KiDS+VIKING-450: Improved cosmological parameter constraints from redshift calibration with self-organising maps

Wright, Angus H.; Hildebrandt, Hendrik; Busch, Jan Luca van den; Heymans, Catherine; Joachimi, Benjamin; Kannawadi, Arun; Kuijken, Konrad

doi:10.1051/0004-6361/202038389

Cited by 76 publications

(102 citation statements)

References 35 publications

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“…We note that this is a different redshift calibration method than that used by the KiDS-1000 cosmology analyses (Asgari et al 2021;Heymans et al 2021;Tröster et al 2021), who used a self-organising map to remove (primarily high-redshift) sources whose redshifts could not be accurately calibrated due to incompleteness in the spectroscopic sample (Wright et al 2020;Hildebrandt et al 2021). Following Robertson et al (in prep.…”

Section: The Kilo-degree Survey (Kids)mentioning

confidence: 99%

The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

Brouwer

Oman²,

Valentijn³

et al. 2021

A&A

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130

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We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.

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Section: The Kilo-degree Survey (Kids)mentioning

confidence: 99%

The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

Brouwer

Oman²,

Valentijn³

et al. 2021

A&A

Self Cite

130

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“…We also note that the DIR is not the only method to estimate the n(z). In particular, the self-organising map method described in Wright et al (2020b) also has a high potential to constrain ∆z at high-z. After we achieve tight priors on both ∆z and m, the strong signal detected in this tomographic bin will likely dominate the cosmological constraining power.…”

Section: Redshift Calibration Of a High-z Samplementioning

confidence: 99%

“…We therefore centre our prior on 0.54, but adopt a wide range so that we span the entire parameter space in the range A IA ∈ [0, 1]. With this choice, we cover the scenarios presented in Fortuna et al (2021), as well as the current constraints from KiDS cosmic shear analyses (Hildebrandt et al 2021;Wright et al 2020b;Asgari et al 2021;Heymans et al 2021).…”

Section: Appendix A: Intrinsic Alignment Priormentioning

confidence: 99%

Strong detection of the CMB lensing and galaxy weak lensing cross-correlation from ACT-DR4,PlanckLegacy, and KiDS-1000

Robertson

Alonso

Harnois-Déraps

et al. 2021

A&A

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We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the Planck Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 < zB < 1.2) and (1.2 < zB < 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7σ. With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3σ, we present joint cosmological constraints on the matter density parameter, Ωm, and the matter fluctuation amplitude parameter, σ8, marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both Planck and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 < zB < 2), with the cross-correlation detected at a significance of 7σ. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.

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“…KiDS 1 is an optical wide-field imaging survey with the Omega-CAM camera (Kuijken 2011) at the VLT Survey Telescope (VST, Capaccioli et al 2012), specifically designed for measuring weak gravitational lensing by galaxies and a large-scale structure (Joudaki et al 2017;van Uitert et al 2018;Asgari et al 2020;Heymans et al 2020;Hildebrandt et al 2020;Wright et al 2020). It consists of 1350 square degrees imaged in four broadband ugri filters.…”

Section: Datamentioning

confidence: 99%

Photometric selection and redshifts for quasars in the Kilo-Degree Survey Data Release 4

Nakoneczny

Bilicki

Pollo

et al. 2021

A&A

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We present a catalog of quasars with their corresponding redshifts derived from the photometric Kilo-Degree Survey (KiDS) Data Release 4. We achieved it by training machine learning (ML) models, using optical ugri and near-infrared ZYJHKs bands, on objects known from Sloan Digital Sky Survey (SDSS) spectroscopy. We define inference subsets from the 45 million objects of the KiDS photometric data limited to 9-band detections, based on a feature space built from magnitudes and their combinations. We show that projections of the high-dimensional feature space on two dimensions can be successfully used, instead of the standard color-color plots, to investigate the photometric estimations, compare them with spectroscopic data, and efficiently support the process of building a catalog. The model selection and fine-tuning employs two subsets of objects: those randomly selected and the faintest ones, which allowed us to properly fit the bias versus variance trade-off. We tested three ML models: random forest (RF), XGBoost (XGB), and artificial neural network (ANN). We find that XGB is the most robust and straightforward model for classification, while ANN performs the best for combined classification and redshift. The ANN inference results are tested using number counts, Gaia parallaxes, and other quasar catalogs that are external to the training set. Based on these tests, we derived the minimum classification probability for quasar candidates which provides the best purity versus completeness trade-off: p(QSOcand) > 0.9 for r < 22 and p(QSOcand) > 0.98 for 22 < r < 23.5. We find 158 000 quasar candidates in the safe inference subset (r < 22) and an additional 185 000 candidates in the reliable extrapolation regime (22 < r < 23.5). Test-data purity equals 97% and completeness is 94%; the latter drops by 3% in the extrapolation to data fainter by one magnitude than the training set. The photometric redshifts were derived with ANN and modeled with Gaussian uncertainties. The test-data redshift error (mean and scatter) equals 0.009 ± 0.12 in the safe subset and −0.0004 ± 0.19 in the extrapolation, averaged over a redshift range of 0.14 < z < 3.63 (first and 99th percentiles). Our success of the extrapolation challenges the way that models are optimized and applied at the faint data end. The resulting catalog is ready for cosmology and active galactic nucleus (AGN) studies.

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KiDS+VIKING-450: Improved cosmological parameter constraints from redshift calibration with self-organising maps

Cited by 76 publications

References 35 publications

The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

Strong detection of the CMB lensing and galaxy weak lensing cross-correlation from ACT-DR4,PlanckLegacy, and KiDS-1000

Photometric selection and redshifts for quasars in the Kilo-Degree Survey Data Release 4

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