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Ken Osato  One of the best experts on this subject based on the ideXlab platform.

Power Spectrum of halo intrinsic alignments in simulations
Monthly Notices of the Royal Astronomical Society, 2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60\% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be Powerful tools to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Physical Review D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the Dark Quest $N$body simulation suite that covers 101 flatgeometry $w$CDM cosmologies around the Planck $\Lambda$CDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to $k \simeq 0.6 \, h \, {\rm Mpc}^{1}$. Our emulator achieves about 1 and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of $\sim 10^{13}h^{1}M_\odot$ that correspond to host halos of the SDSS LOWZ and CMASSlike galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczy\'{n}ski distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds, and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.

Power Spectrum of halo intrinsic alignments in simulations
2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter of galaxy or halo density field. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Phys.Rev.D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work, we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the dark quest Nbody simulation suite that covers 101 flatgeometry wcold dark matter (wCDM) cosmologies around the Planck ΛCDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to k≃0.6h Mpc1. Our emulator achieves about 1% and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of ∼1013h1 M⊙ that correspond to host halos of the Sloan Digital Sky Survey (SDSS) LOWZ and CMASS (constant mass)like galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczyński distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.
Yosuke Kobayashi  One of the best experts on this subject based on the ideXlab platform.

Power Spectrum of halo intrinsic alignments in simulations
Monthly Notices of the Royal Astronomical Society, 2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60\% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be Powerful tools to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Physical Review D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the Dark Quest $N$body simulation suite that covers 101 flatgeometry $w$CDM cosmologies around the Planck $\Lambda$CDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to $k \simeq 0.6 \, h \, {\rm Mpc}^{1}$. Our emulator achieves about 1 and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of $\sim 10^{13}h^{1}M_\odot$ that correspond to host halos of the SDSS LOWZ and CMASSlike galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczy\'{n}ski distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds, and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.

Power Spectrum of halo intrinsic alignments in simulations
2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter of galaxy or halo density field. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Phys.Rev.D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work, we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the dark quest Nbody simulation suite that covers 101 flatgeometry wcold dark matter (wCDM) cosmologies around the Planck ΛCDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to k≃0.6h Mpc1. Our emulator achieves about 1% and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of ∼1013h1 M⊙ that correspond to host halos of the Sloan Digital Sky Survey (SDSS) LOWZ and CMASS (constant mass)like galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczyński distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.
Jérôme Bobin  One of the best experts on this subject based on the ideXlab platform.

PRISM: Sparse Recovery of the Primordial Power Spectrum
Astronomy & Astrophysics, 2014CoAuthors: P. Paykari, Jeanluc Starck, Francois Lanusse, F. Sureau, Jérôme BobinAbstract:The primordial Power Spectrum describes the initial perturbations in the Universe which eventually grew into the largescale structure we observe today, and thereby provides an indirect probe of inflation or other structureformation mechanisms. Here, we introduce a new method to estimate this Spectrum from the empirical Power Spectrum of cosmic microwave background (CMB) maps. A sparsitybased linear inversion method, coined \textbf{PRISM}, is presented. This technique leverages a sparsity prior on features in the primordial Power Spectrum in a wavelet basis to regularise the inverse problem. This nonparametric approach does not assume a strong prior on the shape of the primordial Power Spectrum, yet is able to correctly reconstruct its global shape as well as localised features. These advantages make this method robust for detecting deviations from the currently favoured scaleinvariant Spectrum. We investigate the strength of this method on a set of WMAP 9year simulated data for three types of primordial Power spectra: a nearly scaleinvariant Spectrum, a Spectrum with a small running of the spectral index, and a Spectrum with a localised feature. This technique proves to easily detect deviations from a pure scaleinvariant Power Spectrum and is suitable for distinguishing between simple models of the inflation. We process the WMAP 9year data and find no significant departure from a nearly scaleinvariant Power Spectrum with the spectral index $n_s = 0.972$. A high resolution primordial Power Spectrum can be reconstructed with this technique, where any strong local deviations or small global deviations from a pure scaleinvariant Spectrum can easily be detected.

PRISM: Sparse recovery of the primordial Power Spectrum
Astronomy and Astrophysics  A&A, 2014CoAuthors: P. Paykari, Francois Lanusse, F. Sureau, J.l. Starck, Jérôme BobinAbstract:Aims. The primordial Power Spectrum describes the initial perturbations in the Universe which eventually grew into the largescale structure we observe today, and thereby provides an indirect probe of inflation or other structureformation mechanisms. Here, we introduce a new method to estimate this Spectrum from the empirical Power Spectrum of cosmic microwave background maps. Methods. A sparsitybased linear inversion method, named PRISM, is presented. This technique leverages a sparsity prior on features in the primordial Power Spectrum in a wavelet basis to regularise the inverse problem. This nonparametric approach does not assume a strong prior on the shape of the primordial Power Spectrum, yet is able to correctly reconstruct its global shape as well as localised features. These advantages make this method robust for detecting deviations from the currently favoured scaleinvariant Spectrum. Results. We investigate the strength of this method on a set of WMAP nineyear simulated data for three types of primordial Power spectra: a near scaleinvariant Spectrum, a Spectrum with a small running of the spectral index, and a Spectrum with a localised feature. This technique proves that it can easily detect deviations from a pure scaleinvariant Power Spectrum and is suitable for distinguishing between simple models of the inflation. We process the WMAP nineyear data and find no significant departure from a near scaleinvariant Power Spectrum with the spectral index ns = 0.972. Conclusions. A highresolution primordial Power Spectrum can be reconstructed with this technique, where any strong local deviations or small global deviations from a pure scaleinvariant Spectrum can easily be detected.
Masahiro Takada  One of the best experts on this subject based on the ideXlab platform.

