We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and near infrared data of the Chamaeleon II ( Cha II ) dark cloud .
We perform a census of the young population of Cha II , in a mapped area of \sim 1.75 deg ^ { 2 } , and study the spatial distribution and properties of the cloud members and candidate pre-main sequence ( PMS ) objects and their circumstellar matter .
Our census of PMS objects and candidates in ChaII is complete down to the sub-stellar regime ( M \approx 0.03 ~ { } M _ { \odot } ) , at the assumed cloud distance of 178 pc .
The population consists of 51 certified and 11 candidate PMS objects , most of them located in the Eastern part of the cloud , but approximately following the dust emission lanes of the c2d extinction map .
From the analysis of the volume density of the PMS objects and candidates we find two tight groups of objects with volume densities higher than 25 M _ { \odot } pc ^ { -3 } and 5-10 members each .
These groups correlate well in space with the regions of high extinction .
A multiplicity fraction of about 13 \pm 3 % is observed for objects with separations 0.8 ” < \theta < 6.0 ” ( 142 - 1065 AU ) .
No evidence for variability in the IRAC bands between the two epochs of the c2d data set , \Delta t \sim 6 hours , is detected .
Using the results of masses and ages from a companion paper , we estimate the star formation efficiency to be 1-4 % , consistent with the estimates for Taurus and Lupus , but significantly lower than for Cha I .
This might mean that different star-formation activities in the Chamaeleon clouds reflect a different history of star formation .
We also find that the Cha II cloud is turning some 6-7 M _ { \odot } into stars every Myr , which is low in comparison with the star formation rate in other c2d clouds .
On the other hand , the disk fraction of 70-80 % that we estimate in Cha II is much higher than in other star forming regions and indicates that the population in this cloud is dominated by objects with active accretion , with only a minority being systems with passive and debris disks .
The circumstellar envelope/disk properties of the PMS objects and candidates are also investigated .
Finally , the Cha II outflows are discussed , with particular regard to the discovery of a new Herbig-Haro outflow , HH 939 , driven by the classical T Tauri star Sz 50 .