Magnification bias in galaxy surveys with complex sample selection functions

Wietersheim-Kramsta, Maximilian von; Joachimi, Benjamin; Busch, Jan Luca van den; Heymans, Catherine; Hildebrandt, Hendrik; Asgari, Marika; Tröster, Tilman; Unruh, Sandra; Wright, Angus H.

doi:10.1093/mnras/stab1000

Cited by 27 publications

(8 citation statements)

References 76 publications

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“…The large-scale structure which lies between us and the lens galaxies causes distortions of the shapes of the background source galaxy sample. It also modulates the number densities of both the source and lens galaxies due to lensing magnification [43,92]. This complicates the interpretation of the galaxy-galaxy lensing signal.…”

Section: Galaxy-galaxy Weak Lensing Estimatormentioning

confidence: 99%

See 1 more Smart Citation

Cosmological inference from the emulator based halo model II: Joint analysis of galaxy-galaxy weak lensing and galaxy clustering from HSC-Y1 and SDSS

Miyatake¹,

Sugiyama²,

Takada³

et al. 2021

Preprint

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We present high-fidelity cosmology results from a blinded joint analysis of galaxy-galaxy weak lensing (∆Σ) and projected galaxy clustering (wp) measured from the Hyper Suprime-Cam Year-1 (HSC-Y1) data and spectroscopic Sloan Digital Sky Survey (SDSS) galaxy catalogs in the redshift range 0.15 < z < 0.7. We define luminosity-limited samples of SDSS galaxies to serve as the tracers of wp in three spectroscopic redshift bins, and as the lens samples for ∆Σ. For the ∆Σ measurements, we select a single sample of 4 million source galaxies over 140 deg 2 from HSC-Y1 with photometric redshifts (photo-z) greater than 0.75, enabling a better handle of photo-z errors by comparing the ∆Σ amplitudes for the three lens redshift bins. The deep, high-quality HSC-Y1 data enable significant detections of the ∆Σ signals, with integrated signal-to-noise ratio S/N ∼ 15 in the range 3 ≤ R/[h −1 Mpc] ≤ 30 for the three lens samples, despite the small area coverage. For cosmological parameter inference, we use an input galaxy-halo connection model built on the Dark

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Section: Galaxy-galaxy Weak Lensing Estimatormentioning

confidence: 99%

“…Hence the magnification bias cannot be characterized by a single slope of the number counts in the original sample, and one would have to carefully estimate the effect using the effective slope as done in Ref. [92].…”

Section: Galaxy-galaxy Weak Lensing Estimatormentioning

confidence: 99%

Cosmological inference from the emulator based halo model II: Joint analysis of galaxy-galaxy weak lensing and galaxy clustering from HSC-Y1 and SDSS

Miyatake¹,

Sugiyama²,

Takada³

et al. 2021

Preprint

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“…Furthermore, galaxy samples are in general not purely flux-limited. A novel method for estimating the local count slope for a complex selection function has been developed for the Kilo-Degree Survey (KiDS; see von Wietersheim-Kramsta et al 2021). Assessing whether this method will be accurate enough for Euclid, that is, whether it can be used to estimate the local count slope within a 10% uncertainty, requires further investigation.…”

Section: Cosmological Constraintsmentioning

confidence: 99%

Euclid preparation

Lepori

Tutusaus

Viglione

et al. 2022

A&A

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Aims. We investigate the importance of lensing magnification for estimates of galaxy clustering and its cross-correlation with shear for the photometric sample of Euclid. Using updated specifications, we study the impact of lensing magnification on the constraints and the shift in the estimation of the best fitting cosmological parameters that we expect if this effect is neglected. Methods. We follow the prescriptions of the official Euclid Fisher matrix forecast for the photometric galaxy clustering analysis and the combination of photometric clustering and cosmic shear. The slope of the luminosity function (local count slope), which regulates the amplitude of the lensing magnification, and the galaxy bias have been estimated from the Euclid Flagship simulation. Results. We find that magnification significantly affects both the best-fit estimation of cosmological parameters and the constraints in the galaxy clustering analysis of the photometric sample. In particular, including magnification in the analysis reduces the 1σ errors on Ωm, 0, w0, wa at the level of 20–35%, depending on how well we will be able to independently measure the local count slope. In addition, we find that neglecting magnification in the clustering analysis leads to shifts of up to 1.6σ in the best-fit parameters. In the joint analysis of galaxy clustering, cosmic shear, and galaxy–galaxy lensing, magnification does not improve precision, but it leads to an up to 6σ bias if neglected. Therefore, for all models considered in this work, magnification has to be included in the analysis of galaxy clustering and its cross-correlation with the shear signal (3 × 2pt analysis) for an accurate parameter estimation.

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“…Second, an analysis that included the magnification bias correction in the model and where s was fixed to its fiducial value. Although it is possible to estimate s from the data itself, the standard method consists of fitting the local slope at the faint-end of the luminosity function, which might not be accurate when the selection function is complex (von Wietersheim-Kramsta et al 2021). We therefore also propose an alternative analysis that includes the magnification bias correction in the model, but allows the s parameter to vary.…”

Section: Likelihood Analysismentioning

confidence: 99%

Impact of lensing magnification on the analysis of galaxy clustering in redshift space

Breton

Torre

Piat

2022

A&A

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We study the impact of lensing magnification on the observed three-dimensional galaxy clustering in redshift space. We used the RayGal suite of N-body simulations, from which we extracted samples of dark matter particles and haloes in the redshift regime of interest for future large redshift surveys. Several magnitude-limited samples were built that reproduce various levels of magnification bias ranging from s = 0 to s = 1.2, where s is the logarithmic slope of the cumulative magnitude number counts, in three redshift intervals within 1 < z < 1.95. We studied the two-point correlation function multipole moments in the different cases in the same way as would be applied to real data, and investigated how well the growth rate of structure parameter could be recovered. In the analysis, we used an hybrid model that combines non-linear redshift-space distortions and linear curved-sky lensing magnification. We find that the growth rate is underestimated when magnification bias is not accounted for in the modelling. This bias becomes non-negligible for z > 1.3 and can reach 10% at z ≃ 1.8, depending on the properties of the target sample. In our data, adding the lensing linear correction allowed us to recover an unbiased estimate of the growth rate in most cases when the correction was small, even when the fiducial cosmology was different from that of the data. For larger corrections (high redshifts, low bias, and high s value), we find that the weak-lensing limit has to be treated with caution as it may no longer be a good approximation. Our results also show the importance of knowing s in advance instead of letting this parameter free with flat priors because in this case, the error bars increase significantly.

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Magnification bias in galaxy surveys with complex sample selection functions

Cited by 27 publications

References 76 publications

Cosmological inference from the emulator based halo model II: Joint analysis of galaxy-galaxy weak lensing and galaxy clustering from HSC-Y1 and SDSS

Cosmological inference from the emulator based halo model II: Joint analysis of galaxy-galaxy weak lensing and galaxy clustering from HSC-Y1 and SDSS

Euclid preparation

Impact of lensing magnification on the analysis of galaxy clustering in redshift space

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