Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1708.01534

Dark Energy Survey Year 1 Results: The Impact of Galaxy Neighbours on Weak Lensing Cosmology with im3shape

S. Samuroff·S. L. Bridle·J. Zuntz·M. A. Troxel·D. Gruen·R. P. Rollins·G. M. Bernstein·T. F. Eifler·E. M. Huff·T. Kacprzak·E. Krause·N. MacCrann·F. B. Abdalla·S. Allam·J. Annis·K. Bechtol·A. Benoit-Levy·E. Bertin·D. Brooks·E. Buckley-Geer·A. Carnero Rosell·M. Carrasco Kind·J. Carretero·M. Crocce·C. B. D'Andrea·L. N. da Costa·C. Davis·S. Desai·P. Doel·A. Fausti Neto·B. Flaugher·P. Fosalba·J. Frieman·J. Garcia-Bellido·D. W. Gerdes·R. A. Gruendl·J. Gschwend·G. Gutierrez·K. Honscheid·D. J. James·M. Jarvis·T. Jeltema·D. Kirk·K. Kuehn·S. Kuhlmann·T. S. Li·M. Lima·M. A. G. Maia·M. March·J. L. Marshall·P. Martini·P. Melchior·F. Menanteau·R. Miquel·B. Nord·R. L. C. Ogando·A. A. Plazas·A. Roodman·E. Sanchez·V. Scarpine·R. Schindler·M. Schubnell·I. Sevilla-Noarbe·E. Sheldon·M. Smith·M. Soares-Santos·F. Sobreira·E. Suchyta·G. Tarle·D. Thomas·D. L. Tucker
View original source ↗Read source document ↗Export metadata ↓

Abstract

We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The hoopoe image simulations include realistic blending, galaxy positions, and spatial variations in depth and PSF properties. Using the im3shape maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of $m \sim 0.03 - 0.09$ in the DES Y1 im3shape catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies $n_\mathrm{eff}$ of 30%. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude $S_8\equiv σ_8 (Ω_\mathrm{m} /0.3)^{0.5}$ by $2 σ$ towards low values. Finally, we use the hoopoe simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias. We find the impact on the recovered $S_8$ of ignoring such correlations to be subdominant to statistical error at the current level of precision.

Explore related subjects

astro-ph.CO

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S. Samuroff, S. L. Bridle, J. Zuntz, M. A. Troxel, D. Gruen, R. P. Rollins, G. M. Bernstein, T. F. Eifler, E. M. Huff, T. Kacprzak, E. Krause, N. MacCrann, F. B. Abdalla, S. Allam, J. Annis, K. Bechtol, A. Benoit-Levy, E. Bertin, D. Brooks, E. Buckley-Geer, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, M. Crocce, C. B. D'Andrea, L. N. da Costa, C. Davis, S. Desai, P. Doel, A. Fausti Neto, B. Flaugher, P. Fosalba, J. Frieman, J. Garcia-Bellido, D. W. Gerdes, R. A. Gruendl, J. Gschwend, G. Gutierrez, K. Honscheid, D. J. James, M. Jarvis, T. Jeltema, D. Kirk, K. Kuehn, S. Kuhlmann, T. S. Li, M. Lima, M. A. G. Maia, M. March, J. L. Marshall, P. Martini, P. Melchior, F. Menanteau, R. Miquel, B. Nord, R. L. C. Ogando, A. A. Plazas, A. Roodman, E. Sanchez, V. Scarpine, R. Schindler, M. Schubnell, I. Sevilla-Noarbe, E. Sheldon, M. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, G. Tarle, D. Thomas, D. L. Tucker. 2017-08-04. Dark Energy Survey Year 1 Results: The Impact of Galaxy Neighbours on Weak Lensing Cosmology with im3shape. https://doi.org/10.1093/mnras%2Fstx3282

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Constraints on the Thomson optical depth to the CMB from the Lyman-$α$ forest

We present the first constraints on the electron optical depth to reionization, $τ_{\mathrm{e}}$, from the Lyman-$α$ forest alone for physically motivated reionization models that match the reionization's end-point, $z_{\rm{end}}$, required by the same astrophysical probe, and for symmetric reionization models with fixed duration, $Δz$, commonly adopted in CMB reionization analyses. Compared to traditional estimates from the latter, the Lyman-$α$ forest traces the ionization state of the IGM through its coupling with the thermal state. We find an explicit mapping between the two solving the chemistry and temperature evolution equations for hydrogen and helium. Our results yield $τ_{\mathrm{e}}$=$0.040^{+0.042}_{-0.018}$ (95\% C.L) and $τ_{\mathrm{e}}$=$0.041^{+0.028}_{-0.017}$ for reionization models with $z_{\rm{end}}$ and $Δz$-fixed, respectively. With mock Lyman-$α$ forest data that mimics the precision of future larger quasar sample datasets, we would potentially obtain tighter $τ_{\mathrm{e}}$ constraints, paving the way for CMB-independent constraints on the epoch of reionization from a large-scale structure probe.

astro-ph.CO↗
arXiv2026

Non-minimally Coupled Running Curvaton for DESI-motivated Dynamical Dark Energy

Recent DESI BAO data combined with CMB and supernova measurements suggest a dynamical dark energy that can cross the phantom divide. We show that introducing a non-minimal coupling $ξχ^2R$ to the running-curvaton framework allows a single field to drive early-universe curvature perturbations and late-time phantom-crossing cosmic acceleration without ghost instabilities. Using MCMC background likelihoods with DESI DR2 BAO, Pantheon+ SNe, and a reduced CMB prior, we constrain the cosmological parameters: $H_0 = 67.88^{+0.53}_{-0.61}\,{\rm km\,s^{-1}\,Mpc^{-1}}$, $Ω_m = 0.3072^{+0.0059}_{-0.0054}$, $w_0 = -0.922^{+0.055}_{-0.063}$, and $w_a = -0.205^{+0.173}_{-0.182}$. Parameter degeneracies leave the coupling constants weakly constrained, highlighting the need for full perturbation-level analysis using CMB spectra and lensing.

astro-ph.CO↗
arXiv2026

On the Relation Between Field-Level Posteriors, Correlators, and their Likelihoods

We develop a field-level posterior for cosmological data by marginalizing over initial conditions and noise in a general forward model. While our focus is on large-scale structure data, the results generalize to any weakly non-Gaussian observable. Moreover, the construction is non-perturbative with respect to the forward model and applies equally well to perturbative calculations, simulation-based predictions, and more general effective descriptions. Expanding the FLP around its Gaussian limit, we derive a general expression for the Fisher matrix and reorganize the field-level information into contributions associated with the connected correlators of the evolved field. This makes explicit which terms are captured by likelihood analyses based on the power spectrum, the bispectrum, or finite sets of summary statistics, and which are lost under compression. We recover the standard Gaussian-covariance result for the power spectrum, show that the Gaussian bispectrum likelihood reproduces the corresponding field-level contribution, and show how cross-covariances among summaries progressively reconstruct more of the full field-level information. As an application to the BAO scale, we show how the field contains all the information required for its optimal reconstruction in the presence of noise, and identify the contributions in the FLP needed to attain this limit. We also show that the reconstruction of the initial field arises naturally as a byproduct of our approach, yielding the optimal estimate of the initial conditions given the data and the noise. Our results provide a unified framework to compare field-level and correlator-based inference, to quantify the information loss induced by compression, and to explore the role of stochasticity.

astro-ph.CO↗