Probing a cosmic axion-like particle background within the jets of active galactic nuclei

Abstract

Axions or more generally axion-like particles (ALPs) are pseudo-scalar particles predicted by many extensions of the Standard Model of particle physics (SM) and considered as viable candidates for dark matter (DM) in the universe. If they really exist in nature, they are expected to couple with photons in the presence of an external electromagnetic field through a form of the Primakoff effect. In addition, many string theory models of the early universe motivate the existence of a homogeneous Cosmic ALP Background (CAB) with 0.1-1 keV energies analogous to the Cosmic Microwave Background (CMB), arising via the decay of string theory moduli in the very early universe. The coupling between the CAB ALPs traveling in cosmic magnetic fields and photons allows ALPs to oscillate into photons and vice versa. In this work, we test the CAB model that is put forward to explain the soft X-ray excess in the Coma cluster due to CAB ALPs conversion into photons using the M87 jet environment. Then we demonstrate the potential of the active galactic nuclei (AGNs) jet environment to probe low-mass ALP models, and to potentially constrain the model proposed to better explain the Coma cluster soft X-ray excess. We find that the overall X-ray emission for the M87 AGN requires an ALP-photon coupling g aγ in the range of ∼ 7.50 × 10 −15 -6.56 × 10 −14 GeV −1 for ALP masses m a 10 −13 eV as long as the M87 jet is misaligned by less than about 20 degrees from the line of sight. These values are up to an order of magnitude smaller than the current best fit value on g aγ ∼ 2 × 10 −13 GeV −1 obtained in soft X-ray excess CAB model for the Coma cluster. Our results cast doubt on the current limits of the largest allowed value of g aγ and suggest a new constraint that g aγ 6.56 × 10 −14 GeV −1 when a CAB is assumed.

Potential of SKA to Detect CDM ALPs with Radio Astronomy

“…In our previous paper [19] we found astrophysical evidence to constrain the ALPs properties with mass m a ∼ 10 −13 eV and coupling with photons g aγ ∼ 10 −14 GeV −1 . One can insert these limits to equation (2) and evaluate the perturbative decay time for general ALPs which found to be about ∼ 10 60 years.…”

Probing axions via light circular polarization and event horizon telescope

“…A background field of axion dark matter can influence on the propagation of a linearly polarized light or distortions of the electomagnetic (EM) spectrum [33][34][35][36][37][38][39][40][41]. Several studies have been done to consider the impact of the photon-axion conversion process on the photon polarization in the presence of the astrophysical magnetic field [42][43][44][45][46][47][48][49][50][51].…”

Axion-like particle searches with MeerKAT and SKA

“…This ALP-photon coupling allows for the Primakoff conversion between ALPs and photons in the presence of an external magnetic field (see e.g. [21][22][23][24][25]), as well as for the radiative decay of the ALPs into pairs of photons (see e.g. [26][27][28]).…”