We report “ infall asymmetry ” in the HCO ^ { + } ( 1–0 ) and ( 3–2 ) lines toward NGC 1333 , extended over \sim 0.39 { pc } ^ { 2 } , a larger extent than has been reported before , for any star-forming region .
The infall asymmetry extends over a major portion of the star-forming complex , and is not limited to a single protostar , or to a single dense core , or to a single spectral line .
It seems likely that the infall asymmetry represents inward motions , and that these motions are physically associated with the complex .
Both blue-asymmetric and red-asymmetric lines are seen , but in both the ( 3–2 ) and ( 1–0 ) lines of HCO ^ { + } the vast majority of the asymmetric lines are blue , indicating inward motions .
The ( 3–2 ) line , tracing denser gas , has the spectra with the strongest asymmetry and these spectra are associated with the protostars IRAS 4A and 4B , which most likely indicates a warm central source is affecting the line profiles .
The ( 3–2 ) and ( 1–0 ) lines usually have the same sense of asymmetry in common positions , but their profiles differ significantly , and the ( 1–0 ) line appears to trace motions on much larger spatial scales than does the ( 3–2 ) line .
Line profile models fit the spectra well , but do not strongly constrain their parameters .
The mass accretion rate of the inward motions is of order 10 ^ { -4 } M _ { \odot } /yr , similar to the ratio of stellar mass to cluster age .