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We present the one-loop 2-point function of biased tracers in redshift space computed with Lagrangian perturbation theory, including a full resummation of both long-wavelength (infrared) displacements and associated velocities. The resulting model accurately predicts the power spectrum and correlation function of halos and mock galaxies from two different sets of N-body simulations at the percent level for quasi-linear scales, including the damping of the baryon acoustic oscillation signal due to the bulk motions of galaxies. We compare this full resummation with other, approximate, techniques including the moment expansion and Gaussian streaming model. We discuss infrared resummation in detail and compare our Lagrangian formulation with the Eulerian theory augmented by an infrared resummation based on splitting the input power spectrum into "wiggle"and "no-wiggle"components. We show that our model is able to recover unbiased cosmological parameters in mock data encompassing a volume much larger than what will be available to future galaxy surveys. We demonstrate how to efficiently compute the resulting expressions numerically, making available a fast Python code capable of rapidly computing these statistics in both configuration and Fourier space.

The line-of-sight peculiar velocities of galaxies contribute to theirobserved redshifts, breaking the translational invariance of galaxy clusteringdown to a rotational invariance around the observer. This becomes importantwhen the line-of-sight direction varies significantly across a survey, leadingto what are known as `wide angle' effects in redshift space distortions.Wide-angle effects will also be present in measurements of the momentum field,i.e. the galaxy density-weighted velocity field, in upcoming peculiar velocitysurveys. In this work we study how wide-angle effects modify the predictedcorrelation function and power spectrum for momentum statistics, both inauto-correlation and in cross-correlation with the density field. Using bothlinear theory and the Zeldovich approximation, we find that deviations from theplane-parallel limit are large and could become important in data analysis forlow redshift surveys. We point out that even multipoles in thecross-correlation between density and momentum are non-zero regardless of thechoice of line of sight, and therefore contain new cosmological informationthat could be exploited. We discuss configuration-space, Fourier-space andspherical analyses, providing exact expressions in each case rather thanrelying on an expansion in small angles. We hope these expressions will be ofuse in the analysis of upcoming surveys for redshift-space distortions andpeculiar velocities.

This is an erratum to the paper 'The Zeldovich approximation and wide-angle redshift-space distortions' by Castorina & White (2018). There is a mistake in equation (37) which should read (Equation Presented) where Σ2 and ξij are defined in the main text. The figures and the conclusions are all unchanged, however this mistake propagates to equation (46) which should read (Equation Presented) Equation (51) then becomes (Equation Presented) Equations (52)-(53) are no longer needed. The change affects equation (63) which should read (Equation Presented) Finally, in Appendix C, equations (C10-C13) should read (Equation Presented).

Upcoming 21-cm intensity surveys will use the hyperfine transition in emission to map out neutral hydrogen in large volumes of the universe. Unfortunately, large spatial scales are completely contaminated with spectrally smooth astrophysical foregrounds which are orders of magnitude brighter than the signal. This contamination also leaks into smaller radial and angular modes to form a foreground wedge, further limiting the usefulness of 21-cm observations for different science cases, especially cross-correlations with tracers that have wide kernels in the radial direction. In this paper, we investigate reconstructing these modes within a forward modeling framework. Starting with an initial density field, a suitable bias parameterization and non-linear dynamics to model the observed 21-cm field, our reconstruction proceeds by {combining} the likelihood of a forward simulation to match the observations (under given modeling error and a data noise model) {with the Gaussian prior on initial conditions and maximizing the obtained posterior}. For redshifts z=2 and 4, we are able to reconstruct 21cm field with cross correlation, rc > 0.8 on all scales for both our optimistic and pessimistic assumptions about foreground contamination and for different levels of thermal noise. The performance deteriorates slightly at z=6. The large-scale line-of-sight modes are reconstructed almost perfectly. We demonstrate how our method also provides a technique for density field reconstruction for baryon acoustic oscillations, outperforming standard methods on all scales. We also describe how our reconstructed field can provide superb clustering redshift estimation at high redshifts, where it is otherwise extremely difficult to obtain dense spectroscopic samples, as well as open up a wealth of cross-correlation opportunities with projected fields (e.g. lensing) which are restricted to modes transverse to the line of sight.

