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Takahiro Nishimichi

Publications and source records attributed to Takahiro Nishimichi.

At least 37 records · Page 2Linked to original sources
arXiv2024

Nonlinear redshift space distortion in halo ellipticity correlations: Analytical model and N-body simulations

We present an analytic model of nonlinear correlators of galaxy/halo ellipticities in redshift space. The three-dimensional ellipticity field is not affected by the redshift-space distortion (RSD) at linear order, but by the nonlinear one, known as the Finger-of-God effect, caused by the coordinate transformation from real to redshift space. Adopting a simple Gaussian damping function to describe the nonlinear RSD effect and the nonlinear alignment model for the relation between the observed ellipticity and underlying tidal fields, we derive analytic formulas for the multipole moments of the power spectra of the ellipticity field in redshift space expanded in not only the associated Legendre basis, a natural basis for the projected galaxy shape field, but also the standard Legendre basis, conventionally used in literature. The multipoles of the corresponding correlation functions of the galaxy shape field are shown to be expressed by a simple Hankel transform, as is the case for those of the conventional galaxy density correlations. We measure these multipoles of the power spectra and correlation functions of the halo ellipticity field using large-volume N-body simulations. We then show that the measured alignment signals can be better predicted by our nonlinear model than the existing linear alignment model. The formulas derived here have already been used to place cosmological constraints using from the redshift-space correlation functions of the galaxy shape field measured from the Sloan Digital Sky Survey (Okumura and Taruya, 2023).

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arXiv2024

Exploring the baryonic effect signature in the Hyper Suprime-Cam Year 3 cosmic shear two-point correlations on small scales: the $S_8$ tension remains present

The baryonic feedback effect is considered as a possible solution to the so-called $S_8$ tension indicated in cosmic shear cosmology. The baryonic effect is more significant on smaller scales, and affects the cosmic shear two-point correlation functions (2PCFs) with different scale- and redshift-dependencies from those of the cosmological parameters. In this paper, we use the Hyper Suprime-Cam Year 3 (HSC-Y3) data to measure the cosmic shear 2PCFs ($ξ_{\pm}$) down to 0.28 arcminutes, taking full advantage of the high number density of source galaxies in the deep HSC data, to explore a possible signature of the baryonic effect. While the published HSC analysis used the cosmic shear 2PCFs on angular scales, which are sensitive to the matter power spectrum at $k\lesssim 1~h{\rm Mpc}^{-1}$, the smaller scale HSC cosmic shear signal allows us to probe the signature of matter power spectrum up to $k\simeq 20~h{\rm Mpc}^{-1}$. Using the accurate emulator of the nonlinear matter power spectrum, DarkEmulator2, we show that the dark matter-only model can provide an acceptable fit to the HSC-Y3 2PCFs down to the smallest scales. In other words, we do not find any clear signature of the baryonic effects or do not find a systematic shift in the $S_8$ value with the inclusion of the smaller-scale information as would be expected if the baryonic effect is significant. Alternatively, we use a flexible 6-parameter model of the baryonic effects, which can lead to both enhancement and suppression in the matter power spectrum compared to the dark matter-only model, to perform the parameter inference of the HSC-Y3 2PCFs. We find that the small-scale HSC data allow only a fractional suppression of up to 5 percent in the matter power spectrum at $k\sim 1~h{\rm Mpc}^{-1}$, which is not sufficient to reconcile the $S_8$ tension.

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arXiv2024

Perturbation theory challenge for cosmological parameters estimation II.: Matter power spectrum in redshift space

