Probing the sensitivity of CTAO-N LSTs observations at large zenith angles to the multi-TeV gamma-ray emission from the inner 10 parsecs of the Galactic Center

Abstract Observations of the Galactic Center using Imaging Atmospheric Cherenkov Telescopes (IACTs), such as H.E.S.S., MAGIC, and VERITAS, have revealed a very-high-energy (VHE, E ≳ 100 GeV) gamma-ray source, HESS J1745-290, aligned with the dynamical center of the Milky Way. This source shows point-like emission (≲ 0.1°) and a strong suppression in its differential energy spectrum in the ∼10 TeV energy range, modeled well by a power law with an exponential cutoff. The origin of this emission is debated, with candidate emission scenarios including dark matter annihilation, millisecond pulsars in the central stellar cluster, and hadronic interactions in the vicinity of Sagittarius A*. Deriving the sensitivity to these spectral models is key for distinguishing the physical processes at work. We show that the combined H.E.S.S., MAGIC, and VERITAS archival data are well described by a power law with an exponential energy cutoff within the present uncertainties. Given the imminent deployment of the Large-Sized Telescope (LST) array at CTAO-N, we simulate realistic upcoming observations of the central emission with the four-LST array at CTAO-N to derive the sensitivity to resolve the sharpness of the spectral cutoff. We find that 500 hours of four-LST observations taken at large zenith angles, possibly accumulated over several years, can significantly discriminate the dark matter emission scenario from the leptonic and hadronic ones. In addition, a preliminary 3σ indication for such discrimination could emerge within the first year. We demonstrate, for the first time, that CTAO-N can provide new insights into differentiating among the above-mentioned emission scenarios in the next several years.