Strong winds and ultraviolet ( UV ) radiation from O-type stars disrupt and ionize their molecular core birthplaces , sweeping up material into parsec-size shells .
Owing to dissociation by starlight , the thinnest shells are expected to host low molecular abundances and therefore little star formation .
Here , we expand previous maps made with observations using the IRAM 30m telescope ( at 11 ^ { \prime \prime } \simeq 4,500 AU resolution ) and present square-degree ^ { 12 } CO and ^ { 13 } CO ( J = 2-1 ) maps of the wind-driven “ Veil bubble ” that surrounds the Trapezium cluster and its natal Orion molecular core ( OMC ) .
Although widespread and extended CO emission is largely absent from the Veil , we show that several CO “ globules ” exist that are blueshifted in velocity with respect to OMC and are embedded in the [ C ii ] 158 \upmu m-bright shell that confines the bubble .
This includes the first detection of quiescent CO at negative local standard of rest ( LSR ) velocities in Orion .
Given the harsh UV irradiation conditions in this translucent material , the detection of CO globules is surprising .
These globules are small ( R _ { g } = 7,100 AU ) , not massive ( M _ { g } = 0.3 M _ { \odot } ) , and are moderately dense : n _ { H } = 4 \cdot 10 ^ { 4 } cm ^ { -3 } ( median values ) .
They are confined by the external pressure of the shell , P _ { ext } / k \gtrsim 10 ^ { 7 } cm ^ { -3 } K , and are likely magnetically supported .
They are either transient objects formed by instabilities or have detached from pre-existing molecular structures , sculpted by the passing shock associated with the expanding shell and by UV radiation from the Trapezium .
Some represent the first stages in the formation of small pillars , others of isolated small globules .
Although their masses ( M _ { g } < M _ { Jeans } ) do not suggest they will form stars , one globule matches the position of a known young stellar object .
The lack of extended CO in the “ Veil shell ” demonstrates that feedback from massive stars expels , agitates , and reprocesses most of the disrupted molecular cloud gas , thereby limiting the star-formation rate in the region .
The presence of molecular globules is a result of this feedback .