Pith. sign in

REVIEW 2 major objections 5 minor 1 cited by

The CMZ cloud G+0.693 formed from gas with an initial carbon isotope ratio of about 48, matching material from 3–5 kpc and pointing to bar-driven disc inflow.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

T0 review · grok-4.5

2026-07-11 00:06 UTC pith:PCD6EGMA

load-bearing objection Solid double-isotopologue measurement of 12C/13C ~37 in the CMZ, with a model-dependent step to ~48 that supports bar-driven inflow; the data core is new and usable, the age cut is the soft spot. the 2 major comments →

arxiv 2607.06541 v2 pith:PCD6EGMA submitted 2026-07-07 astro-ph.GA astro-ph.EPastro-ph.SR

High ¹²C/¹³C isotopic ratios toward G+0.693-0.027: evidence for gas inflow to the Central Molecular Zone

L. Colzi , O. Sipil\"a , I. Jim\'enez-Serra , V. M. Rivilla , M. Sanz-Novo , S. Mart\'in , S. Zeng This is my paper
classification astro-ph.GA astro-ph.EPastro-ph.SR
keywords Central Molecular Zonecarbon isotope ratioHC3NHC5Nisotopic fractionationgas inflowGalactic barGalactic chemical evolution
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper measures the carbon isotope ratio in the Galactic Center cloud G+0.693 using optically thin lines of HC3N and HC5N, including rare double-13C species. After correcting for mild isotopic fractionation with chemical models, the authors recover an initial 12C/13C ratio near 48 for the gas that built present-day CMZ clouds. That value is far higher than the long-accepted CMZ range of roughly 3–30 and matches the ratios seen at Galactocentric distances of 3–5 kpc. The result implies that the Central Molecular Zone is still being fed by relatively unprocessed gas streaming inward from the disc under the influence of the Galactic bar, with a possible extra contribution from accreted dwarf-galaxy material. If correct, the finding rewrites the chemical history of the inner Galaxy and supplies a direct isotopic clock for gas-inflow models.

Core claim

Using double-13C isotopologues of HC3N and single-13C isotopologues of HC5N, the observed 12C/13C ratios in the main velocity component of G+0.693 are 36.7 ± 1.0 and 38.8 ± 1.5. Astrochemical models that include 13C fractionation show that these ratios correspond to low-to-intermediate fractionation at early times after the cloud–cloud shock (< 3 × 10^4 yr). Multiplying by the model fractionation factor therefore yields an initial elemental ratio of ~48 for the parent material of CMZ molecular clouds—well above previous CMZ estimates and consistent with gas originating at 3–5 kpc.

What carries the argument

The double-13C isotopologue ratios of HC3N (and the corresponding single-13C ratios of HC5N) combined with the fractionation degree φ(C3) extracted from time-dependent chemical models that track all 13C substitutions up to C3; this pair of observables converts the measured column-density ratios into the primordial 12C/13C of the inflowing gas.

Load-bearing premise

The gas must still be younger than about 30 000 years after the shock, the only epoch at which the models simultaneously match both the observed HC3N abundance and a modest fractionation factor that raises the ratio to 48.

What would settle it

A secure detection of the same double-13C HC3N lines in a second, independently age-dated CMZ cloud that is demonstrably older than 10^5 yr and that still yields an uncorrected ratio near 37 would break the early-time fractionation correction and collapse the inferred initial value of 48.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • The canonical CMZ 12C/13C value of ~20 must be revised upward to at least 35–48 when optically thin tracers are used.
  • Bar-driven gas inflow from the inner disc is required to supply the CMZ with material whose isotopic signature matches 3–5 kpc gas.
  • Chemical-evolution models of the nuclear stellar disc must incorporate recent or ongoing accretion of less-processed gas to reproduce the elevated carbon isotope ratio.
  • Similar high ratios should appear in other optically thin complex species (e.g., HC5N double isotopologues or C34S/13C34S) throughout the CMZ if the inflow scenario is general.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the same ~48 ratio is recovered in ice absorption toward multiple Galactic-center continuum sources, the inflow must pre-date the present molecular-cloud generation by at least one full dynamical time.
  • Spatially resolved maps of double-13C HC3N across the CMZ could distinguish continuous bar-driven streaming from discrete dwarf-galaxy accretion events by revealing whether the high-ratio gas is smoothly distributed or clumped.
  • The same methodology applied to nitrogen and oxygen isotopes in G+0.693 would test whether the entire light-element suite arrived with the same disc-like chemical maturity.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 5 minor

