DenseLens - Using DenseNet ensembles and information criteria for finding and rank-ordering strong gravitational lenses

Convolutional neural networks (CNNs) are the state-of-the-art technique for identifying strong gravitational lenses. Although they are highly successful in recovering genuine lens systems with a high true-positive rate, the unbalanced nature of the data set (lens systems are rare), still leads to a high false positive rate. For these techniques to be successful in upcoming surveys (e.g. with Euclid) most emphasis should be set on reducing false positives, rather than on reducing false negatives. In this paper, we introduce densely connected neural networks (DenseNets) as the CNN architecture in a new pipeline-ensemble model containing an ensemble of classification CNNs and regression CNNs to classify and rank-order lenses, respectively. We show that DenseNets achieve comparable true positive rates but considerably lower false positive rates (when compared to residual networks; ResNets). Thus, we recommend DenseNets for future missions involving large data sets, such as Euclid, where low false positive rates play a key role in the automated follow-up and analysis of large numbers of strong gravitational lens candidates when human vetting is no longer feasible.

Automated summary

Convolutional neural networks (CNNs) are effective for identifying strong gravitational lenses, but the imbalance of the data set leads to a high false positive rate. In this paper, DenseNets are introduced as the CNN architecture in a pipeline-ensemble model, achieving comparable true positive rates with considerably lower false positive rates compared to ResNets. Hence, DenseNets are recommended for future missions involving large data sets where low false positive rates are crucial.