Hiroyuki Hirashita (ASIAA); Denis Burgarella (LAM); Rychard J. Bouwens (Leiden Observatory)
We aim at constraining the dust mass in high-z (here, high z means redshifts typically higher than 5) galaxies using the upper limits obtained by Atacama Large Millimetre/submillimetre Array (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 Lyman break galaxies (LBGs). For Himiko, Model A requires a significant dust extinction, which leads to a dust temperature higher than ~70 K for consistency with the ALMA upper limit. This high dust temperature puts a strong upper limit on the total dust mass (2e6 solar masses, Msun), and the dust mass produced per supernova (SN), md smaller than 0.1 Msun. Such a low md 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 dust mass 2e7 Msun and md ∼ 0.3 Msun. We could distinguish between Models A and B if we observe Himiko at wavelength shorter than 1.2 mm by ALMA. For the LBG sample, we obtain dust mass smaller than 2e6 Msun for a typical LBG at z > 5, but this only puts an upper limit for md as ∼2 Msun. This clarifies the importance of observing UV-bright objects (like Himiko) to constrain the dust production by SNe.