Having established the motivation of the project in Section 1.4, the outline of the rest of the chapters is as follows:
The thesis is based on the observation of a set of calibrators at 610 MHz and 235 MHz using the GMRT. The second chapter introduces the details of radio astronomy and earth rotation aperture synthesis technique which is used in the Giant Meterwave Radio Telescope (GMRT). In this chapter we also discuss about images from a single dish radio telescope and how radio interferometry and aperture synthesis technique are useful for getting images of better resolution. In the last section of this chapter we will discuss about the GMRT, with its details like the GMRT array, antennas and feeds, the receiver system, the correlator system and the software system used at GMRT.
Many of the GMRT observers use the VLA (Very Large Array) calibrator list to find calibrators for the GMRT but this is often uncertain since the properties of the VLA calibrator at the GMRT frequency are not known. The third chapter describes the VLA telescope in brief, it's array configuration, frequency bands used at VLA and VLA calibrator manual. It also discuss the similarity between the VLA and the GMRT except for their operating frequencies. In another section, we discuss about the criteria for sample selection for the observation, observation and receiver setup used and the methodology used for the observation. In the last section we discuss about the strategies used for data reduction, imaging concepts and actual imaging of the sources using AIPS at both 610 MHz and 235 MHz.
In the fourth chapter, we present the GMRT observational results, in particular identified possible calibrators at the two observing frequencies, 235 MHz and 610 MHz. We also present the additional information, e.g, plots of amplitude as a function of sampled Fourier frequencies, a few images of individual mapped fields etc. Also in another section we have defined criteria used for identifying calibrators from the 150 observed sources and list those identified GMRT calibrators at 610 MHz and 235 MHz. We also group these identified GMRT calibrators according to quality as `List 1', `List 2', etc.
The spectra of the radio sources is the main sources of information regarding the physical process inside them. All the GMRT calibrator sources emit non-thermal radiation, which is due to synchrotron emission from high energy electrons spiraling in magnetic fields. In the fifth chapter we discuss about the synchrotron emission mechanism and how it affects the power law spectrum (intensity of the source as a function of frequency). In the last section, we will discuss about the radio spectra and classification of spectra.
Finally, chapter six describes the level of completeness and status of the project. We also propose our future plans as the next course of action.