We present a comprehensive study of disks around 81 young low-mass stars and brown dwarfs in the nearby \sim 2 Myr-old Chamaeleon I star-forming region .
We use mid-infrared photometry from the Spitzer Space Telescope , supplemented by findings from ground-based high-resolution optical spectroscopy and adaptive optics imaging .
We derive disk fractions of 52 \% \pm 6 \% and 58 ^ { +6 } _ { -7 } \% based on 8 \mu m and 24 \mu m colour excesses , respectively , consistent with those reported for other clusters of similar age .
Within the uncertainties , the disk frequency in our sample of K3–M8 objects in Cha I does not depend on stellar mass .
Diskless and disk-bearing objects have similar spatial distributions .
There are no obvious transition disks in our sample , implying a rapid timescale for the inner disk clearing process ; however , we find two objects with weak excess at 3–8 \mu m and substantial excess at 24 \mu m , which may indicate grain growth and dust settling in the inner disk .
For a sub-sample of 35 objects with high-resolution spectra , we investigate the connection between accretion signatures and dusty disks : in the vast majority of cases ( 29/35 ) the two are well correlated , suggesting that , on average , the timescale for gas dissipation is similar to that for clearing the inner dust disk .
The exceptions are six objects for which dust disks appear to persist even though accretion has ceased or dropped below measurable levels .
Adaptive optics images of 65 of our targets reveal that 17 have companions at ( projected ) separations of 10–80 AU .
Of the five \lesssim 20 AU binaries , four lack infrared excess , possibly indicating that a close companion leads to faster disk dispersal .
The closest binary with excess is separated by \sim 20 AU , which sets an upper limit of \sim 8 AU for the outer disk radius .
The overall disk frequency among stars with companions ( 35 ^ { +15 } _ { -13 } \% ) is lower than ( but still statistically consistent with ) the value for the total sample .