Searching for the Bottom of the Initial Mass Function

Thursday, 16 June 2016 8 a.m. — 9 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
TARAN ESPLIN (Pennsylvania State University and NOAO South Visiting Astronomer)

The measurement of the substellar initial mass function (IMF) and its minimum mass and their dependence on environment would provide a fundamental test of theories of star formation. To provide better constraints on these properties of the IMF, we have performed a search for the least-massive members of nearby star-forming clusters and associations (150-300 pc, <10 Myr). To identify candidate brown dwarfs in these regions, we have measured proper motions for sources detected in multi-epoch images from the Spitzer Space Telescope. To enable these measurements and more fully realize IRAC's astrometric capabilities, we measured new distortion corrections for IRAC (0.004" systematic error; Esplin & Luhman 2016) and created a pipeline that extracts astrometric positions with errors of 0.02". The resulting proper motion samples of candidate brown dwarfs were then further refined using their color-magnitude diagrams constructed from deep optical and near-IR images. Through spectroscopic observations, we have confirmed many new members of the regions we studied including the least-massive members in several regions (~5 Jupiter masses).