Chamaeleon

TL;DR

This paper studies the Chamaeleon dark clouds, detailing their properties, star formation activity, and stellar populations, revealing similarities with other star-forming regions and insights into disk lifetimes and initial mass functions.

Contribution

It provides a comprehensive analysis of the stellar content, ages, and disk fractions in Chamaeleon I and II, comparing these with other star-forming regions to enhance understanding of star formation processes.

Findings

Cha I has a median age of ~2 Myr.

IMF peaks at 0.1-0.15 M_sun, similar to IC 348.

Disk fraction is ~50-65%, longer for solar-type stars.

Abstract

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.