A Caltech Library Service

Ensemble photometric redshifts

Padmanabhan, Nikhil and White, Martin and Chang, Tzu-Ching and Cohn, J. D. and Doré, Olivier and Holder, Gil (2019) Ensemble photometric redshifts. . (Unpublished)

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


Upcoming imaging surveys, such as LSST, will provide an unprecedented view of the Universe, but with limited resolution along the line-of-sight. Common ways to increase resolution in the third dimension, and reduce misclassifications, include observing a wider wavelength range and/or combining the broad-band imaging with higher spectral resolution data. The challenge with these approaches is matching the depth of these ancillary data with the original imaging survey. However, while a full 3D map is required for some science, there are many situations where only the statistical distribution of objects (dN/dz) in the line-of-sight direction is needed. In such situations, there is no need to measure the fluxes of individual objects in all of the surveys. Rather a stacking procedure can be used to perform an `ensemble photo-z'. We show how a shallow, higher spectral resolution survey can be used to measure dN/dz for stacks of galaxies which coincide in a deeper, lower resolution survey. The galaxies in the deeper survey do not even need to appear individually in the shallow survey. We give a toy model example to illustrate tradeoffs and considerations for applying this method. This approach will allow deep imaging surveys to leverage the high resolution of spectroscopic and narrow/medium band surveys underway, even when the latter do not have the same reach to high redshift.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Doré, Olivier0000-0002-5009-7563
Additional Information:NP is supported in part by DOE de-sc0008080. T.-C. C. acknowledges support from MoST grant 103-2112-M- 001-002-MY3 and the Simons Foundation. This work was begun and completed at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1066293. This work made extensive use of the NASA Astrophysics Data System and of the astro-ph preprint archive at 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.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0008080
Ministry of Science and Technology (Taipei)103-2112-M- 001-002-MY3
Simons FoundationUNSPECIFIED
Subject Keywords:methods: data analysis; methods: statistical; galaxies: distances and redshifts
Record Number:CaltechAUTHORS:20190930-151031132
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98971
Deposited By: Tony Diaz
Deposited On:30 Sep 2019 22:21
Last Modified:03 Oct 2019 21:46

Repository Staff Only: item control page