How galaxies form and how they evolve thus
requires measurements of various parameters. Although scientists have
successfully studied about stellar masses and formation of stars at different
epochs. But still there is little known about the fuel of star formation.
A Giant Metrewave Radio Telescope has been set up
by NCRA,
centre of school of natural sciences of TIFR. It is a versatile instrument which study various astronomical problems such as concerning pulsars, radio
galaxies and regarding evolution of universe. It is one of the largest radio
telescopes in the world. Galaxies are made up of stars and gas. To understand
galaxies, there is need to know about the evolution of gas and stars with time. For
this purpose GMRT was built to observe many different astronomical objects. GMRT consists of 30 fully steerable gigantic parabolic dishes
of 45m diameter each spread over distances of upto 25 km. The number and
configuration of the dishes was so selected to have high angular resolution as
well as ability to image radio emission from diffuse extended regions. GMRT is being designed to operate in six different
frequency bands between 38 and 1420 MHz. All these provides a purpose of
dual polarization.
GMRT is an indigenous project. The construction of 30 large
dishes at a relatively small cost has been possible due to an important
technological breakthrough achieved by Indian Scientists. 
Scientists of TIFR and IISER Mohali have used the upgraded
GMRT to carry out the distant measurements of atomic hydrogen content of
galaxies in the early universe. They found that the star formation efficiency
of galaxies appear to have not changed significantly over the last 4 billion
years.
Why there was a need to upgrade GMRT?
Scientists answered that most of
the atomic gas is in the form of hydrogen, which emits spectral line at the
radio length of 21.11cm. This emission is so weak that it is not even detected by
powerful telescopes like GMRT. That’s why GMRT has been extended to wide range
frequency covering range even of hydrogen spectrum.
The upgraded version of GMRT has
made possible to have a direct measurements of gas masses of distant galaxies.
