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Title: Redshift inference from the combination of galaxy colours and clustering in a hierarchical Bayesian model – Application to realistic N -body simulations

Abstract

ABSTRACT Photometric galaxy surveys constitute a powerful cosmological probe but rely on the accurate characterization of their redshift distributions using only broad-band imaging, and can be very sensitive to incomplete or biased priors used for redshift calibration. A hierarchical Bayesian model has recently been developed to estimate those from the robust combination of prior information, photometry of single galaxies, and the information contained in the galaxy clustering against a well-characterized tracer population. In this work, we extend the method so that it can be applied to real data, developing some necessary new extensions to it, especially in the treatment of galaxy clustering information, and we test it on realistic simulations. After marginalizing over the mapping between the clustering estimator and the actual density distribution of the sample galaxies, and using prior information from a small patch of the survey, we find the incorporation of clustering information with photo-z’s tightens the redshift posteriors and overcomes biases in the prior that mimic those happening in spectroscopic samples. The method presented here uses all the information at hand to reduce prior biases and incompleteness. Even in cases where we artificially bias the spectroscopic sample to induce a shift in mean redshift of $$\Delta \bar{z} \approx 0.05,$$ the final biases in the posterior are $$\Delta \bar{z} \lesssim 0.003.$$ This robustness to flaws in the redshift prior or training samples would constitute a milestone for the control of redshift systematic uncertainties in future weak lensing analyses.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [2]; ORCiD logo [1]
  1. Institut d’Estudis Espacials de Catalunya (IEEC), E-08193 Barcelona, Spain, Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, E-08193 Barcelona, Spain
  2. Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104, USA
Publication Date:
Research Org.:
Univ. of Pennsylvania, Philadelphia, PA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1664504
Alternate Identifier(s):
OSTI ID: 1851033
Grant/Contract Number:  
SC0007901
Resource Type:
Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 498 Journal Issue: 2; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; astronomy & astrophysics; cosmology: observations; dark energy; large-scale structure of Universe

Citation Formats

Alarcon, Alex, Sánchez, Carles, Bernstein, Gary M., and Gaztañaga, Enrique. Redshift inference from the combination of galaxy colours and clustering in a hierarchical Bayesian model – Application to realistic N -body simulations. United Kingdom: N. p., 2020. Web. doi:10.1093/mnras/staa2478.
Alarcon, Alex, Sánchez, Carles, Bernstein, Gary M., & Gaztañaga, Enrique. Redshift inference from the combination of galaxy colours and clustering in a hierarchical Bayesian model – Application to realistic N -body simulations. United Kingdom. https://doi.org/10.1093/mnras/staa2478
Alarcon, Alex, Sánchez, Carles, Bernstein, Gary M., and Gaztañaga, Enrique. Mon . "Redshift inference from the combination of galaxy colours and clustering in a hierarchical Bayesian model – Application to realistic N -body simulations". United Kingdom. https://doi.org/10.1093/mnras/staa2478.
@article{osti_1664504,
title = {Redshift inference from the combination of galaxy colours and clustering in a hierarchical Bayesian model – Application to realistic N -body simulations},
author = {Alarcon, Alex and Sánchez, Carles and Bernstein, Gary M. and Gaztañaga, Enrique},
abstractNote = {ABSTRACT Photometric galaxy surveys constitute a powerful cosmological probe but rely on the accurate characterization of their redshift distributions using only broad-band imaging, and can be very sensitive to incomplete or biased priors used for redshift calibration. A hierarchical Bayesian model has recently been developed to estimate those from the robust combination of prior information, photometry of single galaxies, and the information contained in the galaxy clustering against a well-characterized tracer population. In this work, we extend the method so that it can be applied to real data, developing some necessary new extensions to it, especially in the treatment of galaxy clustering information, and we test it on realistic simulations. After marginalizing over the mapping between the clustering estimator and the actual density distribution of the sample galaxies, and using prior information from a small patch of the survey, we find the incorporation of clustering information with photo-z’s tightens the redshift posteriors and overcomes biases in the prior that mimic those happening in spectroscopic samples. The method presented here uses all the information at hand to reduce prior biases and incompleteness. Even in cases where we artificially bias the spectroscopic sample to induce a shift in mean redshift of $\Delta \bar{z} \approx 0.05,$ the final biases in the posterior are $\Delta \bar{z} \lesssim 0.003.$ This robustness to flaws in the redshift prior or training samples would constitute a milestone for the control of redshift systematic uncertainties in future weak lensing analyses.},
doi = {10.1093/mnras/staa2478},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 2,
volume = 498,
place = {United Kingdom},
year = {Mon Aug 17 00:00:00 EDT 2020},
month = {Mon Aug 17 00:00:00 EDT 2020}
}

Journal Article:
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https://doi.org/10.1093/mnras/staa2478

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