This paper introduces the HiddenValley simulations, a set of trillion-particle N-body simulations in gigaparsec volumes aimed at intensity mapping science. We present details of the simulations and their convergence, then specialize to the study of 21-cm fluctuations between redshifts 2 and 6. Neutral hydrogen is assigned to halos using three prescriptions, and we investigate the clustering in real and redshift-space at the 2-point level. In common with earlier work we find the bias of HI increases from near 2 at z=2 to 4 at z=6, becoming more scale dependent at high z. The level of scale-dependence and decorrelation with the matter field are as predicted by perturbation theory. Due to the low mass of the hosting halos, the impact of fingers of god is small on the range relevant for proposed 21-cm instruments. We show that baryon acoustic oscillations and redshift-space distortions could be well measured by such instruments. Taking advantage of the large simulation volume, we assess the impact of fluctuations in the ultraviolet background, which change HI clustering primarily at large scales.

Development of the hardware, data analysis, and simulation techniques forlarge compact radio arrays dedicated to mapping the 21 cm line of neutralhydrogen gas has proven to be more difficult than imagined twenty years agowhen such telescopes were first proposed. Despite tremendous technical andmethodological advances, there are several outstanding questions on how tooptimally calibrate and analyze such data. On the positive side, it has becomeclear that the outstanding issues are purely technical in nature and can besolved with sufficient development activity. Such activity will enable scienceacross redshifts, from early galaxy evolution in the pre-reionization era todark energy evolution at low redshift.

We study synergies between three promising methods to measure 22 and suffer from interloper problems even for spectroscopic surveys. Intensity mapping of the 21-cm signal can cover large volumes with exquisite fidelity, but is limited both by loss of information to foreground cleaning and by lack of knowledge of the mean signal. Cosmic microwave background (CMB) lensing is theoretically very clean, but ultimately measures just the projected variations in density. We find that cross-correlation between optical and radio can significantly improve the measurement of growth rate. Combining these with the CMB provides a promising avenue to detecting modified gravity at high redshifts, in particular by independently probing the Weyl and Newtonian potentials and by strengthening control of systematics. We find that cross-correlating a Stage ii 21-cm survey with DESI quasars with a reasonable brightness temperature prior could enable measurements of the growth rate fσ8 at sub 3% and sub 8% levels at z = 3, 4, representing a factor of 4 and 8 improvement over constraints obtainable from DESI quasars alone. Similarly, cross-correlating 21-cm data with a futuristic LBG survey to mUV

Line intensity mapping offers a new avenue for constraining cosmological parameters in the high redshift Universe. However measurements of the growth of structure, a sensitive probe of gravity, are affected by a well known degeneracy with astrophysical parameters, encoded in the mean brightness temperature of the specific line. In this work we show how to break this degeneracy, to a level that could allow constraints of the amplitude of cosmological fluctuations at the percent level, using information in the mildly non-linear regime of structure formation as described by Lagrangian Perturbation Theory. We focus on the 21-cm line with forecasts for HIRAX and the proposed Stage II experiment as illustrations.

We explore Lagrangian perturbation theory (LPT) for biased tracers in the presence of two fluids, focusing on the case of cold dark matter (CDM) and baryons. The presence of two fluids induces corrections to the Lagrangian bias expansion and tracer advection, both of which we formulate as expansions in the three linear modes of the Lagrangian equations of motion. We compute the linear-order two-fluid corrections in the Zeldovich approximation, finding that modifications to the bias expansion and tracer advection both enter as percent-level corrections over a large range of wavenumbers at low redshift and draw parallels with the Eulerian formalism. We then discuss nonlinear corrections in the two-fluid picture, and calculate contributions from the relative velocity effect (vr2) at one loop order. Finally, we conduct an exploratory Fisher analysis to assess the impact of two-fluid corrections on baryon acoustic oscillations (BAO) measurements, finding that while modest values of the relative bias parameters can introduce systematic biases in the measured BAO scale of up to 0.5 σ, fitting for these effects as additional parameters increases the error bar by less than 30% across a wide range of bias values.

