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SUMMARY:Sub-haloes or scattering: Flux ratios anomalies of quadruply lense
 d radio AGN
DTSTART;VALUE=DATE-TIME:20240902T074500Z
DTEND;VALUE=DATE-TIME:20240902T080000Z
DTSTAMP;VALUE=DATE-TIME:20260716T225001Z
UID:indico-contribution-16@cern.ch
DESCRIPTION:Speakers: WEN\, Di (University of Groningen)\nAnomalous flux r
 atios between lensed images can provide a key test of the dark matter sub-
 halo population\, and hence the properties of dark matter particles. Howev
 er\, the observed anomalous flux ratios at radio frequencies can also be t
 he result of systematics associated with our lack of knowledge about the s
 ource 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 Sens
 itivity Array and monitoring with the Very Large Array at 15 GHz of a samp
 le of 6 radio-loud lensed quasars. In some cases\, the high resolution ima
 ging shows evidence of extended source structure\, which provides a more a
 ccurate determination of the image magnification’s compared to when assu
 ming a point source. From high cadence monitoring\, we rule out any intrin
 sic source variability for the systems analyzed thus far. For one system w
 ith frequency-dependent flux ratios caused by scattering in the ionized me
 dium within the lensing galaxy\, we showcase our new method for jointly mo
 deling lensing and scattering\, which will be applied to our new multi-fre
 quency global VLBI observations with the European VLBI Network and the Ver
 y Long Baseline Array.\n\nhttps://events.mpifr-bonn.mpg.de/indico/event/37
 1/session/1/contribution/16
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/1/contributi
 on/16
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