Implications of a prereionization 21-cm absorption signal for fuzzy dark matter
- University of Pennsylvania, Philadelphia, PA (United States)
- Columbia University, New York, NY (United States)
The EDGES experiment recently announced evidence for a broad absorption feature in the sky-averaged radio spectrum around 78 MHz, as may result from absorption in the 21 cm line by neutral hydrogen at z ∼15 – 20. If confirmed, one implication is that the spin temperature of the 21 cm line is coupled to the gas temperature by z = 20. The known mechanism for accomplishing this is the Wouthuysen-Field effect, whereby Lyman-alpha photons scatter in the intergalactic medium (IGM) and impact the hyperfine level populations. This suggests that early star formation had already produced a copious Lyman-alpha background by z = 20, and strongly constrains models in which the linear matter power spectrum is suppressed on small-scales, since halo and star formation are delayed in such scenarios. Here we consider the case that the dark matter consists of ultra-light axions with macroscopic de Broglie wavelengths (fuzzy dark matter, FDM). Here we assume that star formation tracks halo formation and adopt two simple models from the current literature for the halo mass function in FDM. We further suppose that the fraction of halo baryons which form stars is less than a conservative upper limit of f⋆≤ 0.05, and that ∼104 Lyman-alpha to Lyman-limit photons are produced per stellar baryon. We find that the requirement that the 21 cm spin temperature is coupled to the gas temperature by z = 20 places a lower-limit on the FDM particle mass of ma ≥ 5 × 10−21 eV. The constraint is insensitive to the precise minimum mass of halos where stars form. As the global 21 cm measurements are refined, the coupling redshift could change and we quantify how the FDM constraint would be modified. A rough translation of the FDM mass bound to a thermal relic warm dark matter (WDM) mass bound is also provided.
- Research Organization:
- Columbia Univ., New York, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA)
- Grant/Contract Number:
- SC0011941; NXX16AB27G
- OSTI ID:
- 1541178
- Alternate ID(s):
- OSTI ID: 1459755
- Journal Information:
- Physical Review. D., Vol. 98, Issue 2; ISSN 2470-0010
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Fuzzy dark matter at cosmic dawn: new 21-cm constraints
|
journal | April 2019 |
BBN constraints on universally-coupled ultralight scalar dark matter
|
text | January 2020 |
| Black Hole Spin Constraints on the Mass Spectrum and Number of Axion-like Fields | text | January 2018 |
| N-body simulations of structure formation in thermal inflation cosmologies | text | January 2018 |
| Dark Matter microphysics and 21 cm observations | text | January 2018 |
| Baryonic effects for weak lensing. Part II. Combination with X-ray data and extended cosmologies | text | January 2019 |
| Probing the Small-Scale Matter Power Spectrum with Large-Scale 21-cm Data | text | January 2019 |
Similar Records
THE IMPACT OF THE SUPERSONIC BARYON-DARK MATTER VELOCITY DIFFERENCE ON THE z {approx} 20 21 cm BACKGROUND
White noise from dark matter: 21 cm observations of early baryon collapse