Excitation in the middle of M33

This image of the central region of the Triangulum Galaxy, M33, was taken in October 2000 with the Mayall 4-meter telescope at Kitt Peak National Observatory, using the Mosaic imager. It shows data from three of the eight color filters being used by the Local Group Galaxies Survey Team to study this nearby spiral galaxy, the third largest in our Local Group, behind the Milky Way and the Andromeda Galaxy. The colors illustrate the excitation levels and abundance patterns in the galaxy's HII regions. The color blue shows [OIII] (doubly ionized oxygen), green shows visible light, and red denotes H alpha (ionized hydrogen). The observations were taken by Nichole King (Space Telescope Science Institute, Baltimore, MD) and Phil Massey (the Principal Investigator for the survey team, Lowell Observatory, Flagstaff, AZ); Shadrian Holmes (College of Charleston, SC) reduced the data; and George Jacoby (WIYN Observatory, Tucson, AZ) generated the combined color product. The survey will eventually cover all of M33. For more details, see http://www.lowell.edu/users/massey/lgsurvey.html.