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Precision photometric redshift calibration for galaxy-galaxy weak lensing

Mandelbaum, R. ; Seljak, U. ; Hirata, C. M. ; Bardelli, S. ; Bolzonella, M. ; Bongiorno, A. ; Carollo, M. ; Contini, T. ; Cunha, C. E. ; Garilli, B. ; Iovino, A. ; Kampczyk, P. ; Kneib, J.-P ; Knobel, C. ; Koo, D. C. ; Lamareille, F. ; Le Fèvre, O. ; Leborgne, J.-F ; Lilly, S. J. ; Maier, C. ; Mainieri, V. ; Mignoli, M. ; Newman, J. A. ; Oesch, P. A. ; Perez-Montero, E. ; Ricciardelli, E. ; Scodeggio, M. ; Silverman, J. ; Tasca, L.

In: Monthly Notices of the Royal Astronomical Society, 2008, vol. 386, no. 2, p. 781-806

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    Title
    • Precision photometric redshift calibration for galaxy-galaxy weak lensing
    Author
    • Mandelbaum, R.. Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540, USA
    • Seljak, U.. Institute for Theoretical Physics, University of Zurich, Zurich, Switzerland
    • Hirata, C. M.. Mail Code 130-33, Caltech, Pasadena, CA 91125, USA
    • Bardelli, S.. INAF Osservatorio Astronomico di Bologna, Bologna, Italy
    • Bolzonella, M.. INAF Osservatorio Astronomico di Bologna, Bologna, Italy
    • Bongiorno, A.. INAF Osservatorio Astronomico di Bologna, Bologna, Italy
    • Carollo, M.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Contini, T.. Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Toulouse, France
    • Cunha, C. E.. Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
    • Garilli, B.. INAF-IASF Milano, Milan, Italy
    • Iovino, A.. INAF Osservatorio Astronomico di Brera, Milan, Italy
    • Kampczyk, P.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Kneib, J.-P. Laboratoire d'Astrophysique de Marseille, France
    • Knobel, C.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Koo, D. C.. UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
    • Lamareille, F.. Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Toulouse, France
    • Le Fèvre, O.. Laboratoire d'Astrophysique de Marseille, France
    • Leborgne, J.-F. Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Toulouse, France
    • Lilly, S. J.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Maier, C.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Mainieri, V.. European Southern Observatory, Garching, Germany
    • Mignoli, M.. Dipartimento di Astronomia, Università degli Studi di Bologna, Bologna, Italy
    • Newman, J. A.. Physics and Astronomy Department, University of Pittsburgh, Pittsburgh, PA 15260, USA
    • Oesch, P. A.. Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093, Switzerland
    • Perez-Montero, E.. Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Toulouse, France
    • Ricciardelli, E.. Dipartimento di Astronomia, Universita di Padova, Padova, Italy
    • Scodeggio, M.. Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
    • Silverman, J.. Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
    • Tasca, L.. Laboratoire d'Astrophysique de Marseille, France
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:303080
    Summary
    Accurate photometric redshifts are among the key requirements for precision weak lensing measurements. Both the large size of the Sloan Digital Sky Survey (SDSS) and the existence of large spectroscopic redshift samples that are flux-limited beyond its depth have made it the optimal data source for developing methods to properly calibrate photometric redshifts for lensing. Here, we focus on galaxy-galaxy lensing in a survey with spectroscopic lens redshifts, as in the SDSS. We develop statistics that quantify the effect of source redshift errors on the lensing calibration and on the weighting scheme, and show how they can be used in the presence of redshift failure and sampling variance. We then demonstrate their use with 2838 source galaxies with spectroscopy from DEEP2 and zCOSMOS, evaluating several public photometric redshift algorithms, in two cases including a full p(z) for each object, and find lensing calibration biases as low as <1 per cent (due to fortuitous cancellation of two types of bias) or as high as 20 per cent for methods in active use (despite the small mean photoz bias of these algorithms). Our work demonstrates that lensing-specific statistics must be used to reliably calibrate the lensing signal, due to asymmetric effects of (frequently non-Gaussian) photoz errors. We also demonstrate that large-scale structure (LSS) can strongly impact the photoz calibration and its error estimation, due to a correlation between the LSS and the photoz errors, and argue that at least two independent degree-scale spectroscopic samples are needed to suppress its effects. Given the size of our spectroscopic sample, we can reduce the galaxy-galaxy lensing calibration error well below current SDSS statistical errors