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arXiv · 1607.01824

The infrared-dark dust content of high redshift galaxies

A. Ferrara·H. Hirashita·M. Ouchi·S. Fujimoto
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Abstract

We present a theoretical model aimed at explaining the IRX-$\beta$ relation for high redshift (z >5) galaxies. Recent observations (Capak+2015; Bouwens+2016) have shown that early Lyman Break Galaxies, although characterized by a large UV attenuation (e.g. flat UV beta slopes), show a striking FIR deficit, i.e. they are "infrared-dark". This marked deviation from the local IRX-beta relation can be explained by the larger molecular gas content of these systems. While dust in the diffuse ISM attains relatively high temperatures (Td = 45 K for typical size a=0.1 um; smaller grains can reach Td = 60 K), a sizable fraction of the dust mass is embedded in dense gas, and therefore remains cold. If confirmed, the FIR deficit might represent a novel, powerful indicator of the molecular content of high-z galaxies which can be used to pre-select candidates for follow-up deep CO observations. Thus, high-z CO line searches with ALMA might be much more promising than currently thought.

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A. Ferrara, H. Hirashita, M. Ouchi, S. Fujimoto. 2016-07-06. The infrared-dark dust content of high redshift galaxies. https://doi.org/10.1093/mnras/stx1898

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