Constraining cosmological parameters from large-scale structure observations requires precise and accurate tools to compute its properties. While perturbation theory (PT) approaches can serve this purpose, exploration of large parameter space is challenging due to the potentially large computational cost of such calculations. In this study, we show that a response function approach applied to the regularized PT (RegPT) model at 2-loop order, plus correction terms induced by redshift space distortion effects, can reduce the runtime by a factor of 50 compared to direct integration. We illustrate the performance of this approach by performing the parameter inference of five fundamental cosmological parameters from the redshift space power spectrum measured from $N$-body simulations as mock measurements, and inferred cosmological parameters are directly compared with parameters used to generate initial conditions of the simulations. From this \textit{PT challenge} analysis, the constraining power of cosmological parameters and parameter biases are quantified with the survey volume and galaxy number density expected for the \textit{Euclid} mission at the redshift $z = 1$ as a function of the maximum wave-number of data points $k_\mathrm{max}$. We find that RegPT with correction terms reproduces the input cosmological parameters without bias up to maximum wave-number $k_\mathrm{max}= 0.18 \, h\,\mathrm{Mpc}^{-1}$. Moreover, RegPT+, which introduces one free parameter to RegPT to handle the damping feature on small scales, delivers the best performance among the examined models and achieves tighter constraints without significant parameter bias for higher maximum wave-number $k_\mathrm{max} = 0.21 \, h\,\mathrm{Mpc}^{-1}$.

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arXiv2024

Mock Observatory: two thousand lightcone mock catalogues of luminous red galaxies from the Hyper Suprime-Cam Survey for the cosmological large-scale analysis

Estimating a reliable covariance matrix for correlation functions of galaxies is a crucial task to obtain accurate cosmological constraints from galaxy surveys. We generate 2,000 independent lightcone mock luminous red galaxy (LRGs) catalogues at $0.3 \leq z \leq 1.25$, designed to cover CAMIRA LRGs observed by the Subaru Hyper Suprime-Cam Subaru Strategic Programme (HSC SSP). We first produce full-sky lightcone halo catalogues using a COmoving Lagrangian Acceleration (COLA) technique, and then trim them to match the footprints of the HSC SSP S20A Wide layers. The mock LRGs are subsequently populated onto the trimmed halo catalogues according to the halo occupation distribution model constrained by the observed CAMIRA LRGs. The stellar mass ($M_{\star}$) is assigned to each LRG by the subhalo abundance-matching technique using the observed stellar-mass functions of CAMIRA LRGs. We evaluate photometric redshifts (photo-$z$) of mock LRGs by incorporating the photo-$z$ scatter, which is derived from the observed $M_{\star}$--photo-$z$-scatter relations of the CAMIRA LRGs. We validate the constructed full-sky halo and lightcone LRG mock catalogues by comparing their angular clustering statistics (i.e., power spectra and correlation functions) with those measured from the halo catalogues of full $N$-body simulations and the CAMIRA LRG catalogues from the HSC SSP, respectively. We detect clear signatures of baryon acoustic oscillations (BAOs) from our mock LRGs, whose angular scales are well consistent with theoretical predictions. These results demonstrate that our mock LRGs can be used to evaluate covariance matrices at large scales and provide predictions for the BAO detectability and cosmological constraints.

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arXiv2024

Emulating power spectra for pre- and post-reconstructed galaxy samples

The small-scale linear information in galaxy samples typically lost during non-linear growth can be restored to a certain level by the density field reconstruction, which has been demonstrated for improving the precision of the baryon acoustic oscillations (BAO) measurements. As proposed in the literature, a joint analysis of the power spectrum before and after the reconstruction enables an efficient extraction of information carried by high-order statistics. However, the statistics of the post-reconstruction density field are difficult to model. In this work, we circumvent this issue by developing an accurate emulator for the pre-reconstructed, post-reconstructed, and cross power spectra ($P_{\rm pre}$, $P_{\rm post}$, $P_{\rm cross}$) up to $k=0.5~h~{\rm Mpc^{-1}}$ based on the \textsc{Dark Quest} N-body simulations. The accuracy of the emulator is at percent level, namely, the error of the emulated monopole and quadrupole of the power spectra is less than $1\%$ and $10\%$ of the ground truth, respectively. A fit to an example power spectra using the emulator shows that the constraints on cosmological parameters get largely improved using $P_{\rm pre}$+$P_{\rm post}$+$P_{\rm cross}$ with $k_{\rm max}=0.25~h~{\rm Mpc^{-1}}$, compared to that derived from $P_{\rm pre}$ alone, namely, the constraints on ($Ω_m$, $H_0$, $σ_8$) are tightened by $\sim41 \%-55\%$, and the uncertainties of the derived BAO and RSD parameters ($α_{\perp}$, $α_{||}$, $fσ_8$) shrink by $\sim 28\%-54\%$, respectively. This highlights the complementarity among $P_{\rm pre}$, $P_{\rm post}$ and $P_{\rm cross}$, which demonstrates the efficiency and practicability of a joint $P_{\rm pre}$, $P_{\rm post}$ and $P_{\rm cross}$ analysis for cosmological implications.

