arXiv subjects

Meng-Lin Zhao

Publications and source records attributed to Meng-Lin Zhao.

6 recordsLinked to original sources

arXiv2026

High-Redshift Signatures from the Cosmic Dawn and the Epoch of Reionization

In this chapter, we provide a comprehensive overview of the astrophysical and cosmological processes that shape the 21-cm signal during Cosmic Dawn and the Epoch of Reionization. We investigate both standard and exotic signatures potentially observable with SKA-Low. Standard signatures are those expected within the $\Lambda$CDM framework, including contributions from the first stars, galaxies, and black holes. Exotic signatures are more speculative indicating new physics, such as primordial black holes, modifications to the dark matter sector, non-standard primordial fluctuations, or strongly emitting radio galaxies. The effects of these different sources or scenarios are evaluated in the context of the expected sensitivity of SKA-Low, considering the AA* and AA4 configurations. The chapter aims to provide an overview of the theoretical landscape of 21-cm signatures and to highlight how the forthcoming SKA-Low observations will improve our understanding of astrophysical processes at early times and may open the door towards new physics beyond the $\Lambda$CDM framework.

astro-ph.CO↗

arXiv2025

21 cm forest one-dimensional power spectrum as an indirect probe of dark matter particles and primordial black holes

Understanding the nature of dark matter (DM) particles remains a pivotal challenge in modern cosmology. Current cosmological research on these phenomena primarily utilizes cosmic microwave background (CMB) observations and other late-time probes, which predominantly focus on large scales. We introduce a novel probe, the 21 cm forest signal, which can be used to investigate DM properties on small scales during the epoch of reionization, thereby addressing the gap left by other cosmological probes. Annihilation and decay of DM particles, as well as Hawking radiation from PBHs, can heat the intergalactic medium (IGM). This heating suppresses the amplitude of the 21 cm forest 1D power spectrum. Therefore, the 1D power spectrum provides an effective method for constraining DM properties. However, astrophysical heating processes in the early universe can also affect the 21 cm forest 1D power spectrum. In this work, we assess the potential of using the SKA to observe the 21 cm forest 1D power spectrum for constraining DM properties, under the assumption that astrophysical heating can be constrained reliably by other independent probes. Under low astrophysical heating conditions, the 1D power spectrum could constrain the DM annihilation cross section and decay lifetime to $\langle\sigma v\rangle \sim {10^{-31}}\,{\rm cm^{3}\,s^{-1}}$ and $\tau \sim {10^{30}}\,{\rm s}$ for ${10}\,{\rm GeV}$ DM particles, and probe PBHs with masses $\sim {10^{15}}\,{\rm\,g}$ at abundances $f_{\mathrm{PBH}} \simeq 10^{-13}$. These constraints represent improvements of 5-6 orders of magnitude over current limits. Furthermore, the 21 cm forest 1D power spectrum has the potential to exceed existing bounds on sub-GeV DM and to probe PBHs with masses above $10^{18}\,{\rm g}$, which are otherwise inaccessible by conventional cosmological probes.

astro-ph.CO↗

arXiv2025

Prospects for probing dark matter particles and primordial black holes with the Square Kilometre Array using the 21 cm power spectrum at cosmic dawn

Probing the nature of dark matter (DM) remains an outstanding problem in modern cosmology. The 21 cm signal, as a sensitive tracer of neutral hydrogen during cosmic dawn, provides a unique means to investigate DM nature during this critical epoch. Annihilation and decay of DM particles, as well as Hawking radiation of primordial black holes (PBHs), can modify the thermal and ionization histories of the early universe, leaving distinctive imprints on the 21 cm power spectrum. Therefore, the redshifted 21 cm power spectrum serves as a powerful tool to investigate such DM processes. In this work, we systematically assess the potential of the upcoming Square Kilometre Array (SKA) to constrain DM and PBH parameters using the 21 cm power spectrum. Assuming $10,000$ hours of integration time, the SKA is projected to reach sensitivities of $\langle\sigma v\rangle \leq 10^{-28}\,{\rm cm}^{3}\,{\rm s}^{-1}$ and $\tau\geq 10^{28}\,{\rm seconds}$, for $10\,{\rm GeV}$ DM particles. It can also probe PBHs with masses of $10^{16}\,\mathrm{g}$ and abundances $f_{\mathrm{PBH}} \leq 10^{-6}$. These results indicate that the SKA could place constraints on DM annihilation, decay, and PBH Hawking radiation that are up to two to three orders of magnitude stronger than current limits. Furthermore, the SKA is expected to exceed existing bounds on sub-GeV DM and to probe Hawking radiation from PBHs with masses above $10^{17}\,{\rm g}$, which are otherwise inaccessible by conventional cosmological probes. Overall, the SKA holds great promise for advancing our understanding of both DM particles and PBHs, potentially offering new insights into the fundamental nature of DM.