Summary. The paper measures 12C/13C toward the CMZ cloud G+0.693-0.027 from single- and double-13C isotopologues of HC3N and HC5N using ultra-deep IRAM 30m and Yebes 40m spectra. LTE column densities yield robust observed ratios of 36.7±1.0 (HC3N double isotopologues, C1) and 38.8±1.5 (HC5N), higher than most historical CMZ values that were limited by optical depth. Astrochemical models with an updated 13C/15N network indicate low-to-intermediate fractionation (φ(C3)≈1.28) at early post-shock times ≲3×10^4 yr, implying an initial elemental ratio ~48. This range (37–48) matches Galactic-disc values at R_GC≈3–5 kpc and is interpreted as evidence that the CMZ is replenished by bar-driven disc inflow, with possible external accretion of less-processed gas.

Significance. If the high observed ratios and the modest fractionation correction hold, the result revises the commonly adopted CMZ 12C/13C value upward from ~20 and supplies a concrete chemical constraint on gas inflow into the Galactic Center. The observational core is strong: many transitions, double-isotopologue ratios that are largely free of optical-depth bias, and consistent results from two cyanopolyynes. The comparison with the Galactic gradient and with extragalactic starburst nuclei is timely and places the measurement in a broader evolutionary context. The work is therefore a useful contribution to both Galactic chemical evolution and CMZ dynamics, provided the chemical-age and network limitations are stated more carefully.

major comments (2)
  1. Sect. 3.2 and Figs. 7–8: the jump from the robust observed ratio ~37 to the claimed initial ~48 rests on multiplying by φ(C3)≈1.28 evaluated only at t≲3×10^4 yr. That epoch is selected because later times under-produce HC3N abundance (models never fully reach the observed (4.8±0.7)×10^{-9}). The network also omits 13C fractionation in C4H and larger precursors of HC5N. The paper should either (i) present a quantitative sensitivity study of φ versus chemical age, ζ, and network completeness, or (ii) clearly demote the ~48 value to a model-dependent upper bound and base the inflow argument primarily on the model-independent observed range 37–48.
  2. Sect. 3.1 and Table 2: for the C1 component the main-isotopologue HC3N column density is treated as a lower limit because of moderate optical depth (τ~0.1–0.5) and an unconstrained source size. The double-isotopologue ratios are therefore preferred, yet the paper still quotes an average that mixes them with the optically thin HC5N ratios. A short quantitative test of how a finite source size (≳25–30″) would alter the main-isotopologue N and the final average would strengthen the claim that 36.7±1.0 is the definitive C1 value.
minor comments (5)
  1. Abstract and Conclusions: the phrase “initial 12C/13C ratio of ~48” should be qualified as “model-dependent initial ratio” so that the distinction between observed and corrected values is immediately clear to non-specialists.
  2. Fig. 10 caption and Sect. 4.1.2: the linear fits (Eqs. 1–2) include or exclude CMZ points; the text should state explicitly which fit is used when converting 37–48 into the 3–5 kpc range, and whether the Luo et al. (2024) ~1 kpc points are included.
  3. Table C.1 and Appendix A: several upper limits for C2 double isotopologues depend on the adopted Tex of different single-13C species; a single consistent Tex choice (or a short note explaining the range) would improve reproducibility.
  4. Sect. 2.1 and Table 1: the physical parameters of C1 and C2 are taken from Colzi et al. (2024); a one-sentence reminder of how those values were derived would help readers who have not read the earlier paper.
  5. Typographical: “analised” → “analysed” (multiple occurrences); “histrogram” → “histogram” (figure captions); “columndensities” spacing errors in a few places.

