J/A+A/669/L15 Atomic oxygen abundance toward Sgr B2 (Lis+, 2023)
Atomic oxygen abundance toward Sagittarius B2.
Lis D.C., Goldsmith P.F., Guesten R., Schilke P., Wiesemeyer H., Seo Y.,
Werner M.W.
<Astron. Astrophys. 669, L15 (2023)>
=2023A&A...669L..15L 2023A&A...669L..15L (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Abundances ; Spectra, infrared
Keywords: astrochemistry - ISM: abundances - ISM: atoms - ISM: molecules -
ISM: lines and bands - ISM: clouds
Abstract:
A substantial fraction of oxygen in diffuse clouds is unaccounted for
by observations and is postulated to be in an unknown refractory form,
referred to as unidentified depleted oxygen (UDO), which, depending on
the local gas density, may contribute up to 50% of the total oxygen
content. Previous Infrared Space Observatory (ISO) observations
suggest that a significant fraction of oxygen in even denser,
translucent clouds may be in atomic form. We have analyzed
velocity-resolved archival SOFIA observations of the 63um
fine-structure [OI] transition toward the high-mass star-forming
region Sgr B2(M) in the Central Molecular Zone. The foreground
spiral-arm clouds as well as the extended Sgr B2 envelope between the
Sun and the background dust continuum source produce multiple [OI]
absorption components, spectrally separated in velocity space. The
gas-phase atomic oxygen column density in foreground clouds toward
Sgr B2 is well correlated with the total hydrogen column density, with
an average atomic oxygen abundance of (2.51±0.69)x10-4 with
respect to hydrogen nuclei. This value is in good agreement with the
earlier ISO measurements on the same line of sight, and is about 35%
lower than the total interstellar medium oxygen abundance in the
low-density warm gas, as measured in the UV. We find no evidence that
a significant fraction of the oxygen on the line of sight toward
Sagittarius B2 is in the form of UDO.
Description:
Atomic oxygen abundance with respect to hydrogen nuclei and atomic
oxygen column density, with the corresponding ± 1-sigma
uncertainties, on the line of sight toward Sagittarius B2 as a
function of LSR velocity.
Hydrogen nucleus column densities (total, molecular, and atomic
components), with the corresponding ± 1 sigma uncertainties, as a
function of LSR velocity.
The blanking value of -0.100E+04 indicates no data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cden-o.dat 71 141 Atomic oxygen abundances and column densities
(Fig. 2)
cden-h.dat 104 211 Hydrogen nucleus column densities (Fig. B3)
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Byte-by-byte Description of file: cden-o.dat
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Bytes Format Units Label Explanations
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1- 5 F5.0 km/s Vlsr LSR velocity
6- 16 E11.3 --- X(OI) Atomic oxygen abundance wrt H
17- 27 E11.3 --- e_X(OI) Lower uncertainty (-1 sigma) on X(OI)
28- 38 E11.3 --- E_X(OI) Upper uncertainty (+1 sigma) on X(OI)
39- 49 E11.3 cm-2/km/s dN(OI)/dv Atomic oxygen column density
50- 60 E11.3 cm-2/km/s e_dN(OI)/dv Lower uncertainty (-1 sigma) on dN(OI)/dv
61- 71 E11.3 cm-2/km/s E_dN(OI)/dv Upper uncertainty (+1 sigma) on dN(OI)/dv
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Byte-by-byte Description of file: cden-h.dat
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Bytes Format Units Label Explanations
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1- 5 F5.0 km/s Vlsr LSR velocity
6- 16 E11.3 cm-2/km/s dNtot/dv ?=-0.100E+04 Total H nucleus
column density (1)
17- 27 E11.3 cm-2/km/s e_dNtot/dv Lower uncertainty (-1 sigma) on dNtot/dv
28- 38 E11.3 cm-2/km/s E_dNtot/dv Upper uncertainty (+1 sigma) on dNtot/dv
39- 49 E11.3 cm-2/km/s 2dNH2/dv ?=-0.100E+04 Twice molecular H nucleus
column density
50- 60 E11.3 cm-2/km/s e_2dNH2/dv ?=-0.100E+04 Lower uncertainty (-1 sigma)
on 2dNH2/dv
61- 71 E11.3 cm-2/km/s E_2dNH2/dv ?=-0.100E+04 Upper uncertainty (+1 sigma)
on 2dNH2/dv
72- 82 E11.3 cm-2/km/s dNH/dv Atomic H nucleus column density
83- 93 E11.3 cm-2/km/s e_dNH/dv Lower uncertainty (-1 sigma) on dNH/dv
94-104 E11.3 cm-2/km/s E_dNH/dv Upper uncertainty (+1 sigma) on dNH/dv
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Note (1): dNtot/dv = 2(dNH2/dv) + dNH/dv.
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Acknowledgements:
Dariusz C. Lis, dclis(at)jpl.nasa.gov
References:
Lis et al., 2001ApJ...561..823L 2001ApJ...561..823L,
Atomic oxygen abundance in molecular clouds: absorption toward Sagittarius B2.
(End) Patricia Vannier [CDS] 09-Jan-2023