Planck Cold Clumps in the λ Orionis Complex. II. Environmental Effects on Core Formation
Ristorcelli, I.; Soam, Archana; Choi, Minho; Di Francesco, James; Fuller, Gary; Kim, Gwanjeong; Kim, Kee-Tae; Koch, Patrick M.; Lee, Chang Won; Lee, Jeong-Eun; Li, Di; Liu, Hong-Li; Liu, Tie; Liu, Sheng-Yuan; Eden, David; Yi, Hee-Weon; Wang, Ke; Kang, Sung-ju; Wu, Yuefang; Tatematsu, Ken'ichi; White, Glenn J.; Toth, L. V.; Yang, Yao-Lun; Evans, Neal J., II; Juvela, Mika; Thompson, Mark; Hirano, N.; Rawlings, Mark G.; Liu, H. -Y. B.; Sanhueza, Patrico; JCMT Large Program “SCOPE” Collaboration; TRAO Key Science Program “TOP” Collaboration
South Korea, United States, United Kingdom, Canada, Taiwan, Finland, China, Germany, Hong Kong SAR, Chile, France, Japan, Hungary
Abstract
Based on the 850 μm 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(H2) = (9.5 ± 1.2) × 1022 cm-2, number density n(H2) = (2.9 ± 0.4) × 105 cm-3, and mass M core = 1.0 ± 0.3 M ⊙ compared to the cores in the Orion A [R = 0.11 pc, N(H2) = (2.3 ± 0.3) × 1023 cm-2, n(H2) = (3.8 ± 0.5) × 105 cm-3, and M core = 2.4 ± 0.3 M ⊙] and Orion B [R = 0.16 pc, N(H2) = (3.8 ± 0.4) × 1023 cm-2, n(H2) = (15.6 ± 1.8) × 105 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.