Circularity Check

0 steps flagged

No significant circularity: observed ratios are independent measurements; models supply only a multiplicative fractionation factor shown to be independent of the assumed initial ratio.

full rationale

The central observational result (12C/13C ≈ 36.7 from double-13C HC3N and 38.8 from HC5N) is obtained directly from LTE column densities of optically thin lines (Sect. 3.1, Tables 2–3, Figs. 4–6) and does not depend on the chemical models. The models of Sipilä et al. (2023) are used only to evaluate a fractionation degree φ(X) that the authors explicitly test is independent of the initial elemental ratio adopted in the network (Sect. 3.2). The preferred early-time epoch (≲3×10^4 yr) is selected because that is when the modeled HC3N abundance comes closest to the observed value, not because it forces the final isotopic ratio to a preferred number. Physical parameters (n_H2, T_kin, source sizes) are taken from the authors’ prior G+0.693 papers, but those parameters are not the isotopic result itself. The subsequent comparison with the Galactic gradient and the inflow interpretation are ordinary scientific inference, not a closed definitional loop. No self-definitional step, fitted-input-called-prediction, or load-bearing uniqueness theorem appears. Score 1 reflects only the minor, non-load-bearing self-citation of prior source parameters.

Axiom & Free-Parameter Ledger

4 free parameters · 4 axioms · 0 invented entities

The central numerical claim (initial ratio ∼48) rests on observed column-density ratios multiplied by a model-derived fractionation factor evaluated at a chosen early chemical age. Free parameters are the physical conditions of the two velocity components and the cosmic-ray ionization rate; domain assumptions include LTE excitation, completeness of the Sipilä et al. (2023) network for C3 precursors, and the identification of C3 as the dominant carrier of the fractionation signature. No new physical entities are postulated.

free parameters (4)
  • T_kin, n_H2 for C1 and C2 = C1: 140 K, 2e4 cm^-3; C2: 30 K, 5e4 cm^-3
    Taken from Colzi et al. (2024) and held fixed; directly set the exponential fractionation factor e^ΔE/T and the chemical timescales.
  • cosmic-ray ionization rate ζ = 1.3×10^-15 s^-1
    Fixed at 1.3e-15 s^-1 from prior G+0.693 papers; controls late-time reformation of atomic C and therefore the recovery of φ toward unity.
  • chemical age cut-off = <3×10^4 yr
    Only times ≲3×10^4 yr are retained because later times under-produce HC3N by orders of magnitude; this choice selects the higher φ values that raise the initial ratio to ∼48.
  • source size / beam-filling for C1 = extended
    Assumed extended (no beam dilution); if the true size is ≲25–30″ the main-isotopologue optical depths rise and the double-isotopologue ratios remain the preferred values.
axioms (4)
  • domain assumption LTE level populations for all HC3N and HC5N isotopologues once low-J lines with E_up <5 K are excluded
    Justified by rotational-diagram curvature and consistency of T_ex among thin isotopologues (Sect. 3.1).
  • domain assumption The Sipilä et al. (2023) network with 13C exchange reactions up to C3 fully captures the fractionation inherited by HC3N and HC5N
    Larger precursors (C4H) are not isotopically resolved; authors argue C3 is the last key precursor (Figs. D.1–D.2).
  • domain assumption Visual extinction A_V = 40 mag and dust temperature 20 K are appropriate for the shielded CMZ gas
    Standard CMZ values; UV photochemistry is therefore negligible.
  • ad hoc to paper Arithmetic mean of double-isotopologue ratios (and of HC5N single ratios) is the best estimator of the true 12C/13C
    Adopted after discarding main-isotopologue ratios for C1 because of residual optical-depth bias (Table 2).

pith-pipeline@v1.1.0-grok45 · 38911 in / 3183 out tokens · 42812 ms · 2026-07-11T00:06:13.199330+00:00 · methodology

0 comments
read the original abstract

Isotopic ratios are key tracers of Galactic chemical evolution because different isotopes are synthesized through distinct stellar nucleosynthesis processes. While the $^{12}$C/$^{13}$C ratio increases with galactocentric distance across the Galactic disc, measurements in the Central Molecular Zone (CMZ) have historically yielded low values ($\sim$3-30), often affected by high optical depths. We aim to determine the initial $^{12}$C/$^{13}$C ratio of the parent material of the CMZ molecular cloud G+0.693$-$0.027 using optically thin molecular tracers and correcting for isotopic fractionation. We analyzed an ultra-high-sensitivity spectral survey obtained with the IRAM 30m and Yebes 40m telescopes, detecting single and double $^{13}$C isotopologues of HC$_3$N and HC$_5$N. Column densities and isotopic ratios were derived and compared with astrochemical models including $^{13}$C- and $^{15}$N-isotopologues to quantify isotopic fractionation. We derive $^{12}$C/$^{13}$C ratios of $36.7\pm1.0$ for HC$_3$N (using double $^{13}$C isotopologues) and $38.8\pm1.5$ for HC$_5$N, significantly higher than previous CMZ estimates based on simpler molecules. The models indicate low to intermediate isotopic fractionation at early times ($<3\times10^4$ yr), implying an initial $^{12}$C/$^{13}$C ratio of $\sim$48 for the gas from which present-day CMZ molecular clouds formed. The inferred range (37-48) is consistent with values observed at Galactocentric distances of 3-5 kpc, supporting a scenario in which the CMZ is replenished by gas inflows from the Galactic disc driven by the Galactic bar, with a possible contribution from less chemically processed material accreted from external systems such as dwarf galaxies.

