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| molecules:extragalactic:pn_extragalactic [2022/04/04 11:38] – mueller | molecules:extragalactic:pn_extragalactic [2022/04/04 12:36] (current) – mueller |
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| //Astron. Astrophys.// **659**, (2022) Art. No. A158.\\ | //Astron. Astrophys.// **659**, (2022) Art. No. A158.\\ |
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| The //J// = 2 – 1 and //J// = 3 – 2 transitions of PN near 93.980 and 140.968 GHz, respectively, were observed with ALMA in the course of a very extensive molecular line survey (84.2 to 373.2 GHz) of the central molecular zone (CMZ) of the near-by star-burst galaxy NGC 253. The molecular cations were only detected toward the SW image representing denser material with a fairly high molecular fraction overall. They were not seen toward the NE image representing less dense material with a lower molecular fraction overall. Formation of SH<sup>+</sup> thus appears to require higher densities than that best suited for OH<sup>+</sup> or H<sub>2</sub>O<sup>+</sup>.\\ | The //J// = 2 – 1 and //J// = 3 – 2 transitions of PN near 93.980 and 140.968 GHz, respectively, were observed with ALMA in the course of a very extensive molecular line survey (84.2 to 373.2 GHz) of the central molecular zone (CMZ) of the near-by star-burst galaxy NGC 253. Both transitions were detected toward the source GMC 6 with good and fairly good signal-to-noise ratios (S/N), respectively. The //J// = 2 – 1 transition was also detected with reasonable S/N toward the source GMC 4. The two transitions detected toward GMC 6 constrain the excitation temperature to 4.4 ± 1.3 K.\\ |
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| The <sup>32</sup>S/<sup>34</sup>S isotopic ratio is 16.2 ± 1.3, lower than the terrestrial ratio of 22, thus suggesting greater importance of supernovae in the elemental synthesis about 7.5 billion years ago compared to today. On the other hand, the <sup>32</sup>S/<sup>34</sup>S isotopic ratios are still lower, about 10.5, for CS and H<sub>2</sub>S in that galaxy, suggesting an even greater importance of higher-mass supernovae in the probably still denser ISM where these two molecules reside.\\ | Other phosphorus-bearing molecules were searched for, but not detected. The PO/PN ratio was found to be < 1.3 for GMC 6, still compatible with PO/PN > 1 in Galactic sources. The PH<sub>3</sub>/PN ratio was found to be < 2.7 toward the same position.\\ |
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