Walsh, Andrew J., Bourke, Tyler L., and Myers, Philip C. (2006) Observations of global and local infall in NGC 1333. The Astrophysical Journal, 637 (2). pp. 860-868.

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Abstract

We report "infall asymmetry" in the HCO+(1–0) and (3–2) lines toward NGC 1333, extended over 0.39 pc2, 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, a single dense core, or 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; these spectra are associated with the protostars IRAS 4A and 4B, which most likely indicates that 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 104 M yr1, similar to the ratio of stellar mass to cluster age.

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