion of a 60M  progenitor with E=1.8×10 51 erg with extensive fallback  Faint SN [Fe/H]< Z≈2.67 Z 

Faint SN progenitor Mixing and fallback model during the SN explosion internal mixing occurs up to a small region outside the mass cut a small amount of the mixed material is expelled from the star with most of it falling back into the central region Umeda & Nomoto 2002/2003 Tominaga et al. 2007

faint Pop III SN Progenitor of SMSS J Identify the SN progenitor from the observed elemental abundances Limongi & Chieffi 2012 Marassi et al. 2014

Dust formation model: classical nucleation theory Todini &Ferrara (2001), Schneider, Ferrara,Salvaterra (2004), Bianchi & Schneider ( 2007) The formation of solid particles in a gaseous medium happens when a gas becomes supersaturated. It is a two step process: -the formation of a seed clusters (monomers), that is prevented until the condensation barrier is exceeded -the growth of this clusters by accretion of other monomers we follow the formation of different solid compounds: AC (amorphous carbon) Al 2 O 3 (corundum) Fe 3 O 4 (magnetite) MgSiO 3 (enstatite) Mg 2 SiO 4 (forsterite) SiO 2 (silicon dioxide) + CO, SiO, C 2, O 2 Molecule formation and destruction

Dust formation model: updated molecular network we assume that formation/destruction of CO, SiO, C 2 and O 2 is regulated by radiative association process and bimolecular process another destruction process of CO and SiO is the impact with the energetic electrons produced by the radioactive decay of 56 Co

Impact on dust of the ejecta mixing M CO =2.15 M AC = M  3D M CO =1.44 M AC = M  1D layer A: M CO =1.27 M AC = - layer B: M CO =4.3x10 -2 M AC = 0.11

Impact on dust of the reverse shock mass of dust that survives for increasing shock strengths depending on progenitor the fraction of surviving dust is between a few to 80%

The birth environment of SMSS J One-zone semi-analytic collapse calculation to follow the temperature evolution of the cloud polluted by a single SN Chiaki et al fragmentation due to line cooling fragmentation due to dust

prediction vs observations:C - normal and C - rich C-normal star: enriched by normal Pop III SN with silicate dust C-normal star: enriched by normal Pop III SN with silicate dust C-rich star: enriched by faint Pop III SN with carbon dust D TRANS Critical transition discriminant for fine-structure line cooling Frebel et al Range of critical [Si/H] cr abundances to activate dust cooling Chiaki et al Range of critical [C/H] cr abundances to activate dust cooling Marassi et al.2014

Critical conditions in terms of the dust - to - gas ratio Critical dust-to-gas-ratio for dust cooling D cr =[ ]x10 -9 Schneider et al C - normal and C - rich stars populate the region of the plane: the two critical conditions are not mutually exclusive

work in progress…a complete database of dust from Pop III SNe Pop III ordinary core-collapse dust grid

faint Pop III calibrated on 4 iron-poor stars AC [ – 0.3]M 

summarizing We estimate metal yields and dust produced in faint Pop III SN explosions fitting the elemental abundances on the surface of SMSS J Faint Pop III SNe produce dust, but contrary to ordinary core- collapse SNe, only AC forms in the ejecta The amount of dust formed depends on the reverse shock strenght and on mixing efficiency The formation of SMSS J may have been triggered by dust cooling and fragmentation C - normal and C - rich stars may have followed a common formation pathway We are building a complete dust database from Pop III SNe Thanks for you attention