2010A&A...510A..98L


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.25CET09:04:59

2010A&A...510A..98L - Astronomy and Astrophysics, volume 510, A98-98 (2010/2-1)

O18O and C18O observations of ρ Ophiuchi A.

LISEAU R., LARSSON B., BERGMAN P., PAGANI L., BLACK J.H., HJALMARSON A. and JUSTTANONT K.

Abstract (from CDS):

Contrary to theoretical expectation, surprisingly low concentrations of molecular oxygen, O2, have been found in the interstellar medium. Telluric absorption makes ground based O2 observations essentially impossible and observations had to be done from space. Millimetre-wave telescopes on space platforms were necessarily small, which resulted in large, several arcminutes wide, beam patterns. Observations of the (NJ=11-10) ground state transition of O2 with the Odin satellite resulted in a >5σ detection toward the dense core ρ Oph A. At the frequency of the line, 119GHz, the Odin telescope has a beam width of 10', larger than the size of the dense core. The precise nature of the emitting source and its exact location and extent are therefore unknown. The current investigation is intended to remedy this. Although the Earth's atmosphere is entirely opaque to low-lying O2 transitions, it allows ground based observations of the much rarer 16O18O in favourable conditions and at much higher angular resolution with larger telescopes. In addition, ρ Oph A exhibits both multiple radial velocity systems and considerable velocity gradients. Extensive mapping of the region in the proxy C18O (J=3-2) line can be expected to help identify the O2 source on the basis of its line shape and Doppler velocity. Line opacities were determined from observations of optically thin 13C18O (J=3-2). During several observing periods, two C18O intensity maxima in ρ Oph A were searched for O18O in the (21-01) line at 234GHz with the 12m APEX telescope. These positions are associated also with peaks in the mm-continuum emission from dust. Our observations resulted in an upper limit on the integrated O18O intensity of ∫T*Adυ<0.01K.km/s (3σ) into the 26.5" beam. Together with the C18O data, this leads to a ratio of N(C18O)/N(O18O)>16. Combining Odin's O2 with the present O18O observations we infer an O2 abundance 5x10–7<X(O2)≲2.5x10–6. Examining the evidence, which is based primarily on observations in lines of O18O and C18O, leads us to conclude that the source of observed O2 emission is most likely confined to the central regions of the ρ Oph A core. In this limited area, implied O2 abundances could thus be higher than inferred on the basis of Odin observations (5x10–8) by up to two orders of magnitude.

Abstract Copyright:

Journal keyword(s): ISM: abundances - ISM: molecules - ISM: lines and bands - ISM: clouds - ISM: individual objects: ρ Oph A SM 1 - ISM: individual objects: ρ Oph A SM 1N

VizieR on-line data: <Available at CDS (J/A+A/510/A98): maps.dat fits/*>

Nomenclature: Fig. 3, Table 1: [LLB2010] PN (Nos P1-P4).

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 * rho Oph A * 16 25 35.1182364594 -23 26 49.827436721 4.3 5.22 5.05     B2/3V 394 0
2 [DAM2004] Oph A-N1 PoC 16 26 26.4 -24 23 07           ~ 4 0
3 NAME rho Oph A Cloud MoC 16 26 26.4 -24 22 33           ~ 241 1
4 NAME VLA 1623-243 Y*O 16 26 26.42 -24 24 30.0           ~ 375 0
5 [SSG2006] MMS002 smm 16 26 26.50 -24 24 30.9           ~ 241 0
6 NAME rho Oph A SM 1N cor 16 26 27.12 -24 23 34.8           ~ 43 0
7 [DAM2004] Oph A-N5 cor 16 26 27.4 -24 23 30           ~ 4 0
8 NAME rho Oph A SM 1 cor 16 26 27.60 -24 23 55.0           ~ 59 0
9 [JJK2008] SMM J162628-24235 PoC 16 26 27.6 -24 23 55           ~ 8 0
10 [JWM2000] SMM J16264-2422b PoC 16 26 28.3 -24 22 55           ~ 3 0
11 NAME rho Oph C Cloud MoC 16 26 53.1 -24 32 31           ~ 57 0
12 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3066 0

    Equat.    Gal    SGal    Ecl

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