CMU DeepLens: deep learning for automatic image-based galaxy-galaxy strong lens finding

Francois Lanusse, Quanbin Ma, Nan Li, Thomas E. Collett, Chun-Liang Li, Siamak Ravanbakhsh, Rachel Mandelbaum, Barnabas Poczos

Research output: Contribution to journalArticlepeer-review

137 Downloads (Pure)


Galaxy-scale strong gravitational lensing can not only provide a valuable probe of the dark matter distribution of massive galaxies, but also provide valuable cosmological constraints, either by studying the population of strong lenses or by measuring time delays in lensed quasars. Due to the rarity of galaxy-scale strongly lensed systems, fast and reliable automated lens finding methods will be essential in the era of large surveys such as Large Synoptic Survey Telescope, Euclid and Wide-Field Infrared Survey Telescope. To tackle this challenge, we introduce CMU DeepLens, a new fully automated galaxy–galaxy lens finding method based on deep learning. This supervised machine learning approach does not require any tuning after the training step which only requires realistic image simulations of strongly lensed systems. We train and validate our model on a set of 20 000 LSST-like mock observations including a range of lensed systems of various sizes and signal-to-noise ratios (S/N). We find on our simulated data set that for a rejection rate of non-lenses of 99 per cent, a completeness of 90 per cent can be achieved for lenses with Einstein radii larger than 1.4 arcsec and S/N larger than 20 on individual g-band LSST exposures. Finally, we emphasize the importance of realistically complex simulations for training such machine learning methods by demonstrating that the performance of models of significantly different complexities cannot be distinguished on simpler simulations. We make our code publicly available at
Original languageEnglish
Pages (from-to)3895–3906
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date7 Jul 2017
Publication statusPublished - Jan 2018


  • astro-ph.IM
  • astro-ph.CO
  • astro-ph.GA


Dive into the research topics of 'CMU DeepLens: deep learning for automatic image-based galaxy-galaxy strong lens finding'. Together they form a unique fingerprint.

Cite this