Chamaeleon
Abstract
Description
The dark clouds in the constellation of Chamaeleon have distances of 160-180 pc from the Sun and a total mass of ~5000 M_sun. The three main clouds, Cha I, II, and III, have angular sizes of a few square degrees and maximum extinctions of A_V=5-10. Most of the star formation in these clouds is occurring in Cha I, with the remainder in Cha II. The current census of Cha I contains 237 known members, 33 of which have spectral types indicative of brown dwarfs (>M6). Approximately 50 members of Cha II have been identified, including a few brown dwarfs. When interpreted with the evolutionary models of Chabrier and Baraffe, the H-R diagram for Cha I exhibits a median age of ~2 Myr, making it coeval with IC 348 and slightly older than Taurus (~1 Myr). The IMF of Cha I reaches a maximum at a mass of 0.1-0.15 M_sun, and thus closely resembles the IMFs in IC 348 and the Orion Nebula Cluster. The disk fraction in Cha I is roughly constant at ~50% from 0.01 to 0.3 M_sun and increases to ~65% at higher masses. In comparison, IC 348 has a similar disk fraction at low masses but a much lower disk fraction at M>1 M_sun, indicating that solar-type stars have longer disk lifetimes in Cha I.
to appear in the Handbook of Star Forming Regions, ASP Monograph Series
to appear in the Handbook of Star Forming Regions, ASP Monograph Series