2017ApJ...840...28K

We analyze the intrinsic flux ratios of various visible-near-infrared filters with respect to 3.5 µm for simple and composite stellar populations (CSPs), and their dependence on age, metallicity, and star formation history (SFH). UV/optical light from stars is reddened and attenuated by dust, where different sightlines across a galaxy suffer varying amounts of extinction. Tamura et al. (2009) developed an approximate method to correct for dust extinction on a pixel-by-pixel basis, dubbed the "β_V" method, by comparing the observed flux ratio to an empirical estimate of the intrinsic ratio of visible and ∼3.5 µm data. Through extensive modeling, we aim to validate the "β_V" method for various filters spanning the visible through near-infrared wavelength range, for a wide variety of simple and CSPs. Combining Starburst99 and BC03 models, we built spectral energy distributions (SEDs) of simple (SSP) and composite (CSP) stellar populations for various realistic SFHs, while taking metallicity evolution into account. We convolve various 0.44-1.65 µm filter throughput curves with each model SED to obtain intrinsic flux ratios β_λ,0_. When unconstrained in redshift, the total allowed range of β_V,0 is 0.6-4.7, or almost a factor of eight. At known redshifts, and in particular at low redshifts (z <= 0.01), β_V,0 is predicted to span a narrow range of 0.6-1.9, especially for early-type galaxies (0.6-0.7), and is consistent with observed β_V values. The β_λ method can therefore serve as a first-order dust-correction method for large galaxy surveys that combine JWST (rest-frame 3.5 µm) and HST (rest-frame visible-near-IR) data.