A dataset provided by the European Space Agency

Name OT2_philybla_3
Title First detection of 15NH and the determination of the 14N/15N in the diffuse Interstellar Medium


DOI https://doi.org/10.5270/esa-k0svmih
Author European Space Agency
Description Understanding the origin of the elements in the Solar system is an
outstanding question of modern astrophysics, cosmochemistry, and
astrobiology. The origin of nitrogen, though amongst the five to six
most abundant elements in our local Universe, remains poorly
understood. This is due to the lack of observational constraints to
nucleosynthesis models. Elemental isotopic ratio is an extremely
powerful tool in this regard. A value of 440 for the 14N/15N ratio has
been measured in the protosolar nebula. Similar values have been
obtained in cold dense cores and in molecular clouds. Determinations
of the 14N/15N ratio in the interstellar medium (ISM) are indirect and
are based on abundance ratios of N-bearing molecules and their 15N
isotopologues. Hence the interpretation in term of 14N/15N depends on
chemical fractionation processes. Chemical models indicate that these
processes strongly affect nitriles, and recent observations suggest
that ammonia is probably not a reliable tracer for the 14N/15N
ratio. Nonetheless, reliable methods to determine the 14N/15N ratio in
cold and dense gas seem to emerge. The same is unfortunately not true
for the diffuse ISM where very little is known regarding the nitrogen
isotopic ratio, which should be representative of the nucleosynthesis
products. One measurement in the diffuse interstellar medium (ISM)
led to the small value of 240. However, this determination is based on
the nitriles HCN and HC15N, and the translation into 14N/15N is
strongly model-dependent. Chemical considerations show that the NH
molecule is not fractionated in the diffuse gas such that the
14NH/15NH abundance ratio is the best proxy for the 14N/15N ratio. The
NH molecule has been detected by Herschel/HIFI in several diffuse
clouds and offers a unique opportunity to determine the 14N/15N ratio
in the diffuse ISM. The proposed observa...tions aim at the first
detection of 15NH in the ISM which will allow the first robust
determination of the 14N/15N isotopic ratio in the diffuse ISM.
Publication Far-infrared study of tracers of oxygen chemistry in diffuse clouds . Wiesemeyer H. et al. . Astronomy & Astrophysics, Volume 585, id.A76, 18 pp. . 585 . 10.1051\/0004-6361\/201526473 . 2016A&A...585A..76W ,
Instrument HIFI_HifiPoint_dbs
Temporal Coverage 2012-10-17T04:22:05Z/2012-10-24T11:09:20Z
Version SPG v14.1.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/h®erschel/
Date Published 2013-04-24T09:09:03Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2013, First Detection Of 15Nh And The Determination Of The 14N/15N In The Diffuse Interstellar Medium, SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-k0svmih