Nitrogen Fractionation in External Galaxies

Abstract

In star forming regions in our own Galaxy, the 14N/15N ratio is found to vary from $\sim$ 100 in meteorites, comets and protoplanetary disks up to $\sim$ 1000 in pre-stellar and star forming cores, while in external galaxies the very few single-dish large scale measurements of this ratio lead to values of 100-450. The extent of the contribution of isotopic fractionation to these variations is, to date, unknown. In this paper we present a theoretical chemical study of nitrogen fractionation in external galaxies in order to determine the physical conditions that may lead to a spread of the 14N/15N ratio from the solar value of $\sim$440 and hence evaluate the contribution of chemical reactions in the ISM to nitrogen fractionation. We find that the main cause of ISM enrichment of nitrogen fractionation is high gas densities, aided by high fluxes of cosmic rays.

Accepted by MNRAS

References in corpus (34)

• The chemical composition of the Sun
• The UMIST database for astrochemistry 2012
• Structure of Stationary Photodissociation Fronts
• The 2014 KIDA network for interstellar chemistry
• Evaporation of ices near massive stars: models based on laboratory TPD data
• The evolution of CNO isotopes: a new window on cosmic star-formation history and the stellar IMF in the age of ALMA
• Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas
• Isotopic fractionation of carbon, deuterium and nitrogen : a full chemical study
• UCLCHEM: A Gas-Grain Chemical Code
• Lambda = 3 mm line survey of nearby active galaxies
• The 15N-enrichment in dark clouds and Solar System objects
• Water deuteration and ortho-to-para nuclear spin ratio of H2 in molecular clouds formed via the accumulation of HI gas
• Abundances and Isotope Ratios in the Magellanic Clouds: The Star Forming Environment of N113
• The Temperature Distribution of Dense Molecular Gas in the Center of NGC 253
• Nova nucleosynthesis and Galactic evolution of the CNO isotopes
• Detection of (15)NNH+ in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate (14)N/(15)N values
• The detection of extragalactic ${}^{15}$N: Consequences for nitrogen nucleosynthesis and chemical evolution
• Nitrogen fractionation in high-mass star-forming cores across the Galaxy
• Molecular tracers of PDR-dominated galaxies
• Nitrogen Fractionation in Protoplanetary Disks from the H13CN/HC15N Ratio
• Nitrogen and hydrogen fractionation in high-mass star forming cores from observations of HCN and HNC
• Revised Models of Interstellar Nitrogen Isotopic Fractionation
• ${}^{14}$N/${}^{15}$N ratio measurements in prestellar cores with N${}_2$H${}^{+}$: new evidence of ${}^{15}$N-antifractionation
• First measurements of 15N fractionation in N2H+ toward high-mass star forming cores
• Chemical nitrogen fractionation in dense molecular clouds
• Molecular line emission in NGC 4945, imaged with ALMA
• Modelling the molecular composition and nuclear-spin chemistry of collapsing prestellar sources
• First measurement of the 14N/15N ratio in the analogue of the Sun progenitor OMC-2 FIR4
• The C${}^{14}$N/C${}^{15}$N Ratio in Diffuse Molecular Clouds
• Dense Molecular Gas in Nearby Gas-rich Active Galaxies
• Molecular transitions as probes of the physical conditions of extragalactic environments
• 15N Fractionation in Infrared-Dark Cloud Cores
• Deuterium and ${}^{15}$N fractionation in N${}_2$H${}^{+}$ during the formation of a Sun-like star
• Deuterated species in extragalactic star-forming regions

Cited by in corpus (8)

• ALCHEMI: an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory. Survey presentation and first results from the ACA array
• The Molecular ISM in the Super Star Clusters of the Starburst NGC 253
• A chemical study of carbon fractionation in external galaxies
• Interstellar Nitrogen Isotope Ratios: New NH3 Data from the Galactic Center out to the Perseus Arm
• ALMA-IRDC II. First high-angular resolution measurements of the 14N/15N ratio in a large sample of infrared-dark cloud cores
• Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC253 with ALCHEMI
• Seeds of Life in Space (SOLIS). XIII. Nitrogen fractionation towards the protocluster OMC-2 FIR4
• Seed of Life in Space (SOLIS) XI. First measurement of nitrogen fractionation in shocked clumps of the L1157 protostellar outflow