• spectral index map
• CASA
• VLA
• interferometry
• 74 MHz
• 330 MHz
• halo
• AGN
• M87

My thesis presents a study of the extended radio emitting structures of M87, the central active-nucleus giant elliptical galaxy in the Virgo cluster. The galaxy is one of the closest radio galaxy and presents the paradigmatic example of a radio jet fed by a nuclear super- massive black hole, whose mass has been measured dynamically at » 109Md.
Because of its central location, the emergent jet’s interaction with the dense intracluster me- dium forms a complex structure in the kiloparsec scale with a projected end-to-end length for the radio halo of about 80 kpc.
The project aims at providing a consistent physical explanation for the many fine structure features that appear in the maps, especially one enigmatic feature that emerged from this study. This is a localized flattening of the power law spectrum that has no counterparts in the literature. The propagation, aging, and reenergization processes that may be acting in the Virgo cluster core are examined along with the magnetic field distribution and lobe evolution to model the extended structures.
The analysis is performed using new low frequency radio maps at 74 MHz and 330 MHz. These data were obtained by Dr. N. Kassim and Dr. T. Clarke (Naval Research Laboratory Washington) with the low frequency upgrade of the Very Large Array (VLA) radio telescope. The VLA, sited near Socorro (New Mexico, USA), is an element aperture synthesis interfe- rometer composed of 27 radio antennas.
After making some adjustments to the images, the outcome is a low frequency spectral in- dex map with characterization of its relative errors. This kind of map provides information about the aging and acceleration mechanisms for the trapped electrons and on the underlying energy distribution of synchrotron-emitting electrons. This also requires comparisons with wide field multi-wavelength data (e.g. Chandra), which are necessary for understanding the interaction between the extended lobes and the circumgalactic environment.
For the analysis, I used Common Astronomy Software Applications (CASA) that is a set of C++ application libraries with an iPython interface developed for radio astronomical data analysis, having received training during the 14th Synthesis Imaging Workshop in Socorro (New Mexico, USA).