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Phenotypic redshifts with self-organizing maps: A novel method to characterize redshift distributions of source galaxies for weak lensing

Author(s): Buchs, R; Davis, C; Gruen, D; DeRose, J; Alarcon, A; et al

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Abstract: Wide-field imaging surveys such as the Dark Energy Survey (DES) rely on coarse measurements of spectral energy distributions in a few filters to estimate the redshift distribution of source galaxies. In this regime, sample variance, shot noise, and selection effects limit the attainable accuracy of redshift calibration and thus of cosmological constraints. We present a new method to combine wide-field, few-filter measurements with catalogues from deep fields with additional filters and sufficiently low photometric noise to break degeneracies in photometric redshifts. The multiband deep field is used as an intermediary between wide-field observations and accurate redshifts, greatly reducing sample variance, shot noise, and selection effects. Our implementation of the method uses self-organizing maps to group galaxies into phenotypes based on their observed fluxes, and is tested using a mock DES catalogue created from N-body simulations. It yields a typical uncertainty on the mean redshift in each of five tomographic bins for an idealized simulation of the DES Year 3 weak-lensing tomographic analysis of sigma(Delta z) = 0.007, which is a 60 per cent improvement compared to the Year 1 analysis. Although the implementation of the method is tailored to DES, its formalism can be applied to other large photometric surveys with a similar observing strategy.
Publication Date: Oct-2019
Electronic Publication Date: 9-Aug-2019
Citation: Buchs, R, Davis, C, Gruen, D, DeRose, J, Alarcon, A, Bernstein, GM, Sanchez, C, Myles, J, Roodman, A, Allen, S, Amon, A, Choi, A, Masters, DC, Miquel, R, Troxel, MA, Wechsler, RH, Abbott, TMC, Annis, J, Avila, S, Bechtol, K, Bridle, SL, Brooks, D, Buckley-Geer, E, Burke, DL, Carnero Rosell, A, Kind, M Carrasco, Carretero, J, Castander, FJ, Cawthon, R, D Andrea, CB, da Costa, LN, De Vicente, J, Desai, S, Diehl, HT, Doel, P, Drlica-Wagner, A, Eifler, TF, Evrard, AE, Flaugher, B, Fosalba, P, Frieman, J, Garcia-Bellido, J, Gaztanaga, E, Gruend, RA, Gschwend, J, Gutierrez, G, Hartley, WG, Hollowood, DL, Honscheid, K, James, DJ, Kuehn, K, Kuropatkin, N, Lima, M, Lin, H, Maia, MAG, March, M, Marshall, JL, Melchior, P, Menanteau, F, Ogando, RLC, Plazas, AA, Rykoff, ES, Sanchez, E, Scarpine, V, Serrano, S, Sevilla-Noarbe, I, Smith, M, Soares-Santos, M, Sobreira, F, Suchyta, E, Swanson, MEC, Tarle, G, Thomas, D, Vikram, V, Collaboration, DES. (2019). Phenotypic redshifts with self-organizing maps: A novel method to characterize redshift distributions of source galaxies for weak lensing. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 489 (820 - 841. doi:10.1093/mnras/stz2162
DOI: doi:10.1093/mnras/stz2162
ISSN: 0035-8711
EISSN: 1365-2966
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Pages: 820 - 841
Type of Material: Journal Article
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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