scholarly journals A space mission to map the entire observable universe using the CMB as a backlight

2021 ◽  
Author(s):  
Kaustuv Basu ◽  
Mathieu Remazeilles ◽  
Jean-Baptiste Melin ◽  
David Alonso ◽  
James G. Bartlett ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Microwave Frequency ◽  
Resonant Scattering ◽  
White Paper ◽  
Space Mission ◽  
Stellar Content ◽  
Microwave Background ◽  
Free Electrons ◽  
Observable Universe ◽  
Scientific Questions

AbstractThis Science White Paper, prepared in response to the ESA Voyage 2050 call for long-term mission planning, aims to describe the various science possibilities that can be realized with an L-class space observatory that is dedicated to the study of the interactions of cosmic microwave background (CMB) photons with the cosmic web. Our aim is specifically to use the CMB as a backlight – and survey the gas, total mass, and stellar content of the entire observable Universe by means of analyzing the spatial and spectral distortions imprinted on it. These distortions result from two major processes that impact on CMB photons: scattering by free electrons and atoms (Sunyaev-Zeldovich effect in diverse forms, Rayleigh scattering, resonant scattering) and deflection by gravitational potential (lensing effect). Even though the list of topics collected in this White Paper is not exhaustive, it helps to illustrate the exceptional diversity of major scientific questions that can be addressed by a space mission that will reach an angular resolution of 1.5 arcmin (goal 1 arcmin), have an average sensitivity better than 1 μK-arcmin, and span the microwave frequency range from roughly 50 GHz to 1 THz. The current paper also highlights the synergy of our Backlight mission concept with several upcoming and proposed ground-based CMB experiments.

scholarly journals The need for a multi-purpose, optical–NIR space facility after HST and JWST

2021 ◽  
Author(s):  
Knud Jahnke ◽  
Oliver Krause ◽  
Hans-Walter Rix ◽  
Frédéric Courbin ◽  
Adriano Fontana ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
White Paper ◽  
Space Mission ◽  
General Purpose ◽  
List Type ◽  
Space Telescope ◽  
Readiness Level ◽  
Visible Wavelengths

AbstractIn the early 2030s, after the end of operations for the epochal Hubble Space Telescope and the long-anticipated James Webb Space Telescope, astrophysics will lose access to a general purpose high-spatial resolution space observatory to cover the UV–optical–NIR wavelength range with a variety of imaging bandpasses and high-multiplexing mid-resolution spectroscopy. This will greatly impact astrophysical “discovery space” at visible wavelengths, in stark contrast to progress at most other wavelengths enabled by groundbreaking new facilities between 2010 and 2030. This capability gap will foreseeably limit progress in a number of fundamental research directions anticipated to be pressing in the 2030’s and beyond such as: What are the histories of star formation and cosmic element production in nearby galaxies? What can we learn about the nature of dark matter from dwarf galaxies? What is the local value of the Hubble Constant? A multi-purpose optical–NIR imaging and multiplexed spectroscopy Workhorse Camera (HWC) onboard NASA’s 4m-class Habitable Exoplanet Observatory (HabEx) space mission would provide access to these required data. HabEx is currently under study by NASA for the US Decadal Survey on Astronomy and Astrophysics 2020, and if selected would launch around 2035. Aside from its direct imaging of Earth-like exoplanets, it will have a general-observatory complement of instrumentation. The versatile Workhorse Camera will provide imaging and R$\sim $ ∼ 1000 spectroscopy from 370nm to 1800nm, diffraction-limited over the whole wavelength range, with simultaneous observations of the visible and NIR. Spectroscopic multiplexing will be achieved through microshutter arrays. All necessary HWC technology is already at Technology Readiness Level 5, hence technological risks are low. HWC has a rough-order-of-magnitude (ROM) cost of 300 M€, and could be European-funded within the cost envelope of an ESA S-class mission in the Voyage 2050 program, with matching funds by national funding agencies to construct HWC by a European instrument consortium. This White Paper is intended to put a European HabEx Workhorse Camera into ESA’s considerations. If ESA shares the wide interest and if HabEx were to be selected by NASA, there would be ample time to identify interested institutes for a European instrument consortium, including MPIA, to design, finance, and build the HabEx Workhorse Camera.

