2-6 September 2024
CJD Bonn Castell
Europe/Berlin timezone
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Contribution

Resolving extreme star formation and black hole activity in a high redshift quasar

Speakers

  • Ms. Jayde BHANA

Primary authors

Content

Understanding the feedback processes occurring in quasars and the nature of their faint radio emission is needed to reconcile known theories of galaxy formation and AGN evolution. In particular, it is not clear whether the faint radio emission from optically bright quasars is associated with weak jets, ongoing star-formation or another emission process occurring close to the black hole. To shed light on this area, for which there have been several recent statistical studies, I will present new detailed observations of an extremely luminous high redshift quasar that aims to resolve the underlying emission mechanism at radio wavelengths. The extreme radio luminosity of the gravitationally lensed quasar APM08279+5255, at redshift 3.911, results in a star-formation rate density that exceeds the Eddington-limited star-formation rate by a significant fraction. By using very long baseline interferometry (VLBI), we dissect the relationship between star formation and accretion processes driving the quasar activity. First, we present high angular resolution observations (50 to 100 mas) of this AGN with the VLA at 22 GHz and with e-MERLIN at 1.5 and 5 GHz. With these data, we find evidence for a flat-spectrum radio component associated with the optically bright quasar, but also evidence for offset steep spectrum emission. Next, using observations with the European VLBI Network (EVN) at 1.7 GHz, we detect a compact radio core that is co-located with the quasar, whose brightness temperature is consistent with AGN activity. However, a significant amount of radio emission is resolved-out on VLBI-scales, which suggests there is an extended component that is likely associated with star-formation. Finally, to understand the fuelling of such an AGN-starburst composite, we present the deepest (VLA; 80 h) and highest angular resolution imaging (100 mas) of CO (1-0) for such an object, which detects the cold molecular gas around the AGN. Our results demonstrate that high angular resolution imaging of both the continuum and spectral emission from individual objects are needed to interpret the weak radio emission being found for the large fraction for quasars (>65%) observed in recent statistical studies.