Abstract
Context. Over the past few years the Atacama Large Millimeter Array (ALMA) has detected dust-rich galaxies whose cold dust emission is spatially disconnected from the ultraviolet (UV) rest-frame emission. This represents a challenge for modeling their spectral energy distributions (SED) with codes based on an energy budget between the stellar and dust components. This could potentially weaken the solidity of the physical parameters measured with these modeling tools. Aims. We want to verify the validity of energy balance modeling on a sample of galaxies observed from the UV to the sub-millimeter rest frame with ALMA and decipher what information can be reliably retrieved from the analysis of the full SED and from subsets of wavelengths. Methods. We select 17 sources at z ≃ 2 in the Hubble Ultra-Deep Field (HUDF) and in the GOODS-South field detected with ALMA and Herschel and for which UV to near-infrared rest-frame ancillary data are available. We fit the data with CIGALE exploring different configurations for dust attenuation and star formation histories, considering either the full dataset or one that is reduced to the stellar and dust emission. We compare estimates of the dust luminosities, star formation rates, and stellar masses. Results. The fit of the stellar continuum alone with the starburst attenuation law can only reproduce up to 50% of the total dust luminosity observed by Herschel and ALMA. This deficit is found to be marginally consistent with similar quantities estimated in the COSMOS field and is found to increase with the specific star formation rate. The combined stellar and dust SEDs are well fitted when different attenuation laws are introduced. Shallow attenuation curves are needed for the galaxies whose cold dust distribution is very compact compared to starlight. The stellar mass estimates are affected by the choice of the attenuation law. The star formation rates are robustly estimated as long as dust luminosities are available. The large majority of the galaxies are above the average main sequence of star forming galaxies and one source is a strong starburst.
Highlights
Modeling the spectral energy distributions (SED) of galaxies is commonly used to measure some of the most important physical parameters that quantify galaxy evolution such as the star formation rate (SFR) and the stellar mass
We explore which star formation histories (SFHs) and attenuation laws are needed to fit the SED of these galaxies and to what extent the SFR and stellar masses determined from the fit, with and without the IR emission emitted by dust, are reliable
We analyze the SEDs of 17 dust-rich galaxies at z ∼ 2 detected with Atacama Large Millimeter Array (ALMA) from the blind survey conducted by Dunlop et al (2017) in the Hubble Ultra-Deep Field (HUDF) and the massive Herschel galaxies in the GOODS-South field by Elbaz et al (2018)
Summary
Modeling the spectral energy distributions (SED) of galaxies is commonly used to measure some of the most important physical parameters that quantify galaxy evolution such as the star formation rate (SFR) and the stellar mass. These SED fitting codes are all based on simplified assumptions; for example, the emission is supposed to be isotropic at all wavelengths, and the effect of dust on the stellar continuum (and nebular emission for BAGPIPES and CIGALE) is accounted for by applying an effective attenuation law This curve is either measured as for the commonly used starburst law (Calzetti et al 2000) or built to reproduce average observed trends (Charlot & Fall 2000; Lo Faro et al 2017; Cullen et al 2018). We explore which SFHs and attenuation laws are needed to fit the SED of these galaxies and to what extent the SFR and stellar masses determined from the fit, with and without the IR emission emitted by dust, are reliable With this aim in mind, we use data from the Hubble Ultra-Deep Field (HUDF; Dunlop et al 2017) GOODS-South field (Elbaz et al 2018) surveys.
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