ALMA view of the<sup>12</sup>C/<sup>13</sup>C isotopic ratio in starburst galaxies

Tang, Xindi; Henkel, C.; Menten, K. M.; Gong, Y.; Martín, S.; Mühle, S.; Aalto, S.; Müller, S.; García‐Burillo, S.; Levshakov, S. A.; Aladro, R.; Spaans, Marco; Viti, S.; Asiri, H.; Ao, Yiping; Zhang, J. S.; Zheng, Xingwu; Esimbek, Jarken; Zhou, Jianwen

doi:10.1051/0004-6361/201935603

Cited by 46 publications

(35 citation statements)

References 120 publications

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“…The 12 C/ 13 C ratio has been widely studied towards molecular clouds in the Milky Way (e.g. Henkel et al 1982Henkel et al , 1994Steimle et al 1986;Wilson & Rood 1994) and recently, also in the nuclear regions of nearby starburst galaxies (Tang et al 2019).…”

Section: Introductionmentioning

confidence: 99%

First detection of ¹³CH in the interstellar medium

Jacob

Menten

Wiesemeyer

et al. 2020

A&A

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In recent years, a plethora of observations with high spectral resolution of sub-millimetre and far-infrared transitions of methylidene (CH), conducted with Herschel and SOFIA, have demonstrated this radical to be a valuable proxy for molecular hydrogen that can be used for characterising molecular gas within the interstellar medium on a Galactic scale, including the CO-dark component. We report the discovery of the 13CH isotopologue in the interstellar medium using the upGREAT receiver on board SOFIA. We have detected the three hyperfine structure components of the ≈2 THz frequency transition from its X2Π1∕2 ground-state towards the high-mass star-forming regions Sgr B2(M), G34.26+0.15, W49(N), and W51E and determined 13CH column densities. The ubiquity of molecules containing carbon in the interstellar medium has turned the determination of the ratio between the abundances of the two stable isotopes of carbon, 12C/13C, into a cornerstone for Galactic chemical evolution studies. Whilst displaying a rising gradient with galactocentric distance, this ratio, when measured using observations of different molecules (CO, H2CO, and others), shows systematic variations depending on the tracer used. These observed inconsistencies may arise from optical depth effects, chemical fractionation, or isotope-selective photo-dissociation. Formed from C+ either through UV-driven or turbulence-driven chemistry, CH reflects the fractionation of C+, and does not show any significant fractionation effects, unlike other molecules that were previously used to determine the 12C/13C isotopic ratio. This makes it an ideal tracer for the 12C/13C ratio throughout the Galaxy. By comparing the derived column densities of 13CH with previously obtained SOFIA data of the corresponding transitions of the main isotopologue 12CH, we therefore derive 12C/13C isotopic ratios toward Sgr B2(M), G34.26+0.15, W49(N) and W51E. Adding our values derived from 12∕13CH to previous calculations of the Galactic isotopic gradient, we derive a revised value of 12C/13C = 5.87(0.45)RGC + 13.25(2.94).

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Section: Introductionmentioning

confidence: 99%

First detection of ¹³CH in the interstellar medium

Jacob

Menten

Wiesemeyer

et al. 2020

A&A

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“…There have been several observational studies of the 12 C/ 13 C in external galaxies (e.g. Henkel et al 1998Henkel et al , 2010Henkel et al , 2014Martín et al 2005Martín et al , 2006Martín et al , 2019González-Alfonso et al 2012;Aladro et al 2013;Wang et al 2009;Jiang et al 2011;Tang et al 2019; see also Table 2). The molecules most used to determine this ratio in external galaxies are: CN (found to be the best tracer by Henkel et al 2014), CO, H 2 CO, HCO + , HCN and CS.…”

Section: Introductionmentioning

confidence: 99%

A chemical study of carbon fractionation in external galaxies

Viti

Fontani

Jiménez-Serra

2020

Monthly Notices of the Royal Astronomical Society

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In the interstellar medium carbon exists in the form of two stable isotopes 12C and 13C and their ratio is a good indicator of nucleosynthesis in galaxies. However, chemical fractionation can potentially significantly alter this ratio and in fact observations of carbon fractionation within the same galaxy has been found to vary from species to species. In this paper we theoretically investigate the carbon fractionation for selected abundant carbon-bearing species in order to determine the conditions that may lead to a spread of the 12C/13C ratio in external galaxies. We find that carbon fractionation is sensitive to almost all the physical conditions we investigated, it strongly varies with time for all species but CO, and shows pronounced differences across species. Finally we discuss our theoretical results in the context of the few observations of the 12C/13C in both local and higher redshift galaxies.

