Supernova Diversity from Galaxy Diversity: Rates and Hints on Supernova Progenitors

Supernovae (SNe) are dramatic and violent end-points of stellar evolution, and lie at the heart of some of the most important problems of modern astrophysics. They provide natural laboratories for studying the physics of hydrodynamics, nuclear processes in extreme conditions and are involved in the formation of neutron stars (NSs), black holes (BHs), and gamma-ray bursts (GRBs). SNe are also sources of gravitational waves, neutrino emission, and candidate sites for high-energy cosmic ray acceleration. In addition, SNe are responsible for driving the chemical evolution of galaxies and they are the main producers of heavy elements, which are indispensable for life. SNe play an important role in the extragalactic distance scale debate, particularly the well calibrated light-curves of SNe Ia showed that the expansion of the universe is accelerated. Thus, it is of broad astrophysical importance to understand the progenitor models and physical mechanisms of these spectacular explosions. In Chapter 1 of this thesis, I provide a brief introduction to the SN events, by starting with an historical overview and presenting the SN types and subtypes, their explosion mechanisms and brie y discuss the open questions. At the end of the chapter, I summarise the work that has been done in this thesis. In Chapter 2, I will discuss the SN rates. I start the chapter by describing earlier works in this eld, subsequently, I present the techniques for SN rate measurements and discuss the importance of the SN rate studies. Due to the numerous SN surveys, the increasing number of SN discovery is boosting this research eld. In Chapter 3, I describe the SUDARE survey. SUDARE is a SN survey which has been conduced on VST (VLT Survey Telescope) at ESO Paranal Observatory. The main purpose of the survey is to discover SNe at intermediate redshift 0:2 < z < 0:8. In the chapter, I introduce the survey strategy, data reduction pipelines and the goals of the survey. As well as, I present the obtained SN sample and the galaxy catalogs which have been used to measure the SN rates. In Chapter 4, I nally will discuss the results of Cappellaro et al. 2015, (Paper I, hereafter). In Paper I, the SN rates per unit volume of both types, Ia and CC, have been measured as a function of cosmic time. The rates are then compared with the theoretical expectation with two dierent SFH assumptions. I present also the comparison of the observations with the theoretical tracks of SN Ia for dierent progenitor scenarios. Furthermore, in Chapter 5, I introduce the results of Botticella et al. 2017, (Paper II, hereafter). In Paper II, the trend of SN rates per unit mass has been calculated as a function of intrinsic colors, the star-formation activity and the mass of the parent galaxy. An attempt has been undertaken to constrain the SN progenitor systems and also to answer the open questions related to SN explosion mechanisms. The derived rates have been compared with the four models of the SN Ia progenitors with dierent DTD model predictions and a mass range of 840M for the CC SN progenitors. In Chapter 6, I summarise the results of Harutyunyan et al. 2017 (Paper III, hereafter). In Paper III an attempt has been embarked to estimate the hidden fraction of CC SNe in B/LIRGs at intermediate redshifts. We measure the SN rates of both types, Ia and CC, in radio-loud and luminous infrared passive galaxies and see how they change with the redshift. The measured SN rates are then being compared with the previous works. Finally, in Chapter 7, I provide a summary and discuss the future prospects of the eld.