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arXiv2024

The Intrinsic Alignment of Galaxy Clusters and Impact of Projection Effects

Galaxy clusters, being the most massive objects in the Universe, exhibit the strongest alignment with the large-scale structure. However, mis-identification of members due to projection effects from the large scale structure can occur. We studied the impact of projection effects on the measurement of the intrinsic alignment of galaxy clusters, using galaxy cluster mock catalogs. Our findings showed that projection effects result in a decrease of the large scale intrinsic alignment signal of the cluster and produce a bump at $r_p\sim 1h^{-1}/Mpc$, most likely due to interlopers and missed member galaxies. This decrease in signal explains the observed similar alignment strength between bright central galaxies and clusters in the SDSS redMaPPer cluster catalog. The projection effect and cluster intrinsic alignment signal are coupled, with clusters having lower fractions of missing members or having higher fraction of interlopers exhibiting higher alignment signals in their projected shapes. We aim to use these findings to determine the impact of projection effects on galaxy cluster cosmology in future studies.

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arXiv2023

Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Minimal Bias Model

We present cosmological parameter constraints from a blind joint analysis of three two-point correlation functions measured from the Year 3 Hyper Suprime-Cam (HSC-Y3) imaging data, covering 416 deg$^2$, and the SDSS DR11 spectroscopic galaxies spanning the redshift range $[0.15, 0.70]$. We subdivide the SDSS galaxies into three volume-limited samples separated in redshift, each of which acts as a large-scale structure tracer characterized by the measurement of the projected correlation function, $w_{\rm p}(R)$. We also use the measurements of the galaxy-galaxy weak lensing signal $ΔΣ(R)$ for each of these SDSS samples which act as lenses for a secure sample of source galaxies selected from the HSC-Y3 shape catalog based on their photometric redshifts. We combine these measurements with the cosmic shear correlation functions, $ξ_{\pm}(\vartheta)$, measured for our HSC source sample. We model these observables with the minimal bias model of the galaxy clustering observables in the context of a flat $Λ$CDM cosmology. We use conservative scale cuts, $R>12$ and $8~h^{-1}$Mpc, for $ΔΣ$ and $w_{\rm p}$, respectively, where the minimal bias model is valid, in addition to conservative prior on the residual bias in the mean redshift of the HSC photometric source galaxies. Our baseline analysis yields $S_8=0.775^{+0.043}_{-0.038}$ (68% C.I.) for the $Λ$CDM model, after marginalizing over uncertainties in other parameters. Our value of $S_8$ is consistent with that from the Planck 2018 data, but the credible interval of our result is still relatively large. Our results are statistically consistent with those of a companion paper, which extends this analysis to smaller scales with an emulator-based halo model.

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arXiv2023

Multi-stream radial structure of cold dark matter haloes from particle trajectories: deep inside splashback radius

By tracking trajectories of dark matter (DM) particles accreting onto haloes in cosmological $N$-body simulations, we investigate the radial phase-space distribution of cold dark matter (CDM) haloes, paying attention to their inner regions deep inside the halo boundary called the splashback radius, where the particles undergo multi-stream flows. Improving the analysis by Sugiura et al., we classify DM particles by the number of apocenter passages, $p$, and count it up to $p=40$ for each halo over a wide mass range. Quantifying the radial density profile for particles having the same value of $p$, we find that it generally exhibits a double-power law feature, whose indices of inner and outer slopes are well-described by $-1$ and $-8$, respectively. Its characteristic scale and density are given as a simple fitting function of $p$, with a weak halo mass dependence. Interestingly, summing up these double-power law profiles beyond $p=40$ reproduces well the total density profile of simulated haloes. The double-power law nature is persistent and generic not only in mass-selected haloes but also in haloes selected in different criteria. Our results are compared with self-similar solutions that describe the stationary and spherical accretion of DM. We find that even when introducing a non-zero angular momentum, none of them explain the radial multi-stream structure. The analysis with particle trajectories tracing back to higher redshifts suggests that the double-power law nature has been established during an early accretion phase and remains stable.

