Spectral index of the diffuse radio emission in SpARCS1049+56

Determine the radio spectral index of the diffuse cluster-associated emission (including the candidate radio mini-halo) in SpARCS1049+56 by obtaining multi-frequency observations, as it cannot be reliably derived from the existing LOFAR High Band Antenna (120–168 MHz) detection alone.

Background

Characterizing the spectral index of diffuse radio emission is essential for comparing the source to the known mini-halo population (typically with $\alpha \sim -1.15$) and for discriminating between physical models (e.g., reacceleration vs. hadronic scenarios). The current dataset provides a single-frequency LOFAR HBA detection at ~144 MHz without complementary measurements at other frequencies, precluding a reliable spectral index determination.

The authors note that additional observations, such as JVLA P-band or LOFAR LBA, are needed to confirm the mini-halo nature and to measure the spectral index, which is a key diagnostic for consistency with the mini-halo population.