Background
Massive stars are brilliant but short-lived. They
end their lives as supernovae (SNe) within a few millions of years
as they exhaust their nuclear fuel within this time.
Energetic radiation from associations of these stars ionize the interstellar medium in
galaxies and produce localized HII regions as well as diffuse ionized gas.
SNe of various types explode from the massive stars that form
in these associations which in turn pressurize and churn the interstellar
medium. A subset of SNe are also believed to host Long duration Gamma
Ray Bursts (LGRBs) which have engine-driven relativistic outflows.
Individual SNe blow bubbles in the interstellar medium and these can
be seen for thousands of years as supernova remnants (SNRs). But when many
massive stars explode close to each other, they can for much larger
and longer lived cavities called supershells. They form and evolve due to
the continuous mechanical energy injection by stellar
winds and SNe in massive parent OB associations. The outer shocks of the
superbubbles sweep up the ambient interstellar medium
into a thin cool shell. These
supershells may also play a role in triggering the formation of the
next generation of stars.
Proposed investigations
A comprehensive description of the feedback processes from SNe, LGRBs,
SNRs and supershells would span time scales of a few days to a few million years.
A broad understanding may be achieved by systematic observations of
a multitude of these events at different stages of evolution and connecting
all of them using our theoretical understanding of the underlying physical principles.
We propose to conduct observations of a number of these astrophysical objects.
This will entail the use of the
Giant Metrewave Radio Telescope (GMRT) operated by TIFR, and other
national and international telescope facilities. These multi wavelength observations
shall reveal the nature of non-relativistic outflows
from common SNe, relativistic outflows from LGRBs and possibly a (hitherto unreported)
subset of SNe.
Our comprehensive study will constrain their progenitors and the physical processes
by which they interact with the circumstellar and interstellar medium.
A broad understanding of the feedback processes from these cosmic explosions,
both in isolation and in associations, will further the understanding of their role
in energy injection and metal enrichment of the baryonic matter in the universe
throughout cosmic history.