A NEW NEARBY DWARF GALAXY 

INT+WFC

The Wide Angle Survey, one of the ING Wide Field Survey programmes, brings together a diverse range of scientific topics, merging the observational programme to increase scientific effectiveness.

As part of the Virgo survey component some 25 square degrees of Virgo were obtained in the B photometric band, and the pipeline processed object catalogues were analysed. More than 500 Low Surface Brightness galaxies B_tot<21 were discovered by comparing the light profiles of the millions of objects in the data frames with those of previously known template LSB galaxies.

Using this data astronomers at Cambridge discovered a new nearby dwarf galaxy in the constellation of Cepheus. This LSB dwarf galaxy is a typical example of previously unknown nearby galaxies, and it had been previously overlooked because of its low surface brightness relative to the night sky.

Most Local Group galaxies are satellites of the Milky Way and Andromeda systems leaving only a few outliers to use as probes of the dynamical evolution of the Local Group and for characterizing the unperturbed evolution of nearby dwarf galaxies. 

The luminosity function in Virgo, when combined with the much flatter function found in the field, will enable the efficiency of low mass galaxy formation in differing environments to be investigated. First results are indicating a strong environmental dependence, which would need to be taken into consideration by Cold Dark Matter theories.

Colour composite of Cepheus galaxy created from 1200 second exposures in g', r' and i'-band images taken in sub-arcsec conditions using the Wide Field Camera on the INT  [ JPEG | TIFF ]

Some references: 

• CCI Annual Report 2001, 18.
• N. A. Walton et al., 2001, "Science Highlights from the ING Wide Field Survey", ING Newsl., 4, 3.