Supernova Dust Synthesis—Carbonaceous Dust in the Very Early Universe

Recent observations have revealed the spectral features of carbonaceous grains even in very distant galaxies. We develop a state-of-the-art dust synthesis code by self-consistently solving molecule and dust formation in supernova (SN) ejecta that contain various elements in different layers. With a progenitor mass 25 M⊙ and explosion energy 1052 erg, we run the following four test calculations to investigate the impact of input physics. (i) With molecule formation solved, our SN model produces 8.45 × 10−2 M⊙ carbonaceous grains. (ii) If all available C and Si were initially depleted into CO and SiO molecules, respectively, the C grain mass could be underestimated by ∼40%. In these two models producing 0.07 M⊙56 Ni without mixing fallback, a large amount of silicates (0.260 M⊙) created in O-rich layers are also ejected and likely to hide the spectral feature of carbonaceous grains. We then consider mixing fallback that can reproduce the observed elemental abundance ratios of C-normal and C-enhanced extremely metal-poor stars in the Milky Way. (iii) In the former, the mass ratio of carbonaceous to silicate grains is still small (∼0.3). However, (iv) in the latter (known as a “faint SN”), while the C grain mass is unchanged (6.78 × 10−2 M⊙), the silicate mass is reduced (9.98 × 10−3 M⊙). Therefore, we conclude that faint supernovae could be significant carbonaceous dust factories in the early Universe.