Abstract
We present a new power spectrum emulator named EuclidEmulator that estimates the nonlinear correction to the linear dark matter power spectrum depending on the six cosmological parameters ...ωb, ωm, ns, h, $w$0, and σ8. It is constructed using the uncertainty quantification software UQLab using a spectral decomposition method called polynomial chaos expansion. All steps in its construction have been tested and optimized: the large high-resolution N-body simulations carried out with PKDGRAV3 were validated using a simulation from the Euclid Flagship campaign and demonstrated to have converged up to wavenumbers $k\approx 5\, h\, {\rm Mpc}^{-1}$ for redshifts $z$ ≤ 5. The emulator is based on 100 input cosmologies simulated in boxes of (1250 Mpc/h)3 using 20483 particles. We show that by creating mock emulators it is possible to successfully predict and optimize the performance of the final emulator prior to performing any N-body simulations. The absolute accuracy of the final nonlinear power spectrum is as good as one obtained with N-body simulations, conservatively, ${\sim } 1$ per cent for $k\lesssim 1\, h\, {\rm Mpc}^{-1}$ and $z$ ≲ 1. This enables efficient forward modelling in the nonlinear regime, allowing for estimation of cosmological parameters using Markov Chain Monte Carlo methods. EuclidEmulator has been compared to HALOFIT, CosmicEmu, and NGenHalofit, and shown to be more accurate than these other approaches. This work paves a new way for optimal construction of future emulators that also consider other cosmological observables, use higher resolution input simulations, and investigate higher dimensional cosmological parameter spaces.
Seafloor deformation monitoring is now routinely performed in the marine sector of the Campi Flegrei volcanic area (Southern Italy). The MEDUSA infrastructure is formed by four buoys deployed at a ...water depth ranging from 40 to 96 m, and equipped with cGPS receivers, accelerometers and magnetic compasses to monitor the buoy status and a seafloor module with a bottom pressure recorder and other onboard instruments. The analysis of the time series data acquired by the MEDUSA monitoring infrastructure system allows to study the seafloor deformation in the Campi Flegrei caldera with geodetic accuracy. In a previous work, we show that the time series acquired by the Campi Flegrei cGPS onland network and MEDUSA over the period 2017–2020 are in good agreement with the ground deformation field predicted by a Mogi model which is widely used to describe the observed deformation of an active volcano in terms of magma intrusion. Only for one of the buoys, CFBA (A), the data differ significantly from the model prediction, at a level of
≃
6.9
σ
and of
≃
23.7
σ
for the seafloor horizontal speed and direction, respectively. For this reason, we devised a new method to reconstruct the horizontal sea bottom displacement considering in the analysis both cGPS and compass data. The method, applied to the CFBA buoy measurements and validated also on the CFBC (C) buoy, uses compass data to correct cGPS positions accounting for the pole inclination. Including also systematic errors, the internal consistency, always within
∼
3
σ
for the speed and
∼
2
σ
for the angle, between the results derived for different maximum inclinations of the buoy pole (up to 3.5
∘
) indicates that the method allows to significantly reduce the impact of the pole inclination which, if not properly taken into account, can alter the estimation of the horizontal seafloor deformation. In particular, we find a good convergence of the retrieved velocity and deformation angle as we include in the analysis data from increasing values of the buoy pole inclination. Taking the result derived assuming the maximum allowed cutoff and accounting for statistical and systematic errors, we found a speed
v
= (3.521 ± 0.039 (
stat
) ± 0.352 (
syst
)) cm/yr and a deformation direction angle
α
= (
-
115.159
± 0.670 (
stat
) ± 7.630 (
syst
))
∘
(statistical errors at 1
σ
quoted from the rms of their values, main systematic errors added linearly). The relative impact of the main potential systematic (statistical) effects increases (decreases) with the cutoff. Our analysis provides a horizontal speed consistent with the model at a level of
≃
5.2
σ
(
stat
only) or of
≃
0.5
σ
(
stat
and
syst
added linearly), and a deformation angle consistent with the model at
≃
4.3
σ
level (
stat
only) or at
≃
0.3
σ
level (
stat
and
syst
added linearly). Correspondingly, the module of the vectorial difference between the velocity retrieved from the data and the velocity of the adopted Mogi model diminishes by a factor of
≃
7.65 ± 1.23 (
stat
) or ± 5.78 (
stat
+
syst
) with respect to the previous work. A list of potential improvements to be implemented in the system and instruments is also discussed.
Cosmic background radiation has been observed to deviate from the Planck law expected from a blackbody at ∼2.7 K at frequencies below ∼3 GHz. We discuss the abundance of the low-energy photons from ...the perspective of nonequilibrium statistical mechanics. We propose a mechanism of stochastic frequency diffusion, the counterpart to stochastic acceleration for charged particles in a turbulent plasma, to modify the standard Kompaneets equation. The resulting violation of the Einstein relation allows us to take advantage of low-frequency localization and finally leads to photon cooling. The modified equation predicts a frequency distribution in agreement with the absolute temperature measurements of the cosmic background radiation down to about 20 MHz, for which we offer an updated compilation. In that sense, the so-called space roar we observe today is interpreted as a nonequilibrium echo of the early universe and more specifically of nonequilibrium conditions in the primordial plasma.
