Global 21-cm Cosmology from the Farside of the Moon
Jack Burns, Stuart Bale, Richard Bradley, Z. Ahmed, S. W. Allen, J. Bowman, S. Furlanetto, R. MacDowall, J. Mirocha, B. Nhan, M. Pivovaroff, M. Pulupa, D. Rapet… 展开作者
Jack Burns, Stuart Bale, Richard Bradley, Z. Ahmed, S. W. Allen, J. Bowman, S. Furlanetto, R. MacDowall, J. Mirocha, B. Nhan, M. Pivovaroff, M. Pulupa, D. Rapetti, A. Slosar, K. Tauscher
One of the last unexplored windows to the cosmos, the Dark Ages and Cosmic Dawn, can be opened using a simple low frequency radio telescope from the stable, quiet lunar farside to measure the Global 21-cm spectrum. This frontier remains an enormous gap in our knowledge of the Universe. Standard models of physics and cosmology are untested during this critical epoch. The messenger of information about this period is the 1420 MHz (21-cm) radiation from the hyperfine transition of neutral hydrogen, Doppler-shifted to low radio astronomy frequencies by the expansion of the Universe. The Global 21-cm spectrum uniquely probes the cosmological model during the Dark Ages plus the evolving astrophysics during Cosmic Dawn, yielding constraints on the first stars, on accreting black holes, and on exotic physics such as dark matter-baryon interactions. A single low frequency radio telescope can measure the Global spectrum between ~10-110 MHz because of the ubiquity of neutral hydrogen. Precise characterizations of the telescope and its surroundings are required to detect this weak, isotropic emission of hydrogen amidst the bright foreground Galactic radiation. We describe how two antennas will permit observations over the full frequency band: a pair of orthogonal wire antennas and a 0.3-m$^3$ patch antenna. A four-channel correlation spectropolarimeter forms the core of the detector electronics. Technology challenges include advanced calibration techniques to disentangle covariances between a bright foreground and a weak 21-cm signal, using techniques similar to those for the CMB, thermal management for temperature swings of >250C, and efficient power to allow operations through a two-week lunar night. This simple telescope sets the stage for a lunar farside interferometric array to measure the Dark Ages power spectrum.
An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10…
The next generation of space-based experiments will go hunting for answers to cosmology's key open questions which revolve around inflation, dark matter and dark energy. Low earth orbit and lunar missions within the European Space Agency's Human and Robotic Exploration programme can push our knowledge forward in all of these three fields. A radio interferometer on the Moon, a cold atom interferometer in low earth orbit and a gravitational wave interferometer on the Moon are highlighted as the most fruitful missions to plan and execute in the mid-term.
We outline a concept for OWL-Moon, a 50-100m aperture telescope located on the surface of the Moon, to address three major areas in astronomy, namely the detection of biosignatures on habitable exoplanets, the geophysics of exoplanets, and cosmology. Such a large lunar telescope, when coupled with large Earth-based telescopes, would allow Intensity Interferometric measurements, leading to pico-arcsecond angular resolution. This would have applications in many areas of astronomy and is timely in light of the renewed interest of space agencies in returning to the Moon.
The Moon is a unique platform for fundamental astrophysical measurements of gravitation, the Sun, and the Universe. Lacking a permanent ionosphere and, on the farside, shielded from terrestrial radio emissions, a radio telescope on the Moon will be an unparalleled heliospheric and astrophysical observatory. Crucial stages in particle acceleration near the Sun can be imaged and tracked. The evolution of the Universe before and during the formation of the first stars will be traced, yielding high precision cosmological constraints. Lunar Laser Ranging of the Earth-Moon distance provides extremel…
The lunar surface allows a unique way forward in cosmology, to go beyond current limits. The far side provides an unexcelled radio-quiet environment for probing the dark ages via 21 cm interferometry to seek elusive clues on the nature of the infinitesimal fluctuations that seeded galaxy formation. Far-infrared telescopes in cold and dark lunar polar craters will probe back to the first months of the Big Bang and study associated spectral distortions in the CMB. Optical and IR megatelescopes will image the first star clusters in the universe and seek biosignatures in the atmospheres of unprece…
