AR_final file_2018-19

three body problem with radiation pressure and oblateness. We examine nature of asteroids orbit with Lyapunov Characteristic Exponents (LCEs) over a finite intervals of time. LCE of the system confirms that the motion of asteroid is chaotic in nature. With the effect of radiation pressure and oblateness the length of the curve varies in both the planes. Oblateness factor is found to be more perturbative than radiation pressure. To see the precision of result obtained from numerical integra- tion, we show that the error propagation and the numerical stability are assured around the singular- ity by applying regularized equations of motion for precise long-term study. This monitoring work has been done in collaboration with Rishikesh Dutta Tiwary, and Bhola Ishwar. Smriti Mahajan The Star Formation Reference Survey - III: A multi wavelength view of star formation in nearby galax- ies We present multi-wavelength global star formation rate (SFR) estimates for 326 galaxies from the Star Formation Reference Survey (SFRS) in order to determine the mutual scatter and range of valid- ity of different indicators. The widely used em- pirical SFR recipes based on 1.4 GHz continuum, 8.0 µ m polycyclic aromatic hydrocarbons (PAH), and a combination of far-infrared (FIR) plus ultra- violet (UV) emission are mutually consistent with scatter of . 0 . 3 dex . The scatter is even smaller, . 0 . 24 dex , in the intermediate luminosity range 9 . 3 < log ( L 60 µm/L ⊙ ) < 10 . 7. The data prefer a non-linear relation between 1.4 GHz luminosity and other SFR measures. PAH luminosity under- estimates SFR for galaxies with strong UV emis- sion. A bolometric extinction correction to far- ultraviolet luminosity yields SFR within 0.2 dex of the total SFR estimate, but extinction correc- tions based on UV spectral slope or nuclear Balmer decrement give SFRs that may differ from the total SFR by up to 2 dex. However, for the minority of galaxies with UV luminosity > 5 × 10 9 L ⊙ or with implied far-UV extinction < 1 mag, the UV spec- tral slope gives extinction corrections with 0.22 dex uncertainty. This work has been done in collabora- tion with M. L. N. Ashby, S. P. Willner, P. Barmby, G. G. Fazio,..., Somak Raychaudhury, et al. Ultraviolet and optical view of galaxies in the Co- masSupercluster The Coma supercluster (100 h − 1 Mpc) offers an unprecedented contiguous range of environments in the nearby Universe. In this work, we present a catalogue of spectroscopically confirmed galaxies in the Coma supercluster detected in the ultraviolet (UV) wavebands. We use the arsenal of UV and optical data, covering ∼ 500 deg 2 on the sky to study their photometric and spectroscopic proper- ties as a function of environment at various scales. We identify the different components of the cosmic- web: large-scale filaments and voids using Dis- crete Persistent Structures Extractor, and groups and clusters using Hierarchical Density-based spa- tial clustering of applications with noise, respec- tively. We find that in the Coma supercluster, the median emission in H α inclines, while the g − r and FUV − NUV colours of galaxies become bluer moving further away from the spine of the filaments out to a radius of ∼ 1 Mpc. On the other hand, an opposite trend is observed as the distance be- tween the galaxy and centre of the nearest cluster or group decreases. Our analysis supports the hy- pothesis that properties of galaxies are not just de- fined by its stellar mass and large-scale density, but also by the environmental processes resulting due to the intrafilament medium, whose role in accel- erating galaxy transformations needs to be investi- gated thoroughly using multiwavelength data. This work has been done in collaboration with Ankit Singh, and Devika Shobhana. Manzoor A. Malik Confronting phantom inflation with Planck data The latest Planck results are in excellent agreement with the theoretical expectations predicted from standard normal inflation based on slow-roll ap- proximation, which assumes equation-of-state ω ≥ − 1 . In this work, we study the phantom infla- tion ( ω < − 1 ) as an alternative cosmological model within the slow-climb approximation using two hybrid inflationary fields. We perform Chain Monte Carlo analysis to determine the posterior distribution and best fit values for the cosmologi- cal parameters using Planck data, and show that current CMB data does not discriminate between normal and phantom inflation. Interestingly, un- like in normal inflation, ω in phantom induced in- flation evolves very slowly away from − 1 during ( 198 )