• DOI:10.1086/301456
• Corpus ID: 18819321

New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence

@article{Gizis2000NewNF,
  title={New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence},
  author={John E. Gizis and David G. Monet and I. N. Reid and J. Davy Kirkpatrick and James William Liebert and Rik J. Williams IPACCaltech and Usno Flagstaff and University of Pennsylvania and University of Arizona and Caltech},
  journal={The Astronomical Journal},
  year={2000},
  volume={120},
  pages={1085-1099}
}

• J. Gizis, D. Monet, +7 authors Caltech
• Published 26 April 2000
• Physics, Geology
• The Astronomical Journal

We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with Ks 6 A) ultracool M dwarfs are consistent with an ordinary old disk stellar population, while the kinematics of inactive ultracool M dwarfs are more typical of a 0.5 Gyr old population. The early L dwarfs in the sample have kinematics consistent with old ages, suggesting that the hydrogen-burning limit is near spectral types L2–L4. We use the available data on M and L dwarfs to show that chromospheric activity drops with decreasing mass and temperature and that at a given (M8 or later) spectral type, the younger field (brown) dwarfs are less active than many of the older, more massive field stellar dwarfs. Thus, contrary to the well-known stellar age-activity relationship, low activity in field ultracool dwarfs can be an indication of comparative youth and substellar mass.