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arxiv: 2606.25932 · v2 · pith:633JB3UMnew · submitted 2026-06-24 · 🌌 astro-ph.HE

Using SKA-Low to Detect PeV Gamma-rays from Galactic Sources

Anna Nelles , Philipp Laub , Haoning He , Felix Schl\"uter , Sjoerd Bouma , Justin Bray , Stijn Buitink , Arthur Corstanje
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Vital De Henau Edwin Dickinson Brian Hare J\"org H\"orandel Tim Huege Clancy James Xingyu Li Hermann-Josef Mathes Katharine Mulrey Subhadip Saha Olaf Scholten Ralph Spencer Christopher Sterpka Karen Terveer Satyendra Thoudam Gia Trinh Paulina Turekova Darko Veberic Keito Watanabe Hiroaki Yamamoto Chao Zhang Pengfei Zhang Yi Zhang
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Pith reviewed 2026-06-26 05:42 UTC · model grok-4.3

classification 🌌 astro-ph.HE
keywords SKA-LowPeV gamma raysair showersradio detectionPeVatronscosmic raysgalactic sources
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The pith

SKA-Low can detect PeV gamma rays from galactic sources with radio air-shower detection

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper claims that SKA-Low, thanks to its large number of antennas, can lower the energy threshold for radio detection of air showers to the PeV range. The core's size would provide enough effective area to measure fluxes from galactic PeVatrons. This would open a new observational window on the accelerators of the highest energy cosmic rays in the Galaxy and achieve the first radio detection of gamma-ray air showers.

Core claim

SKA-Low with its unprecedented number of antennas can reach lower in energy for air shower detection while the size of the core is sufficiently large to provide a significant effective area to measure PeV fluxes, promising a novel angle towards understanding the cosmic ray accelerators in our Galaxy and the first detection of gamma-ray air showers using radio emission.

What carries the argument

Radio emission from air showers induced by PeV gamma rays detected with the dense SKA-Low antenna array

If this is right

  • PeV gamma-ray fluxes from galactic sources become measurable
  • PeVatrons can be identified through radio observations
  • The first detection of gamma-ray air showers using radio emission is achieved
  • A new method is available to study cosmic ray accelerators in the Galaxy

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This method could be combined with other gamma-ray observatories for multi-messenger studies
  • Simulations of radio signals at PeV energies would be needed to confirm the sensitivity
  • It might enable detection of transient or variable PeV sources

Load-bearing premise

The previously demonstrated 50 PeV radio detection threshold for air showers can be lowered with SKA-Low to enable meaningful PeV gamma-ray flux measurements.

What would settle it

A simulation demonstrating that SKA-Low's sensitivity at PeV energies is too low to detect expected gamma-ray fluxes from galactic sources would disprove the claim.

Figures

Figures reproduced from arXiv: 2606.25932 by Anna Nelles, Arthur Corstanje, Brian Hare, Chao Zhang, Christopher Sterpka, Clancy James, Darko Veberic, Edwin Dickinson, Felix Schl\"uter, Gia Trinh, Haoning He, Hermann-Josef Mathes, Hiroaki Yamamoto, J\"org H\"orandel, Justin Bray, Karen Terveer, Katharine Mulrey, Keito Watanabe, Olaf Scholten, Paulina Turekova, Pengfei Zhang, Philipp Laub, Ralph Spencer, Satyendra Thoudam, Sjoerd Bouma, Stijn Buitink, Subhadip Saha, Tim Huege, Vital De Henau, Xingyu Li, Yi Zhang.