The expansion of the Universe is understood to have accelerated during twoepochs: in its very first moments during a period of Inflation and much morerecently, at $z < 1$, when Dark Energy is hypothesized to drive cosmicacceleration. The undiscovered mechanisms behind these two epochs representsome of the most important open problems in fundamental physics. The largecosmological volume at $2 < z < 5$, together with the ability to efficientlytarget high-$z$ galaxies with known techniques, enables large gains in thestudy of Inflation and Dark Energy. A future spectroscopic survey can test theGaussianity of the initial conditions up to a factor of ~50 better than ourcurrent bounds, crossing the crucial theoretical threshold of$\sigma(f_{NL}^{\rm local})$ of order unity that separates single field andmulti-field models. Simultaneously, it can measure the fraction of Dark Energyat the percent level up to $z = 5$, thus serving as an unprecedented test ofthe standard model and opening up a tremendous discovery space.

The hot dense environment of the early universe is known to have producedlarge numbers of baryons, photons, and neutrinos. These extreme conditions mayhave also produced other long-lived species, including new light particles(such as axions or sterile neutrinos) or gravitational waves. The gravitationaleffects of any such light relics can be observed through their unique imprintin the cosmic microwave background (CMB), the large-scale structure, and theprimordial light element abundances, and are important in determining theinitial conditions of the universe. We argue that future cosmologicalobservations, in particular improved maps of the CMB on small angular scales,can be orders of magnitude more sensitive for probing the thermal history ofthe early universe than current experiments. These observations offer a uniqueand broad discovery space for new physics in the dark sector and beyond, evenwhen its effects would not be visible in terrestrial experiments or inastrophysical environments. A detection of an excess light relic abundancewould be a clear indication of new physics and would provide the first directinformation about the universe between the times of reheating and neutrinodecoupling one second later.

Our current understanding of the Universe is established through the pristinemeasurements of structure in the cosmic microwave background (CMB) and thedistribution and shapes of galaxies tracing the large scale structure (LSS) ofthe Universe. One key ingredient that underlies cosmological observables isthat the field that sources the observed structure is assumed to be initiallyGaussian with high precision. Nevertheless, a minimal deviation fromGaussianityis perhaps the most robust theoretical prediction of models thatexplain the observed Universe; itis necessarily present even in the simplestscenarios. In addition, most inflationary models produce far higher levels ofnon-Gaussianity. Since non-Gaussianity directly probes the dynamics in theearly Universe, a detection would present a monumental discovery in cosmology,providing clues about physics at energy scales as high as the GUT scale.

Astrophysical observations currently provide the only robust, empiricalmeasurements of dark matter. In the coming decade, astrophysical observationswill guide other experimental efforts, while simultaneously probing uniqueregions of dark matter parameter space. This white paper summarizesastrophysical observations that can constrain the fundamental physics of darkmatter in the era of LSST. We describe how astrophysical observations willinform our understanding of the fundamental properties of dark matter, such asparticle mass, self-interaction strength, non-gravitational interactions withthe Standard Model, and compact object abundances. Additionally, we highlighttheoretical work and experimental/observational facilities that will complementLSST to strengthen our understanding of the fundamental characteristics of darkmatter.

The contribution of line-of-sight (LOS) peculiar velocities to the observed redshift of objects breaks the translational symmetry of the underlying theory, modifying the predicted two-point functions. These 'wide-angle effects' have mostly been studied using linear perturbation theory in the context of the multipoles of the correlation function and power spectrum. In this work, we present the first calculation of wide-angle terms in the Zeldovich approximation, which is known to be more accurate than linear theory on scales probed by the next generation of galaxy surveys.We present the exact result for dark matter and perturbatively biased tracers as well as the small angle expansion of the configuration- and Fourier-space two-point functions and the connection to the multifrequency angular power spectrum. We compare different definitions of the LOS direction and discuss how to translate between them. We show that wide-angle terms can reach tens of percent of the total signal in a measurement at low redshift in some approximations, and that a generic feature of wide-angle effects is to slightly shift the Baryon Acoustic Oscillation scale.

