Subproject B6: The Mass Function of Low-Mass Stars and Substellar Objects

Extension of the determination of the mass function to the end of the main sequence and into the brown dwarf regime in field populations and selected nearby star clusters and associations. Star formation history of the Solar neighborhood. Complete census of substellar objects down to very low masses.

The present-day stellar mass function in the Solar neighborhood is the product of the complex interplay between star formation, stellar evolution, the dynamical dissipation of young associations, and the subsequent mixing of stars. The mass functions of the clusters themselves tell us about the initial conditions impacting star formation and subsequent dynamical interactions. In the first funding period, detailed studies of the mass functions of the three nearby open clusters Hyades, Praesepe, and the Orion Nebula Cluster (ONC) were carried out, focusing on low-mass stars. Extra attention was paid to interloper removal. Mass segregation was found in the older clusters. The much younger ONC shows a yet unexplained steep decline of the mass function at low mass. An advantage of the proximity of the three clusters is that the studies can be extended to very low-mass objects, something currently only possible in the Solar neighbourhood and with very wide-field coverage.

Publications

Da Rio, N., Robberto, M., Hillenbrand, L.A., Henning, T., Stassun, K.G.: “The initial mass function of the Orion nebula cluster accros the H-burning limit”, ApJ 718, 14 (2012)

Deacon, D.,..., Goldman, B.,...: “Four New T Dwarfs Identified in Pan-STARRS 1 Commissioning Data”, AJ 142, 77 (2011)

Deacon, D.,..., Goldman, B.,...: HIP 38939B: “A New Benchmark T Dwarf in the Galactic Plane Discovered with Pan-STARRS1”, ApJ 755, 94 (2012)

Goldman, B., Röser, S., Schilbach, E.,..., Henning, Th.,...: “Towards a complete stellar mass function of the Hyades. I. Pan-STARRS1 optical observations of the low-mass stellar content”, A&A 559, 43 (2013)

Liu, M.,..., Goldman, B.,...: “A Search for High Proper Motion T Dwarfs with PAN-STARRS1 + 2MASS + WISE”, ApJ 740, 32 (2011)

Manjavacas, E., Goldman, B., Reffert, S., Henning, T.: “Parallax measurements of cool brown dwarfs”, A&A 560, A52 (2013)

Tremblay, P.E.,..., Goldman, B.: “Spectroscopic and photometric studies of white dwarfs in the Hyades”, A&A 547, 99 (2012)

Wang, W.,..., Goldman, B., Henning, T.,..., Bailer-Jones, C. A. L.: “The substellar mass function in the central region of the open cluster Praesepe from deep LBT observations”, A&A 531, 164 (2011)