2010A&A...521L..26L

Query : 2010A&A...521L..26L

2010A&A...521L..26L - Astronomy and Astrophysics, volume 521, L26-26 (2010/10-1)

Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C.

LIS D.C., PHILLIPS T.G., GOLDSMITH P.F., NEUFELD D.A., HERBST E., COMITO C., SCHILKE P., MUELLER H.S.P., BERGIN E.A., GERIN M., BELL T.A., EMPRECHTINGER M., BLACK J.H., BLAKE G.A., BOULANGER F., CAUX E., CECCARELLI C., CERNICHARO J., COUTENS A., CROCKETT N.R., DANIEL F., DARTOIS E., DE LUCA M., DUBERNET M.-L., ENCRENAZ P., FALGARONE E., GEBALLE T.R., GODARD B., GIESEN T.F., GOICOECHEA J.R., GRY C., GUPTA H., HENNEBELLE P., HILY-BLANT P., KOLOS R., KRELOWSKI J., JOBLIN C., JOHNSTONE D., KAZMIERCZAK M., LORD S.D., MARET S., MARTIN P.G., MARTIN-PINTADO J., MELNICK G.J., MENTEN K.M., MONJE R., MOOKERJEA B., MORRIS P., MURPHY J.A., OSSENKOPF V., PEARSON J.C., PERAULT M., PERSSON C., PLUME R., QIN S.-L., SALEZ M., SCHLEMMER S., SCHMIDT M., SONNENTRUCKER P., STUTZKI J., TEYSSIER D., TRAPPE N., VAN DER TAK F.F.S., VASTEL C., WANG S., YORKE H.W., YU S., ZMUIDZINAS J., BOOGERT A., ERICKSON N., KARPOV A., KOOI J., MAIWALD F.W., SCHIEDER R. and ZAAL P.

Abstract (from CDS):

We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H₂¹⁶O and H₂¹⁸O in absorption towards Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of 2.35±0.35, corresponding to a spin temperature of ∼27K, towards Sagittarius B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.

Abstract Copyright: ∼

Journal keyword(s): astrochemistry - ISM: abundances - ISM: molecules - molecular processes - submillimeter: ISM

Simbad objects: 8

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Number of rows : 8

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Sp type	#ref 1850 - 2023	#notes
1	NAME Galactic Center	reg	17 45 39.60213	-29 00 22.0000	~	13907	0
2	NAME Sgr B2	MoC	17 47 20.4	-28 23 07	~	2199	1
3	NAME Sgr B2 (South)	HII	17 47 20.430	-28 23 45.06	~	96	0
4	NAME Sgr B2 Main	Rad	17 47 20.5	-28 23 06	~	390	1
5	W 31c	HII	18 10 29.1	-19 56 05	~	336	0
6	NAME Sgr Arm	PoG	19 00	-30.0	~	625	1
7	NAME Scutum Spiral Arm	PoG	~	~	~	341	0
8	NAME Ori Arm	PoG	~	~	~	199	0

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