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Session: Extragalactic Astronomy and Astrophysics

Name: Mr. Nikolaos Mandarakas (IA-FORTH & Univ. of Crete)
Coauthors: No coauthors were included.
Type: Oral
Title: Optical Polarimetry of nearby galaxies
Abstract:

It has been proposed that measuring the integrated optical polarization of galaxies affected by the cosmic shear can shrink significantly the uncertainties and provide constraints in the measured dark matter parameters. This is based on the following two arguments: 1) The position angle (or electric vector position angle - EVPA) of the integrated galactic polarization can be a proxy of the orientation of its major axis, prior to lensing. 2) Gravitational lensing does not alter the position angle of the polarization of light, contrary to the observed position angle of the galaxy. Therefore, if we measure the polarization angle and the position angle of lensed galaxies, we could directly infer the original position angle, before lensing, and thus, the rotation on the position angle produced by weak lensing. This would tremendously constrain the derived dark matter parameters. However, there are not enough observational evidence for the first argument. I have performed a 3-filter study of integrated optical polarization of nearby galaxies using the RoboPol instrument. I am going to present preliminary results, focusing on the correlation between EVPA and galactic orientation, as well as discuss the polarization levels observed in those galaxies and other potential correlations. Apart from the weak-lensing aspect, this kind of study can help understand what are the potential mechanisms that produce polarization in galaxies, and how morphological characteristics may affect it.