English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Axion-like particles (ALPs) are a well-motivated extension to the standardmodel of particle physics, and X-ray observations of cluster-hosted AGNcurrently place the most stringent constraints on the ALP coupling toelectromagnetism, $g_{a \gamma}$, for very light ALPs ($m_a\lesssim10^{-11}$eV). We revisit limits obtained by Reynolds et al. (2020) using Chandra X-raygrating spectroscopy of NGC 1275, the central AGN in the Perseus cluster,examining the impact of the X-ray spectral model and magnetic field model. Wealso present a new publicly available code, ALPro, which we use to solve theALP propagation problem. We discuss evidence for turbulent magnetic fields inPerseus and show that it can be important to resolve the magnetic fieldstructure on scales below the coherence length. We re-analyse the NGC 1275X-ray spectra using an improved data reduction and baseline spectral model. Wefind the limits are insensitive to whether a partially covering absorber isused in the fits. At low $m_a$ ($m_a\lesssim10^{-13}$ eV), we find marginallyweaker limits on $g_{a \gamma}$ (by $0.1-0.3$ dex) with different magneticfield models, compared to Model B from Reynolds et al. (2020). A Gaussianrandom field (GRF) model designed to mimic $\sim50$ kpc scale coherentstructures also results in only slightly weaker limits. We conclude that theexisting Model B limits are robust assuming that $\beta_{\rm pl}\approx100$,and are insensitive to whether cell-based or GRF methods are used. However,astrophysical uncertainties regarding the strength and structure of clustermagnetic fields persist, motivating high sensitivity RM observations andtighter constraints on the radial profile of $\beta_{\rm pl}$.

How do Magnetic Field Models Affect Astrophysical Limits on Light Axion-like Particles? An X-ray Case Study with NGC 1275