ISOTOPIC RATIOS OF
                    <sup>18</sup>
                    O/
                    <sup>17</sup>
                    O IN THE GALACTIC CENTRAL REGION

Zhang, J. S.; Sun, Lijun; Riquelme, D.; Henkel, C.; Lu, Dong-Fei; Zhang, Y.; Wang, J. Z.; Wang, M.; Li, J.

doi:10.1088/0067-0049/219/2/28

Cited by 19 publications

(23 citation statements)

References 28 publications

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“…It is 4.35±0.45 and >5.27 for sources at 3 kpc<D GC <11 kpc and D GC >11 kpc, respectively which is consistent with their results. Combining with our mapping results that provide a ratio value of 3.01±0.14 in the Galactic cen-ter region (Zhang et al 2015), a linear least-squares fit gives 18 O/ 17 O=(0.18±0.04)D GC +(2.91±0.27), with a Spearman's rank correlation coefficient R = 0.85. However, we have to note that our sources with galactocentric distance larger than 11 kpc are still not enough, and the J = 1 − 0 transitions alone (C 18 O and C 17 O) are not sufficient when trying to account for radiative transfer effects.…”

Section: Discussionsupporting

confidence: 65%

“…We are undertaking a systematic observational study on the ratio of 18 O to 17 O. This includes detailed mapping towards more molecular clouds in the Galactic center (Zhang et al 2015) and single point observations toward disk molecular clouds with different galactocentric distances, especially more sources with large galactocentric distances, to check the existence of the ratio 18 O/ 17 O gradient along the Galactic disk (this work).…”

Section: Introductionmentioning

confidence: 99%

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Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Zhang

Liu

et al. 2016

Res. Astron. Astrophys.

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We present our observations of the J = 1 − 0 rotation transitions in molecular isotopes C 18 O and C 17 O toward a sample of molecular clouds with different galactocentric distances, using the Delingha 13.7 m (DLH 13.7 m) telescope, administered by Purple Mountain Observatory, and its 9-beam SIS receiver. Complementary observations toward several sources with large galactocentric distance are obtained with the IRAM 30m and Mopra 22m telescopes. C 18 O/C 17 O abundance ratios reflecting the 18 O/ 17 O isotope ratios are obtained from integrated intensity ratios of C 18 O and C 17 O. We derived the ratio value for 13 sources covering a galactocentric distance range of 3 kpc to 16 kpc. In combination with our mapping results that provide a ratio value of 3.01±0.14 in the Galactic center region, it shows that the abundance ratio tends to increase with galactocentric distance, i.e., it supports a radial gradient along the Galactic disk for the abundance ratio. This is consistent with the inside-out formation scenario of our Galaxy. However, our results may suffer from small samples with large galactocentric distance. Combining our data with multitransition lines of C 18 O and C 17 O will be helpful for constraining opacities and abundances and further confirming the Galactic radial gradient shown by the isotope ratio 18 O/ 17 O.

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Section: Discussionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Zhang

Liu

et al. 2016

Res. Astron. Astrophys.

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“…Therefore, it is important to also cover the inner region of the Milky Way to find out whether the trend proposed by Chin et al (1996) is also valid for the inner Galaxy as has been reported for the 12 C/ 13 C (see e.g. Yan et al 2019), 14 N/ 15 N (Adande & Ziurys 2012) and 18 O/ 17 O (Wouterloot et al 2008;Zhang et al 2015) isotopic ratios.…”

