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Interloper bias in future large-scale structure surveys

Pullen, Anthony R. and Hirata, Christopher M. and Doré, Olivier and Raccanelli, Alvise (2016) Interloper bias in future large-scale structure surveys. Publications of the Astronomical Society of Japan, 68 (1). Art. No. 12. ISSN 0004-6264.

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Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter measurement bias, demonstrating that a 0.15%–0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity from upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines rescaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST Hα survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [O iii] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g., with deep training samples). These results are optimistic as the CMC does not capture the full set of correlations of galaxy properties in the real Universe, and they do not include blending effects. Mitigating interloper contamination will be crucial to the next generation of emission line surveys.

Item Type:Article
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URLURL TypeDescription Paper
Hirata, Christopher M.0000-0002-2951-4932
Doré, Olivier0000-0002-5009-7563
Additional Information:© 2015 The Author. Published by Oxford University Press on behalf of the Astronomical Society of Japan. Received 2015 August 1; Accepted 2015 November 9; First published online December 14, 2015. AP was supported by the McWilliams Fellowship of the Bruce and Astrid McWilliams Center for Cosmology. Part of the research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. AP was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by Oak Ridge Associated Universities through a contract with NASA. CH is supported by the David and Lucile Packard Foundation, the Simons Foundation, and the U.S. Department of Energy. AR is supported by the John Templeton Foundation. We thank P. Capak, D. Eisenstein, S. Ho, M. Seiffert, and M. Takada for helpful comments and useful discussions. We also thank J.-P. Kneib for his assistance with the COSMOS Mock Catalog, in particular for providing access to the Y-band photometry.
Funding AgencyGrant Number
Bruce and Astrid McWilliams Center for CosmologyUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Simons FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
John Templeton FoundationUNSPECIFIED
Subject Keywords:galaxies: distances and redshift—gravitation—large-scale structure of universe— line: identification—surveys
Issue or Number:1
Record Number:CaltechAUTHORS:20160707-125356612
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Official Citation:Anthony R. Pullen, Christopher M. Hirata, Olivier Doré, and Alvise Raccanelli Interloper bias in future large-scale structure surveys Publ Astron Soc Jpn (February 2016) 68 (1), 12, doi:10.1093/pasj/psv118 first published online December 14, 2015 (22 pages)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68892
Deposited By: Tony Diaz
Deposited On:07 Jul 2016 22:00
Last Modified:03 Oct 2019 10:17

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