Kim, Dong-Woo, Anderson, Craig, Burke, Doug, Fabbiano, Giuseppina, Fruscione, Antonella, Lauer, Jen, McCollough, Michael, Morgan, Doug, Mossman, Amy, O'Sullivan, Ewan, Paggi, Alessandro, Vrtilek, Saeqa, and Trinchieri, Ginevra. 2018. "Disturbed Fossil Group Galaxy NGC 1132." The Astrophysical Journal 853:129. https://doi.org/10.3847/1538-4357/aaa43a
We have analyzed the Chandra archival data of NGC 1132, a well-known fossil group, i.e., a system expected to be old and relaxed long after the giant elliptical galaxy assembly. Instead, the Chandra data reveal that the hot gas morphology is disturbed and asymmetrical, with a cold front following a possible bow shock. We discuss possible origins of the disturbed hot halo, including sloshing by a nearby object, merger, ram pressure by external hotter gas, and nuclear outburst. We consider that the first two mechanisms are likely explanations for the disturbed hot halo, with a slight preference for a minor merger with a low impact parameter because of the match with simulations and previous optical observations. In this case, NGC 1132 may be a rare example of unusual late mergers seen in recent simulations. Regardless of the origin of the disturbed hot halo, the paradigm of the fossil system needs to be reconsidered.