AAS 195th Meeting, January 2000
Session 49. Molecules, Masers, and Star Formation
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[49.03] An Investigation of C18O J=1-0 Emission from Young Stellar Objects in the NGC 1333 and L1448 Star Formation Regions

N. H. Volgenau, L. G. Mundy (U. Maryland), L. W. Looney (MPE, Garching), W. J. Welch (UC, Berkeley)

Observations of the C180 J=1-0 emission from the envelopes surrounding three Young Stellar Objects (YSOs) in the NGC 1333 and L1448 star formation regions were made with the BIMA millimeter-wave interferometer. We present C18O maps of the NGC 1333 IRAS4A, NGC 1333 IRAS2A, and L1448B envelopes made with resolutions of 10", 5", 3", and 2" and compare them with maps of the 2.7mm continuum emission. In all sources, C18O emission is present at all resolutions; however, the emission in the narrowest beam appears displaced from the center of the continuum emission. Spectra toward these sources show flux above the 1-sigma noise for velocities on the blue side of the line center; this blueward asymmetry suggests the presence of infalling material.

To explore the extent of molecular depletion in the envelopes, synthetic spectra were fitted to the data based on the envelope models derived by Looney (1998). For all three sources, models that reproduce the observed line profiles require a C18O abundance reduced from the typical interstellar value; for IRAS4A, the C18O abundance must be reduced by approximately an order of magnitude. Simple models with a normal abundance shell surrounding a depleted central core cannot produce the morphology of the observed emission. Models with a central core of normal abundance, surrounded by a depleted outer core, are explored and compared to expectations based on the sublimation temperatures of likely grain mantle materials.

This work is supported by NSF grant 96-13716 and NASA grant NAG 54429.

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