AR_final file_2018-19

analysis of five-membered ring PAH molecule has been reported to further compare with observations and to identify any observational counterpart. This study has been done in collaboration with G. Devi, and M. Buragohain. Modelling 30 Doradus in the Large Magellanic Cloud The HII regions in the Large Magellanic Cloud (LMC) provide an ideal laboratory to study vari- ous processes of dust formation and evolution. The LMC has been targeted by many space-based tele- scopes, including NASAs Spitzer Space Telescope, and more recently, JAXAs AKARI satellite owing to its known distance and nearly face-on orientation with respect to the Miky Way (MW). The highest LMC reddening occurs in the 30 Doradus HII re- gion, where the colour excess E B − V reaches a max- imum of 0.29. We have done correlation studies in this region between far-ultraviolet (FUV) observa- tions made by the FUSE telescope, and infrared (IR) observations made by AKARI in the recent past. We have attempted to model the FUV scat- tering by 20 hot stars in the 30 Doradus region within a 1 deg radius. We have chosen an ideal dust distribution facilitating us to study the emission properties around the centre of the nebula. This study has been done in collaboration with Gautam Saikia, Jaikhomba Singha, P. Shalima, and Rupjy- oti Gogoi. Madhav K. Patil Merging cold front and AGN feedback in the pecu- liar galaxy cluster Abell 2626 We present the analysis of combined 134 ks Chan- dra data of a peculiar galaxy cluster Abell 2626. This study confirms the earlier detection of the east cavity at 13 kpc and reports the detection of a new cavity at ∼ 39 kpc to the west of the X-ray peak. The average mechanical power injected by the ac- tive galactic nucleus outburst P cav ∼ 6 . 6 × 10 44 erg/s is ∼ 29 times more than required to compen- sate the cooling luminosity L cool = 2 . 30 ± 0 . 02 × 10 43 erg/s. The edges in the surface brightness (SB) to the west and south-west at ∼ 36 kpc and 33 kpc, respectively, have gas compressions of 1.57 ± 0.08 and 2.06 ± 0.44, and are spatially associated with the arcs in temperature and metallicity maps due to the merging cold fronts. A systematic study of the nuclear sources exhibited dramatic changes over the span of 10 years. The NE source that emit- ted mostly in the soft band in the past had disap- peared in recent observations. Instead, an excess emission was seen at 2.2 arcsec to its west that re- quired an unrealistic line-of-sight velocity of ∼ 675 × c if it is due to its movement. The count rate anal- ysis and spectral analysis exhibited a change in the state of the SW source from a soft to a hard state due to the change in the mass accretion rate. No such spectral change was noticed for the NE source. This study has been done in collaboration with S. K. Kadam, S. S. Sonkamble, and P. K. Pawar. Cavities, shocks and a cold front around 3C 320 We present results obtained from the analysis of a total of 110 ks of Chandra observations of the Fa- naroffRiley class II (FR II) radio galaxy 3C 320, located at the centre of a cluster of galaxies at redshift z = 0.342. A pair of X-ray cavities has been detected at an average distance of ∼ 38 kpc along the east and west directions, with cavity en- ergy, age, and total power equal to ∼ 7 . 7 × 10 59 erg, ∼ 7 × 10 7 yr and ∼ 3 . 5 × 10 44 erg/s, respec- tively. The cooling luminosity within the cooling radius of 100 kpc was found to be L cool ∼ 8.5 × 10 43 erg/s. Comparison of these two estimates (to- tal cavity power and cooling luminosity) implies that the cavity power is sufficiently high to bal- ance radiative loss. A pair of weak shocks has also been detected at distances of 47 and 76 kpc sur- rounding the radio bubbles. Using the observed density jumps of 1.8 and 2.1 at the shock locations along the east and west directions, we estimate the Mach numbers to be ∼ 1.6 and ∼ 1.8, respectively. A sharp surface-brightness edge was also detected at a relatively larger radius ( ∼ 80 kpc) along the south direction. The density jump at this surface- brightness edge was estimated to be ∼ 1.6 and it is probably due to the presence of a cold front in this cluster. The far-infrared luminosity yielded a star formation rate of 51 M ⊙ yr − 1 , which is a quarter of the cooling rate ∼ 192 M ⊙ yr − 1 . This study has been done in collaboration with Nilkant D. Vagshethe, and Sachidra Naik. Bikash Chandra Paul Emergent Universe with wormhole in massive grav- ity? Emergent Universe (EU) is obtained in the Ein- stein gravity with non-linear equation of state in ( 206 )