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We present the first deep low frequency radio observations of the massive andhighly disturbed galaxy cluster Abell 2744 using the upgraded Giant MetrewaveRadio Telescope (uGMRT). The cluster is experiencing a very complex multiplemerger and hosts a giant halo and four radio relics. The uGMRT observations,together with existing VLA and Chandra observations, allow us to study thecomplexity of the physical mechanisms active in this system. Our new imagesreveal that the central halo emission is more extended toward low frequencies.We find that the integrated spectrum of the halo follows a power-law between150 MHz and 3 GHz, while its subregions show significantly different spectra,also featuring high frequency spectral steepening. The halo also shows localregions in which the spectral index is significantly different from the averagevalue. Our results highlight that an overall power-law spectrum, as observed inmany radio halos, may also arise from the superposition of differentsubcomponents. The comparison of the radio surface brightness and spectralindex with the X-ray brightness and temperature reveals for the first timedifferent trends, indicating that the halo consists of two main components. Allfour relics in this system follow a power-law radio spectrum, compatible withshocks with Mach numbers in the range $3.0-4.5$. All relics are also highlypolarized from 1-4 GHz and show low Faraday dispersion measures, suggestingthat they are located in the outermost regions of the cluster. The complexityin the distribution and properties of nonthermal components in Abell 2744supports a multiple merger scenario, as also highlighted by previous X-ray andlensing studies. Our unique results demonstrate the importance of sensitive andhigh-resolution, multi-frequency radio observations for understanding theinterplay between the thermal and non-thermal components of the ICM.

Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis