  The aims of this study are to determine the properties and spatial
distribution of dense cores in Ori B9, and to estimate their ages and dynamical
timescales. The cloud was mapped in the 870 micron continuum with APEX/LABOCA,
and selected positions were observed in the lines of N2H+ and N2D+ using
IRAM-30m. These were used together with our previous H2D+ observations.
Moreover, archival FIR Spitzer/MIPS maps were combined with the LABOCA map to
distinguish between pre- and protostellar cores, and to estimate the
evolutionary stages of protostars. Twelve dense cores were detected at 870
micron in the Ori B9 cloud. The submm cores constitute ~4% of the total mass of
the Ori B9 region. There is an equal number of pre- and protostellar cores. Two
of the submm sources, which we call SMM 3 and SMM 4, are previously unknown
Class 0 candidates. We found a moderate degree of deuteration in N2H+
(0.03-0.04). There is, furthermore, evidence for N2H+ depletion in the core SMM
4. We derive a relatively high degree of ionization (~10^-7) in the clump
associated with IRAS 05405-0117. The ambipolar diffusion timescales for two of
the cores are ~70-100 times longer than the free-fall time. The distribution
and masses of dense cores in Ori B9 are similar to those observed in more
active regions in Orion, where the statistical core properties have been
explained by turbulent fragmentation. The 50/50 proportions of pre- and
protostellar cores suggest that duration of the prestellar phase is comparable
to the free-fall time. This timescale can be questioned, however, on the basis
of chemical data on the IRAS 05405-0117 region. A possible explanation is that
this survey samples only the densest, i.e., dynamically most advanced cores.
