Forskning ved Københavns Universitet - Københavns Universitet


The young population of the Chamaeleon II dark cloud

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  • Loredana Spezzi
  • Juan M. Alcalá
  • Elvira Covino
  • Antonio Frasca
  • Davide Gandolfi
  • Isa Oliveira
  • Nicholas Chapman
  • Neal J., II Evans
  • Tracy L. Huard
  • Jørgensen, Jes Kristian
  • Bruno Merín
  • Karl R. Stapelfeldt

We discuss the results of the optical spectroscopic follow-up of pre-main-sequence (PMS) objects and candidates selected in the Chamaeleon II dark cloud based on data from the Spitzer Legacy survey "From Molecular Cores to Planet Forming Disks" (c2d) and from previous surveys. Our sample includes both objects with infrared excess selected according to c2d criteria and referred to as young stellar objects and other cloud members and candidates selected from complementary optical and near-infrared data. We characterize the sample of objects by deriving their physical parameters. The vast majority of objects have masses M ≤ 1 M and ages <6 Myr. Several of the PMS objects and candidates lie very close to or below the hydrogen-burning limit. A first estimate of the slope of the initial mass function in Cha II is consistent with that of other T associations. The star formation efficiency in the cloud (1%-4%) is consistent with our own estimates for Taurus and Lupus, but significantly lower than for Cha I. This might mean that different star formation activities in the Chamaeleon clouds may reflect a different history of star formation. We also find that the Cha II cloud is turning some 8 M∞⊙ into stars every megayear, which is less than the star formation rate in the other c2d clouds. However, the star formation rate is not steady and evidence is found that the star formation in Cha II might have occurred very rapidly. The Hα emission of the Cha II PMS objects, as well as possible correlations between their stellar and disk properties, is also investigated.

TidsskriftAstrophysical Journal
Udgave nummer2
Sider (fra-til)1295-1318
Antal sider24
StatusUdgivet - 20 jun. 2008
Eksternt udgivetJa

ID: 229739643