Thermal Conductivity of Single-Crystal and Sintered RBa2Cu3O7 at low Temperatures

1987 ◽  
Vol 99 ◽  
Author(s):  
J. E. Graebner ◽  
L. F. Schneemeyer ◽  
R. J. Cava ◽  
J. V. Waszczak ◽  
E. A. Rietman
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Single Crystals ◽  
Free Path ◽  
Low Temperatures ◽  
Rayleigh Scattering ◽  
Resonant Scattering ◽  
Sintered Sample ◽  
Mean Free Path ◽  
Strong Scattering

ABSTRACTThe thermal conductivity k of micro-twinned single crystals of YBa2Cu3O7 and HoBa2Cu3O7 and a sintered sample of YBa2Cu3O7 has been measured for temperatures 0.03<T<5K. For the single crystals, k is small and varies as T1.8-1.9 This behavior resembles k for glassy insulators except for the lack of a plateau above IK. It is concluded that the thermal carriers are phonons with their mean free path limited by resonant scattering from tunneling entities, as in glasses. Suggestions for the location of tunneling systems are given. For the sinter, k is still smaller but does not follow a power law T-dependence. It is similar to other sintered ceramics with the same particle size, where the phonon mean free path is dominated by Rayleigh scattering from the particles. This strong scattering from the microstructure presumably masks the scattering from TS within each particle.

scholarly journals Rayleigh Scattering and Microwave Background Fluctuations

2001 ◽  
Vol 558 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Qingjuan Yu ◽  
David N. Spergel ◽  
Jeremiah P. Ostriker
Keyword(s):  
Rayleigh Scattering ◽  
Microwave Background

Detecting Topology in a Nearly Flat Hyperbolic Universe

2003 ◽  
Vol 18 (30) ◽  
pp. 2099-2107 ◽  
Author(s):  
Jeffrey R. Weeks
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Observable Universe ◽  
Multiply Connected ◽  
Background Data ◽  
Cosmic Microwave Background Data

Cosmic microwave background data shows the observable universe to be nearly flat, but leaves open the question of whether it is simply or multiply connected. Several authors have investigated whether the topology of a multiconnected hyperbolic universe would be detectable when 0.9<Ω<1. However, the possibility of detecting a given topology varies depending on the location of the observer within the space. Recent studies have assumed the observer sits at a favorable location. The present paper extends that work to consider observers at all points in the space, and (for given values of Ωm and ΩΛ and a given topology) computes the probability that a randomly placed observer could detect the topology. The computations show that when Ω=0.98 a randomly placed observer has a reasonable chance (~50%) of detecting a hyperbolic topology, but when Ω=0.99 the chances are low (<10%) and decrease still further as Ω approaches one.

scholarly journals Explaining cosmological anisotropy: evidence for causal horizons from CMB data

2021 ◽  
Author(s):  
Pablo Fosalba ◽  
Enrique Gaztañaga
Keyword(s):  
Large Scale ◽  
Cosmological Parameter ◽  
Cosmic Acceleration ◽  
Statistical Fluctuation ◽  
Temperature Anisotropy ◽  
Microwave Background ◽  
Dark Energy Density ◽  
Observable Universe ◽  
Open Question ◽  
The Universe

