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First Measurement of the 14N/15N Ratio in the Analog of the Sun Progenitor OMC-2 FIR4

Abstract : We present a complete census of the 14N/15N isotopic ratio in the most abundant N-bearing molecules toward the cold envelope of the protocluster OMC-2 FIR4, the best known Sun progenitor. To this scope, we analyzed the unbiased spectral survey obtained with the IRAM 30 m telescope at 3, 2, and 1 mm. We detected several lines of CN, HCN, HNC, HC3N, N2H+, and their respective 13C and 15N isotopologues. The lines’ relative fluxes are compatible with LTE conditions, and moderate line opacities have been corrected via a population diagram method or theoretical relative intensity ratios of the hyperfine structures. The five species lead to very similar 14N/15N isotopic ratios, without any systematic difference between amine- and nitrile-bearing species as previously found in other protostellar sources. The weighted average of the 14N/15N isotopic ratio is 270 ± 30. This 14N/15N value is remarkably consistent with the [250-350] range measured for the local galactic ratio but significantly differs from the ratio measured in comets (around 140). High-angular resolution observations are needed to examine whether this discrepancy is maintained at smaller scales. In addition, using the CN, HCN, and HC3N lines, we derived a 12C/13C isotopic ratio of 50 ± 5.
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Submitted on : Friday, June 10, 2022 - 3:36:35 PM
Last modification on : Saturday, June 25, 2022 - 3:06:34 AM

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Claudine Kahane, Ali Jaber Al-Edhari, Cecilia Ceccarelli, Ana López-Sepulcre, Francesco Fontani, et al.. First Measurement of the 14N/15N Ratio in the Analog of the Sun Progenitor OMC-2 FIR4. The Astrophysical Journal, 2018, 852, ⟨10.3847/1538-4357/aa9e88⟩. ⟨insu-03693584⟩



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