Power Spectrum of halo intrinsic alignments in simulations
Monthly Notices of the Royal Astronomical Society, 2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60\% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be Powerful tools to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Physical Review D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the Dark Quest $N$body simulation suite that covers 101 flatgeometry $w$CDM cosmologies around the Planck $\Lambda$CDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to $k \simeq 0.6 \, h \, {\rm Mpc}^{1}$. Our emulator achieves about 1 and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of $\sim 10^{13}h^{1}M_\odot$ that correspond to host halos of the SDSS LOWZ and CMASSlike galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczy\'{n}ski distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds, and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.

Power Spectrum of halo intrinsic alignments in simulations
2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter of galaxy or halo density field. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Phys.Rev.D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work, we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the dark quest Nbody simulation suite that covers 101 flatgeometry wcold dark matter (wCDM) cosmologies around the Planck ΛCDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to k≃0.6h Mpc1. Our emulator achieves about 1% and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of ∼1013h1 M⊙ that correspond to host halos of the Sloan Digital Sky Survey (SDSS) LOWZ and CMASS (constant mass)like galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczyński distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.
Takahiro Nishimichi  One of the best experts on this subject based on the ideXlab platform.

Power Spectrum of halo intrinsic alignments in simulations
Monthly Notices of the Royal Astronomical Society, 2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60\% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be Powerful tools to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Physical Review D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the Dark Quest $N$body simulation suite that covers 101 flatgeometry $w$CDM cosmologies around the Planck $\Lambda$CDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to $k \simeq 0.6 \, h \, {\rm Mpc}^{1}$. Our emulator achieves about 1 and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of $\sim 10^{13}h^{1}M_\odot$ that correspond to host halos of the SDSS LOWZ and CMASSlike galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczy\'{n}ski distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds, and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.

Power Spectrum of halo intrinsic alignments in simulations
2020CoAuthors: Toshiki Kurita, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken Osato, Yosuke KobayashiAbstract:We use a suite of $N$body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the $\Lambda$CDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional Power Spectrum of the $E$mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the autoPower Spectrum of the $E$ mode, $P^{(\ell)}_{EE}(k)$, based on the $E$/$B$mode decomposition. The IA Power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at $k\lesssim 0.1~h~{\rm Mpc}^{1}$ are related to the matter Power Spectrum via a constant coefficient ($A_{\rm IA}$), similar to the linear bias parameter of galaxy or halo density field. We find that the cross and autoPower spectra $P_{\delta E}$ and $P_{EE}$ at nonlinear scales, $k\gtrsim 0.1~h~{\rm Mpc}^{1}$, show different $k$dependences relative to the matter Power Spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA Power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters ($\Omega_{\rm m}, S_8$). The cumulative signaltonoise ratio for the IA Power spectra is about 60% of that for the halo density Power Spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA Power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter Power Spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density Power Spectrum.

Accurate emulator for the redshiftspace Power Spectrum of dark matter halos and its application to galaxy Power Spectrum
Phys.Rev.D, 2020CoAuthors: Yosuke Kobayashi, Masahiro Takada, Takahiro Nishimichi, Ryuichi Takahashi, Ken OsatoAbstract:An accurate theoretical template of the redshiftspace galaxy Power Spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work, we develop a simulationbased template, socalled emulator, for the redshiftspace Power Spectrum of dark matter halos. Using the redshiftspace halo Power spectra measured from the dark quest Nbody simulation suite that covers 101 flatgeometry wcold dark matter (wCDM) cosmologies around the Planck ΛCDM model, we feed these data into a feedforward neural network to build the fast and accurate emulation of the Power Spectrum from the linear to nonlinear scales up to k≃0.6h Mpc1. Our emulator achieves about 1% and 5% fractional accuracies in predicting the monopole and quadrupole moments of the Power Spectrum, respectively, for halos of ∼1013h1 M⊙ that correspond to host halos of the Sloan Digital Sky Survey (SDSS) LOWZ and CMASS (constant mass)like galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the Power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshiftspace Power Spectrum of galaxies by employing userfed models for the halogalaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the FingerofGod effect due to the virial motions of galaxies and the AlcockPaczyński distortions. Our code can compute the redshiftspace galaxy Power Spectrum in a CPU subseconds and is ready to perform the emulatorbased cosmological analysis for the exiting and upcoming galaxy redshift surveys.