A.Taruya: Overview M.Takada: Some thoughts on intrinsic alignments T.Nishimichi: On the nonlinear growth of anisotropic clustering S.Saga: Imprints of relativistic effects on the dipole anisotropy of the density-intrinsic alignment cross-correlation Z.Vlah: EFT of galaxy shapes P.Motloch: Correlations between galaxy angular momenta and initial conditions C.Bottrell: TNG50 galaxies observed in the HSC-SSP! U.Pen: What do alignments tell us about initial conditions of the universe? J.Lee: Cosmology Dependence of the Transition Mass of Halo Spins J.Blazek: How large are alignments for lensing sources galaxies? H.Yu: Numerical study of cosmic spin reconstructions
K.Osato: Intrinsic alignments with numerical simulations K.Akitsu: Imprint of gravitational waves on large-scale structure in simulations K.Kogai: Statistical properties of galaxy shapes with angular dependent primordial non-Gaussianities J.Shi: Galaxy Intrinsic Alignment Power Spectrum in IllustrisTNG B.Zhang: Forecasting z~2 direct galaxy-cosmic web alignment for Subaru-PFS T.Okumura: Tightening geometric and dynamical constraints on dark energy and gravity with galaxy intrinsic alignment Y-T.Chuang: Intrinsic alignments of dark matter halos in f(R) gravity simulations T.Kurita: FFT-based estimators for line-of-sight dependent intrinsic alignment signals
Title and Abstract
Some thoughts on intrinsic alignments
On the nonlinear growth of anisotropic clustering
Imprints of relativistic effects on the dipole anisotropy of the density-intrinsic alignment cross-correlation
Recent our numerical and analytical investigations imply that the observed density fields are distorted due to not only the Doppler effects but also gravitational redshift effects of halo potentials particularly at small scales. Taking into account both effect, we will present the quasi-linear model of the density-intrinsic alignment (GI) cross-correlation dipole, and discuss the detectability. Thus, the GI dipole would be a new cosmological probe to investigate gravitational redshift effects.
EFT of galaxy shapes
I will present a perturbative effective field theory (EFT) description of galaxy shapes. We apply this formalism to compute the relevant one-loop two-point and three-level bispectrum correlations. Our results can be presented in terms of three-dimensional statistics for two- and three-point functions of both galaxy shapes and number counts. We use a spherical tensor basis to decompose the tensor perturbations in different helicity modes, which allows us to utilize the isotropy and parity properties of the correlators.
Correlations between galaxy angular momenta and initial conditions
Angular momenta of galaxies are determined by the initial conditions (ICs) in the vicinity of the corresponding protohaloes. Measuring galaxy angular momenta can thus in principle be used to better reconstruct the ICs in the local Universe. In this talk I will describe our observational efforts studying this correlation, using ICs determined from SDSS galaxy positions. We find that galaxy angular momenta inferred from shapes of spiral galaxies correlate with the initial tidal field around the corresponding protohaloes. Explicitly, we find that galaxies tend to be preferentially face on (edge on) oriented when the major (minor) axis of the initial tidal field is aligned with the line of sight. I also describe similar correlation study using galaxy angular momenta inferred from the sense of rotation of the spiral arms of spiral galaxies / from integral field spectroscopy, where we also find a correlation with ICs, though at a lower statistical significance. Finally, I mention how we use galaxy spins to probe chirality violations in the early Universe.
What do alignments tell us about initial conditions of the universe?
Alignments and Spin are fossils from the early universe, and currently the most abundant probe of small scale initial conditions. Early torquing is sensitive to neutrino mass and parity violation. I describe the basic dependencies on the three and four point functions, and end with open problems, including how spins depend on f_NL and g_NL.
Cosmology Dependence of the Transition Mass of Halo Spins
I will present recent numerical findings that the transition mass of halo spins is in principle a complementary probe of the background cosmology.
How large are alignments for lensing sources galaxies?
Despite significant progress in understanding IA, we remain uncertain how large of a contaminant it is for weak lensing. The highest signal-to-noise measurements of IA are for luminous, usually red, galaxies. Typical lensing sources are comparatively faint and blue, a regime where measurements are challenging and hydrodynamic simulations disagree. Until recently, the lensing community seemed to be converging on a scenario in which lensing sources had large enough IA to be clearly measured in Stage-III surveys and would require complex models for Stage-IV. However, the most recent cosmological results, including from DES, KiDS, and HSC, have hinted that perhaps IA is smaller than expected. I will discuss our current state of understanding and some ideas for how we can learn more in the near future.
TNG50 galaxies observed in the HSC-SSP!
Interpretation of the observed shapes of galaxies, their statistics, and their evolution with cosmic time requires a synergy between theoretical and observational galaxy astronomy. The most direct approach of facilitating this synergy is the forward-modelling of galaxies produced in hydrodynamical simulations. Using dusty radiative transfer with SKIRT9, I have produced over 100,000 survey-realistic HSC-SSP Joint images of z<1 galaxies from the high-resolution TNG50 hydrodynamical simulation. The images are injected into real HSC fields so that they incorporate the same observational nuisance factors and biases that affect real galaxy shape/morphology measurements. These images will facilitate (1) direct confrontation of theory and observations and (2) interpretation of observed galaxy shape and morphology statistics and (3) calibration of machine learning models which connect observables with unknowns.
