Kelsey Johnson (P.I.; UVa), John Hibbard (NRAO), Sarah Gallagher (UCLA), Ann Hornschemeier (GSFC), Jane Charlton (PSU), Amanda Heiderman (NRAO-REU), et al.

Above: falsecolor represenation of IRAC 3.6um (blue), 4.5um (green), and 8um (red) images for HCG 07

This project involves Spitzer IRAC 3.6-8um and MIPS 24um observations of a sample of 12 nearby Hickson Compact Groups, chosen to sample a range of evolutionary stages. There are many aspects of this project, with different people in the above list taking charge of various scientific topics. My interest is in using the mid-IR indicators of activity to understand the evolution of the neutral hydrogen content. According to the evolutionary scenario of Verdes Montenegro et al. (2001), in less evolved compact groups the neutral hydrogen is normal or mildly deficient (compared to isolated spirals of similar Hubble Type and luminosity). In the intermediate stages, the HI is drawn into tidal features, and the group as a whole is deficient in HI. In the late stages, the spirals are highly deficient, and there is often an X-ray intergroup medium. I believe that studying this sequence will help us understand how star formation may be abruptly truncated as galaxies evolve, as suggested by some recent observations.

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Last modified: Tue Dec 13 11:12:48 EST 2005