astro-ph.CO↗

arXiv2024

Prospects for probing dark matter particles and primordial black holes with the Hongmeng mission using the 21 cm global spectrum at cosmic dawn

Probing dark matter particles and primordial black holes remains a pivotal challenge in modern cosmology. Exotic energy injections from dark matter annihilation, decay, and PBH Hawking evaporation can alter the thermal and ionization histories of the early universe, leaving distinctive imprints on the 21 cm global spectrum. We assess the potential of the upcoming space project, the Hongmeng mission, to probe dark matter particles and PBHs using the 21 cm global spectrum. Under ideal conditions with 1000 hours of integration time and negligible foreground residuals, the Hongmeng project can reach sensitivities to dark matter annihilation cross sections and decay lifetimes to $\langle \sigma v \rangle \sim 10^{-28}\,\mathrm{cm^3\,s^{-1}}$ and $\tau \sim 10^{28}\,\mathrm{s}$, respectively, for dark matter particles with a mass of $10\,\mathrm{GeV}$. It can also probe PBHs with masses of $10^{16}\,\mathrm{g}$ and abundances as low as $f_{\mathrm{PBH}} \simeq 10^{-6}$. These results indicate that the Hongmeng mission can improve current constraints on dark matter annihilation, decay, and PBH Hawking radiation by nearly two orders of magnitude. Moreover, the Hongmeng mission surpasses current limits on sub-GeV dark matter probing and enables the probing of Hawking radiation from PBHs with masses above $10^{17}\,\mathrm{g}$, which remain undetectable through conventional cosmological means. Overall, the upcoming Hongmeng project holds great promise for advancing the investigation of both dark matter and PBHs, potentially deepening our understanding of the nature of dark matter.

astro-ph.CO↗

arXiv2024

Analytical modeling of the one-dimensional power spectrum of 21-cm forest based on a halo model method

The 21-cm forest, composed of spectral absorption features from high-redshift background radio sources, provides a unique probe for studying small-scale structures during the epoch of reionization. It is particularly sensitive to detecting small-scale structures and early heating processes. Despite the rich information contained in the 21-cm forest signal, the complexity of directly modeling the signal has led to a lack of effective analytical models. However, the one-dimensional (1D) power spectrum of the 21-cm forest contains valuable information about the matter power spectrum, making analytical modeling feasible. This work employs an analytical modeling approach based on the halo model, which links the distribution of matter to dark matter halos, allowing for effective predictions of cosmic structure formation and its impact on the 21-cm signal. By considering various parameter scenarios within the halo model framework, particularly different dark matter particle masses and varying levels of cosmic heating, we can capture the complexities of small-scale structures and make the 1D power spectrum modeling applicable across a wide range of parameters. This method not only enhances our understanding of the 21-cm forest signal but also provides theoretical support for future observational data. Observing the 21-cm forest with large radio telescopes, such as the Square Kilometre Array, is anticipated to enable simultaneous exploration of dark matter properties and the heating history of the early universe.

astro-ph.CO↗

arXiv2024

Search for the Hawking radiation of primordial black holes: prospective sensitivity of LHAASO

Primordial black holes (PBHs), more generally, BHs, undergo evaporation and, in principle, will end their lives in bursts of very high-energy gamma rays. The notable aspect of the PBHs with an initial mass of $\sim10^{14}$ g is that they are expected to end their lives today. In this work, we assess the potential sensitivity of the Large High Altitude Air Shower Observatory (LHAASO) in detecting the local burst rate density of PBHs. Our results suggest that LHAASO is capable of probing for PBH bursts within a proximity of $\sim0.1$ pc from the Sun, measuring a local burst rate density of $\sim$ 1200 (or 700)$\,\mathrm{pc}^{-3}\,\mathrm{yr}^{-1}$ with $99\%$ confidence during a 3-year (or 5-year) observational campaign. This level of sensitivity surpasses the most rigorous observational constraint provided by the High Altitude Water Cherenkov Observatory (HAWC) by an order of magnitude. Additionally, we propose data analysis strategies for LHAASO to optimize the search for PBHs and reach its potential detection limits.

astro-ph.HE↗