2018A&A...615L..16F


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.14CET16:29:54

2018A&A...615L..16F - Astronomy and Astrophysics, volume 615, L16-16 (2018/7-1)

Depletion of 15N in the center of L1544: Early transition from atomic to molecular nitrogen?

FURUYA K., WATANABE Y., SAKAI T., AIKAWA Y. and YAMAMOTO S.

Abstract (from CDS):

We performed sensitive observations of the N15ND+(1-0) and 15NND+(1-0) lines toward the prestellar core L1544 using the IRAM 30m telescope. The lines are not detected down to 3σ levels in 0.2km/s channels of ∼6mK. The non-detection provides the lower limit of the 14N/15N ratio for N2D+ of ∼700-800, which is much higher than the elemental abundance ratio in the local interstellar medium of ∼200-300. The result indicates that N2 is depleted in 15N in the central part of L1544, because N2D+ preferentially traces the cold dense gas, and because it is a daughter molecule of N2. In situ chemistry is probably not responsible for the 15N depletion in N2; neither low-temperature gas phase chemistry nor isotope selective photodissociation of N2 explains the 15N depletion; the former prefers transferring 15N to N2, while the latter requires the penetration of interstellar far-ultraviolet (FUV) photons into the core center. The most likely explanation is that 15N is preferentially partitioned into ices compared to 14N via the combination of isotope selective photodissociation of N2 and grain surface chemistry in the parent cloud of L1544 or in the outer regions of L1544, which are not fully shielded from the interstellar FUV radiation. The mechanism is most efficient at the chemical transition from atomic to molecular nitrogen. In other words, our result suggests that the gas in the central part of L1544 has previously gone trough the transition from atomic to molecular nitrogen in the earlier evolutionary stage, and that N2 is currently the primary form of gas-phase nitrogen.

Abstract Copyright: © ESO 2018

Journal keyword(s): astrochemistry - ISM: clouds - ISM: molecules - ISM: individual objects: L1544

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 1333 SFR 03 28 55 +31 22.2   10.9       ~ 1182 1
2 Barnard 1 MoC 03 33 16.3 +31 07 51           ~ 247 0
3 ICRF J043917.7+304507 Bz? 04 39 17.77456164 +30 45 07.5523405       22.50   ~ 13 1
4 NAME Taurus Dark Cloud SFR 04 41.0 +25 52           ~ 3322 0
5 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 655 0
6 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 674 1
7 LDN 57 DNe 17 22 38.2 -23 49 34           ~ 276 1
8 LDN 429 DNe 18 16 44 -08 18.9           ~ 31 0
9 [LM99] L694-2 cor 19 41 04.6 +10 57 02           ~ 58 0

    Equat.    Gal    SGal    Ecl

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2019.11.14-16:29:54

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