Figure 1
Figure 1. Figure 1: SKA-Low field of view to air showers in equatorial coordinates. The colorbar shows the daily observable fraction (year-averaged). Overlaid are sources of interest as detected with LHAASO (Cao et al., 2024a) and H.E.S.S (Abdalla et al., 2018). Figure from Schlüter et al. (2025) source or where the accelerated cosmic rays interact with a target? This makes the association of sources often not unique (e.g. Mi… view at source ↗
Figure 2
Figure 2. Figure 2: Number of expected showers above a given energy 𝐸 as function of threshold detection energy for an area corresponding to the entire SKA-Low core, which is a simplified assumption. Shown are expectations for various 𝛾-ray sources, as well as the cosmic-ray background. Figure from Schlüter et al. (2025). greatly expanding the accessible sky and observation time [PITH_FULL_IMAGE:figures/full_fig_p007_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Illustration of noiseless air shower signals to be measured with a single SKA-Low antenna. Left: Time-domain signals as expected in one antenna (location in the antenna array marked in the inset; the shower core is at (0, 0)). Right: Corresponding frequency spectrum. Different frequency spectra correspond to different distances from the shower axis. Shown is the 𝐸𝜃 electric field component for simplicity, … view at source ↗
Figure 4
Figure 4. Figure 4: Simulated footprints from air showers initiated by a 𝛾-ray at 15 degrees zenith angle as they would be detected with SKA-Low. Top row, left: Shower energy 0.5 PeV, no noise; right: Same shower with instrumental and Galactic noise added. Bottom row: the same shower (arrival direction), but at 25 PeV (left) and 50 PeV (right), both including noise. might be needed. The SWG High Energy Cosmic Particles is cur… view at source ↗
Figure 5
Figure 5. Figure 5: Beamformed signal amplitude (see Equation 1) as function of atmospheric depth and slice along the shower axis, defined by shower axis (𝑣®) and geomagnetic field (𝐵®) for one example air shower as detected with SKA-Low. The shower development from the top of the atmosphere (𝑋 = 0) to the observer height is imaged in this simplified beamforming. and air showers. This coordinate system is defined by the showe… view at source ↗
Figure 6
Figure 6. Figure 6: Left: Best beamformed trace (dark green) from scan along the shower axis for a 300 TeV gamma ray shower with a zenith angle of 15 ◦ (simulation). The noise parts used for noise RMS calculation are marked in light green, excluding both the pulse and edge effects. Right: Obtained Beamforming signal-to￾noise ratio (SNR) as function of distance to shower maximum along the shower axis for an example gamma ray s… view at source ↗
Figure 7
Figure 7. Figure 7: Signal-to-noise ratio (SNR) of the best beamformed signal as function of the simulated gamma ray energy for a zenith angle of 15◦ (left) and several different zenith angle bins (right). The zenith angle is defined as 0 ◦ pointing upwards. The shower core lies within 400 meters of the SKA array core (quality cut). Antennas within 200 meters from the shower axis are used for beamforming. The shower axis is a… view at source ↗
Figure 8
Figure 8. Figure 8: SNR of the best beamformed signal as a function of the simulated gamma ray energy for different distances between shower core and SKA array core, see legend. Antennas within 200 meters from the shower axis are used for beamforming. The shower axis is assumed to be known. antenna array i.e. how contained the shower must be in order to detect a signal using beamforming. At least out to 500 m the method conti… view at source ↗
Figure 9
Figure 9. Figure 9: Height of shower maximum as function of energy for simulated air showers of different primary particle. Shown are the 90 % contours for different primaries. These results are based on CORSIKA simulations with CONEX using approx. 2500 showers per primary. 4 Open Questions towards Gamma-Ray Detection Compared to 𝛾-ray detection, the strategy of detecting hadronic cosmic rays with SKA-Low is much more mature.… view at source ↗
read the original abstract

Detecting so called PeVatrons is considered one of the prime goals of $\gamma$-ray astronomy. PeVatrons are astrophysical objects in the Galaxy that are sources of cosmic rays exceeding PeV ($10^{15}$ eV) energies, the highest in our Galaxy. Their nature is unknown as of now, with some candidates reaching barely above PeV energies just having been identified. Serendipitously, the energy threshold of air shower detection using radio emission, has been proven at 50 PeV. There is a case to be made that SKA-Low with its unprecedented number of antennas, can reach lower in energy, while the size of the core is sufficiently large provide a significant effective area to measure PeV fluxes. While this promises a novel angle towards understanding the cosmic ray accelerators in our Galaxy, it also would be the first detection of $\gamma$-ray air showers using radio emission.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper proposes that SKA-Low can detect PeV gamma-ray air showers from galactic sources via radio emission. It notes prior radio detection at 50 PeV and argues that SKA-Low's unprecedented antenna count and core size will lower the energy threshold to PeV while providing sufficient effective area for flux measurements, enabling the first radio gamma-ray air-shower detection and new insights into galactic cosmic-ray accelerators.

