A team of astronomers led by ASTRON astronomer Dr. George Heald has
discovered a previously unknown gigantic radio galaxy, using initial
images from a new, ongoing all-sky radio survey. The galaxy was found
using the powerful International LOFAR Telescope (ILT), built and
designed by ASTRON. The team is currently performing LOFAR's first
all-sky imaging survey, the Multi-frequency Snapshot Sky Survey (MSSS).
While browsing the first set of MSSS images, Dr. Heald identified a new
source the size of the full moon projected on the sky. The radio
emission is associated with material ejected from one member of an
interacting galaxy triplet system tens to hundreds of millions of years
ago. The physical extent of the material is much larger than the galaxy
system itself, extending millions of light years across intergalactic
space. The MSSS survey is still ongoing, and is poised to discover many
new sources like this one.
The new galaxy is a member of a class of objects called Giant Radio
Galaxies (GRGs). GRGs are a type of radio galaxy with extremely large
physical size, suggesting that they are either very powerful or very
old. LOFAR is an effective tool to find new GRGs like this one because
of its extreme sensitivity to such large objects, combined with its
operation at low frequencies that are well suited to observing old
sources.
The center of the new GRG is associated with one member of a galaxy
triplet known as UGC 09555. The central galaxy is located at a redshift
of z=0.054536, or 750 million light years from Earth. The central radio
source was previously known and has a flat radio spectrum, typical of
giant radio galaxies.
LOFAR's MSSS survey is a concerted effort to image the entire northern
sky at very low radio frequencies, between 30 and 160 MHz (wavelengths
from 2m to 10m). The primary aim of the survey is to perform an initial
shallow scan of the sky, in order to create an all-sky model that will
support the calibration of much deeper observations. It is comparable in
sensitivity and angular resolution to previous surveys with ‘classical'
radio telescopes like the Very Large Array (VLA) in the USA, ASTRON's
Westerbork Synthesis Radio Telescope (WSRT), and the Giant Metrewave
Radio Telescope (GMRT) in India. MSSS is unique in that it operates at
substantially lower frequencies, and is therefore poised to uncover new
sources that were missed by previous surveys. Its broad bandwidth
coverage is also novel in all-sky radio surveys, and will be used to
provide additional information about the detected objects.
The international team of astronomers that is performing the MSSS survey
is made up of about fifty members from various institutes, mostly in
the Netherlands, Germany, the UK, Poland, France and Italy.
For more information please contact:
Caption to the image: Overlay of the new GRG (blue-white colors) on an optical image from the Digitized Sky survey. The inset shows the central galaxy triplet (image from Sloan Digital Sky Survey). The image is about 2 Mpc across.
More information about MSSS can be found on the ASTRON website: http://www.astron.nl/radio-observatory/lofar-msss/lofar-msss.
