| Description |
The so called Hickson Compact Groups (HCGs) occupy a unique position in the range of galaxy environments found in the local universe. While their density enhancements are high, close to those seen in rich clusters, the over-densities appear to be more locally contained. Dynamical interactions between the galaxies in the groups lead to consumption of the available gas, star formation, and a rapid evolution compared to field galaxies. It has been shown that HCGs contain significant amounts of dust, which has so far hampered a detailed understanding of those objects based on optical observations alone. Based on recent Spitzer observations, we have embarked in the first multiwavelength analysis of how groups affect galaxy evolution. We used the state-of-the-art theoretical models in order to interpret the complete spectral energy distribution of the galaxies from the UV to the IR, and compare them with samples of field galaxies and interacting systems. However, due to the
proximity among the various galaxies in groups none of the past far-IR facilities (IRAS, Akari) had the angular resolution necessary to trace the far-IR emission of the individual group members, essential to determine the global energetics and dust content of the systems.
We propose to obtain deep broad-band far-IR images of 20 HCGs at various stages of evolution for which UV, optical, near-IR, and mid-IR data also exist. Herschel observations with their unique depth and high angular resolution, will enable us a) to accurately calculate the far-IR luminosity, dust mass and temperature of galaxies in HCGs in order to examine how the group environment affects them and b) determine the total dust budget in the groups by detecting the cold intragroup dust, studying its temperature, clumpiness, and spatial distribution. The proposed program requires a modest investment of 13.3 hrs. |
