NGC 7125/6, SINGG Survey

Gas-rich galaxies display a wide range of structures and properties, but one thing they all seem to have are some newly formed stars. Images from the Survey for Ionization in Neutral Gas Galaxies (SINGG), an NOAO Survey Program (obtained with the CTIO 1.5m telescope), are designed to highlight areas of star formation in gas rich galaxies. The SINGG images are particularly good for finding companion galaxies. In this image we see the very obvious (and spectacular) interacting pair NGC7125/NGC7126. In addition we see a faint dwarf galaxy in the same system. It is between the two galaxies and offset to the left (East). Whereas the two spirals have hundreds of HII regions (the yellow to red dots), the dwarf has only two. The image is displayed so that stars have a cyan-blue appearance, while ionized hydrogen (H-alpha) emission appears orange-red to yellow. The H-alpha emission marks where the gas in the galaxies has been stripped of electrons, and is now recombining. It takes very hot O stars to ionize the gas; these stars have very short lifetimes (a few million years). As a result, red tones in these images typically mark the location of newly formed hot stars. Gerhardt Meurer of The Johns Hopkins University, Baltimore, MD, is the principal investigator for SINGG. For more information, see: http://sungg.pha.jhu.edu/