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The Initial Mass Function (IMF) describes the distribution of stellar masses formed through an episode of star formation. For any physical interpretation of optical light, especially for external galaxies, an IMF is needed --- that is, assumed. But measuring the IMF directly is complicated. There are many technical (i.e. measurement) and intrinsic difficulties in ascertaining the masses that stars were at their birth, often billions of years in the past. Many different methods exist to indirectly constrain this concept, each with their own strengths and pit-falls. They are routinely applied to heterogeneous samples of galaxies with heterogeneous data sets, yet then compared in an attempt to constrain the IMF and its variability across space and time. I will tell the story of ESO286-G022, a massive early-type galaxy for which we have many independent probes of the IMF. Even for this one galaxy, these methods do not agree in their predicted IMF. I will describe our increasingly-sophisticated attempts to determine why they do not agree, and what we learn in the process. |
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