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arXiv2023

Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Two-point Correlation Functions

We perform a blinded cosmology analysis with cosmic shear two-point correlation functions (2PCFs) measured from more than 25 million galaxies in the Hyper Suprime-Cam three-year shear catalog in four tomographic redshift bins ranging from 0.3 to 1.5. After conservative masking and galaxy selection, the survey covers 416 deg$^2$ of the northern sky with an effective galaxy number density of 15 arcmin$^{-2}$ over the four redshift bins. The 2PCFs adopted for cosmology analysis are measured in the angular range: $7.1 < θ/{\rm arcmin} < 56.6$ for $ξ_+$ and $31.2 <θ/{\rm arcmin} < 248$ for $ξ_-$, with a total signal-to-noise ratio of 26.6. We apply a conservative, wide, flat prior on the photometric redshift errors on the last two tomographic bins, and the relative magnitudes of the cosmic shear amplitude across four redshift bins allow us to calibrate the photometric redshift errors. With this flat prior on redshift errors, we find $Ω_{\rm m}=0.256_{-0.044}^{+0.056}$ and $S_8\equiv σ_8 \sqrt{Ω_{\rm m}/0.3}=0.769_{-0.034}^{+0.031}$ (both 68\% CI) for a flat $Λ$ cold dark matter cosmology. We find, after unblinding, that our constraint on $S_8$ is consistent with the Fourier space cosmic shear and the 3$\times$2pt analyses on the same HSC dataset. We carefully study the potential systematics from astrophysical and systematic model uncertainties in our fiducial analysis using synthetic data, and report no biases (including projection bias in the posterior space) greater than $0.5σ$ in the estimation of $S_8$. Our analysis hints that the mean redshifts of the two highest tomographic bins are higher than initially estimated. In addition, a number of consistency tests are conducted to assess the robustness of our analysis. Comparing our result with Planck-2018 cosmic microwave background observations, we find a ~$2σ$ tension for the $Λ$CDM model.

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arXiv2023

Hyper Suprime-Cam Year 3 Results: Measurements of Clustering of SDSS-BOSS Galaxies, Galaxy-Galaxy Lensing and Cosmic Shear

We use the Sloan Digital Sky Survey (SDSS) BOSS galaxies and their overlap with approximately 416 sq. degree of deep $grizy$-band imaging from the Subaru Hyper Suprime-Cam Survey (HSC). We measure three two-point correlations that form the basis of the cosmological inference presented in our companion papers, Miyatake et al. and Sugiyama et al. We use three approximately volume limited subsamples of spectroscopic galaxies by their $i$-band magnitude from the SDSS-BOSS: LOWZ (0.1<z<0.35), CMASS1 (0.43<z<0.55) and CMASS2 (0.55<z<0.7), respectively. We present high signal-to-noise ratio measurements of the projected correlation functions of these galaxies, which is expected to be proportional to the matter correlation function times the bias of galaxies on large scales. In order to break the degeneracy between the amplitude of the matter correlation and the bias of these galaxies, we use the distortions of the shapes of galaxies in HSC due to weak gravitational lensing, to measure the galaxy-galaxy lensing signal, which probes the galaxy-matter cross-correlation of the SDSS-BOSS galaxies. We also measure the cosmic shear correlation functions from HSC galaxies which is related to the projected matter correlation function. We demonstrate the robustness of our measurements with a variety of systematic tests. Our use of a single sample of HSC source galaxies is crucial to calibrate any residual systematic biases in the inferred redshifts of our galaxies. We also describe the construction of a suite of mocks: i) spectroscopic galaxy catalogs which obey the clustering and abundance of each of the three SDSS-BOSS subsamples, and ii) galaxy shape catalogs which obey the footprint of the HSC survey and have been appropriately sheared by the large-scale structure expected in a $Λ$-CDM model. We use these mock catalogs to compute the covariance of each of our observables.

