´¡³Ü³Ù³ó´Ç°ù²õ:ÌýJack Burns, Richard Bradley, Keith Tauscher, Steven Furlanetto, Jordan Mirocha, Raul Monsalve, David Rapetti, William Purcell, David Newell, David Draper, Robert MacDowall, Judd Bowman, Bang Nhan, Edward Wollack, Anastasia Fialkov, Dayton Jones, Justin Kasper, Abraham Loeb, Abhirup Datta, Jonathan Pritchard, Eric Switzer, Michael Bicay
´¡²ú²õ³Ù°ù²¹³¦³Ù:ÌýThe redshifted 21-cm monopole is expected to be a powerful probe of the epoch of the first stars and galaxies (10 < z < 35), never before observed. This hyperfine transition of HI is sensitive to the thermal and ionization state of hydrogen gas and thus provides a tracer of sources of energetic photons – primarily hot stars and accreting black holes – which ionize and heat the high redshift intergalactic medium. Sky-averaged spectra of the redshifted 21-cm background are expected to exhibit broad absorption and emission features relative to the microwave background at low radio frequencies, ≈40−120 MHz. In a low altitude lunar orbit, night-time spectral observations while on the farside avoid terrestrial radio frequency interference, ionospheric corruption, and solar radio emissions. The distinctive frequency structure, uniformity over large scales, and unpolarized state of the redshifted 21-cm spectrum are distinct from the spectrally featureless, spatially-varying and polarized emission from bright Galactic foregrounds. This allows a clean separation between the primordial signal and foregrounds using Bayesian inference techniques such as Markov Chain Monte Carlo. We illustrate how this signal can be detected in the presence of foregrounds using the instrument parameters for the Dark Ages Radio Explorer (DARE), and to subsequently constrain the properties of the high-z intergalactic medium and the parameters of a simple first stars model.
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