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Radiative properties of the first galaxies: rapid transition between UV and infrared bright phases

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Original languageEnglish
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Early online date10 Jul 2019
Publication statusPublished - 1 Sep 2019


Recent observations have successfully detected UV-bright and infrared-bright galaxies in the epoch of reionization. However, the origin of their radiative properties has not been understood yet. Combining cosmological hydrodynamic simulations and radiative transfer calculations, we present predictions of multiwavelength radiative properties of the first galaxies at z ∼ 6–15. Using zoom-in initial conditions, we investigate three massive galaxies and their satellites in different environment and halo masses at z = 6: Mh=2.4×1010⁠, 1.6×1011⁠, and 0.7×1012M⊙⁠. We find that most of the gas and dust are ejected from star-forming regions by supernova feedback, which allows the UV photons to escape. We show that the peak of the spectral energy distribution (SED) rapidly changes between UV and infrared wavelengths on a time-scale of ∼ 100 Myr due to intermittent star formation and feedback, and the escape fraction of UV photons fluctuates in the range of 0.2–0.8 at z < 10 with a time-averaged value of 0.3. When dusty gas covers the star-forming regions, the galaxies become bright in the observed-frame sub-millimeter wavelengths. We predict the detectability of high-z galaxies with the Atacama Large Millimeter Array (ALMA). For a sensitivity limit of 0.1mJy at 850μm⁠, the detection probability of galaxies in haloes Mh≳1011M⊙ at z ≲ 7 exceeds fifty per cent. We argue that supernova feedback can produce the observed diversity of SEDs for high-z galaxies.

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  • astro-ph.GA

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