Dust masses of $z>5$ galaxies from SED fitting and ALMA upper limits

We aim at constraining the dust mass in high-redshift ($z\gtrsim 5$) galaxies using the upper limits obtained by ALMA in combination with the rest-frame UV–optical spectral energy distributions (SEDs). For SED fitting, because of degeneracy between dust extinction and stellar age, we focus on two extremes: continuous star formation (Model A) and instantaneous star formation (Model B). We apply these models to Himiko (as a representative UV-bright object) and a composite SED of $z>5$ Lyman break galaxies (LBGs). For Himiko, Model A requires a significant dust extinction, which leads to a high dust temperature $>70$ K for consistency with the ALMA upper limit. This high dust temperature puts a strong upper limit on the total dust mass $M_$\mathrm{d}$\lesssim 2\times 10^6$M${\odot}$,andthedustmassproducedpersupernova(SN)$m$\mathrm{d},\mathrm{S}\mathrm{N}$\lesssim 0.1$M${\odot}$\mathrm{.}Suchalow$m$\mathrm{d},\mathrm{S}\mathrm{N}$$ suggests significant loss of dust by reverse shock destruction or outflow, and implies that SNe are not the dominant source of dust at high $z$. Model B allows $M_{\mathrm{d}}\sim 2\times {10}^7$ M${}_{\odot }$ and $m_$\mathrm{d},\mathrm{S}\mathrm{N}$\sim 0.3$M$_{\odot}$.} We could distinguish between Models A and B if we observe Himiko at {wavelength $<$ 1.2 mm by ALMA. For the LBG sample, we obtain $M_{\mathrm{d}}\lesssim 2\times {10}^6$ M${}_{\odot }$ for a typical LBG at $z>5$, but this only puts an upper limit for $m_{\mathrm{d},\mathrm{S}\mathrm{N}}$ as $\sim 2$ M${}_{\odot }$. This clarifies the importance of observing UV-bright objects (like Himiko) to constrain the dust production by SNe.