Numerical study of cosmic spin reconstructions
Intrinsic alignments with numerical simulations
Numerical simulations of large-scale structures is a powerful tool for intrinsic alignments since nonlinear growth of structures is taken into account down to small scales. Furthermore, galaxy formation hydrodynamical simulations enable one to generate realistic galaxy images and we can calibrate the analysis pipeline by leveraging these galaxy mocks. In this talk, I will overview recent progress of intrinsic alignments with numerical simulations and present preliminary results of intrinsic alignments with mock emission line galaxies.
Imprint of gravitational waves on large-scale structure in simulations
Statistical properties of galaxy shapes with angular dependent primordial non-Gaussianities
Recently, the weak gravitational lensing analysis with imaging surveys has attracted much attention and the success that we access to the distribution of the dark matter is novel. This analysis is based on the fact that dark matters in the foreground distort the observed galaxies in the background. In practice, focused on the large scale, the intrinsic shapes of galaxies are known to be distorted by the external tidal field caused by large-scale structure, which is called the linear alignment model. In this study, we investigate how the intrinsic shapes of galaxies can respond to the non-Gaussianity of the initial gravitational potential. As a result, we find that the intrinsic shapes respond to the angular dependent primordial squeezed bispectra, which are motivated by the imprint of the massive higher spin particles to be predicted such as string theory, and that the moment decomposition of intrinsic shape may extract the non-Gaussianity corresponding to the order of the moment of the multipoles of primordial squeezed bispectrum.
Galaxy Intrinsic Alignment Power Spectrum in IllustrisTNG
Galaxy intrinsic alignment is a main contamination for cosmic shear measurement. However it also contains useful cosmological information. We have studied the galaxy shape/spin alignments in cosmological hydrodynamical simulations using 3d intrinsic alignment power spectrum for galaxies with varying mass, redshift, morphology, and environment. We also developed a new shape estimator that can be applied to ongoing/future cosmology survey, for extracting the cosmological information encoded in intrinsic alignment.
Forecasting z~2 direct galaxy-cosmic web alignment for Subaru-PFS
I will review recent work in measuring direct alignments between large-scale structure (LSS) and galaxy angular momenta and shapes, using hydrodynamic cosmological simulations. I will then preview an upcoming forecast of the LSS-galaxy alignment signal which will be measured by the Subaru Prime Focus Spectrograph (PFS), with LSS reconstruction through IGM tomography. We adopt a novel “viewing-angle agnostic” approach for our forecast, and quantify the effects of observer viewing-angle variance on position-angle alignment signals for the first time.
Tightening geometric and dynamical constraints on dark energy and gravity with galaxy intrinsic alignment
In this talk, we present how well one can improve the cosmological constraints from the combination of the galaxy density field with velocity and tidal fields, which are observed via the kinetic Sunyaev-Zel’dovich (kSZ) and galaxy intrinsic alignment (IA) effects, respectively. For illustration, we consider the deep galaxy survey by Subaru Prime Focus Spectrograph, whose survey footprint perfectly overlaps with the imaging survey of the Hyper Suprime-Cam and the CMB-S4 experiment. We find that adding the kSZ and IA effects significantly improves cosmological constraints, particularly when we adopt the non-flat cold dark matter model which allows both time variation of the dark energy equation-of-state and deviation of the gravity law from general relativity. As another example, we also consider the wide galaxy survey by the Euclid satellite, in which shapes of galaxies are noisier but the survey volume is much larger. We demonstrate that under the model mentioned above, the clustering analysis combined with kSZ and IA from the deep survey can achieve tighter cosmological constraints than the clustering-only analysis from the wide survey. If time allows, I will also present the latest measurement of IA at z > 1 by the cross correlation between CFHTLens and FastSound galaxy samples.
Intrinsic alignments of dark matter halos in f(R) gravity simulations
There is a growing interest in utilizing intrinsic alignment (IA) of galaxy shapes as a geometric and dynamical probe of cosmology. I will present our recent work on the measurements of IA using the gravitational shear-intrinsic ellipticity correlation(GI) and intrinsic ellipticity-ellipticity correlation(II) functions of dark-matter halos from the f(R) gravity model. By comparing them with the same statistics measured in ΛCDM simulations, we find that IA statistics enhance detectability of the imprint of f(R) gravity on large-scale structures by ∼ 20% when combined with the conventional halo clustering in redshift space. Thus, the GI and II correlations are useful in distinguishing between the ΛCDM and f(R) gravity models.
FFT-based estimators for line-of-sight dependent intrinsic alignment signals
The intrinsic galaxy shapes have been recently considered to be a new cosmological tracer of large-scale structure. Although the measurements and analysis of the IA correlation functions have been studied, a method of measuring the IA power spectrum from a realistic survey geometry has yet to be developed. In this talk, I will describe our attempt to develop an estimator of the IA power spectrum using the local plane-parallel approximation which should be valid in a realistic SDSS-like survey geometry. The estimator is based on Fast Fourier Transforms (FFTs) similar to the existing clustering estimator, the so-called Yamamoto estimator, requiring ~O(10) times more FFTs for IA power spectrum than that for clustering power spectrum at the same multipole moment. I will also show some validation tests of our estimator by hypothetical observation using simulation.