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arXiv2023

Flat to nonflat: Calculating nonlinear power spectra of biased tracers for nonflat $Λ$CDM model

The growth of large-scale structure, together with the geometrical information of cosmic expansion history and cosmological distances, can be used to obtain constraints on the spatial curvature of the universe that probes the early universe physics, whereas modeling the nonlinear growth in a nonflat universe is still challenging due to computational expense of simulations in a high-dimensional cosmological parameter space. In this paper, we develop an approximate method to compute the halo-matter and halo-auto power spectra for nonflat $Λ$CDM model, from quantities representing the nonlinear evolution of the corresponding flat $Λ$CDM model, based on the separate universe (SU) method. By utilizing the fact that the growth response to long-wavelength fluctuations (equivalently the curvature), $T_{δ_{\rm b}}(k)$, is approximated by the response to the Hubble parameter, $T_h(k)$, our method allows one to estimate the nonlinear power spectra in a nonflat universe efficiently from the power spectra of the flat universe. We use $N$-body simulations to show that the estimator can provide the halo-matter (halo-auto) power spectrum at $\sim 1\%$ ($\sim 2\%$ ) accuracy up to $k \simeq 3 (1) \, h {\rm Mpc}^{-1}$ even for a model with large curvature $Ω_K = \pm 0.1$. Using the estimator we can extend the prediction of the existing emulators such as Dark Emulator to nonflat models without degrading their accuracy. Since the response to long-wavelength fluctuations is also a key quantity for estimating the super sample covariance (SSC), we discuss that the approximate identity $T_{δ_{\rm b}}(k) \approx T_h(k)$ can be used to calculate the SSC terms analytically.

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arXiv2023

Robustness of Baryon Acoustic Oscillations Measurements with Photometric Redshift Uncertainties

We investigate the robustness of baryon acoustic oscillations (BAO) measurements with a photometric galaxy sample using mock galaxy catalogues with various sizes of photometric redshift (photo-$z$) uncertainties. We first conduct the robustness of BAO measurements, assuming we have a perfect knowledge of photo-$z$ uncertainties. We find that the BAO shift parameter $α$ can be constrained in an unbiased manner even for 3% photometric redshift uncertainties up to $z\sim 1$. For instance, $α=1.006 \pm 0.078$ with 95% confidence level is obtained from 3% photo-$z$ uncertainty data at $z=1.03$ using the sample of $M_* \ge 10^{10.25} M_{\odot}/h^2$. We also find that a sparse galaxy sample, e.g. $<2\times10^{-4}$ [$h$ Mpc$^{-1}]^3$ causes additional noise in the covariance matrix calculation and can bias the constraint on $α$. Following this, we look into the scenario where incorrect photometric redshift uncertainties are assumed in the fitting model. We find that underestimating the photo-$z$ uncertainty leads to a degradation in the constraining power on $α$. However, the constrained value of $α$ is not biased. We also quantify the constraining power on $Ω_{\rm m0}$ assuming the LSST-like covariance and find that the 95% confidence level is $σ(Ω_{\rm m0})\sim0.03$-$0.05$ corresponding to the photo-$z$ uncertainties of 1% to 3% respectively. Finally, we examine whether the skewness in the photometric redshift can bias the constraint on $α$ and confirm that the constraint on $α$ is unbiased, even assuming a Gaussian photo-$z$ uncertainty in our model.

