Planck Cold Clumps in the λ Orionis Complex. II. Environmental Effects on Core Formation

Abstract

Based on the 850 μ m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the λ Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the λ Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant H II region. PGCCs in the λ Orionis cloud have higher dust temperatures ( T d  = 16.13 ± 0.15 K) and lower values of dust emissivity spectral index ( β  = 1.65 ± 0.02) than PGCCs in the Orion A ( T d  = 13.79 ± 0.21 K, β  = 2.07 ± 0.03) and Orion B ( T d  = 13.82 ± 0.19 K, β  = 1.96 ± 0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the λ Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the λ Orionis cloud show much lower mean values of size R  = 0.08 pc, column density N (H 2 ) = (9.5 ± 1.2) × 10 22 cm −2 , number density n (H 2 ) = (2.9 ± 0.4) × 10 5 cm −3 , and mass M core  = 1.0 ± 0.3 M ⊙ compared to the cores in the Orion A [ R  = 0.11 pc, N (H 2 ) = (2.3 ± 0.3) × 10 23 cm −2 , n (H 2 ) = (3.8 ± 0.5) × 10 5 cm −3 , and M core  = 2.4 ± 0.3 M ⊙ ] and Orion B [ R  = 0.16 pc, N (H 2 ) = (3.8 ± 0.4) × 10 23 cm −2 , n (H 2 ) = (15.6 ± 1.8) × 10 5 cm −3 , and M core  = 2.7 ± 0.3 M ⊙ ] clouds. These core properties in the λ Orionis cloud can be attributed to the photodissociation and external heating by the nearby H II region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.