Galaxy Optical Variability of Virgo Cluster: New Tracer for
  Environmental Influences on Galaxies
  We investigate the relationship between the optical variability of galaxies
and their distances from the centre of the Virgo Cluster using Palomar
Transient Factory data. We define the ratio between the standard deviation of
the galaxy brightness and the mean value of the standard deviation as a measure
of a galaxy's optical variability. A sample of 814 Virgo galaxies with 230263
observations shows a monotonically decreasing trend of optical variability with
increasing clustercentric distance. The variability level inside the cluster is
3.2$\sigma$ higher than the level outside. We fit the variability with a linear
function and find that the data reject a distance-independent model. We examine
217 background galaxies for comparison and find no significant trend in galaxy
variability. We assess the relation with Monte Carlo simulation by rebuilding
the brightness of each galaxy. The simulation shows a monotonically decreasing
relation for member galaxy variability and a distance-independent relation for
background galaxies. Our result is consistent with the theory that the cold gas
flowing inwards the cluster centre fuels AGN activity. This work is a new
implementation of the method using optical variability to investigate the
relation between galaxies evolution and their environment.
