Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

Abstract

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology.

Axion-like Particle Searches with IACTs

“…It is also shown that, in case of the sources embedded in strong cluster magnetic fields of dense environments, this effect is not relevant, so the constrains set by Abramowski et al [36], Ajello et al [41] are still valid. In the future, photon-ALP mixing in the blazar jet might become relevant and, with the new generation of Cherenkov telescopes ( [42], e.g., the Cherenkov Telescope Array (CTA)) the detection of more blazars at a higher redshift is expected. In conclusion, very detailed magnetic field models are needed to address the photon-ALP mixing in a more accurate way.…”

“…These conditions guarantee that the probability of interaction is maximal (see Equation ( 8)). Recently, Abdalla et al [42] quantified the importance of the intensity of the magnetic field and the source brightness, showing that, for example, a factor of 2.5 more intense magnetic field could result in factor 10 stronger constraints on the ALP coupling ([42] Figure 7). In the gamma-ray TeV sky, sources often display a flaring state, as opposed to a baseline emission state.…”

“…The next generation of IACTs, CTA, is expected to lower the uncertainties in the spectra of astrophysical sources such as active galaxies and BL Lacs and increase the sensitivity to photon-ALP oscillations [42]. In that way, they may surpass the current constraints by broadening the part of the ALPs parameter space available for γ-ray studies, and excluding it even further.…”

“…In particular, CTA is expected to probe the energies up to E γ ≈ 300 TeV, which directly improves the possibility of studying ALPs manifestations. Abdalla et al [42] created simulations of the observation of the radio galaxy NGC 1275. The magnetic field of the Perseus cluster is modeled following Jansson and Farrar [37], with morphology modeled as a random field with Gaussian turbulence.…”

“…The magnetic field of the Perseus cluster is modeled following Jansson and Farrar [37], with morphology modeled as a random field with Gaussian turbulence. The conservative value of the central magneticfield strength was set to 10 µG, along with the other parameters listed in [42]. Using three different sets of ALPs parameters with 100 different magnetic field realizations, P γγ was calculated using the GAMMAALPs code 4 .…”