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

CJD Bonn Castell

Sub-haloes or scattering: Flux ratios anomalies of quadruply lensed radio AGN

Speakers

  • Di WEN

Primary authors

  • Di WEN (University of Groningen)

Content

Anomalous flux ratios between lensed images can provide a key test of the dark matter sub-halo population, and hence the properties of dark matter particles. However, the observed anomalous flux ratios at radio frequencies can also be the result of systematics associated with our lack of knowledge about the source structure, source variability, and propagation effects within the lensing galaxy. Removing or ruling-out these systematic effects is crucial for confirming and improving existing constraints on dark matter. Here, I present some early results of high-resolution imaging with the High Sensitivity Array and monitoring with the Very Large Array at 15 GHz of a sample of 6 radio-loud lensed quasars. In some cases, the high resolution imaging shows evidence of extended source structure, which provides a more accurate determination of the image magnification’s compared to when assuming a point source. From high cadence monitoring, we rule out any intrinsic source variability for the systems analyzed thus far. For one system with frequency-dependent flux ratios caused by scattering in the ionized medium within the lensing galaxy, we showcase our new method for jointly modeling lensing and scattering, which will be applied to our new multi-frequency global VLBI observations with the European VLBI Network and the Very Long Baseline Array.