Abstract The origin of power asymmetry and other measures of statistical anisotropy on the largest scales of the universe, as manifested in Cosmic Microwave Background (CMB) and large-scale structure data, is a long-standing open question in cosmology. In this paper we analyse the Planck Legacy temperature anisotropy data and find strong evidence for a violation of the Cosmological principle of isotropy, with a probability of being a statistical fluctuation of order ∼10−9. The detected anisotropy is related to large-scale directional ΛCDM cosmological parameter variations across the CMB sky, that are sourced by three distinct patches in the maps with circularly-averaged sizes between 40 to 70 degrees in radius. We discuss the robustness of our findings to different foreground separation methods and analysis choices, and find consistent results from WMAP data when limiting the analysis to the same scales. We argue that these well-defined regions within the cosmological parameter maps may reflect finite and casually disjoint horizons across the observable universe. In particular we show that the observed relation between horizon size and mean dark energy density within a given horizon is in good agreement with expectations from a recently proposed model of the universe that explains cosmic acceleration and cosmological parameter tensions between the high and low redshift universe from the existence of casual horizons within our universe.

scholarly journals Polarized Continuum Radiation from Stellar Atmospheres

2014 ◽  
Vol 10 (S305) ◽  
pp. 395-400 ◽  
Author(s):  
J. Patrick Harrington
Keyword(s):  
Rayleigh Scattering ◽  
Accurate Method ◽  
Stellar Atmospheres ◽  
Early Type ◽  
Late Type ◽  
Hydrogen Atoms ◽  
Free Electrons ◽  
Continuum Radiation ◽  
Early Type Stars ◽  
Limb Darkening

AbstractContinuum scattering by free electrons can be significant in early type stars, while in late type stars Rayleigh scattering by hydrogen atoms or molecules may be important. Computer programs used to construct models of stellar atmospheres generally treat the scattering of the continuum radiation as isotropic and unpolarized, but this scattering has a dipole angular dependence and will produce polarization. We review an accurate method for evaluating the polarization and limb darkening of the radiation from model stellar atmospheres. We use this method to obtain results for: (i) Late type stars, based on the MARCS code models (Gustafsson et al. 2008), and (ii) Early type stars, based on the NLTE code TLUSTY (Lanz and Hubeny 2003). These results are tabulated at http://www.astro.umd.edu/~jph/Stellar_Polarization.html While the net polarization vanishes for an unresolved spherical star, this symmetry is broken by rapid rotation or by the masking of part of the star by a binary companion or during the transit of an exoplanet. We give some numerical results for these last cases.

scholarly journals Cosmology with Rayleigh scattering of the cosmic microwave background

2021 ◽  
Vol 2021 (01) ◽  
pp. 060-060
Author(s):  
Benjamin Beringue ◽  
P. Daniel Meerburg ◽  
Joel Meyers ◽  
Nicholas Battaglia
Keyword(s):  
Cosmic Microwave Background ◽  
Rayleigh Scattering ◽  
Microwave Background

scholarly journals Detectability of Torus Topology

2014 ◽  
Vol 10 (S306) ◽  
pp. 139-143
Author(s):  
Ophélia Fabre ◽  
Simon Prunet ◽  
Jean-Philippe Uzan
Keyword(s):  
Temperature Fluctuations ◽  
Connected Space ◽  
Microwave Background ◽  
Efficient Tool ◽  
Local Universe ◽  
Observable Universe ◽  
Leibler Divergence ◽  
Topology Of The Universe ◽  
The Universe ◽  
Cmb Temperature

AbstractThe global shape, or topology, of the universe is not constrained by the equations of General Relativity, which only describe the local universe. As a consequence, the boundaries of space are not fixed and topologies different from the trivial infinite Euclidean space are possible. The cosmic microwave background (CMB) is the most efficient tool to study topology and test alternative models. Multi-connected topologies, such as the 3-torus, are of great interest because they are anisotropic and allow us to test a possible violation of isotropy in CMB data. We show that the correlation function of the coefficients of the expansion of the temperature and polarization anisotropies in spherical harmonics encodes a topological signature. This signature can be used to distinguish an infinite space from a multi-connected space on sizes larger than the diameter of the last scattering surface (DLSS). With the help of the Kullback-Leibler divergence, we set the size of the edge of the biggest distinguishable torus with CMB temperature fluctuations and E-modes of polarization to 1.15 DLSS. CMB temperature fluctuations allow us to detect universes bigger than the observable universe, whereas E-modes are efficient to detect universes smaller than the observable universe.

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