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

International audienceWe aim at constraining the dust mass in high‐z (z greater than or similar to 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 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‐d less than or similar to 2 x 10(6) M‐circle dot, and the dust mass produced per supernova (SN) m(d,SN) less than or similar to 0.1 M‐circle dot. Such a low md, SN 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‐d similar to 2 x 10(7) M‐circle dot and m(d,SN) similar to 0.3 M‐circle dot. We could distinguish between Models A and B if we observe Himiko at wavelength 5, but this only puts an upper limit for m(d,SN) as similar to 2 M‐circle dot. This clarifies the importance of observing UV‐bright objects (like Himiko) to constrain the dust production by SNe