Using Host Galaxy Photometric Redshifts to Improve Cosmological Constraints with Type Ia Supernova in the LSST Era

Ayan Mitra; Renee Hlozek; Richard Kessler; Surhud More; The LSST Dark Energy Science Collaboration

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Using Host Galaxy Photometric Redshifts to Improve Cosmological Constraints with Type Ia Supernova in the LSST Era

Ayan Mitra, Richard Kessler, Surhud More, Renee Hlozek, The LSST Dark Energy Science Collaboration

Cosmology and Nongalactic Astrophysics · Submitted 14 Oct 2022

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim Compared to using the zspec subset, including events with SN+host photo-z results in i) more precise distances for z>0.5, ii) a Hubble diagram that extends 0.3 further in redshift, and iii) a 50 % increase in the Dark Energy Task Force figure of merit (FoM) based on the w0-wa CDM model.

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arXiv ID2210.07560 (version 2)

Pith IDS5E7EPU7, Pith's permanent record of this paper and its review

CitationAyan Mitra, Renee Hlozek, Richard Kessler, Surhud More, The LSST Dark Energy Science Collaboration. "Using Host Galaxy Photometric Redshifts to Improve Cosmological Constraints with Type Ia Supernova in the LSST Era." arXiv:2210.07560 (2022). https://pith.science/paper/S5E7EPU7

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What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.90 · human participants 0.01 · controlled comparison 0.95 · randomized assignment 0.03 · states quantitative result 0.98 · compares with prior results 0.96 · mentions code or data availability 0.02.

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We perform a rigorous cosmology analysis on simulated type Ia supernovae (SN~Ia) and evaluate the improvement from including photometric host-galaxy redshifts compared to using only the "zspec" subset with spectroscopic redshifts from the host or SN. We use the Deep Drilling Fields (~50 deg^2) from the Photometric LSST Astronomical Time-Series Classification Challenge (PLaSTiCC), in combination with a low-z sample based on Data Challenge2 (DC2). The analysis includes light curve fitting to standardize the SN brightness, a high-statistics simulation to obtain a bias-corrected Hubble diagram, a statistical+systematics covariance matrix including calibration and photo-z uncertainties, and cosmology fitting with a prior from the cosmic microwave background. Compared to using the zspec subset, including events with SN+host photo-z results in i) more precise distances for z>0.5, ii) a Hubble diagram that extends 0.3 further in redshift, and iii) a 50 % increase in the Dark Energy Task Force figure of merit (FoM) based on the w0-wa CDM model. Analyzing 25 simulated data samples, the average bias on w0 and wa is consistent with zero. The host photo-z systematic of 0.01 reduces FoM by only 2 % because i) most z<0.5 events are in the zspec subset, ii) the combined SN+host photo-z has X 2 smaller bias, and iii) the anti-correlation between fitted redshift and color self corrects distance errors. To prepare for analysing real data, the next SNIa-cosmology analysis with photo-z's should include non SN-Ia contamination and host galaxy mis-associations.

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What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We perform a rigorous cosmology analysis on simulated type Ia supernovae (SN~Ia) and evaluate the improvement from including photometric host-galaxy redshifts compared to using only the "zspec" subset with spectroscopic redshifts from the host or SN.	contribution 1.00	0.95	0.09	asserted 0.96
s1	We use the Deep Drilling Fields (~50 deg^2) from the Photometric LSST Astronomical Time-Series Classification Challenge (PLaSTiCC), in combination with a low-z sample based on Data Challenge2 (DC2).	method 1.00	0.75	0.02	asserted 0.97
s2	The analysis includes light curve fitting to standardize the SN brightness, a high-statistics simulation to obtain a bias-corrected Hubble diagram, a statistical+systematics covariance matrix including calibration and photo-z uncertainties, and cosmology fitting with a prior from the cosmic microwave background.	method 1.00	0.93	0.03	asserted 0.97
s3	Compared to using the zspec subset, including events with SN+host photo-z results in i) more precise distances for z>0.5, ii) a Hubble diagram that extends 0.3 further in redshift, and iii) a 50 % increase in the Dark Energy Task Force figure of merit (FoM) based on the w0-wa CDM model.	result 1.00	0.95	0.88	asserted 1.00
s4	Analyzing 25 simulated data samples, the average bias on w0 and wa is consistent with zero.	result 1.00	0.96	0.05	asserted 0.51
s5	The host photo-z systematic of 0.01 reduces FoM by only 2 % because i) most z<0.5 events are in the zspec subset, ii) the combined SN+host photo-z has X 2 smaller bias, and iii) the anti-correlation between fitted redshift and color self corrects distance errors.	result 0.66	0.90	0.09	asserted 1.00
s6	To prepare for analysing real data, the next SNIa-cosmology analysis with photo-z's should include non SN-Ia contamination and host galaxy mis-associations.	future work 1.00	0.07	0.03	hedged possibility 0.61

What kind of paper the classifier reports this is: simulation study 1.00 · evidence from simulation or computation 1.00.

