Hunting for Brown Dwarfs in Globular Clusters: Second Epoch Deep IR observations of the Globular Clusters M4

We propose to obtain a second epoch of deep WFC3/F110W imaging of the globular cluster M4 to confirm (or rule out) the first brown dwarfs (BDs) detected in this cluster. In a first epoch of deep WFC3 IR imaging of M4, four good BD candidates were identified. We will use a second epoch to test whether the BD candidates share the proper motion of the cluster population or not, thereby confirming (or ruling out) these sources as genuine cluster members. Confirming these sources as cluster BDs is crucial if we want to fill the observational plane with old and metal-poor benchmark sources that are much needed if we are to test and calibrate models about BD atmospheres, BD formation and evolution.