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“…13 CH + : A broad absorption feature is detected at 120.55 µm, which could be associated with either 13 CH + 3 − 2 and/or to SH (see below). To check if it can be reproduced with only 13 CH + , a model with a fixed abundance ratio 13 CH + /CH + = 0.05 is used, appropriate for the central regions of starburst galaxies (Tang et al 2019). The resulting modeled 13 CH + 3 − 2 absorption accounts for approximately half of the observed 120.55 µm feature.…”

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“…The resulting modeled 13 CH + 3 − 2 absorption accounts for approximately half of the observed 120.55 µm feature. It is possible that the 13 CH + abundance in ESO 320-G030 is even higher than the adopted value, as in the very center of NGC 4945 (Tang et al 2019). SH: We have attempted to fill in the remaining 120.55 µm absorption by including a model for SH; the transition that may contribute to the observed absorption feature is 2 Π 3/2 J = 9/2 ← 7/2 (E lower ≈ 160 K).…”

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A proto-pseudobulge in ESO 320-G030 fed by a massive molecular inflow driven by a nuclear bar

González-Alfonso

Pereira-Santaella

Fischer

et al. 2021

A&A

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Galaxies with nuclear bars are believed to efficiently drive gas inward, generating a nuclear starburst and possibly an active galactic nucleus (AGN). We confirm this scenario for the isolated, double-barred, luminous infrared galaxy ESO 320-G030 based on an analysis of Herschel and ALMA spectroscopic observations. Herschel/PACS and SPIRE observations of ESO 320-G030 show absorption or emission in 18 lines of H 2 O, which we combine with the ALMA H 2 O 4 23 − 3 30 448 GHz line (E upper ∼ 400 K) and continuum images to study the physical properties of the nuclear region. Radiative transfer models indicate that three nuclear components are required to account for the multi-transition H 2 O and continuum data. An envelope, with radius R ∼ 130 − 150 pc, dust temperature T dust ≈ 50 K, and N H2 ∼ 2 × 10 23 cm −2 , surrounds a nuclear disk with R ∼ 40 pc that is optically thick in the far-infrared (τ 100 µm ∼ 1.5 − 3, N H2 ∼ 2 × 10 24 cm −2). In addition, an extremely compact (R ∼ 12 pc), warm (≈ 100 K), and buried (τ 100 µm > 5, N H2 5 × 10 24 cm −2) core component is required to account for the very high-lying H 2 O absorption lines. The three nuclear components account for 70% of the galaxy luminosity (SFR ∼ 16−18 M yr −1). The nucleus is fed by a molecular inflow observed in CO 2-1 with ALMA, which is associated with the nuclear bar. With decreasing radius (r = 450 − 225 pc), the mass inflow rate increases up tȯ M inf ∼ 20 M yr −1 , which is similar to the nuclear star formation rate (SFR), indicating that the starburst is sustained by the inflow. At lower r, ∼ 100 − 150 pc, the inflow is best probed by the far-infrared OH ground-state doublets, with an estimatedṀ inf ∼ 30 M yr −1. The inferred short timescale of ∼ 20 Myr for nuclear gas replenishment indicates quick secular evolution, and indicates that we are witnessing an intermediate stage (< 100 Myr) proto-pseudobulge fed by a massive inflow that is driven by a strong nuclear bar. We also apply the H 2 O model to the Herschel far-infrared spectroscopic observations of H 18 2

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ALMA view of the¹²C/¹³C isotopic ratio in starburst galaxies

Cited by 46 publications

References 120 publications

First detection of ¹³CH in the interstellar medium

First detection of ¹³CH in the interstellar medium

A chemical study of carbon fractionation in external galaxies

A proto-pseudobulge in ESO 320-G030 fed by a massive molecular inflow driven by a nuclear bar

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ALMA view of the12C/13C isotopic ratio in starburst galaxies

Cited by 46 publications

References 120 publications

First detection of 13CH in the interstellar medium

First detection of 13CH in the interstellar medium

A chemical study of carbon fractionation in external galaxies

A proto-pseudobulge in ESO 320-G030 fed by a massive molecular inflow driven by a nuclear bar

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ALMA view of the¹²C/¹³C isotopic ratio in starburst galaxies

First detection of ¹³CH in the interstellar medium

First detection of ¹³CH in the interstellar medium