The thermal and non-thermal components within and between galaxy clusters Abell 399 and Abell 401

• Main Authors: Radiconi, Federico, Vacca, Valentina, Battistelli, Elia, Bonafede, Annalisa, Capalbo, Valentina, Devlin, Mark J, Di Mascolo, Luca, Feretti, Luigina, Gallardo, Patricio A, Gill, Ajay, Giovannini, Gabriele, Govoni, Federica, Guan, Yilun, Hilton, Matt, Hincks, Adam D, Hughes, John P, Iacobelli, Marco, Isopi, Giovanni, Loi, Francesca, Moodley, Kavilan, Mroczkowski, Tony, Murgia, Matteo, Orrù, Emanuela, Paladino, Rosita, Partridge, Bruce, Sarazin, Craig L, Scherer, Jack Orlowski, Sifón, Cristóbal, Vargas, Cristian, Vazza, Franco, Wollack, Edward J
• Format: Journal Article
• Language: English
• Published: 19-10-2022
• Subjects: Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.2206.04697

We measure the local correlation between radio emission and Compton-$y$
signal across two galaxy clusters, Abell~399 and Abell~401, using maps from the
Low-Frequency Array (LOFAR) and the Atacama Cosmology Telescope (ACT) +
\Planck. These datasets allow us to make the first measurement of this kind at
$\sim$arcminute resolution. We find that the radio brightness scales as
$F_{\mathrm{radio}} \propto y^{1.5}$ for Abell~401 and $F_{\mathrm{radio}}
\propto y^{2.8}$ for Abell~399. Furthermore, using \XMM data, we derive a
sublinear correlation between radio and X-ray brightness for both the clusters
($F_{\mathrm{radio}} \propto F_{\rm X}^{0.7}$). Finally, we correlate the
Compton-$y$ and X-ray data, finding that an isothermal model is consistent with
the cluster profiles, $y \propto F_{\rm X}^{0.5}$. By adopting an
isothermal--$\beta$ model, we are able, for the first time, to jointly use
radio, X-ray, and Compton-$y$ data to estimate the scaling index for the
magnetic field profile, $B(r) \propto n_{\mathrm{e}}(r)^{\eta}$ in the
injection and re-acceleration scenarios. Applying this model, we find that the
combined radio and Compton-$y$ signal exhibits a significantly tighter
correlation with the X-ray across the clusters than when the datasets are
independently correlated. We find $\eta \sim 0.6{-}0.8$. These results are
consistent with the upper limit we derive for the scaling index of the magnetic
field using rotation measure values for two radio galaxies in Abell~401. We
also measure the radio, Compton-$y$, and X-ray correlations in the filament
between the clusters but conclude that deeper data are required for a
convincing determination of the correlations in the filament.