Planck cold clumps in the $\lambda$ Orionis complex: I. Discovery of an
  extremely young Class 0 protostellar object and a proto-brown dwarf candidate
  in a bright rimmed clump PGCC G192.32-11.88
  We are performing a series of observations with ground-based telescopes
toward Planck Galactic cold clumps (PGCCs) in the $\lambda$ Orionis complex in
order to systematically investigate the effects of stellar feedback. In the
particular case of PGCC G192.32-11.88, we discovered an extremely young Class 0
protostellar object (G192N) and a proto-brown dwarf candidate (G192S). G192N
and G192S are located in a gravitationally bound bright-rimmed clump. The
velocity and temperature gradients seen in line emission of CO isotopologues
indicate that PGCC G192.32-11.88 is externally heated and compressed. G192N
probably has the lowest bolometric luminosity ($\sim0.8$ L$_{\sun}$) and
accretion rate (6.3$\times10^{-7}$ M$_{\sun}$~yr$^{-1}$) when compared with
other young Class 0 sources (e.g. PACS Bright Red sources (PBRs)) in the Orion
complex. It has slightly larger internal luminosity ($0.21\pm0.01$ L$_{\sun}$)
and outflow velocity ($\sim$14 km~s$^{-1}$) than the predictions of first
hydrostatic cores (FHSCs). G192N might be among the youngest Class 0 sources,
which are slightly more evolved than a FHSC. Considering its low internal
luminosity ($0.08\pm0.01$ L$_{\odot}$) and accretion rate (2.8$\times10^{-8}$
M$_{\sun}$~yr$^{-1}$), G192S is an ideal proto-brown dwarf candidate. The star
formation efficiency ($\sim$0.3\%-0.4\%) and core formation efficiency
($\sim$1\%) in PGCC G192.32-11.88 are significantly smaller than in other giant
molecular clouds or filaments, indicating that the star formation therein is
greatly suppressed due to stellar feedback.
