2017MNRAS.464.1365M -
Mon. Not. R. Astron. Soc., 464, 1365-1379 (2017/January-2)
The global 21-cm signal in the context of the high-z galaxy luminosity function.
MIROCHA J., FURLANETTO S.R. and SUN G.
Abstract (from CDS):
We build a new model for the global 21-cm signal that is calibrated to measurements of the high-z galaxy luminosity function (LF) and further tuned to match the Thomson scattering optical depth of the cosmic microwave background, τe. Assuming that the z <= 8 galaxy population can be smoothly extrapolated to higher redshifts, the recent decline in best-fitting values of τe and the inefficient heating induced by X-ray binaries (the presumptive sources of the high-z X-ray background) imply that the entirety of cosmic reionization and reheating occurs at z <= 12. In contrast to past global 21-cm models, whose z ∼ 20 (ν ∼ 70 MHz) absorption features and strong ∼25 mK emission features were driven largely by the assumption of efficient early star formation and X-ray heating, our new models peak in absorption at ν ∼ 110 MHz at depths ∼-160 mK and have negligible emission components. Current uncertainties in the faint-end of the LF, binary populations in star-forming galaxies, and UV and X-ray escape fractions introduce ∼20 MHz (∼50 mK) deviations in the trough's frequency (amplitude), while emission signals remain weak (<=10 mK) and are confined to ν >= 140 MHz. These predictions, which are intentionally conservative, suggest that the detection of a 21-cm absorption minimum at frequencies below ∼90 MHz and/or emission signals stronger than ∼10mK at ν <= 140 MHz would provide strong evidence for 'new' sources at high redshifts, such as Population III stars and their remnants.
Abstract Copyright:
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
galaxies: high-redshift - intergalactic medium - galaxies: luminosity function, mass function - dark ages, reionization, first stars - diffuse radiation - diffuse radiation
Simbad objects:
1
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