The 21 cm Power Spectrum from the Cosmic Dawn: First Results from the OVRO-LWA

Eastwood, Michael; Anderson, Marin; Monroe, Ryan; Hallinan, Gregg; Catha, Morgan; Dowell, Jayce; Garsden, Hugh; Greenhill, L. J.; Hicks, B. C.; Kocz, J.; Price, Danny C.; Schinzel, F. K.; Vedantham, H. K.; Wang, Yuankun

doi:10.3847/1538-3881/ab2629

Cited by 110 publications

(73 citation statements)

References 57 publications

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“…In this work we will focus on upcoming measurements of the 21-cm power spectrum from the hydrogen epoch of reionization array (HERA) [117], currently under construction in South Africa. A similar analysis could be carried out for other interferometers, such as the low-frequency array (LOFAR) [118], the longwavelength array (LWA) [119], or the square-kilometer array (SKA) [120].…”

Section: -Cm Fluctuationsmentioning

confidence: 99%

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

2020

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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.

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Section: -Cm Fluctuationsmentioning

confidence: 99%

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

2020

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“…Recently, upper limits were provided for even higher redshifts. Gehlot et al (2019) placed upper limits on the power spectrum in the redshift range z = 19.8 − 25.2 using observations with the LOFAR-Low Band Antenna array and Eastwood et al (2019) placed upper limits at z ≈ 18.4 using observations with the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) 6 . Mertens et al (2020) have provided the second LOFAR upper limit on the 21-cm power spectrum at redshift ≈ 9.1 using 10 nights of observations.…”

Section: Introductionmentioning

confidence: 99%

“…Patil et al (2017) published the first upper limit on the power spectrum of the signal from redshift between 9.6 and 10.6 using LOFAR observations. Later, Gehlot et al (2019Gehlot et al ( , 2020 and Eastwood et al (2019) probed a higher redshift range and also provided upper limits on the power spectrum using observations with the LOFAR-Low Band Antenna array and the OVRO-LWA, respectively. Recently, Mertens et al (2020) analysed 10 nights of LOFAR observations of the North Celestial Pole and obtained a 2 upper limit on the 21-cm signal power spectrum at ≈ 9.1 of Δ 2 ( = 0.075 ℎ Mpc −1 ) = (73) 2 mK 2 .…”

Section: Introductionmentioning

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

106

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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.

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“…In this paper we report the first analysis of solar data from the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), located near Big Pine, CA. At the time of observation, the array consisted of 288 dual-polarization dipole antennas which are optimized to minimize side-lobes; 256 residing in a 200 m diameter core, and the remaining 32 extending to maximum baselines of ≈1.6 km (Anderson et al 2019;Eastwood et al 2019), allowing it to spatially resolve the Sun in the frequency range 27-85 MHz with high spectral resolution. The spatial resolution is about 8 5 at 80 MHz.…”

Section: Introductionmentioning

confidence: 99%

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

Chhabra

Gary

Hallinan

et al. 2021

ApJ

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We present the first results of a solar radio event observed with the Owens Valley Radio Observatory Long Wavelength Array at metric wavelengths. We examine a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M2.1 GOES soft X-ray flare from 2015 September 20. Images of 9 s cadence are used to analyze the event over a 120 minute period, and solar emission is observed out to a distance of ≈3.5 R e , with an instantaneous bandwidth covering 22 MHz within the frequency range of 40-70 MHz. We present our results from the investigation of the radio event, focusing particularly on one burst source that exhibits outward motion, which we classify as a moving type IV burst. We image the event at multiple frequencies and use the source centroids to obtain the velocity for the outward motion. Spatial and temporal comparison with observations of the CME in white light from the C2 coronagraph of the Large Angle and Spectrometric COronagraph, indicates an association of the outward motion with the core of the CME. By performing graduated-cylindrical-shell reconstruction of the CME, we constrain the density in the volume. The electron plasma frequency obtained from the density estimates do not allow us to completely dismiss plasma emission as the underlying mechanism. However, based on source height and smoothness of the emission in frequency and time, we argue that gyrosynchrotron is the more plausible mechanism. We use gyrosynchrotron spectral-fitting techniques to estimate the evolving physical conditions during the outward motion of this burst source.

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The 21 cm Power Spectrum from the Cosmic Dawn: First Results from the OVRO-LWA

Cited by 110 publications

References 57 publications

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

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

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

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

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