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arXiv2023

Universal multi-stream radial structures of cold dark matter halos

Virialized halos of cold dark matter generically exhibit multi-stream structures of accreted dark matter within an outermost radial caustic known as the splashback radius. By tracking the particle trajectories that accrete onto the halos in cosmological $N$-body simulations, we count their number of apocenter passages ($p$), and use them to characterize the multi-stream structure of dark matter particles. We find that the radial density profile for each stream, classified by the number of apocenter passages, exhibits universal features, and can be described by a double power-law function comprising inner shallow and outer steep slopes of indices of $-1$ and $-8$, respectively. Surprisingly, these properties hold over a wide range of halo masses. The double-power law feature is persistent when dividing the sample by concentration or accretion rate. The dependence of the characteristic scale and amplitude of the profile on $p$ cannot be replicated by known self-similar solutions, requiring consideration of complexities such as the distribution of angular momentum or mergers.

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arXiv2023

Machine Learning for Observational Cosmology

An array of large observational programs using ground-based and space-borne telescopes is planned in the next decade. The forthcoming wide-field sky surveys are expected to deliver a sheer volume of data exceeding an exabyte. Processing the large amount of multiplex astronomical data is technically challenging, and fully automated technologies based on machine learning and artificial intelligence are urgently needed. Maximizing scientific returns from the big data requires community-wide efforts. We summarize recent progress in machine learning applications in observational cosmology. We also address crucial issues in high-performance computing that are needed for the data processing and statistical analysis.

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arXiv2023

Hyper Suprime-Cam Year 3 Results: Cosmology from Galaxy Clustering and Weak Lensing with HSC and SDSS using the Emulator Based Halo Model

We present cosmology results from a blinded joint analysis of cosmic shear, $ξ_{\pm}(\vartheta)$, galaxy-galaxy weak lensing, $Δ\!Σ(R)$, and projected galaxy clustering, $w_{\rm p}(R)$, measured from the Hyper Suprime-Cam three-year (HSC-Y3) shape catalog and the Sloan Digital Sky Survey (SDSS) DR11 spectroscopic galaxy catalog - a 3$\times$2pt cosmology analysis. We define luminosity-cut samples of SDSS galaxies to serve as the tracers of $w_{\rm p}$ and as the lens samples for $Δ\!Σ$ in three spectroscopic redshift bins spanning the range $0.15<z<0.7$. For the $ξ_{\pm}$ and $Δ\!Σ$ measurements, we use a single source sample over 416 deg$^2$, selected from HSC-Y3 based on having photometric redshifts (photo-$z$) greater than 0.75. For cosmological parameter inference, we use Dark Emulator combined with a halo occupation distribution prescription to model $w_{\rm p}$ and $Δ\!Σ$ down to quasi-nonlinear scales. In our baseline analysis we employ an uninformative flat prior of the residual photo-$z$ error to model a residual bias in the mean redshift of HSC source galaxies. We obtain a robust constraint on the cosmological parameters for the flat $Λ$CDM model: $S_8=σ_8(Ω_{\rm m}/0.3)^{0.5}=0.763^{+0.040}_{-0.036}$ (68% C.I.), or the best-constrained parameter given by $S'_8=σ_8(Ω_{\rm m}/0.3)^{0.22}=0.721\pm 0.028$, determined with about 4% fractional precision. Our HSC-Y3 data exhibits about 2.5$σ$ tension with the Planck inferred $S_8$ value for the $Λ$CDM model, and hints at a non-zero residual photo-$z$ bias implying that the true mean redshift of the HSC galaxies at $z\gtrsim 0.75$ is higher than that implied by the original photo-$z$ estimates.