Redshift -space distortions privilege the location of the observer in cosmological redshift surveys, breaking the translational symmetry of the underlying theory. This violation of statistical homogeneity has consequences for the modelling of clustering observables, leading to what are frequently called 'wide-angle effects'.We study these effects analytically, computing their signature in the clustering of the multipoles in configuration and Fourier space. We take into account both physical wide-angle contributions as well as the terms generated by the galaxy selection function. Similar considerations also affect the way power spectrum estimators are constructed. We quantify in an analytical way the biases that enter and clarify the relation between what we measure and the underlying theoretical modelling. The presence of an angular window function is also discussed. Motivated by this analysis, we present new estimators for the three dimensional Cartesian power spectrum and bispectrum multipoles written in terms of spherical Fourier-Bessel coefficients.We show how the latter have several interesting properties, allowing in particular a clear separation between angular and radial modes.

We update the ingredients of the Gaussian streaming model (GSM) for the redshift-space clustering of biased tracers using the techniques of Lagrangian perturbation theory, effective field theory (EFT) and a generalized Lagrangian bias expansion. After relating the GSM to the cumulant expansion, we present new results for the real-space correlation function, mean pairwise velocity and pairwise velocity dispersion including counter terms from EFT and bias terms through third order in the linear density, its leading derivatives and its shear up to second order. We discuss the connection to the Gaussian peaks formalism. We compare the ingredients of the GSM to a suite of large N-body simulations, and show the performance of the theory on the low order multipoles of the redshift-space correlation function and power spectrum. We highlight the importance of a general biasing scheme, which we find to be as important as higher-order corrections due to non-linear evolution for the halos we consider on the scales of interest to us.

We present severalmethods to accurately estimate Lagrangian bias parameters and substantiate them using simulations. In particular, we focus on the quadratic terms, both the local and the non-local ones, and show the first clear evidence for the latter in the simulations. Using Fourier space correlations, we also show for the first time, the scale dependence of the quadratic and non-local bias coefficients. For the linear bias, we fit for the scale dependence and demonstrate the validity of a consistency relation between linear bias parameters. Furthermore, we employ real-space estimators, using both cross-correlations and the peak-background split argument. This is the first time the latter is used to measure anisotropic bias coefficients. We find good agreement for all the parameters among these different methods, and also good agreement for local bias with Excursion set constraints τ theory predictions. We also try to exploit possible relations among the different bias parameters. Finally, we show how including higher order bias reduces the magnitude and scale dependence of stochasticity of the halo field. [ABSTRACT FROM AUTHOR]

The spatial distribution of neutral hydrogen (H I) in the Universe contains a wealth of cosmological information. The 21-cm emission line can be used to map the HI up to very high redshift and therefore reveal us something about the evolution of the large-scale structures in the Universe. However, little is known about the abundance and clustering properties of the HI over cosmic time. Motivated by this, we build an analytic framework where the relevant parameters that govern how the HI is distributed among dark matter haloes can be fixed using observations. At the same time, we provide tools to study the column density distribution function of the HI absorbers together with their clustering properties. Our formalism is the first one able to account for all observations at a single redshift, z = 2.3. The linear bias of the HI and the mean number density of HI sources, two main ingredients in the calculation of the signal-to-noise ratio of a cosmological survey, are then discussed in detail, also extrapolating the results to low and high redshift. We find that HI bias is relatively higher than the value reported in similar studies, but the shot noise level is always sub-dominant, making the HI power spectrum always a high signal-to-noise measurement up to z ≅ 5 in the limit of no instrumental noise and foreground contamination. [ABSTRACT FROM AUTHOR]

