Multi-Frequency Observations of the Gravitational Lens B Anupreeta More Max-Planck-Institut fuer Radioastronomie, Bonn Supervisor : Richard Porcas (MPIfR) Collaborator: Mike Garrett (JIVE)

Outline  Introduction Background Koopmans scenario  VLBI Observations 18cm, 6cm and 3.6cm Results  Summary

B MERLIN map at 6cm D (z=1.01) Courtsey: CASTLES website A B C ~ 3.4 arcsec Source z = 3.27

Koopmans Scenario  C is a pair of images of a part of the background source  C has a high magnification ~ 300 Koopmans et al. (2002) Radio Optical doublequad Host galaxy of background source caustic D

My Work Spectral Analysis of Image A, Image B and Region C with the help of -- GLOBAL VLBI observations at 18cm and 6cm HSA observations at 3.6cm  To look for any counterparts of Region C components in Images A and B which will confirm Koopmans Scenario

18cm 6cm3.6 cm A B a1 a2 a5 a3a4 b4 b1 b5 b2 b3 10 mas

C 18 cm 3.6 cm 6 cm C1-1C1-2 C2-2 C mas

Spectra of components in Image A Frequency (GHz)

Spectra of components in Region C

Comparing spectra of a2+a5 and C

Summary  High resolution maps reveal more subcomponents in Images A and B demonstrating the expected opposite parity  Similarity in the spectra of C with the north-west sub- components in A and B are consistent with the Koopmans scenario