Are classification metrics good proxies for SN Ia cosmological constraining power?

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Main Authors: Malz, Alex I., Dai, Mi, Ponder, Kara A., Ishida, Emille E. O., Gonzalez-Gaitain, Santiago, Durgesh, Rupesh, Krone-Martins, Alberto, de Souza, Rafael S., Kennamer, Noble, Sreejith, Sreevarsha, Galbany, Lluis, Collaboration, The LSST Dark Energy Science, Initiative, The Cosmostatistics
Format: Preprint
Published: 2023
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author Malz, Alex I.
Dai, Mi
Ponder, Kara A.
Ishida, Emille E. O.
Gonzalez-Gaitain, Santiago
Durgesh, Rupesh
Krone-Martins, Alberto
de Souza, Rafael S.
Kennamer, Noble
Sreejith, Sreevarsha
Galbany, Lluis
Collaboration, The LSST Dark Energy Science
Initiative, The Cosmostatistics
author_facet Malz, Alex I.
Dai, Mi
Ponder, Kara A.
Ishida, Emille E. O.
Gonzalez-Gaitain, Santiago
Durgesh, Rupesh
Krone-Martins, Alberto
de Souza, Rafael S.
Kennamer, Noble
Sreejith, Sreevarsha
Galbany, Lluis
Collaboration, The LSST Dark Energy Science
Initiative, The Cosmostatistics
contents Context: When selecting a classifier to use for a supernova Ia (SN Ia) cosmological analysis, it is common to make decisions based on metrics of classification performance, i.e. contamination within the photometrically classified SN Ia sample, rather than a measure of cosmological constraining power. If the former is an appropriate proxy for the latter, this practice would save those designing an analysis pipeline from the computational expense of a full cosmology forecast. Aims: This study tests the assumption that classification metrics are an appropriate proxy for cosmology metrics. Methods: We emulate photometric SN Ia cosmology samples with controlled contamination rates of individual contaminant classes and evaluate each of them under a set of classification metrics. We then derive cosmological parameter constraints from all samples under two common analysis approaches and quantify the impact of contamination by each contaminant class on the resulting cosmological parameter estimates. Results: We observe that cosmology metrics are sensitive to both the contamination rate and the class of the contaminating population, whereas the classification metrics are insensitive to the latter. Conclusions: We therefore discourage exclusive reliance on classification-based metrics for cosmological analysis design decisions, e.g. classifier choice, and instead recommend optimizing using a metric of cosmological parameter constraining power.
format Preprint
id arxiv_https___arxiv_org_abs_2305_14421
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Are classification metrics good proxies for SN Ia cosmological constraining power?
Malz, Alex I.
Dai, Mi
Ponder, Kara A.
Ishida, Emille E. O.
Gonzalez-Gaitain, Santiago
Durgesh, Rupesh
Krone-Martins, Alberto
de Souza, Rafael S.
Kennamer, Noble
Sreejith, Sreevarsha
Galbany, Lluis
Collaboration, The LSST Dark Energy Science
Initiative, The Cosmostatistics
Cosmology and Nongalactic Astrophysics
Instrumentation and Methods for Astrophysics
Context: When selecting a classifier to use for a supernova Ia (SN Ia) cosmological analysis, it is common to make decisions based on metrics of classification performance, i.e. contamination within the photometrically classified SN Ia sample, rather than a measure of cosmological constraining power. If the former is an appropriate proxy for the latter, this practice would save those designing an analysis pipeline from the computational expense of a full cosmology forecast. Aims: This study tests the assumption that classification metrics are an appropriate proxy for cosmology metrics. Methods: We emulate photometric SN Ia cosmology samples with controlled contamination rates of individual contaminant classes and evaluate each of them under a set of classification metrics. We then derive cosmological parameter constraints from all samples under two common analysis approaches and quantify the impact of contamination by each contaminant class on the resulting cosmological parameter estimates. Results: We observe that cosmology metrics are sensitive to both the contamination rate and the class of the contaminating population, whereas the classification metrics are insensitive to the latter. Conclusions: We therefore discourage exclusive reliance on classification-based metrics for cosmological analysis design decisions, e.g. classifier choice, and instead recommend optimizing using a metric of cosmological parameter constraining power.
title Are classification metrics good proxies for SN Ia cosmological constraining power?
topic Cosmology and Nongalactic Astrophysics
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2305.14421