The end of star formation in Chamaeleon I ? A LABOCA census of starless
  and protostellar cores
  Chamaeleon I is the most active region in terms of star formation in the
Chamaeleon molecular cloud complex. Its population of prestellar and
protostellar cores is not known and a controversy exists concerning its history
of star formation. Our goal is to characterize the earliest stages of star
formation in this cloud. We used the bolometer array LABOCA at APEX to map the
cloud in dust continuum emission at 870 micron. The detected sources are
analysed by carefully taking into account the spatial filtering inherent in the
data reduction process. A search for associations with YSOs is performed using
Spitzer data and the SIMBAD database. Most of the detected 870 micron emission
is distributed in 5 filaments. We identify 59 starless cores, one candidate
first hydrostatic core, and 21 sources associated with more evolved YSOs. The
starless cores are only found above a visual extinction threshold of 5 mag.
They are less dense than those detected in other nearby molecular clouds by a
factor of a few on average. The core mass distribution is consistent with the
IMF at the high-mass end but is overpopulated at the low-mass end. In addition,
at most 17% of the cores have a mass larger than the critical Bonnor-Ebert
mass. Both results suggest that a large fraction of the starless cores may not
be prestellar. Based on the census of prestellar cores, Class 0 protostars, and
more evolved YSOs, we conclude that the star formation rate has decreased with
time in this cloud. The low fraction of candidate prestellar cores among the
population of starless cores, the small number of Class 0 protostars, the high
global star formation efficiency, the decrease of the star formation rate with
time, and the low mass per unit length of the detected filaments all suggest
that we may be witnessing the end of the star formation process in Cha I
{abridged}.
