2005A&A...433L...5W


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.22CEST22:21:05

2005A&A...433L...5W - Astronomy and Astrophysics, volume 433, L5-8 (2005/4-1)

Searching for O2 in the SMC: Constraints on oxygen chemistry at low metallicities.

WILSON C.D., OLOFSSON A.O.H., PAGANI L., BOOTH R.S., FRISK U., HJALMARSON A., OLBERG M. and SANDQVIST A.

Abstract (from CDS):

We present a 39h integration with the Odin satellite on the ground-state 118.75 GHz line of O2 towards the region of strongest molecular emission in the Small Magellanic Cloud. Our 3σ upper limit to the O2 integrated intensity of <0.049K.km/s in a 9' (160pc) diameter beam corresponds to an upper limit on the O2/H2 abundance ratio of <1.3x10–6. Although a factor of 20 above the best limit on the O2 abundance obtained for a Galactic source, our result has interesting implications for understanding oxygen chemistry at sub-solar metal abundances. We compare our abundance limit to a variety of astrochemical models and find that, at low metallicities, the low O2 abundance is most likely produced by the effects of photo-dissociation on molecular cloud structure. Freeze-out of molecules onto dust grains may also be consistent with the observed abundance limit, although such models have not yet been run at sub-solar initial metallicities.

Abstract Copyright:

Journal keyword(s): galaxies: individual: SMC - ISM: molecules - astrochemistry

CDS comments: p.L5 radio source B0218+357 = QSO B0218+357, p.L6 SMC SW-1 = [RGM91] SW-1, p.L7 L 134N = LDN 134N

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 [RGM91] SW-1 MoC 00 46 30 -73 21.1           ~ 4 0
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9092 1
3 QSO B0218+357 QSO 02 21 05.5 +35 56 14   20.0 20.0 19.60   ~ 488 3
4 M 42 HII 05 35 17.3 -05 23 28           ~ 3658 0
5 NAME Ori A MoC 05 38 -07.1           ~ 2611 0
6 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 674 1
7 NAME rho Oph A Cloud MoC 16 26 26.4 -24 22 33           ~ 235 1

    Equat.    Gal    SGal    Ecl

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2019.10.22-22:21:05

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