相关论文: Nitrogen Fractionation in External Galaxies
Interstellar objects provide a unique opportunity to further our understanding of the planetary formation process by studying in detail material formed around another star. Their ices contain precious clues about the environment and…
The abundance of nitrogen in the interstellar medium is a powerful probe of star for- mation processes over cosmological timescales. Since nitrogen can be produced both in massive and intermediate-mass stars with metallicity-dependent…
The isotopic ratio of nitrogen in nearby protoplanetary disks, recently measured in CN and HCN, indicates that a fractionated reservoir of nitrogen is available at the stage of comet formation. This reservoir presents a 3:1 enrichment in…
We combine a new Galactic plane survey of Hydrogen Radio Recombination Lines (RRLs) with far-infrared (FIR) surveys of ionized Nitrogen, N+, to determine Nitrogen abundance across Galactic radius. RRLs were observed with NASA DSS-43 70m…
Observations conducted using the Atacama Large Millimeter/submillimeter Array on the protoplanetary disk around TW Hya show the nitrogen fractionation of HCN molecules in HC$^{14}$N/HC$^{15}$N $\sim$120 at a radius of $\sim$20 AU. In this…
Although chemical models predict that the deuterium fractionation in N$_2$H$^+$ is a good evolutionary tracer in the star formation process, the fractionation of nitrogen is still a poorly understood process. Recent models have questioned…
Recent new high-precision abundance data for Galactic halo stars suggest important primary nitrogen production in very metal-poor massive stars. Here, we compute a new model for the chemical evolution of the Milky Way aimed at explaining…
Context: The $^{15}$N fractionation has been observed to show large variations among astrophysical sources, depending both on the type of target and on the molecular tracer used. These variations cannot be reproduced by the current chemical…
We analyze the behavior of N/O and C/O abundance ratios as a function of metallicity as gauged by O/H in large, extant Galactic and extragalactic H II region abundance samples. Numerical chemical evolution models are computed using…
The 14N/15N ratio in molecules exhibits a large variation in star-forming regions, especially when measured from N2H+ isotopologues. However, there are only a few studies performed at high-angular resolution. We present the first…
Many chemical models of dense interstellar clouds predict that the majority of gas-phase elemental nitrogen should be present as N2, with an abundance approximately five orders of magnitude less than that of hydrogen. As a homonuclear…
The abundance ratio of $^{14}$N$/^{15}$N is, in principle, a powerful tool for tracing stellar nucleosynthesis. This work aims to measure and analyze ($^{14}$N/$^{15}$N)$\times$($^{13}$C/$^{12}$C) and $^{14}$N$/^{15}$N abundance ratios in…
The degree of isospin fractionation is measured by $(N/Z)_{n}$ / $(N/Z)_{N_{imf}}$, where $(N/Z)_{n}$ and $(N/Z)_{N_{imf}}$ are the saturated neutron-proton ratio of nucleon emissions (gas phase) and that of fragment emissions (liquid…
Understanding the evolution of the N/O ratio in the interstellar medium (ISM) of galaxies is essential if we are to complete our picture of the chemical evolution of galaxies at high redshift, since most observational calibrations of O/H…
Stellar and nebular abundance indicators reveal that there exists significant abundance fluctuations in the interstellar medium (ISM) of gas-rich galaxies. It is shown that at the present observed solar level of O/H $\sim 6 \times 10^{-4}$,…
The variations of elemental abundance and their ratios along the Galactocentric radius result from the chemical evolution of the Milky Way disks. The $\rm ^{12}C/^{13}C$ ratio in particular is often used as a proxy to determine other…
We present a new gas-grain chemical model for the combined isotopic fractionation of carbon and nitrogen in molecular clouds, in which the isotope chemistry of carbon and nitrogen is coupled with a time-dependent description of spin-state…
Observations of low mass protostars which probe small enough size scales to be within likely CO depletion regions show the highest [NH2D]/[NH3] ratios yet measured, of 4--33%. These molecular D/H ratios are higher than those measured on…
We propose an evolutionary scenario by successive bursts of star formation to reproduce the chemical properties of massive nearby Starburst Nucleus Galaxies (SBNGs). The N/O abundance ratios in SBNGs are 0.2 dex higher than in normal HII…
We show that the excess of nitrogen emission observed in a large sample of Starburst Nucleus Galaxies (SBNGs) can only be explained at a given metallicity by an overabundance of nitrogen with respect to normal HII regions in the disks of…