In spite of the great recent results from the Planck satellite supporting cosmological reionization scenarios almost compatible with astrophysical models for the evolution of structure, galaxy and ...star formation, the full understanding of the reionization and thermal history since recombination epoch is still far to be consolidated. The radio to sub-millimeter background provides a very important window for studying cosmological reionization process in a global approach, to arrive to the complete comprehension of the involved photon and energy sources. CMB polarization provides global information of ionization history, 21-cm line tomographic view allows to reconstruct ionization and clumping history, CMB spectral distortion provides global information on these aspects and a direct view of the global energy dissipations. Given the relevance of cosmological reionization for the comprehension of early phases of structure formation and evolution and its connection with a large variety of astrophysical and cosmological questions, it is important to discriminate among the various models compatible with current data. A brief overview of the proposals of future CMB missions and of radio namely the Square Kilometer Array (SKA) and its precursor/pathfinders projects is presented. We then describe the scientific outcome of future CMB missions, focussing on the information carried out by polarization anisotropies, spectral (absolute temperature) distortion and dipole (anisotroy) distortions, and discuss the promising perspectives opened by forthcoming and future radio surveys, focussing on the information carried out by the redshifted 21-cm line and by the free-free diffuse emission. Finally, we describe the contribution of future radio surveys to reionization studies with CMB polarization projects.
Planck, SPT, and ACT surveys have clearly demonstrated that Cosmic Microwave Background (CMB) experiments, while optimized for cosmological measurements, have made important contributions to the ...field of extragalactic astrophysics in the last decade. Future CMB experiments have the potential to make even greater contributions. One example is the detection of high-z galaxies with extreme gravitational amplifications. The combination of flux boosting and of stretching of the images has allowed the investigation of the structure of galaxies at z ≃ 3 with the astounding spatial resolution of about 60 pc. Another example is the detection of proto-clusters of dusty galaxies at high z when they may not yet possess the hot intergalactic medium allowing their detection in X-rays or via the Sunyaev-Zeldovich effect. Next generation CMB experiments, like PICO, CORE, CMB-Bharat from space and Simons Observatory and CMB-S4 from the ground, will discover several thousands of strongly lensed galaxies out to z ~ 6 or more and of galaxy proto-clusters caught in the phase when their member galaxies where forming the bulk of their stars. They will also detect tens of thousands of local dusty galaxies and thousands of radio sources at least up to z ≃ 5. Moreover they will measure the polarized emission of thousands of radio sources and of dusty galaxies at mm/sub-mm wavelengths.
The
Planck On-the-Flight Forecaster (POFF) is a tool to predict when a position in the sky will be within a selected angular distance from any instrument receiver direction in the
Planck satellite ...taking into consideration its programmed observational plan. The tool has been developed in the framework of the
Planck LFI Core Team activities, but it is now used by the whole
Planck collaboration.
In this paper we describe the tool and its applications to plan observations of point sources with other instruments which are expected to increase the scientific importance of
Planck data, once they are publicly available. Collecting simultaneous multi-frequency data, like those that can be planned with the POFF, will aid the investigation of variability in point sources and also allow the reconstruction of point source spectral energy distributions over wide frequency range, thus minimizing the effect of variability itself.
POFF is a combination of IDL routines which combine the publicly available information about the
Planck scanning strategy with the focal plane shape to identify if a given (list of) position(s) could be observed by the satellite at a given frequency and/or by selected receivers in a given time range. The output can be displayed with any reasonable desired time resolution and with various sorting options.
The code is not a
Planck product, but has been validated with the
Planck LFI pipeline, by searching for sources in the first satellite datasets. It has been implemented as one of the general tools of the LFI Data Processing Center. The code format and its large number of options make the program flexible and suitable for many applications, facilitating fast results.
POFF is currently successfully used to plan activities within the
Planck collaboration, including observations with several ground-based facilities, and is also available to the larger scientific community.
This paper discusses the science case for a sensitive spectro-polarimetric survey of the microwave sky. Such a survey would provide a tomographic and dynamic census of the three-dimensional ...distribution of hot gas, velocity flows, early metals, dust, and mass distribution in the entire Hubble volume, exploit CMB temperature and polarisation anisotropies down to fundamental limits, and track energy injection and absorption into the radiation background across cosmic times by measuring spectral distortions of the CMB blackbody emission. In addition to its exceptional capability for cosmology and fundamental physics, such a survey would provide an unprecedented view of microwave emissions at sub-arcminute to few-arcminute angular resolution in hundreds of frequency channels, a data set that would be of immense legacy value for many branches of astrophysics. We propose that this survey be carried out with a large space mission featuring a broad-band polarised imager and a moderate resolution spectro-imager at the focus of a 3.5 m aperture telescope actively cooled to about 8K, complemented with absolutely-calibrated Fourier Transform Spectrometer modules observing at degree-scale angular resolution in the 10–2000 GHz frequency range. We propose two observing modes: a survey mode to map the entire sky as well as a few selected wide fields, and an observatory mode for deeper observations of regions of specific interest.
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