Decomposition of stellar populations in CosmoDC2 galaxies using SCARLET and Deep Learning

Abstract

We are presenting a novel, Deep Learning based approach to estimate the normalized broad-band spectral energy distribution (SED) of different stellar populations in synthetic galaxies. In contrast to the non-parametric multiband source separation algorithm, SCARLET - where the SED and morphology are simultaneously fitted, in our study we provide a morphology-independent, statistical determination of the SEDs, where we only use the colour distribution of the galaxy. We developed a neural network (sedNN) that accurately predicts the SEDs of the old, red and young, blue stellar populations of realistic synthetic galaxies from the colour distribution of the galaxy-related pixels in simulated broad-band images. We trained and tested the network on a subset of the recently published CosmoDC2 simulated galaxy catalogue containing about 3600 galaxies. The model performance was compared to the results of SCARLET, where we found that sedNN can predict the SEDs with 4-5 per cent accuracy on average, which is about two times better than applying SCARLET. We also investigated the effect of this improvement on the flux determination accuracy of the bulge and disc. We found that using more accurate SEDs decreases the error in the flux determination of the components by approximately 30 per cent.