Speaker
Description
When we have an unobscured view of the accretion disc, which peaks in the UV, QSOs display very blue UV–optical colours. However, we have recently discovered a hidden population of QSOs, obscured by dust, which are almost completely uncharacterised by previous spectroscopic surveys. These dusty QSOs could represent an important short-lived transitional phase in the evolution of galaxies (a “blow-out” phase). Utilising data from DESI we can now, for the first time, explore a statistically significant sample of these reddened QSOs. Combining DESI spectra with radio data from the LoTSS DR2, we find a striking positive relationship between the amount of dust extinction and the radio detection fraction in DESI QSOs. This demonstrates an intrinsic connection between opacity and the production of radio emission in QSOs. In our latest study, we construct sensitive radio SEDs of 38 QSOs across 0.144-3 GHz frequencies, with additional ~kpc scale e-MERLIN imaging, in order to probe the origin of the enhanced radio emission in dusty QSOs. We find that dusty QSOs tend to display steeper radio spectral slopes compared to typical blue QSOs, which is likely due to outflow-driven shocks on the surrounding ISM. These results are consistent with dusty QSOs representing an important blow-out phase in the evolution of galaxies.
