Relics of Double Radio Sources
  We have formed a new sample which consists of extended extragalactic radio
sources without obvious active galactic nuclei (AGN) in them. Most of these
sources appear to be dead double radio sources. These sources with steep
spectra ($\alpha < $ -1.8; S $\propto \nu^{\alpha}$) were identified using the
74 (VLSS) and the 1400 MHz (NVSS) surveys and further imaged using the Very
Large Array (VLA) and the Giant Meterwave RadioTelescope (GMRT). The radio
morphologies of these sources are rather unusual in the sense that no obvious
cores and jets are detected in these sources, but, two extended lobes are
detected in most. The mean redshift of 4 of the 10 sources reported here is
$\sim$ 0.2. At a redshift of 0.2, the linear extents of the sources in the
current sample are $\sim$ 250 kpc with their spectral luminosities at 1.4 GHz
in the range 2-25 x 10$^{23}$ W Hz$^{-1}$. The steep spectra of these sources
is a result of the cessation of AGN activities in them about 15 -- 100 million
years ago. Before the cessation of AGN activity, the radio luminosities of
these galaxies were $\sim$ 1000 times brighter than their current luminosities
and would have been comparable to those of the brightest active radio galaxies
detected in the local universe (L$_{1.4} \sim$ 10$^{27}$ W Hz$^{-1}$). The dead
radio galaxies reported here represent the $'$tip of the iceberg$'$ and
quantifying the abundance of such a population has important implications to
the life cycle of the AGN.
