Daniel Persson Ilonen presenterar sitt examensarbete "Polarimetry of a giant radio galaxy", utfört vid institutionen för rymd-, geo- och miljövetenskap.
Oppontent: Ana Mari Petrova
Examinator: Cathy Horellou
Handledare: Cathy Horellou
Radio galaxies come in different sizes and and shapes, but the origin of their radio emission is always related to an active galactic nucleus near a supermassive black hole located at the center of their host galaxy. Depending on their intrinsic power, their age and their environment, radio galaxies can be compact or extended, and display jets and lobes of radio emission that extend well beyond the host galaxy. The radio structures are valuable probes of the history and the environment of the galaxies into which they expand. Polarimetry provides additional information of the magneto-ionic medium in and around radio galaxies.
In this thesis new observational data of synchrotron emission from the recently discovered giant radio galaxy named the Double Irony were imaged and analysed. The radio galaxy is relatively nearby, at a redshift of 0.138, located in a group of galaxies, and has a total length of about 1100 kiloparsecs. The observations were made by the Jansky Very Large Array interferometer in the 4.2 to 8.2 GHz frequency range, with a 2 MHz spectral resolution. The Stokes I data were calibrated using a calibration pipeline. Polarimetric data were manually calibrated using the output of the calibration pipeline as a starting point.
The wideband Stokes I continuum was first imaged. The resulting images have a higher angular resolution than in previous works, with a synthesised beam of about 3 arcseconds (or 8 kiloparsecs), and reveal the structure of the radio galaxy in great detail. After primary beam attenuation correction the spectral index map was calculated, using both wideband images and individual frequency bands of 128 MHz.
Rotation Measure Synthesis was performed on the Stokes Q and U wideband data that were corrected for Faraday rotation. Linear polarisation intensity and linear polarisation angles were obtained, and the magnetic field orientation in different structures of Double Irony was determined. The polarimetric data show signs of helical magnetic fields, with a toroidal component in some parts of the jets. The distribution of the radio intensity and of the polarization in different parts of the radio galaxy (jets, lobes, plumes) is presented and discussed.
Gröna rummet, meeting room, Maskingränd 2, EDIT trappa F, G och H