Section: A222 Page 1 Of 15mentioning

confidence: 91%

Sulphur and carbon isotopes towards Galactic centre clouds

Humire

Thiel

Henkel

et al. 2020

A&A

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Context. Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. Aims. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50 km s−1 Cloud and several line-of-sight clouds towards Sgr B2(N). Methods. Towards the +50 km s−1 Cloud, we observed the J = 2–1 rotational transitions of 12C32S, 12C34S, 13C32S, 12C33S, and 13C34S, and the J = 3–2 transitions of 12C32S and 12C34S with the IRAM-30 m telescope, as well as the J = 6–5 transitions of 12C34S and 13C32S with the APEX 12 m telescope, all in emission. The J = 2–1 rotational transitions of 12C32S, 12C34S, 13C32S, and 13C34S were observed with ALMA in the envelope of Sgr B2(N), with those of 12C32S and 12C34S also observed in the line-of-sight clouds towards Sgr B2(N), all in absorption. Results. In the +50 km s−1 Cloud we derive a 12C/13C isotopic ratio of 22.1−2.4+3.3, that leads, with the measured 13C32S/12C34S line intensity ratio, to a 32S/34S ratio of 16.3−2.4+3.0. We also derive the 32S/34S isotopic ratio more directly from the two isotopologues 13C32S and 13C34S, which leads to an independent 32S/34S estimation of 16.3−1.7+2.1 and 17.9 ± 5.0 for the +50 km s−1 Cloud and Sgr B2(N), respectively. We also obtain a 34S/33S ratio of 4.3 ± 0.2 in the +50 km s−1 Cloud. Conclusions. Previous studies observed a decreasing trend in the 32S/34S isotopic ratios when approaching the Galactic centre. Our result indicates a termination of this tendency at least at a galactocentric distance of 130−30+60 pc. This is at variance with findings based on 12C/13C, 14N/15N, and 18O/17O isotope ratios, where the above-mentioned trend is observed to continue right to the central molecular zone. This can indicate a drop in the production of massive stars at the Galactic centre, in the same line as recent metallicity gradient ([Fe/H]) studies, and opens the work towards a comparison with Galactic and stellar evolution models.

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“…As is shown in Figure 2, the peak intensities of OH are -0.03 K and -0.15 K for Sgr B2(N) and Sgr B2(M), respectively. Since 16 O/ 17 O is observed to be up to 1000 in Sgr B2 (Polehampton et al 2005;Zhang et al 2015), 17 OH should appear as absorption line with very low peak intensity, which could be ignored safely.…”

Section: Line Identificationsmentioning

confidence: 99%

Widespread Presence of Glycolaldehyde and Ethylene Glycol around Sagittarius B2

Shen

Wang

et al. 2017

ApJ

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We report the detection of widespread CH 2 OHCHO and HOCH 2 CH 2 OH emission in Galactic center giant molecular cloud Sagittarius B2 using the Shanghai Tianma 65m Radio Telescope. Our observations show for the first time that the spatial distribution of these two important prebiotic molecules extends over 15 arc-minutes, corresponding to a linear size of approximately 36 pc. These two molecules are not just distributed in or near the hot cores. The abundance of these two molecules seems to decrease from the cold outer region to the central region associated with star-formation activity. Results present here suggest that these two molecules are likely to form through a low temperature process. Recent theoretical and experimental studies demonstrated that prebiotic molecules can be efficiently formed in icy grain mantles through several pathways. However, these complex ice features cannot be directly observed, and most constraints on the ice compositions come from millimeter observations of desorbed ice chemistry products. These results, combined with laboratory studies, strongly support the existence of abundant prebiotic molecules in ices.

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ISOTOPIC RATIOS OF ¹⁸ O/ ¹⁷ O IN THE GALACTIC CENTRAL REGION

Abstract: O abundance ratios toward the GC region relative to molecular clouds in the Galactic disk. Furthermore, even inside the GC region, ratios appear not to be uniform. The low GC values are consistent with an inside-out formation scenario for our Galaxy.

Cited by 19 publications

References 28 publications

Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Sulphur and carbon isotopes towards Galactic centre clouds

Widespread Presence of Glycolaldehyde and Ethylene Glycol around Sagittarius B2

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ISOTOPIC RATIOS OF 18 O/ 17 O IN THE GALACTIC CENTRAL REGION

Abstract: O abundance ratios toward the GC region relative to molecular clouds in the Galactic disk. Furthermore, even inside the GC region, ratios appear not to be uniform. The low GC values are consistent with an inside-out formation scenario for our Galaxy.

Cited by 19 publications

References 28 publications

Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Oxygen isotopic ratios toward molecular clouds in the Galactic disk

Sulphur and carbon isotopes towards Galactic centre clouds

Widespread Presence of Glycolaldehyde and Ethylene Glycol around Sagittarius B2

Contact Info

Product

Resources

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ISOTOPIC RATIOS OF ¹⁸ O/ ¹⁷ O IN THE GALACTIC CENTRAL REGION