Concerns about modelling of the EDGES data

We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift ≈ 9.1 using new upper limits on the 21-cm power spectrum measured by the LO-FAR radio-telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations. We have used results from the reionization simulation code GRIZZLY and a Bayesian inference framework to constrain the parameters which describe the physical state of the IGM. We find that, if the gas heating remains negligible, an IGM with ionized fraction 0.13 and a distribution of the ionized regions with a characteristic size 8 h −1 comoving megaparsec (Mpc) and a full width at the half maximum (FWHM) 16 h −1 Mpc is ruled out. For an IGM with a uniform spin temperature T S 3 K, no constraints on the ionized component can be computed. If the large-scale fluctuations of the signal are driven by spin temperature fluctuations, an IGM with a volume fraction 0.34 of heated regions with a temperature larger than CMB, average gas temperature 7-160 K and a distribution of the heated regions with characteristic size 3.5-70 h −1 Mpc and FWHM of 110 h −1 Mpc is ruled out. These constraints are within the 95 per cent credible intervals. With more stringent future upper limits from LOFAR at multiple redshifts, the constraints will become tighter and will exclude an increasingly large region of the parameter space.

show abstract

“…Furthermore, the systematics for the EDGES results are not fully known (e.g. Hills et al 2018;Singh & Subrahmanyan 2019).…”

Section: Discussionmentioning

confidence: 99%

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Ghara

Giri

Mellema

et al. 2020

Monthly Notices of the Royal Astronomical Society

105

View full text Add to dashboard Cite

show abstract

“…These are the strongest bounds to date that follow from the low-mass cutoff of the halo mass function. However, the validity of the EDGES result and its interpretation have been questioned [123].…”

Section: Validating Merger Treesmentioning

confidence: 99%

Small-scale structure of fuzzy and axion-like dark matter

Niemeyer

2020

Progress in Particle and Nuclear Physics

154

View full text Add to dashboard Cite

Axion-like particle (ALP) dark matter shows distinctive behavior on scales where wavelike effects dominate over self-gravity. Ultralight axions are candidates for fuzzy dark matter (FDM) whose de Broglie wavelength in virialized halos reaches scales of kiloparsecs. Important features of FDM scenarios are the formation of solitonic halo cores, suppressed small-scale perturbations, and enhanced gravitational relaxation. More massive ALPs, including the QCD axion, behave like CDM on galactic scales but may be clumped into axion miniclusters if they were produced after inflation. Just as FDM halos, axion miniclusters may host the formation of coherent bound objects (axion stars) by Bose-Einstein condensation. This article presents a selection of topics in this field that are currently under active investigation.

show abstract

“…Before leaving the global-signal studies, let us find what constraints can be achieved with the first claimed 21-cm detection, by the EDGES collaboration [87] (see, however, Refs. [94,95] for criticisms regarding foregrounds and systematics). This first claimed detection is centered around ν = 78 MHz, with a width of ∆ν = 20 MHz (corresponding to z ≈ 15 − 20).…”

Section: E Edges Datamentioning

confidence: 99%

Probing the small-scale matter power spectrum with large-scale 21-cm data

2020

View full text Add to dashboard Cite

The distribution of matter fluctuations in our universe is key for understanding the nature of dark matter and the physics of the early cosmos. Different observables have been able to map this distribution at large scales, corresponding to wavenumbers k 10 Mpc −1 , but smaller scales remain much less constrained. In this work we study the sensitivity of upcoming measurements of the 21-cm line of neutral hydrogen to the small-scale matter power spectrum. The 21-cm line is a promising tracer of early stellar formation, which took place in small haloes (with masses M ∼ 10 6 − 10 8 M ), formed out of matter overdensities with wavenumbers as large as k ≈ 100 Mpc −1 . Here we forecast how well both the 21-cm global signal, and its fluctuations, could probe the matter power spectrum during cosmic dawn (z = 12−25). In both cases we find that the long-wavelength modes (with k 40 Mpc −1 ) are highly degenerate with astrophysical parameters, whereas the modes with k = (40 − 80) Mpc −1 are more readily observable. This is further illustrated in terms of the principal components of the matter power spectrum, which peak at k ∼ 50 Mpc −1 both for a typical experiment measuring the 21-cm global signal and its fluctuations. We find that, imposing broad priors on astrophysical parameters, a global-signal experiment can measure the amplitude of the matter power spectrum integrated over k = (40−80) Mpc −1 with a precision of tens of percent. A fluctuation experiment, on the other hand, can constrain the power spectrum to a similar accuracy over both the k = (40 − 60) Mpc −1 and (60 − 80) Mpc −1 ranges even without astrophysical priors. The constraints outlined in this work would be able to test the behavior of dark matter at the smallest scales yet measured, for instance probing warm-dark matter masses up to mWDM = 8 keV for the global signal and 14 keV for the 21-cm fluctuations. This could shed light on the nature of dark matter beyond the reach of other cosmic probes.

show abstract

Concerns about modelling of the EDGES data

Cited by 279 publications

References 11 publications

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Small-scale structure of fuzzy and axion-like dark matter

Probing the small-scale matter power spectrum with large-scale 21-cm data

Contact Info

Product

Resources

About