The Tadpole -OR- The Chainsaw ?
In 2001, Westerbork observations of the disturbed galaxy
named VV-29 (alias Arp-188, UGC-10214) showed that there is
second smaller galaxy (named VV-29c) that appears behind the
western side of the main body of the distorted galaxy. Through its
gravitational forces during a close orbital encounter, this second galaxy
appears to have been responsible for raising the long `tail of the
tadpole' that extends
outward from VV-29.
VV-29 received wide press coverage during May 2002, when it appeared on the
front pages of major newspapers to announce the commissioning of the
Hubble Space Telescope's Advanced Camera. The galaxy was featured as
the May 2, 2002
Astronomy Picture of the Day. The bright, blue-ish center of the new galaxy
VV-29c can be seen through the double spiral arms of VV-29.
The mosaic of images below compares the HST image with two other
diagnostic images: one comes from the
Westerbork Radio Synthesis Telescope,
and the second from the
2.5m Isaac Newton optical telescope
in La Palma. The images are oriented with north upward and east to the
The color radio image records the emission from the galaxy in
the 21cm line of neutral hydrogen, indicating both the extent of the
hydrogen gas and its velocity along the line of sight to the observer
(using the Doppler effect). The blue end of the spectrum indicates the
regions in the galaxy that are approaching us, while the red regions of
the `velocity field' indicate recession. The WSRT observations revealed
the second galaxy VV29c through its velocity offset, which you can
see as the red background object that is viewed through the
artificial perforation in the velocity field on the right side of
The very deep Isaac Newton Telescope image has also been heavily
smoothed to bring out the faintest diffuse light levels. This
reveals additional structures not seen in the HST image: a faint
counter-arm to the right, and a vertical spur on the left side
of the main body of the galaxy.
GALAXY NAMES: Galaxies acquire names when their coordinates in the
sky are measured and they are listed in catalogs for subsequent study by
astronomers. For example, the interesting system pictured above has
a large number of `aliases', which result from its listing in several
popular catalogs. The first catalog to list it was the Vorontsov-Velyaminov
"Atlas and Catalog of Interacting Galaxies", published in 1959. This galaxy was
the 29th object listed in the catalog. In fact, Vorontsov-Velyaminov actually
split the galaxy into two parts: VV-29a, the main body of the galaxy, and
VV-29b, the tidal tail that extends to the east (left) in the pictures.
When the third galaxy was discovered in the WSRT data, the observing
team (Briggs, Moller, Higdon, Trentham, Ramirez-Ruiz) decided to continue
this convention by naming the new galaxy VV-29c.
VV-29 has other names, which result from its appearance in many catalogs:
Arp-188 (in Arp's "Atlas of Peculiar Galaxies," 1966), CGCG275-023
(in Zwicky's "Catalogue of Galaxies and of Clusters of Galaxies," 1966),
UGC10214 (in Nilson's "Uppsala General Catalogue of Galaxies," 1973).
When VV-29 had its 15 minutes of fame in May 2002, it appeared under the
name "The Tadpole Galaxy," but based on the images above, we will always
think of it as "The CHAINSAW"!
PUBLISHED PAPER: 2001, A&A, 380, 418 (Briggs, Moller, Higdon, Trentham, Ramirez-Ruiz).
"Did VV 29 collide with a dark Dark-Matter halo?"
Last modified on: September 6, 2002
Concerning this webpage please write to: