Predicting the global far-infrared SED of galaxies via machine learning
  techniques
  Dust plays an important role in shaping a galaxy's spectral energy
distribution (SED). It absorbs ultraviolet (UV) to near-infrared (NIR)
radiation and re-emits this energy in the far-infrared (FIR). The FIR is
essential to understand dust in galaxies. However, deep FIR observations
require a space mission, none of which are still active today. We aim to infer
the FIR emission across six Herschel bands, along with dust luminosity, mass,
and effective temperature, based on the available UV to mid-infrared (MIR)
observations. We also want to estimate the uncertainties of these predictions,
compare our method to energy balance SED fitting, and determine possible
limitations of the model. We propose a machine learning framework to predict
the FIR fluxes from 14 UV-MIR broadband fluxes. We used a low redshift sample
by combining DustPedia and H-ATLAS, and extracted Bayesian flux posteriors
through SED fitting. We trained shallow neural networks to predict the
far-infrared fluxes, uncertainties, and dust properties. We evaluated them on a
test set using a root mean square error (RMSE) in log-space. Our results (RMSE
= 0.19 dex) significantly outperform UV-MIR energy balance SED fitting (RMSE =
0.38 dex), and are inherently unbiased. We can identify when the predictions
are off, for example when the input has large uncertainties on WISE 22, or when
the input does not resemble the training set. The galaxies for which we have
UV-FIR observations can be used as a blueprint for galaxies that lack FIR data.
This results in a 'virtual FIR telescope', which can be applied to large
optical-MIR galaxy samples. This helps bridge the gap until the next FIR
mission.
