MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

Astronomy & Astrophysics 50 Universe had undergone a rapid expansion phase in the very early stages. This phase is referred to as inflation and models for inflation were proposed in late 1970s and early 1980s. One of the key predictions of these models is the presence of perturbations at very large scales and this has been verified in observations of the cosmic microwave background radiation anisotropies.Anumber of research groups have contributed to constructingmodels for inflation, working out theoretical ideas related with inflation, confronting models of inflation with observations, etc. One critical idea related to inflation is the possibility that large scale magnetic fields were generated during this era. Much work has been done on ideas related to cosmicmagnetismand its implications by groups in Indian institutes. Abundance of clusters of galaxies has been shown to be sensitive to the power spectrum of fluctuations in matter density. Further, the evolution of abundance and the variation seen using different types of observations are sensitive to cosmological parameters like the total density parameter, baryon density parameter, etc. Observations of clusters in the optical, radio and X-rays have been combined to constrain cosmological parameters. Similar efforts have been made by astronomers to use the abundance of galaxies at high redshifts to put constraints on the mass of neutrinos. Constraining the baryon density of the Universe through the observations of Deuterium in metal poor gas in the early universe is yet another important study. 4.1.12 Gravitational Lensing Gravitational lensing is a phenomenon by which light from a distant galaxy (object) is distorted by the gravitational effects of a foreground galaxy that acts like a lens, and makes the distant source appear distorted, but magnified, forming characteristic rings of light, known as Einstein rings. Gravitational lensing was observationally confirmed in 1919, also confirming Einstein's prediction using general theory of relativity. In the last five decades, observations of gravitational lensing of distant galaxies have been used to measure mass of galaxies and clusters, thereby confirming the presence of dark matter that outweighs normal matter by a factor of more than six. Observations from the Ooty radio telescope led to the discovery of a strongly lensed radio source PKS1830-211. Gravitational lensing is an extremely good cosmological tool as it enables observations of distant objects. Indian astronomers have contributed significantly to the theory of gravitational lensing as well as modelling of mass distribution on observed lensing systems. In a study published in 1995, a new population of lensing sources were discovered in theAbell cluster based on sensitiveVLAmaps in 21cm. The past decade has seen a resurgence of interest in this field as upcoming surveys will increase the number of gravitationally lensed systems by more than an order of magnitude. Participating in several international collaborations, Indian astronomers have been studying gravitationally lensed sources to estimate the Hubble constant, measure the mass of galaxies, estimate the amount of darkmatter in galaxies, etc. A recent development in the field of gravitational lensing is micro-lensing of gravitational waves where the wave interference effects are important and geometric optics limit is not valid. Indian astronomers have contributed to development of ideas as well as detailed predictions for observations and have also participated in international collaborations in the search and detailedmonitoring of micro-lensing events. Distortions in the shape of background galaxies by the foreground large-scale structure (called “weak gravitational lensing”) provides an important probe of cosmological parameters and evolution of structures in the Universe. Weak MEGA SCIENCE VISION-2035