185 research outputs found
On the reach of perturbative methods for dark matter density fields
We study the mapping from Lagrangian to Eulerian space in the context of the
Effective Field Theory (EFT) of Large Scale Structure. We compute Lagrangian
displacements with Lagrangian Perturbation Theory (LPT) and perform the full
non-perturbative transformation from displacement to density. When expanded up
to a given order, this transformation reproduces the standard Eulerian
Perturbation Theory (SPT) at the same order. However, the full transformation
from displacement to density also includes higher order terms. These terms
explicitly resum long wavelength motions, thus making the resulting density
field better correlated with the true non-linear density field. As a result,
the regime of validity of this approach is expected to extend that of the
Eulerian EFT, and match that of the IR-resummed Eulerian EFT. This approach
thus effectively enables a test of the IR-resummed EFT at the field level. We
estimate the size of stochastic, non-perturbative contributions to the matter
density power spectrum. We find that in our highest order calculation, at
redshift z=0 the power spectrum of the density field is reproduced with an
accuracy of 1 % (10 %) up to k=0.25 h/Mpc (k=0.46 h/Mpc). We believe that the
dominant source of the remaining error is the stochastic contribution.
Unfortunately, on these scales the stochastic term does not yet scale as
as it does in the very low-k regime. Thus, modeling this contribution might be
challenging.Comment: 22 pages, 10 figure
On the reach of perturbative descriptions for dark matter displacement fields
We study Lagrangian Perturbation Theory (LPT) and its regularization in the
Effective Field Theory (EFT) approach. We evaluate the LPT displacement with
the same phases as a corresponding -body simulation, which allows us to
compare perturbation theory to the non-linear simulation with significantly
reduced cosmic variance, and provides a more stringent test than simply
comparing power spectra. We reliably detect a non-vanishing leading order EFT
coefficient and a stochastic displacement term, uncorrelated with the LPT
terms. This stochastic term is expected in the EFT framework, and, to the best
of our understanding, is not an artifact of numerical errors or transients in
our simulations. This term constitutes a limit to the accuracy of perturbative
descriptions of the displacement field and its phases, corresponding to a
error on the non-linear power spectrum at /Mpc at . Predicting
the displacement power spectrum to higher accuracy or larger wavenumbers thus
requires a model for the stochastic displacement.Comment: 48 pages, 29 figures, comments welcom
Weak Lensing of Intensity Mapping: the Cosmic Infrared Background
Gravitational lensing deflects the paths of cosmic infrared background (CIB)
photons, leaving a measurable imprint on CIB maps. The resulting statistical
anisotropy can be used to reconstruct the matter distribution out to the
redshifts of CIB sources. To this end, we generalize the CMB lensing quadratic
estimator to any weakly non-Gaussian source field, by deriving the optimal
lensing weights. We point out the additional noise and bias caused by the
non-Gaussianity and the `self-lensing' of the source field. We propose methods
to reduce, subtract or model these non-Gaussianities. We show that CIB lensing
should be detectable with Planck data, and detectable at high significance for
future CMB experiments like CCAT-Prime. The CIB thus constitutes a new source
image for lensing studies, providing constraints on the amplitude of structure
at intermediate redshifts between galaxies and the CMB. CIB lensing
measurements will also give valuable information on the star formation history
in the universe, constraining CIB halo models beyond the CIB power spectrum. By
laying out a detailed treatment of lens reconstruction from a weakly
non-Gaussian source field, this work constitutes a stepping stone towards lens
reconstruction from continuum or line intensity mapping data, such as the
Lyman-alpha emission, absorption, and the 21cm radiation.Comment: Accepted in Physical Review
Future constraints on halo thermodynamics from combined Sunyaev-Zel'dovich measurements
The improving sensitivity of measurements of the kinetic Sunyaev-Zel'dovich
(SZ) effect opens a new window into the thermodynamic properties of the baryons
in halos. We propose a methodology to constrain these thermodynamic properties
by combining the kinetic SZ, which is an unbiased probe of the free electron
density, and the thermal SZ, which probes their thermal pressure. We forecast
that our method constrains the average thermodynamic processes that govern the
energetics of galaxy evolution like energetic feedback across all redshift
ranges where viable halos sample are available. Current Stage-3 cosmic
microwave background (CMB) experiments like AdvACT and SPT-3G can measure the
kSZ and tSZ to greater than 100 if combined with a DESI-like
spectroscopic survey. Such measurements translate into percent-level
constraints on the baryonic density and pressure profiles and on the feedback
and non-thermal pressure support parameters for a given ICM model. This in turn
will provide critical thermodynamic tests for sub-grid models of feedback in
cosmological simulations of galaxy formation. The high fidelity measurements
promised by the next generation CMB experiment, CMB-S4, allow one to further
sub-divide these constraints beyond redshift into other classifications, like
stellar mass or galaxy type.Comment: 11 pages, 3 figures, Accepted to JCA
Photo-z outlier self-calibration in weak lensing surveys
Calibrating photometric redshift errors in weak lensing surveys with external
data is extremely challenging. We show that both Gaussian and outlier photo-z
parameters can be self-calibrated from the data alone. This comes at no cost
for the neutrino masses, curvature and dark energy equation of state , but
with a 65% degradation when both and are varied. We perform a
realistic forecast for the Vera Rubin Observatory (VRO) Legacy Survey of Space
and Time (LSST) 3x2 analysis, combining cosmic shear, projected galaxy
clustering and galaxy - galaxy lensing. We confirm the importance of
marginalizing over photo-z outliers. We examine a subset of internal
cross-correlations, dubbed "null correlations", which are usually ignored in
3x2 analyses. Despite contributing only 10% of the total
signal-to-noise, these null correlations improve the constraints on photo-z
parameters by up to an order of magnitude. Using the same galaxy sample as
sources and lenses dramatically improves the photo-z uncertainties too.
Together, these methods add robustness to any claim of detected new Physics,
and reduce the statistical errors on cosmology by 15% and 10% respectively.
Finally, including CMB lensing from an experiment like Simons Observatory or
CMB-S4 improves the cosmological and photo-z posterior constraints by about
10%, and further improves the robustness to systematics. To give intuition on
the Fisher forecasts, we examine in detail several toy models that explain the
origin of the photo-z self-calibration. Our Fisher code LaSSI (Large-Scale
Structure Information), which includes the effect of Gaussian and outlier
photo-z, shear multiplicative bias, linear galaxy bias, and extensions to
CDM, is publicly available at https://github.com/EmmanuelSchaan/LaSSI .Comment: Accepted in JCAP on 10/08/2020. Code publicly available at
https://github.com/EmmanuelSchaan/LaSS
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