Alladi Ramakrishnan Hall

Multi-wavelength Emission from Astrophysical Jets: Insights using Numerical Simulations

Bhargav Vaidya

University of Torino

Jets and outflows are an ubiquitous phenomenon observed in wide variety of astrophysical
objects like young stars, AGN, pulsars etc. From the observational point of view, these
fast collimated flows of plasma have been studied at multiple wavelengths. Even fluid
dynamical simulations have been widely used to study the macroscopic dynamical com-
plexities in these jets. With an aim of to extend dynamical models and create a synthetic
observatory for such astrophysical jets, numerical simulations should incorporate effects
due to microscopic processes. In this talk, I will focus on two such microscopic processes,
viz. thermo-chemical evolution and particle acceleration, that have been implemented in
the PLUTO code.
The study of molecular emission from young stellar jets should incorporate relevant
chemical processes along with dynamical evolution. For this purpose, we have developed a
thermo-chemical module that simultaneously evolves the important chemical reactions for
hydrogen species along with the bulk fluid flow in jets. Additionally, we have implemented
a thermodynamically consistent equation of state (EoS) that can account for various
molecular and atomic processes for a system in thermodynamic equilibrium and also in
presence of non-equilibrium cooling. I will present results on applying this module to
study synthetic sub-mm line emission from SiO and CO in young stellar jets e.g., L1448
and HH 211.
Powerful AGN jets, unlike their stellar counterparts, propagate at relativistic speeds
are considered to be factories of high energy particles observed in the universe. I will
present an implementation of a fully parallel, hybrid framework that allows the evolution
of Lagrangian particles coupled to relativistic MHD flows. Effects due to several phys-
ical processes like diffusive shock acceleration, turbulence, magnetic reconnection, syn-
chrotron and Inverse Compton processes are taken into account to synthetically model
non-thermal emission from AGN jets. Such a spectral evolution study in conjunction with
propagation of particles through regions of varying magnetic field provides a consistent
picture of particle energetics.