ALMA-IRDC - II. First high-angular resolution measurements of the N-14/N-15 ratio in a large sample of infrared-dark cloud cores
Journal article, 2021

The N-14/N-15 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 interferometric survey of the N-14/N-15 ratio in N2H+ obtained with Atacama Large Millimeter Array observations towards four infrared-dark clouds harbouring 3 mm continuum cores associated with different physical properties. We detect (NNH+)-N-15 (1-0) in of the cores, depending on the host cloud. The N-14/N-15 values measured towards the millimetre continuum cores range from a minimum of similar to 80 up to a maximum of similar to 400. The spread of values is narrower than that found in any previous single-dish survey of high-mass star-forming regions and than that obtained using the total power data only. This suggests that the N-14/N-15 ratio is on average higher in the diffuse gaseous envelope of the cores and stresses the need for high-angular resolution maps to measure correctly the N-14/N-15 ratio in dense cores embedded in IRDCs. The average N-14/N-15 ratio of similar to 210 is also lower than the interstellar value at the Galactocentric distance of the clouds (similar to 300-330), although the sensitivity of our observations does not allow us to unveil N-14/N-15 ratios higher than similar to 400. No clear trend is found between the N-14/N-15 ratio and the core physical properties. We find only a tentative positive trend between N-14/N-15 and H-2 column density. However, firmer conclusions can be drawn only with higher sensitivity measurements.

stars: formation

ISM: clouds

ISM: molecules

Author

F. Fontani

Istituto nazionale di astrofisica (INAF)

Max Planck Institute for Extraterrestrial Physics

A. T. Barnes

University of Bonn

P. Caselli

Max Planck Institute for Extraterrestrial Physics

J. D. Henshaw

Max Planck Society

Giuliana Cosentino

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

I Jimenez-Serra

Spanish Astrobiology Center (INTA-CSIC)

Jonathan Tan

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

J. E. Pineda

Max Planck Institute for Extraterrestrial Physics

Chi Yan Law

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 503 3 4320-4335

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Other Physics Topics

DOI

10.1093/mnras/stab700

More information

Latest update

6/18/2021