13CO (J=1–0) Survey of Molecular Clouds toward the Monoceros and Canis Major Region

Abstract

Abstract Through a large-scale ${{13\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) survey toward a region in Monoceros and Canis Major, we present following results: (1) We identified in total 115 clouds. (2) Group I (CMa OB1 and G220.8$-$1.7) may physically connected with Group II (Mon R2 and NGC 2149). (3) 496 YSO candidates were chosen from IRAS point source catalog (IPC). (4) The mass spectrum of the Local clouds shows a power-law relation with an index of $-1.55 \pm 0.09$. (5) The number fraction of star-forming clouds increases as the cloud mass increases. Especially, massive clouds of $M_\mathrm{cloud} \ge 10^{3.5} \,{{{M}_{\odot}}}$ are all star-forming clouds. (6) The line width–cloud radius relation is best fitted as $\Delta V_\mathrm{comp} \propto r_\mathrm{cloud}^{0.47}$ ($\mbox{correlation coefficient} = 0.87$ correlation coefficient$= 0.87$). (7) The distribution of $(M_\mathrm{vir} / M_\mathrm{cloud})$ shows that star-forming clouds tend to be more virialized than no star-forming clouds. (8) Star formation in Group I is more active than that in Group II. (9) Unexpected small number of low-mass clouds in Group I may be due to strong UV radiation from O-type stars in the vicinity of the clouds. (10) Star formation in Group II might occurred by self-gravitational, except for the most massive cloud.