Planck Galactic Cold Clumps Research Articles

PLANCK COLD CLUMPS IN THE λ ORIONIS COMPLEX. I. DISCOVERY OF AN EXTREMELY YOUNG CLASS 0 PROTOSTELLAR OBJECT AND A PROTO-BROWN DWARF CANDIDATE IN THE BRIGHT-RIMMED CLUMP PGCC G192.32–11.88

ABSTRACT We are performing a series of observations with ground-based telescopes toward Planck Galactic cold clumps (PGCCs) in the λ 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 (∼0.8 L ☉ ?> ) and accretion rate (6.3 × 10−7 M ☉ ?> yr−1) when compared with other young Class 0 sources (e.g., PACS Bright Red Sources) in the Orion complex. It has slightly larger internal luminosity (0.21 ± 0.01 L ☉ ?> ) and outflow velocity (∼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 an FHSC. Considering its low internal luminosity (0.08 ± 0.01 L ⊙ ?> ) and accretion rate (2.8 × 10−8 M ☉ ?> yr−1), G192S is an ideal proto-brown dwarf candidate. The star formation efficiency (∼0.3%–0.4%) and core formation efficiency (∼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 owing to stellar feedback.

Kinematics of Selected Planck Galactic Cold Clumps

We have completed a kinematical analysis of 184 selected Planck Galactic Cold Clumps (PGCC) (Planck Collaboration, 2015) in order to understand better the stability of molecular clouds and the induced star formations. Most of our clumps are in the second quadrant of the Galaxy. For the investigation we used 12CO, 13CO, C18O line observations which covered the 184 PGCC fully or partially. The majority of the data were observed with the Osaka 1.85 m telescope in Japan (Nishimura et al. 2015) and we also have some observations with the KOSMA 3 m telescope, from Switzerland (Kramer et al. 2000) and with the IRAM 30 m telescope, Spain (www.iram-institute.org).