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K. M. Freed (Metropolitan State College of Denver), J. G. Mangum (National Radio Astronomy Observatory)
Many protostars have been studied with the use of nitrogen bearing molecules because of their volatile nature and low binding energy. Short chemical history, large abundance, and simple radiative transfer have made N2H+ and NH3 excellent molecular tracers of the dense cold regions within the cores of protostars. However, high resolution observations of the IRAM 04191+1522 protostar have shown a significant depletion of N2H+ and NH3 in its core. IRAM 04191+1522, a class 0 protostar, is identified by an age ~ 104 years, a central density ~ 106 cm-3 and a temperature ~ 12K. N2H+ and NH3 were thought to be unaffected by depletion to densities of 107 cm-3, so the cause of the disappearance remains a mystery. There are four scenarios which will be discussed in this talk that may be able to account for some depletion of N2H+ and NH3: 1) N2 (the parent molecule of both N2H+ and NH3) condenses onto dust grains, 2) an underestimation of the molecular cloud temperature results in severe depletion of N2H+ and NH3, 3) high levels of deuterium fractionation create deuterated species of N2H+ and NH3, and 4) isotopic fractionation of nitrogen create species of N2H+ and NH3 that contain the 15N isotope. This work was conducted as a part of the National Radio Astronomy Observatory Summer Student Program with partial support from the National Science Foundation.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.