2025/01/17 by V. A. Fawcett, C. M. Harrison, Fawcett, V. A. +21 · 1 voice · 1 citation
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #astro-ph.GA
paper · pdf · doi:10.48550/arxiv.2501.10501
Recent studies have found a striking positive correlation between the amount of dust obscuration and enhanced radio emission in quasi-stellar objects (QSOs). However, what causes this connection remains unclear. In this paper we analyse uGMRT Band-3 (400 MHz) and Band-4 (650 MHz) data of a sample of 38 1.0 < z < 1.5 QSOs with existing high-resolution 0.2'' e-MERLIN 1.4 GHz imaging. In combination with archival radio data, we have constructed sensitive 4-5 band radio SEDs across 0.144-3 GHz to further characterize the radio emission in dusty QSOs. We find that the dusty QSOs (those with E(B-V) > 0.1 mag) are more likely to exhibit steep spectral slopes (α< -0.5; Sν ∝ να) than the non-dusty QSOs (E(B-V) < 0.1 mag), with fractions of 46±12 and 12±4 per cent, respectively. A higher fraction of the non-dusty QSOs have peaked radio SEDs (48±9 per cent) compared to the dusty QSOs (23±8 per cent). We discuss the origin of the radio emission, finding that the majority of the peaked, predominantly non-dusty, QSOs have consistent sizes and luminosities with compact jetted radio galaxies. However, the connection between steepness and dust obscuration implies an outflow-driven shock origin for the enhanced radio more commonly found in dusty QSOs. These results add to the emerging picture whereby dusty QSOs are in an earlier blow-out phase, with shocks that heat and destroy the surrounding dust, eventually revealing a typical non-dusty QSO.