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

Astronomy & Astrophysics 56 generates additional optical and UV emission from the disk, were provided via X-ray/UV/optical correlation time delay observations. AGN feedback, i.e., how theAGN emission and outflow affect their surroundings is another area studied using X-ray and radio observations of AGN and the intergalactic medium, together with theoretical cosmological simulations. In the very early days of AGN feedback related science, observation and dynamics of the evacuation of the interstellar medium in an AGN host galaxy and its effect on the AGN itself were discussed. Indian astronomers have made important contributions in understanding the radio emission fromAGN. In particular, original contributions were made in morphological classification, orientation dependent unification of AGN, evolutionary scheme of AGN, dual or binary AGN, radio jet interactions with the ambient medium, luminosity function and their redshift evolution. GMRT is also playing a very crucial role in detecting cold gas around AGN and very large radio sources extending upto mega-parsec scales, and in quantifying past activities ofAGN through the detection of double -double radio galaxies. Blazars are AGNs containing a prominent jet pointing towards our line of sight. The jet emission is relativistically beamed in the observer's frame and, therefore the observed emission from the blazars is dominated by that from the jet. Hence, blazars are excellent laboratories to study the structure and properties of relativistic jets including synchrotron and inverse-Compton processes and acceleration of particles to GeV-TeV energies. Indian astronomers have contributed substantially to the characterization of intraday variability (IDV) of blazar emission, and have discovered quasiperiodicity in some of those cases. The fast variability is useful in constraining the size of the emission region. It has been shown that IDV is more common in high synchrotron peaked blazars, and such short timescale variability is highly correlated at soft and hard X-ray bands. Various groups have theoretically modelled the spectral energy distribution (SED) of blazars. Fitting the models with observed SEDs, magnetic field and energy distribution of emitting particles have been estimated, and the emitting particles have been constrained to be leptonic. It has also been shown that the flux distribution of several blazars is log-normal, which implies that some form of a multiplicative process drives the jet emission. AstroSat's SXT and UVIT telecopes are carrying out multi-wavelength studies of several Seyfert galaxies and blazars. In a Seyfert known as IC 4329A, the variability amplitude is larger in the UVband than in the X–ray bands thus suggesting that UV emission from the accretion disk is the primary driver producing X- rays via thermal Comptonization. Ablazar, known as OJ 287 (believed to contain a binary system of SMBH), is being tracked extensively withAstroSat to study its different flux states tracing its spectral evolution on time scales of years andmonths. In the 1990s, using EGRET observations, it was suggested that the extragalactic diffuse ɤ-ray emission is due to unresolved blazars. The properties of the Galactic and extragalactic diffuse ɤ-ray emission were characterised. ɤ-ray emission from normal galaxies in the local group were studied to constrain the cosmic ray energy density in those galaxies. 4.1.16 GravitationalWaves Gravitational waves (GWs) were predicted by Einstein's general theory of relativity. It was known even then that these will be very difficult to detect, though efforts to do so were started in 1950s. An indirect confirmation of gravitational waves was observed in the change of orbital parameters of a pulsar in a binary system: this change occurs due to emission of gravitational waves. International effort to observe gravitational waves using L-shaped interferometers MEGA SCIENCE VISION-2035