• Fudamoto, Y.
• Ferrara, A.
• Smit, R.
• Bouwens, R.
• Pallottini, Andrea
• Gonzalez, V.
• Algera, H. S. B.
• Bremer, J.
• Riechers, D.
• Bowler, R. A. A.
• Stark, D.
• Schneider, R.
• Stefanon, M.
• Sommovigo, L.
• Da Cunha, E.
• Dayal, P.
• Inami, H.
• Oesch, P. A.
• Graziani, Luca
• Aravena, M.
• Endsley, R.
• De Looze, I.
• Hodge, J.
• Kobayashi, C.
• Schouws, S.

Abstract

We include a fully coupled treatment of metal and dust enrichment into the DELPHI semi-analytic model of galaxy formation to explain the dust content of 13 Lyman break galaxies (LBGs) detected by the Atacama Large millimetre Array (ALMA) REBELS Large Program at z ≃ 7. We find that the galaxy dust mass, M<SUB>d</SUB>, is regulated by the combination of Type II supernova dust production, astration, shock destruction, and ejection in outflows; grain growth (with a standard time-scale τ<SUB>0</SUB> = 30 Myr) plays a negligible role. The model predicts a dust-to-stellar mass ratio of $ 0.07\!-\!0.1{{\per\ cent}}$ and a UV-to-total star formation rate relation such that log(ψ<SUB>UV</SUB>) = -0.05 [log(ψ)]<SUP>2</SUP> + 0.86 log(ψ) - 0.05 (implying that 55-80 per cent of the star formation is obscured) for REBELS galaxies with stellar mass $M_* = 10^{9}\!-\!10^{10}M_$. This relation reconciles the intrinsic UV luminosity of LBGs with their observed luminosity function at z = 7. However, 2 out of the 13 systems show dust-to-stellar mass ratios ($ 0.94\!-\!1.1{{\per\ cent}}$) that are up to 18 times larger than expected from the fiducial relation. Due to the physical coupling between dust and metal enrichment, even decreasing τ<SUB>0</SUB> to very low values (0.3 Myr) only increases the dust-to-stellar mass ratio by a factor of ~2. Given that grain growth is not a viable explanation for such high observed ratios of the dust-to-stellar mass, we propose alternative solutions....

Topics

• impedance spectroscopy
• grain
• grain growth