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arXiv2023

Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Power Spectra

We measure weak lensing cosmic shear power spectra from the three-year galaxy shear catalog of the Hyper Suprime-Cam (HSC) Subaru Strategic Program imaging survey. The shear catalog covers $416 \ \mathrm{deg}^2$ of the northern sky, with a mean $i$-band seeing of 0.59 arcsec and an effective galaxy number density of 15 $\mathrm{arcmin}^{-2}$ within our adopted redshift range. With an $i$-band magnitude limit of 24.5 mag, and four tomographic redshift bins spanning $0.3 \leq z_{\mathrm{ph}} \leq 1.5$ based on photometric redshifts, we obtain a high-significance measurement of the cosmic shear power spectra, with a signal-to-noise ratio of approximately 26.4 in the multipole range $300<\ell<1800$. The accuracy of our power spectrum measurement is tested against realistic mock shear catalogs, and we use these catalogs to get a reliable measurement of the covariance of the power spectrum measurements. We use a robust blinding procedure to avoid confirmation bias, and model various uncertainties and sources of bias in our analysis, including point spread function systematics, redshift distribution uncertainties, the intrinsic alignment of galaxies and the modeling of the matter power spectrum. For a flat $Λ$CDM model, we find $S_8 \equiv σ_8 (Ω_m/0.3)^{0.5} =0.776^{+0.032}_{-0.033}$, which is in excellent agreement with the constraints from the other HSC Year 3 cosmology analyses, as well as those from a number of other cosmic shear experiments. This result implies a $\sim$$2σ$-level tension with the Planck 2018 cosmology. We study the effect that various systematic errors and modeling choices could have on this value, and find that they can shift the best-fit value of $S_8$ by no more than $\sim$$0.5σ$, indicating that our result is robust to such systematics.

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arXiv2023

Cluster cosmology with anisotropic boosts: Validation of a novel forward modeling analysis and application on SDSS redMaPPer clusters

We present a novel analysis for cluster cosmology that fully forward models the abundances, weak lensing, and the clustering of galaxy clusters. Our analysis notably includes an empirical model for the anisotropic boosts impacting the lensing and clustering signals of optical clusters. These boosts arise from a preferential selection of clusters surrounded by anisotropic large scale structure, a consequence of the limited discrimination between line-of-sight interlopers and true cluster members offered by photometric surveys. We validate our analysis via a blind cosmology challenge on mocks, and find that we can obtain tight and unbiased cosmological constraints without informative priors or external calibrations on any of our model parameters. We then apply our analysis on the SDSS redMaPPer clusters, and find results favoring low $Ω_\mathrm{m}$ and high $σ_8$, combining to yield the lensing strength constraint $S_8 = 0.718_{-0.021}^{+0.024}$. We investigate potential drivers behind these results through a series of post-unblinding tests, noting that our results are consistent with existing cluster cosmology constraints but clearly inconsistent with other CMB/LSS based cosmology results. From these tests, we find hints that a suppression in the cluster lensing signal may be driving our results.

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arXiv2023

Cosmology with the Galaxy Bispectrum Multipoles: Optimal Estimation and Application to BOSS Data

We present a framework for self-consistent cosmological analyses of the full-shape anisotropic bispectrum, including the quadrupole $(\ell=2)$ and hexadecapole $(\ell=4)$ moments. This features a novel window-free algorithm for extracting the latter quantities from data, derived using a maximum-likelihood prescription. Furthermore, we introduce a theoretical model for the bispectrum multipoles (which does not introduce new free parameters), and test both aspects of the pipeline on several high-fidelity mocks, including the PT Challenge suite of gigantic cumulative volume. This establishes that the systematic error is significantly below the statistical threshold, both for the measurement and modeling. As a realistic example, we extract the large-scale bispectrum multipoles from BOSS DR12 and analyze them in combination with the power spectrum data. Assuming a minimal $Λ$CDM model, with a BBN prior on the baryon density and a \textit{Planck} prior on $n_s$, we can extract the remaining cosmological parameters directly from the clustering data. The inclusion of the unwindowed higher-order $(\ell>0)$ large-scale bispectrum multipoles is found to moderately improve one-dimensional cosmological parameter posteriors (at the $5\%-10\%$ level), though these multipoles are detected only in three out of four BOSS data segments at $\approx 5σ$. Combining information from the power spectrum and bispectrum multipoles, the real space power spectrum, and the post-reconstructed BAO data, we find $H_0 = 68.2\pm 0.8~\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$, $Ω_m =0.33\pm 0.01$ and $σ_8 = 0.736\pm 0.033$ (the tightest yet found in perturbative full-shape analyses). Our estimate of the growth parameter $S_8=0.77\pm 0.04$ agrees with both weak lensing and CMB results.

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