Exploring the Metallicity-Motion Relationship in M and L Dwarfs

Brown dwarfs are characterized by low masses that preclude the sustained hydrogen fusion characteristic of stars on the main sequence. Very cool, low mass M dwarfs are abundant within our galaxy and can be identified through various spectral features, such as the presence of TiO absorption bands. L dwarfs, though less common, are even cooler than M dwarfs, and are characterized by the presence of metallic hydrides in their spectra. We analyze the optical and infrared spectra of 42 M and L dwarfs, observed with the Magellan Echellette (MagE) optical spectrograph and Magellan infrared spectrometer FIRE in order to investigate the relationship between metallicity and galactic dynamics for these low mass objects. In particular, we examine whether older, higher metallicity objects have an increased galactic motion due to movement away from the galactic disk. We first look for evidence of this relationship within the two subsamples of M dwarfs and L dwarfs. We then compare the motions of the L Dwarfs and M dwarfs in our sample to see if the proposed metallicity-motion relationship provides kinematic evidence that M Dwarfs are older than L Dwarfs.