CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy

Colzi, L.; Romano, D.; Fontani, F.; Rivilla, V. M.; Bizzocchi, L.; Beltrán, M. T.; Caselli, P.; Elia, D.; Magrini, L.

doi:10.1051/0004-6361/202244631

Cited by 8 publications

(4 citation statements)

References 70 publications

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“…However, observations of 34 S/ 36 S and 32 S/ 36 S isotope ratios are still relatively few, especially in the CMZ and the inner disk within R GC = 5.0 kpc. -The predicted 12 C/ 13 C ratios from the latest Galactic chemical evolution models (e.g.,Kobayashi et al 2020;Romano et al 2021;Colzi et al 2022) are in good agreement with our results, while 32 S/ 34 S and 32 S/ 36 S ratios show significant differences at larger galactocentric distances. 32 S/ 33 S ratios even show clear offsets along the entire inner 12 kpc of the Milky Way.…”

supporting

confidence: 91%

“…4.9). The dark green, light green, magenta, and pink lines refer to the predicted gradients from models in Table 2 from Colzi et al (2022).…”

Section: Discussionmentioning

confidence: 99%

“…While 14 N appears to be less secondary than 15 N (Audouze et al 1975;Henkel et al 1994;Wilson 1999;Adande & Ziurys 2012;Ritchey et al 2015;Colzi et al 2018;Chen et al 2021), in this case we do not have a clear calibration against an isotope that can be considered to be mainly primary. Remarkably, Colzi et al (2022) reported a rising 14 N/ 15 N gradient that peaks at R GC = 11 kpc and then decreases, and suggested that 15 N could be mainly produced by novae on long timescales. 2011) with updates with respect to new solar abundances and also accounting for failed supernovae, super-AGB stars, the s-process from AGB stars, and various r-process sites.…”

Section: Chemical Fractionationmentioning

confidence: 94%

“…Very recently, Colzi et al (2022) predicted 12 C/ 13 C gradients with four different models addressing nova systems (see details in their Table 2 and Sect. 4), following Romano et al (2017Romano et al ( , 2019Romano et al ( , 2021.…”

Section: Galactic Chemical Environmentmentioning

confidence: 99%

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Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Yan

Henkel

Menten

et al. 2023

A&A

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Context. Isotope abundance ratios provide a powerful tool for tracing stellar nucleosynthesis, evaluating the composition of stellar ejecta, and constraining the chemical evolution of the Milky Way. Aims. We aim to measure the 12C/13C, 32S/34S, 32S/33S, 32S/36S, 34S/33S, 34S/36S, and 33S/36S isotope ratios across the Milky Way. Methods. With the IRAM 30 meter telescope, we performed observations of the J = 2−1 transitions of CS, C33S, C34S, C36S, 13CS, 13C33S, and 13C34S as well as the J = 3−2 transitions of C33S, C34S, C36S, and 13CS toward a large sample of 110 high-mass star-forming regions. Results. We measured the 12C/13C, 32S/34S, 32S/33S, 32S/36S, 34S/33S, 34S/36S, and 33S/36S abundance ratios with rare isotopologs of CS, thus avoiding significant saturation effects. With accurate distances obtained from parallax data, we confirm previously identified 12C/13C and 32S/34S gradients as a function of galactocentric distance. In the central molecular zone, 12C/13C ratios are higher than suggested by a linear fit to the disk values as a function of galactocentric radius. While 32S/34S ratios near the Galactic center and in the inner disk are similar, this is not the case for 12C/13C, when comparing central values with those near galactocentric radii of 5 kpc. As was already known, there is no 34S/33S gradient but the average ratio of 4.35 ± 0.44 derived from the J = 2−1 transition lines of C34S and C33S is well below previously reported values. A comparison between solar and local interstellar 32S/34S and 34S/33S ratios suggests that the Solar System may have been formed from gas with a particularly high 34S abundance. For the first time, we report positive gradients of 32S/33S, 34S/36S, 33S/36S, and 32S/36S in our Galaxy. The predicted 12C/13C ratios from the latest Galactic chemical-evolution models are in good agreement with our results. While 32S/34S and 32S/36S ratios show larger differences at larger galactocentric distances, 32S/33S ratios show an offset across the entire inner 12 kpc of the Milky Way.

