Natural Explanation for 21 cm Absorption Signals via Axion-Induced Cooling

Houston, Nick; Li, Chuang; Li, Tianjun; Yang, Qiaoli; Zhang, Xin

doi:10.1103/physrevlett.121.111301

Cited by 37 publications

(28 citation statements)

References 131 publications

(271 reference statements)

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“…The Experiment to Detect the Global Epoch-of-Reionization Signatures (EDGES) team has recently reported the detection of a 21 cm absorption profile, centered at 78 MHz, with a 19 MHz width and an amplitude of 520 mK (Bowman et al 2018a). This result is more than a factor two stronger than standard theoretical predictions and has triggered exotic explanations like interaction with dark matter (e.g., Barkana 2018;Fraser et al 2018) or Axion-Induced Cooling (e.g., Houston et al 2018) and a debate on a possible lowfrequency excess radio background (e.g., Ewall-Wice et al 2018;Feng & Holder 2018;Sharma 2018). The unexpected EDGES result is awaiting for independent confirmation from the other ongoing global signal experiments.…”

Section: Introductionmentioning

confidence: 81%

On the contamination of the global 21 cm signal from polarized foregrounds

Spinelli

Bernardi

Santos

2019

Monthly Notices of the Royal Astronomical Society

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Global (i.e. sky-averaged) 21 cm signal experiments can measure the evolution of the universe from the Cosmic Dawn to the Epoch of Reionization. These measurements are challenged by the presence of bright foreground emission that can be separated from the cosmological signal if its spectrum is smooth. This assumption fails in the case of single polarization antennas as they measure linearly polarized foreground emission -which is inevitably Faraday rotated through the interstellar medium. We investigate the impact of Galactic polarized foregrounds on the extraction of the global 21 cm signal through realistic sky and dipole simulations both in a low frequency band from 50 to 100 MHz, where a 21 cm absorption profile is expected, and in a higher frequency band (100 − 200 MHz). We find that the presence of a polarized contaminant with complex frequency structure can bias the amplitude and the shape of the reconstructed signal parameters in both bands. We investigate if polarized foregrounds can explain the unexpected 21 cm Cosmic Dawn signal recently reported by the EDGES collaboration. We find that unaccounted polarized foreground contamination can produce an enhanced and distorted 21 cm absorption trough similar to the anomalous profile reported by Bowman et al. (2018), and whose amplitude is in mild tension with the assumed input Gaussian profile (at ∼ 1.5σ level). Moreover, we note that, under the hypothesis of contamination from polarized foreground, the amplitude of the reconstructed EDGES signal can be overestimated by around 30%, mitigating the requirement for an explanation based on exotic physics.

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Section: Introductionmentioning

confidence: 81%

On the contamination of the global 21 cm signal from polarized foregrounds

Spinelli

Bernardi

Santos

2019

Monthly Notices of the Royal Astronomical Society

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“…Subsequently, a number of other works have been devoted to proposing alternative explanations for the anomalous EDGES detection, or utilizing such a signal to place constraints on fundamental physics assuming the signal itself is genuine (see e.g. [157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181] for a very limited list of works in these directions). We shall also follow this approach here: restricting our attention to the unified dark sector models we discussed in Sec.…”

Section: B the Edges Detectionmentioning

confidence: 99%

Dawn of the dark: unified dark sectors and the EDGES Cosmic Dawn 21-cm signal

Yang

Pan

Vagnozzi

et al. 2019

J. Cosmol. Astropart. Phys.

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While the origin and composition of dark matter and dark energy remains unknown, it is possible that they might represent two manifestations of a single entity, as occurring in unified dark sector models. On the other hand, advances in our understanding of the dark sector of the Universe might arise from Cosmic Dawn, the epoch when the first stars formed. In particular, the first detection of the global 21-cm absorption signal at Cosmic Dawn from the EDGES experiment opens up a new arena wherein to test models of dark matter and dark energy. Here, we consider generalized and modified Chaplygin gas models as candidate unified dark sector models. We first constrain these models against Cosmic Microwave Background data from the Planck satellite, before exploring how the inclusion of the global 21-cm signal measured by EDGES can improve limits on the model parameters, finding that the uncertainties on the parameters of the Chaplygin gas models can be reduced by a factor between 1.5 and 10. We also find that within the generalized Chaplygin gas model, the tension between the CMB and local determinations of the Hubble constant H0 is reduced from ≈ 4σ to ≈ 1.3σ. In conclusion, we find that the global 21-cm signal at Cosmic Dawn can provide an extraordinary window onto the physics of unified dark sectors.

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“…Whereas the redshift of the observed signal agrees with the theoretical predictions, the measured magnitude of the absorption feature greatly exceeds the ΛCDM expectations, consequently raising the problem of its origin. Explanations of the EDGES result proposed in literature invoke either new mechanisms for cooling the gaseous medium [4][5][6][7][8][9][10][11][12][13][14][15] or the presence of an additional soft photon component [16][17][18][19][20][21]. However, the mechanism beyond the anomaly remains to-date unclear.…”

Section: Introductionmentioning

confidence: 99%

Constraints on ALPs and excited dark matter from the EDGES 21 cm absorption signal

et al. 2018

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The recent observation of the 21 cm absorption signal by the EDGES experiment provides a new observational window into the dynamics of the young Universe. Based on this result, we constrain the properties of ALPs and excited dark matter via the energy injections into the gaseous medium that these models produce. In particular, we derive bounds that outperform the present constraints for energy injections in the 10.2 eV to 50 keV range by analysing the intensity of Lyman-α photons and the electron emissivity produced by ionising radiation. Our results also show that once the standard temperature of the soft radiation background is assumed, the explanations of the observed 3.5 keV photon signal within the considered dark matter model are excluded at 95% confidence level.

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Natural Explanation for 21 cm Absorption Signals via Axion-Induced Cooling

Cited by 37 publications

References 131 publications

On the contamination of the global 21 cm signal from polarized foregrounds

On the contamination of the global 21 cm signal from polarized foregrounds

Dawn of the dark: unified dark sectors and the EDGES Cosmic Dawn 21-cm signal

Constraints on ALPs and excited dark matter from the EDGES 21 cm absorption signal

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