A Roadmap to Photometric Redshifts for the LSST Object Catalog

Abstract

This roadmap guides the Rubin Observatory Data Management (DM) team’s efforts to engage with the scientific community of data-rights holders in order to validate and implement one or more existing photometric redshift (photo-z) estimators into the Data Release (DR) processing pipeline, and serve the resulting photo-z data products for the DR Object catalogs.

The DR Object catalog photo-z estimates will initially meet a set of minimum scientific attributes and serve the widest variety of science applications. DM will select one or more existing, community-vetted algorithms to generate the DR photo-z. The evaluation criteria will include technical considerations related to the DM System.

The Rubin science community has a considerable wealth of expertise in generating photo-z catalogs and will be the primary users of the DR Object catalog photo-z data products. Therefore, the evaluation, implementation, and validation of the DR Objects photo-z estimator(s) will be a joint venture between the Rubin construction team and the Rubin science community.

This roadmap is a living document to guide this joint venture, and it will evolve over time to incorporate input from the science community. The primary milestone in this roadmap is DM’s call for “Letters of Recommendation” from the science community regarding photo-z estimators (deadline 2021-09-30). From these letters, DM will generate a shortlist of community-vetted photo-z options that meet both the science community’s needs for DR Object photo-z and the technical directives of the DM System.

In support of this milestone, starting in early 2021, DM will host a series of “LSST Photo-z Virtual Forums”, discussions open to all interested people, which will focus on defining the evaluation criteria for photo-z estimators (§ [sec:eval]) and facilitating the development of “Letters of Recommendation” (§ [sec:lor]). Further on in this roadmap DM will facilitate science community participation in a “Photo-z Validation Cooperative” based on commissioning data for the shortlisted estimators (§ [sec:pzcoop]; dates TBD).

This roadmap includes possible in-kind contributions from international partnerships to Object catalog photo-z for DR1 and beyond, as well as potential processes of improving the DR Object catalog photo-z and/or federating user-generated photo-z catalogs during Rubin operations.