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arXiv listing abstract v2

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Original abstract

We perform a rigorous cosmology analysis on simulated type Ia supernovae (SN~Ia) and evaluate the improvement from including photometric host-galaxy redshifts compared to using only the "zspec" subset with spectroscopic redshifts from the host or SN. We use the Deep Drilling Fields (~50 deg^2) from the Photometric LSST Astronomical Time-Series Classification Challenge (PLaSTiCC), in combination with a low-z sample based on Data Challenge2 (DC2). The analysis includes light curve fitting to standardize the SN brightness, a high-statistics simulation to obtain a bias-corrected Hubble diagram, a statistical+systematics covariance matrix including calibration and photo-z uncertainties, and cosmology fitting with a prior from the cosmic microwave background. Compared to using the zspec subset, including events with SN+host photo-z results in i) more precise distances for z>0.5, ii) a Hubble diagram that extends 0.3 further in redshift, and iii) a 50 % increase in the Dark Energy Task Force figure of merit (FoM) based on the w0-wa CDM model. Analyzing 25 simulated data samples, the average bias on w0 and wa is consistent with zero. The host photo-z systematic of 0.01 reduces FoM by only 2 % because i) most z<0.5 events are in the zspec subset, ii) the combined SN+host photo-z has X 2 smaller bias, and iii) the anti-correlation between fitted redshift and color self corrects distance errors. To prepare for analysing real data, the next SNIa-cosmology analysis with photo-z's should include non SN-Ia contamination and host galaxy mis-associations.

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References

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Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

2Flow2SN: Dusty Supernova Cosmology with Photometric Redshifts and Contamination using Neural Simulation-Based Inference
astro-ph.CO 2026-10 conditional novelty 6.0 of 10

FlowSN2 recovers cosmological and supernova population parameters from simulated photometric supernova samples under selection, photometric redshift uncertainty, and contamination, with amortized inference over multip...
jax-SNANA: A GPU-accelerated Supernova Framework for the SBI Era
astro-ph.IM 2026-10 accept novelty 5.0 of 10

jax-SNANA is a fast, GPU-accelerated supernova simulation and inference framework that shows excellent agreement with SNANA while providing transformational speedups for LSST-era cosmology.

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6 arXiv papers cite this in 19 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 12 sentences without a confident label

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The procedure encompasses four primary stages, depicted in Figure 4 of [ref] .

Litmus tests of the flat $\Lambda$CDM model and model-independent measurement of $H_0r_\mathrm{d}$ with LSST and DESI · Mock Data Generation · 0.90

Uses its data or values 1 paper

The covariance matrix corresponds to the combined statistical and systematic errors, where the latter encompasses all individual systematics, detailed in Table 3 of [ref] .

Litmus tests of the flat $\Lambda$CDM model and model-independent measurement of $H_0r_\mathrm{d}$ with LSST and DESI · Mock Data Generation · 0.97

Compares with it 2 papers

While our unbiased results are encouraging, we note that [ref] reported a significant cosmology bias using an unbinned HD from a simulated LSST data sample of pure SNe Ia.

Binning is Sinning: Redemption for Hubble Diagram using Photometrically Classified Type Ia Supernovae · Conclusion · 0.83
While the analysis by [ref] relies solely on SNIa with spectroscopically confirmed host redshifts, [ref] broadens the scope by including a comprehensive end-to-end analysis that incorporates both spectroscopic and photometric redshifts of host galaxies.

Litmus tests of the flat $\Lambda$CDM model and model-independent measurement of $H_0r_\mathrm{d}$ with LSST and DESI · Mock Data Generation · 0.96

What it cites · 3 sentences without a confident label

Builds on 1 paper

This analysis is similar to the recent DC2-SNIa cosmology analysis in [ref] , except here we include DDF and use photo-$z$ information.

SNIa-Cosmology Analysis Results from Simulated LSST Images: from Difference Imaging to Constraints on Dark Energy · Analysis · 0.90

Uses data or values from 1 paper

We adopt the detection efficiency vs. signal-to-noise ratio (SNR) from the DC2 analysis as shown in Fig. 9 of [ref] .

SNIa-Cosmology Analysis Results from Simulated LSST Images: from Difference Imaging to Constraints on Dark Energy · High-$z$ data : · 0.98

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