Supernova dust synthesis --- Carbonaceous dust in the very early universe
Recent observations have revealed the spectral feature of carbonaceous grains even in a very distant galaxy. 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 $25~M_{\odot}$ and explosion energy $10^{52}$ erg, we run the following four test calculations to investigate the impact of input physics. (i) With molecule formation solved, our SN model produces $8.45\times 10^{-2}~M_{\odot}$ 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 $\sim 40\%$. In these two models producing $0.07~M_{\odot}$ $^{56}$Ni without mixing fallback, a large amount of silicates ($0.260~M_{\odot}$) 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 ($\sim 0.3$). However, (iv) in the latter (known as a ``faint SN''), while the C grain mass is unchanged ($6.78\times 10^{-2}~M_{\odot}$), the silicate mass is reduced ($9.98\times 10^{-3}~M_{\odot}$). Therefore, we conclude that faint SNe can be a significant carbonaceous dust factory in the early Universe.