Dipanjan Mukherjee (University of Torino, Italy)
Relativistic jets from AGNs are an important driver of feedback in galaxies. Although primarily considered in the context of energy deposition at scales of ~100 kpc to regulate mass inflow, the jets first interact with the host galaxy's ISM before breaking out to larger scales. Our recent 3D relativistic hydrodynamic simulations, performed on scales of several kpc, investigates the interaction of such jets with an inhomogeneous turbulent ISM within the potential of a galaxy. These simulations address the local gas physics, which is often missed in large scale cosmological simulations due to lack of sufficient resolution. The jets are found to couple strongly with the turbulent ISM, driving fast moving lateral outflows of multi-phase gas. The resultant outflows though strong, do not escape the galaxy, supporting a galactic fountain scenario of feedback, rather than a blow out phase as envisaged previously. We compare the effect of jet power and ISM density on the feedback efficiency. We show that low power jets remain confined within the host for a longer time driving shocks through the ISM, potentially quenching star formation on a large scale. We have performed simulations with two different ISM morphologies: spherical and disk. Jet-ISM coupling is stronger in spherically distributed gas. In gas disks, although the jet breaks out easily, the ensuing high pressure bubble compresses the disk driving shocks. Jets inclined to the disk behave differently, launching sub-relativistic vertical outflows while strongly perturbing the disk, as observed in galaxies like NGC 1052, IC 5063 etc. I will discuss the implications of these results on the evolution of the ISM of the host galaxy, and the effects on observable diagnostics.
Naosad Alam (Saha Institute of Nuclear Physics)
The bulk properties of neutron stars are predominantly governed by the equation of state (EoS) of asymmetric nuclear matter. The nuclear matter EoS for an arbitrary isospin asymmetry is characterized by the nuclear matter parameters, like, incompressibility coefficient, symmetry energy coefficient and their density derivatives. However, the knowledge of these nuclear parameters is limited. One can access the information about these nuclear parameters through their correlations with various observational properties of neutron stars. In this presentation, I will focus on the correlation of neutron star properties with various key parameters of nuclear matter equation of state. I will show a strong and almost model-independent correlation of neutron star radii with the linear combination of the slopes of the nuclear matter incompressibility coefficient and symmetry energy coefficient. I will also discuss the influence of the density dependence of symmetry energy on the critical parameters of asymmetric nuclear matter which are important for core-collapse simulations and the crustal properties of neutron stars.
Andrew Hamilton (JILA, Boulder)
This seminar will tell three stories about what happens inside astronomical black holes. The first story is about the simplest kind of black hole, a non-rotating Schwarzschild black hole. I show that the singularity is a surface, not a point, and I show that Hawking radiation diverges near the singular surface. There is no firewall paradox. The second story is about rotating black holes. A rotating black hole has an inner horizon where there is a (Poisson-Israel) instability, which I call the black hole particle accelerator, which is the most violent instability in the Universe, including the Big Bang. I show that the instability gives way to complicated oscillatory (Belinskii-Khalatnikov-Lifshitz) collapse. The third story is the most fantastic. You will have to attend the seminar to hear it.
Attention: the talk will start at 1:30 pm.
Dipanjan Mukherjee (Dipartimento di Fisica, Universit`a degli Studi di Torino)
Relativistic jets from AGNs are an important driver of feedback in galaxies. Although primarily considered in the context of energy deposition at scales of ~100 kpc to regulate mass inflow, the jets first interact with the host galaxy's ISM before breaking out to larger scales. Our recent 3D relativistic hydrodynamic simulations, performed on scales of several kpc, investigates the interaction of such jets with an inhomogeneous turbulent ISM within the potential of a galaxy. These simulations address the local gas physics, which is often missed in large scale cosmological simulations due to lack of sufficient resolution. The jets are found to couple strongly with the turbulent ISM, driving fast moving lateral outflows of multi-phase gas. The resultant outflows though strong, do not escape the galaxy, supporting a galactic fountain scenario of feedback, rather than a blow out phase as envisaged previously. We compare the effect of jet power and ISM density on the feedback efficiency. We show that low power jets remain confined within the host for a longer time driving shocks through the ISM, potentially quenching star formation on a large scale. We have performed simulations with two different ISM morphologies: spherical and disk. Jet-ISM coupling is stronger in spherically distributed gas. In gas disks, although the jet breaks out easily, the ensuing high pressure bubble compresses the disk driving shocks. Jets inclined to the disk behave differently, launching sub-relativistic vertical outflows while strongly perturbing the disk, as observed in galaxies like NGC 1052, IC 5063 etc. I will discuss the implications of these results on the evolution of the ISM of the host galaxy, and the effects on observable diagnostics.
