SERENADE. II. An ALMA Multiband Dust Continuum Analysis of 28 Galaxies at 5<z<8 and the Physical Origin of the Dust Temperature Evolution
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Date
2024
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Abstract
We present an analysis of the Atacama Large Millimeter-submillimeter Array (ALMA) multiband dust continuum observations for 28 spectroscopically confirmed bright Lyman break galaxies at 5 < z < 8. Our sample consists of 11 galaxies at z similar to 6 newly observed in our ALMA program, which substantially increases the number of 5 < z < 8 galaxies with both rest-frame 88 and 158 mu m continuum observations, allowing us to simultaneously measure the IR luminosity and dust temperature for a statistical sample of z greater than or similar to 5 galaxies for the first time. We derive the relationship between the ultraviolet (UV) slope (beta(UV)) and infrared excess (IRX) for the z similar to 6 galaxies, and find a shallower IRX-beta(UV) relation compared to the previous results at z similar to 2-4. Based on the IRX-beta(UV) relation consistent with our results and the beta(UV)-M-UV relation including fainter galaxies in the literature, we find a limited contribution of the dust-obscured star formation to the total star formation rate density, similar to 30% at z similar to 6. Our measurements of the dust temperature at z similar to 6-7, T-dust = 40.9(-9.1)(+10.0) K on average, support a gentle increase of T-dust from z = 0 to z similar to 6-7. Using an analytic model with parameters consistent with recent James Webb Space Telescope results, we discuss that the observed redshift evolution of the dust temperature can be reproduced by an similar to 0.6 dex decrease in the gas depletion timescale and similar to 0.4 dex decrease in the metallicity. The variety of T-dust observed at high redshifts can also be naturally explained by scatters around the star formation main sequence and average mass-metallicity relation including an extremely high dust temperature of T-dust > 80 K observed in a galaxy at z = 8.3.