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supporting

confidence: 91%

“…4.9). The dark green, light green, magenta, and pink lines refer to the predicted gradients from models in Table 2 from Colzi et al (2022).…”

Section: Discussionmentioning

confidence: 99%

Section: Chemical Fractionationmentioning

confidence: 94%

Section: Galactic Chemical Environmentmentioning

confidence: 99%

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Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Yan

Henkel

Menten

et al. 2023

A&A

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Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI

Butterworth,

Viti,

Van der Werf

et al. 2024

A&A

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Determining the evolution of the CNO isotopes in the interstellar medium (ISM) of starburst galaxies can yield important constraints on the ages of super star clusters (SSCs), or on other aspects and factors contributing to their evolution, such as the initial mass function (IMF). Due to the time-dependent nature of the abundances of isotopes within the ISM ---as they are supplied from processes such as nucleosynthesis or chemical fractionation---, this provides the opportunity to test whether or not isotope ratios trace the ages of highly star-forming regions, such as SSCs. The goal of this study is to investigate whether the isotopic variations in SSC regions within NGC 253 are correlated with their different ages as derived from stellar population modelling. We measured abundance ratios of CO, HCN, and HCO isotopologues in six regions containing SSCs within NGC 253 using high-spatial-resolution (1.6",$ 28$pc) data from the ALCHEMI (ALma Comprehensive High-resolution Extragalactic Molecular Inventory) ALMA Large program. We then analysed these ratios using RADEX radiative transfer modelling, with the parameter space sampled using the nested sampling Monte Carlo algorithm MLFriends. These abundance ratios were then compared to ages predicted in each region via the fitting of observed star-formation tracers (such as Brgamma ) to Starburst99 starburst stellar population evolution models. We determined the isotopic column density ratios across multiple regions of SSC activity in NGC 253 using non-LTE radiative transfer modelling. We do not find any significant trend with age for the CO and HCN isotopologue ratios on timescales of the ages of the SSC* regions observed. However, HCO may show a correlation with age over these timescales in C/ C. The driving factors of these ratios within SSCs could be the IMF or fractionation effects. To further probe these effects in SSCs over time, a larger sample of SSCs must be observed spanning a larger age range.

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A new measurement of the Galactic ¹²C/¹³C gradient from sensitive HCO⁺ absorption observations

Luo,

Colzi,

Liu

et al. 2024

A&A

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We present a new constraint on the Galactic 12C/13C gradient with sensitive HCO$^+$ absorption observations against strong continuum sources. The new measurements suffer less from beam dilution, optical depths, and chemical fractionation, allowing us to derive the isotopic ratios precisely. The measured 12C/13C ratio in the solar neighborhood (66pm 5) is consistent with those obtained from CH$^+$. Two measurements toward the GC are 42.2pm 1.7 and 37.5pm 6.5. Though the values are a factor of two to three higher than those derived from dense gas tracers (e.g., H$_2$CO, complex organic molecules) toward Sagittarius (Sgr) B2 regions, our results are consistent with the absorption measurements from c-C$_3$H$_2$ toward Sgr B2 (sim 40) and those from CH$^+$ toward Sgr A$^*$ and Sgr B2(N) ($>$30). We have calculated a new Galactic 12C/13C gradient of (6.4pm 1.9)$R_ GC $/kpc+(25.9pm 10.5) and found an increasing trend of the 12C/13C gradient obtained from high-density to low-density gas tracers, suggesting that opacity effects and chemical fractionation may have a strong impact on the isotopic ratios observed in high-density regions.

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CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy

Cited by 8 publications

References 70 publications

Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI

A new measurement of the Galactic ¹²C/¹³C gradient from sensitive HCO⁺ absorption observations

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CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy

Cited by 8 publications

References 70 publications

Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI

A new measurement of the Galactic 12C/13C gradient from sensitive HCO+ absorption observations

Contact Info

Product

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A new measurement of the Galactic ¹²C/¹³C gradient from sensitive HCO⁺ absorption observations