NASA APoD: Halo of the Cat's Eye I am a PhD student at the Kapteyn Astronomical Institute, the astronomy department of the University of Groningen, in the Netherlands. I received my masters degree in 2012 ceremonially from the University of Rome Tor Vergata in Italy, although officially the degree was granted jointly by the 5 partner universities of the Erasmus Mundus Master Course in Astronomy and Astrophysics (Astromundus), that I was enrolled in.
As part of my PhD project, currently I, under the supervision of prof. dr. Leon Koopmans, and with dr. Vibor Jelic and dr. Vishhambhar Pandey, am working on quantifying polarisation leakage in LOFAR observations caused by various systematic errors to facilitate the detection of the EoR signal, the cosmological 21-cm signal coming from the Epoch of Reionization. This signal will provide an excellent probe of structure formation and physical cosmology. The difficulty in detecting it stems from the fact that, it is heavily contaminated by foregrounds and instrumental systematics, e.g. Galactic foreground (diffuse synchrotron and free-free emission) and extragalactic foreground (radio galaxies and galaxy clusters), Earth's ionosphere, Radio Frequency Interference (RFI) and the errors related to the telescope itself. We can hope to detect the EoR signal only after removing all the foregrounds and correcting all the errors, which is done step by step. First, the extragalactic foregrounds, mostly point sources, are removed. Then, we are left with the Galactic diffuse foreground which is subtracted by availing ourself of the (assumed) dichotomy that, the diffuse foreground does not fluctuate as a function of frequency, while the EoR signal does. However, the polarized foreground emission is not a smooth function of frequency. If some polarised foreground emission is leaked into the total intensity, the foreground might also fluctuate along frequency direction, mimicing the EoR signal, and giving rise to the possibility of removing some parts of the expected signal during the foregound subtraction process. So quantifying the amount of foreground polarization leakage is a crucial step in the process of detecting the EoR signal.
We aim to quantify the amount of leakage caused by different types of systematic errors in the LOFAR observations of the EoR signal. Antenna gain errors, and instrumental cross-talk between the receivers of the observing stations are Direction Independent Errors (DIE) as they are same towards all directions of the sky. On the other hand, errors in determining the exact response of a station, i.e. its primary beam, and the cross-polarization between the two perpendicular components of a beam give rise to Direction Dependent Errors (DDE). The DDEs can cause significant polarisation leakage, and the DIEs, although negligible, cannot be ignored. By quantifying the individual leakages caused by these effects we are not only facilitating the EoR detection, but also understanding the Galactic diffuse emission at low frequencies that is still largely unexplored.
Master thesis project
I worked on Chandra X-ray observations of galaxy clusters during my masters under Prof dr. Pasquale Mazzotta, Dr. Herve Bourdian, and Dr. Chiara Ferrari. The title of my master thesis was: "Study of the formation of Cold Fronts and Radio Mini-halos induced by the Intergalactic Gas Sloshing in the Cores of Galaxy Clusters". We analysed the Chandra observations of the intracluster medium of 6 clusters in order to find sloshing cold fronts around their central minihalos.