Geometry-effects-on-dust-attenuation-curves-with-different-grain-sources-at-high-redshift

Dust has been detected in high-redshift ($z>5$) galaxies but its origin is still being debated. Dust production in high-redshift galaxies could be dominated by stellar production or accretion (dust growth) in the interstellar medium. Previous studies have shown that these two dust sources predict different grain size distributions, corresponding to vastly different extinction curves.In this paper, we investigate how the dust attenuation curves predicted by the above extinction curves could be modulated by various radiation transfer effects. To investigate the major effects of dust--stars distribution geometry, we investigate two representative cases: the well-mixed geometry (star and dust are homogeneously mixed) and the two-layer geometry (young stars are more concentrated in the centre) under a spherical symmetry.In both cases, we confirmed that the steepening (by scattering and differential extinctions between young and old stellar populations) and flattening (by the existence of unobscured stellar population) effects drastically modify the attenuation curves. We could reproduce similar attenuation curves even with very different extinction curves. Thus, we conclude that it is difficult to distinguish the dust sources only with attenuation curves. However, if we include information on dust emission and construct the so-called IRX--$\beta$ diagram, a wider area covered by the observational data is more easily explained if dust sources are dominated by dust growth.