Nitrogen Fractionation in Protoplanetary Disks from the H{sup 13}CN/HC{sup 15}N Ratio

Journal Article · Fri Feb 10 04:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/836/1/30· OSTI ID:22869414

Guzmán, V. V.; Öberg, K. I.; Huang, J.; Loomis, R.

Nitrogen fractionation is commonly used to assess the thermal history of solar system volatiles. With ALMA it is for the first time possible to directly measure {sup 14}N/{sup 15}N ratios in common molecules during the assembly of planetary systems. We present ALMA observations of the H{sup 13}CN and HC{sup 15}N J=3−2 lines at 0.″5 angular resolution, toward a sample of six protoplanetary disks, selected to span a range of stellar and disk structure properties. Adopting a typical {sup 12}C/{sup 13}C ratio of 70, we find comet-like {sup 14}N/{sup 15}N ratios of 80–160 in five of the disks (3 T Tauri and 2 Herbig Ae disks) and lack constraints for one of the T Tauri disks (IM Lup). There are no systematic differences between T Tauri and Herbig Ae disks, or between full and transition disks within the sample. In addition, no correlation is observed between disk-averaged D/H and {sup 14}N/{sup 15}N ratios in the sample. One of the disks, V4046 Sgr, presents unusually bright HCN isotopologue emission, enabling us to model the radial profiles of H{sup 13}CN and HC{sup 15}N. We find tentative evidence of an increasing {sup 14}N/{sup 15}N ratio with radius, indicating that selective photodissociation in the inner disk is important in setting the {sup 14}N/{sup 15}N ratio during planet formation.

• OSTI ID: 22869414
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 836; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON 12
CARBON 13
COMETS
CONCENTRATION RATIO
CORRELATIONS
DISSOCIATION
EMISSION
HYDROCYANIC ACID
ISOTOPE RATIO
MOLECULES
NITROGEN 14
NITROGEN 15
PHOTOLYSIS
PLANETS
PROTOPLANETS
SOLAR SYSTEM