A key result of hydrogravitational dynamics cosmology relevant to astrobiology is the early formation of vast numbers of hot primordial-gas planets in million-solar-mass clumps as the dark matter of galaxies and the hosts of first life. Photon viscous forces in the expanding universe of the turbulent big bang prevent fragmentations of the plasma for mass scales smaller than protogalaxies. At the plasma to gas transition 300,000 years after the big bang, the 10^7 decrease in kinematic viscosity ν explains why ~3x10^7 planets are observed to exist per star in typical galaxies like the Milky Way,…
The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard LCDM cosmological model. Divergences from that model would indicate new physics, such as dark matter decay (heating) or baryonic cooling beyond that expected from adiabatic expansion of the Universe. In the early Universe, most of the baryonic matter was in the form of neutral hydrogen (HI), detectable via its ground state's spin-flip transition. A measurement of the redshifted 21-cm spectrum maps the history of the HI gas through the Dark Ages and Cosmic Dawn and up to the Epoch of…
The FarView Low Frequency Radio Array on the Moon's Far Side: Science and Array Architecture
University of Colorado Boulder（科罗拉多大学博尔德分校）；Arizona State University（亚利桑那州立大学）；California Institute of Technology（加州理工学院）；Space Science Institute（空间科学研究所）；National Radio Astronomy Observatory（美国国家射电天文台）；Brown University（布朗大学）；Lunar Resources, Inc.（月球资源公司）；CSIRO, Space & Astronomy（澳大利亚联邦科学与工业研究组织，太空与天文部）
We investigate the impact of radiation from primordial black holes (PBHs), in the mass range of $10^{15} \lesssim M_{\rm PBH} \lesssim 10^{17}~\rm g$ and $10^{2} \lesssim M_{\rm PBH} \lesssim 10^{4}~M_{\odot}$, on the 21-cm angular-power spectrum in the dark ages. PBHs in the former mass range effect the 21-cm angular-power spectrum through the evaporation known as Hawking radiation, while the radiation from the accretion process in the latter mass range. In the dark ages, radiation from PBHs can increase the ionization fraction and temperature of the intergalactic medium, change the global 21…
Baryonic matter can be accreted on to primordial back holes (PBHs) formed in the early Universe. The radiation from accreting PBHs is capable of altering the evolution of the intergalactic medium (IGM), leaving marks on the global 21 cm signal in the dark ages. For accreting PBHs with mass $M_{\rm PBH}=10^{3}(10^{4})~M_{\odot}$ and mass fraction $f_{\rm PBH}=10^{-1}(10^{-3})$, the brightness temperature deviation $ΔδT_{b}$ reaches $\sim 18~(26)~\rm mK$ at redshift $z\sim 90$ ($ν\sim 16~\rm MHz$), and the gradient of the brightness temperature $dδT_{b}/dν$ reaches $ \sim 0.8~(0.5)~\rm mK~MHz^{-…
A concept for a new space-based cosmology mission called the Dark Ages Radio Explore (DARE) is presented in this paper. DARE's science objectives include (1) When did the first stars form? (2) When did the first accreting black holes form? (3) When did Reionization begin? (4) What surprises does the end of the Dark Ages hold (e.g., Dark Matter decay)? DARE will use the highly-redshifted hyperfine 21-cm transition from neutral hydrogen to track the formation of the first luminous objects by their impact on the intergalactic medium during the end of the Dark Ages and during Cosmic Dawn (redshift…
Several large-scale experimental facilities and space-missions are being suggested to probe the universe across the gravitational-wave (GW) spectrum. Here we propose Gravitational-wave Lunar Observatory for Cosmology (GLOC) - the first concept design in the NASA Artemis era for a GW observatory on the Moon. Using feasible interferometer technologies, we find that a lunar-based observatory is ideal for probing GW frequencies in the range between deci-Hz to 5 Hz, an astrophysically rich regime that is very challenging for both Earth- and space-based detectors. GLOC can survey binaries with neutr…
Hydrogravitional-dynamics (HGD) cosmology of Gibson/Schild 1996 predicts proto-globular-star-cluster PGC clumps of Earth-mass planets fragmented from plasma at ~0.3 Myr. Protogalaxies retained the ~0.03 Myr baryonic density existing at the time of the first viscous-gravitational plasma fragmentation. Stars promptly formed from mergers of these gas planets, seeded by chemicals C, N, O, Fe etc. created by the first stars and their supernovae at ~ 0.33 Myr. Hot hydrogen gas planets reduced seeded oxides to hot water oceans over metal-rock cores at water critical temperature 647 K, at ~2 Myr. Merg…
The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1$^\circ \lesssim θ\leq$ 90$^\circ$ with the aim of characterizing primordial gravitational waves and cosmic reionization. We report on the on-sky performance of the CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic G-band (150/220 GHz) receivers that have been operational at the CLASS site in the Atacama desert since June 2016, May 2018, and September 2019, respectively. We show that the noise-equivalent power measured by the detectors matches the expected …