Cross-correlations between biased tracers and the dark matter field encode information about the physical variables that characterize these tracers. However, if the physical variables of interest are correlated with one another, then extracting this information is not as straightforward as one might naively have thought. We show how to exploit these correlations so as to estimate scale-independent bias factors of all orders in a model-independent way. We also show that failure to account for this will lead to incorrect conclusions about which variables matter and which do not. Moreover, accounting for this allows one to use the scale dependence of bias to constrain the physics of halo formation; to date, the argument has been phrased the other way around. We illustrate by showing that the scale dependence of linear and non-linear bias, measured on non-linear scales, can be used to provide consistent estimates of how the critical density for halo formation depends on halo mass. Our methods work even when the bias is non-local and stochastic, such as when, in addition to the spherically averaged density field and its derivatives, the quadrupolar shear field also matters for halo formation. In such models, the non-local bias factors are closely related to the more familiar local non-linear bias factors, which are much easier to measure. Our analysis emphasizes the fact that biased tracers are biased because they do not sample fields (density, velocity, shear, etc.) at all positions in space in the same way as the dark matter does. [ABSTRACT FROM AUTHOR]

We present the latest version of pinocchio, a code that generates catalogues of dark matter haloes in an approximate but fast way with respect to an N-body simulation. This code version implements a new on-the-fly production of halo catalogue on the past light cone with continuous time sampling, and the computation of particle and halo displacements are extended up to third-order Lagrangian perturbation theory (LPT), in contrast with previous versions that used Zel'dovich approximation. We run pinocchio on the same initial configuration of a reference N-body simulation, so that the comparison extends to the object-by-object level. We consider haloes at redshifts 0 and 1, using different LPT orders either for halo construction or to compute halo final positions. We compare the clustering properties of pinocchio haloes with those from the simulation by computing the power spectrum and two-point correlation function in real and redshift space (monopole and quadrupole), the bispectrum and the phase difference of halo distributions. We find that 2LPT and 3LPT give noticeable improvement. 3LPT provides the best agreement with N-body when it is used to displace haloes, while 2LPT gives better results for constructing haloes. At the highest orders, linear bias is typically recovered at a few per cent level. In Fourier space and using 3LPT for halo displacements, the halo power spectrum is recovered to within 10 per cent up to kmax ~0.5 h Mpc-1. The results presented in this paper have interesting implications for the generation of large ensemble of mock surveys for the scientific exploitation of data from big surveys. [ABSTRACT FROM AUTHOR]

We develop a new method to constrain primordial non-Gaussianities of the local kind using unclustered tracers of the large scale structure. We show that, in the limit of low noise, zero bias tracers yield large improvement over standard methods, mostly due to vanishing sampling variance. We propose a simple technique to construct such a tracer, using environmental information obtained from the original sample and validate our method with N-body simulations. Our results indicate that σflocNL≃1 can be reached using only information on a single tracer of sufficiently high number density. [ABSTRACT FROM AUTHOR]

Cosmology offers opportunities to test dark matter independently of its interactions with the standard model. We study the imprints of long-range forces acting solely in the dark sector on the distribution of galaxies, the so-called large scale structure (LSS). We derive the strongest constraint on such forces from a combination of Planck and BOSS data. Along the way we consistently develop, for the first time, the effective field theory of LSS in the presence of new dynamics in the dark sector. We forecast that future surveys will improve the current bound by an order of magnitude.

The large scale limit of the galaxy power spectrum provides a unique window into the early Universe through a possible detection of scale dependent bias produced by primordial non Gaussianities. On such large scales, relativistic effects could become important and be confused for a primordial signal. In this Letter we provide the first consistent estimate of such effects in the observed galaxy power spectrum, and discuss their possible degeneracy with local primordial non Gaussianities. We also clarify the physical differences between the two signatures, as revealed by their different sensitivity to the large scale gravitational potential. Our results indicate that, while relativistic effects could easily account for 10% of the observed power spectrum, the subset of those with a similar scale dependence to a primordial signal can be safely ignored for current galaxy surveys, but it will become relevant for future observational programs.