Significance. If the feasibility claim holds, the result would be significant for gamma-ray astronomy by opening a radio-based channel for PeVatron studies with potentially large effective areas. The approach could complement existing techniques if quantitative support for threshold reduction and sensitivity is provided.

major comments (2)
  1. [Abstract] Abstract: The central claim that SKA-Low antenna density and core size can lower the radio air-shower detection threshold from the demonstrated 50 PeV to PeV energies is asserted without any scaling relation, Monte Carlo result, or derivation showing how the ~10^4–10^5 increase in antennas compensates for the factor ~50 drop in primary energy (where radio field strength scales linearly or quadratically with energy).
  2. [The manuscript] The manuscript: No effective-area estimates for the SKA-Low core are compared to expected PeV gamma-ray fluxes from galactic sources, nor is any sensitivity calculation or benchmark against the 50 PeV experimental result supplied to support the feasibility of meaningful measurements.
minor comments (1)
  1. [Abstract] Abstract: The phrase 'the size of the core is sufficiently large provide a significant effective area' is missing the word 'to' before 'provide'.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback highlighting the need for quantitative support. We agree the claims require more explicit justification and will revise the manuscript accordingly to strengthen the feasibility argument.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The central claim that SKA-Low antenna density and core size can lower the radio air-shower detection threshold from the demonstrated 50 PeV to PeV energies is asserted without any scaling relation, Monte Carlo result, or derivation showing how the ~10^4–10^5 increase in antennas compensates for the factor ~50 drop in primary energy (where radio field strength scales linearly or quadratically with energy).

    Authors: We acknowledge that the current abstract and text assert the threshold reduction without an explicit derivation. Radio emission from air showers is coherent, with electric-field amplitude scaling linearly with primary energy. The ~10^4–10^5 increase in antenna number provides both denser sampling of the lateral distribution and substantial averaging to reduce noise, which can offset the factor-of-50 reduction in signal strength. In the revised manuscript we will insert a short scaling section with this back-of-the-envelope estimate and a comparison to the published 50 PeV result. revision: yes

  2. Referee: [The manuscript] The manuscript: No effective-area estimates for the SKA-Low core are compared to expected PeV gamma-ray fluxes from galactic sources, nor is any sensitivity calculation or benchmark against the 50 PeV experimental result supplied to support the feasibility of meaningful measurements.

    Authors: The present version is a concise feasibility note and therefore omits detailed sensitivity calculations. We agree this weakens the case. In revision we will add (i) an estimate of the effective area set by the SKA-Low core diameter, (ii) a comparison to published PeV gamma-ray fluxes from galactic candidates, and (iii) a rough benchmark against the 50 PeV radio detection to show that the increased collecting power enables statistically useful event rates. revision: yes

Circularity Check

0 steps flagged

No derivation chain or quantitative predictions; claim remains qualitative

full rationale

The manuscript is a conceptual proposal paper. Its central claim—that SKA-Low's antenna density and core size can lower the radio air-shower threshold from the demonstrated 50 PeV to PeV energies—rests on a qualitative scaling argument with no equations, fitted parameters, Monte Carlo results, or self-referential definitions supplied in the text. No load-bearing step reduces to a prior result by construction, no self-citation chain is invoked to justify uniqueness, and no ansatz is smuggled in. The absence of any formal derivation means the circularity patterns cannot be exhibited; the paper is therefore self-contained against external benchmarks at the level of its stated claims.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Ledger constructed from abstract only; no explicit free parameters, invented entities, or detailed axioms are stated.

axioms (1)
  • domain assumption Radio emission from extensive air showers at PeV energies remains detectable when antenna density and core size are increased beyond current arrays.
    Invoked implicitly as the basis for lowering the energy threshold with SKA-Low.

pith-pipeline@v0.9.1-grok · 5818 in / 1153 out tokens · 29324 ms · 2026-06-26T05:42:43.982022+00:00 · methodology

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