2014A&A...572L..10C


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST18:48:29

2014A&A...572L..10C - Astronomy and Astrophysics, volume 572, L10-10 (2014/12-1)

A non-equilibrium ortho-to-para ratio of water in the Orion PDR.

CHOI Y., VAN DER TAK F.F.S., BERGIN E.A. and PLUME R.

Abstract (from CDS):

The ortho-to-para ratio (OPR) of H2O is thought to be sensitive to the temperature of water formation. The OPR of H2O is thus useful for studying the formation mechanism of water. We investigate the OPR of water in the Orion PDR (photon-dominated region), at the Orion Bar and Orion S positions, using data from Herschel/HIFI. We detect the ground-state lines of ortho- and para-H218O in the Orion Bar and Orion S and estimate the column densities using local thermodynamical equilibrium (LTE) and non-LTE methods. Based on our calculations, the OPR in the Orion Bar is 0.1-0.5, which is unexpectedly low given the gas temperature of ∼85K, and also lower than the values measured for other interstellar clouds and protoplanetary disks. Toward Orion S, our OPR estimate is below 2. This low OPR at 2 positions in the Orion PDR is inconsistent with gas phase formation and with thermal evaporation from dust grains, but it may be explained by photodesorption.

Abstract Copyright:

Journal keyword(s): ISM: molecules - ISM: individual objects: Orion Bar - ISM: individual objects: Orion S

Simbad objects: 12

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Number of rows : 12

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 [JCC87] IRAS 4A Y*O 03 29 10.49 +31 13 30.8           ~ 596 1
2 [JCC87] IRAS 4 FIR 03 29 10.9 +31 13 26           ~ 465 0
3 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 553 0
4 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 681 0
5 NAME Orion S reg 05 35 12.9 -05 24 10           ~ 121 0
6 NAME OMC1 Ridge reg 05 35 13.4 -05 23 07           ~ 123 0
7 NAME OMC-1 MoC 05 35 14 -05 22.4           ~ 1015 2
8 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2001 1
9 NAME Trapezium Cluster As* 05 35 16.5 -05 23 14           ~ 1467 1
10 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 716 0
11 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 848 1
12 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1532 1

    Equat.    Gal    SGal    Ecl

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2020.07.14-18:48:29

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