Figures

Figures reproduced from arXiv: 2607.06541 by I. Jim\'enez-Serra, L. Colzi, M. Sanz-Novo, O. Sipil\"a, S. Mart\'in, S. Zeng, V. M. Rivilla.

Figure 1
Figure 1. Figure 1: H13CCCN observed transitions used for the LTE analysis (black histrogram). For each panel, the corresponding transition is indicated in the upper right corner. The green and orange solid lines are the best LTE fit to the C1, and C2 components, respectively. The dark gold line is the sum of the two components. The blue line indicates the total modeled line emission, including also the contribution of all mo… view at source ↗
Figure 2
Figure 2. Figure 2: Same as Fig. 1 but for HC [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 2
Figure 2. Figure 2: Same as Fig. 1 but for HC [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Same as Fig. 2 but for HC [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 3
Figure 3. Figure 3: Same as Fig. 2 but for HC [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Carbon isotopic ratios (12C/13C) measured for different isotopologues of HC3N toward G+0.693 (C1 component) in the Galactic Center. From left to right, the panels show the ratios obtained with HC3N, H13CCCN, HC13CCN, and HCC13CN in the numerator, respectively. Black dashed horizontal lines indicate the canonical Galactic Center value of ∼20. Points with arrows denote lower limits, and scatter points with e… view at source ↗
Figure 4
Figure 4. Figure 4: Carbon isotopic ratios (12C/13C) measured for different isotopologues of HC3N toward G+0.693 (C1 component) in the Galactic Center. From left to right, the panels show the ratios obtained with HC3N, H13CCCN, HC13CCN, and HCC13CN in the numerator, respectively. Black dashed horizontal lines indicate the canonical Galactic Center value of ∼20. Points with arrows denote lower limits, and scatter points with e… view at source ↗
Figure 5
Figure 5. Figure 5: Same as Fig. 4, but for C2. Black dashed horizontal lines indicate the canonical Galactic Center value of [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 5
Figure 5. Figure 5: Same as Fig. 4, but for C2. Black dashed horizontal lines indicate the canonical Galactic Center value of [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: 12C/13C ratios derived from HC5N for the C1 component (left panel) and the C2 component (right panel). In both panels the black dashed horizontal lines indicate the canonical Galactic Center value of ∼20. In the left panel, the light green dashed line and shaded region indicate the average value and its uncertainty derived from HC5N. In the right panel, the dark orange line and shaded region show the avera… view at source ↗
Figure 6
Figure 6. Figure 6: 12C/13C ratios derived from HC5N for the C1 component (left panel) and the C2 component (right panel). In both panels the black dashed horizontal lines indicate the canonical Galactic Center value of ∼20. In the left panel, the light green dashed line and shaded region indicate the average value and its uncertainty derived from HC5N. In the right panel, the dark orange line and shaded region show the avera… view at source ↗
Figure 7
Figure 7. Figure 7: Time evolution of the simulated abundances (relative to H [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 7
Figure 7. Figure 7: Time evolution of the simulated abundances (relative to H [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Predicted isotopic fractionation degree, [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
Figure 8
Figure 8. Figure 8: Predicted isotopic fractionation degree, [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Same as Fig. 8 but for CN, HNC, CO, and HCO [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
Figure 9
Figure 9. Figure 9: Same as Fig. 8 but for CN, HNC, CO, and HCO [PITH_FULL_IMAGE:figures/full_fig_p009_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: 12C/13C ratios measured in the CMZ (left panel) and across the Galactic disc (right panel). In both panels, the purple dashed line indicates the value derived in this work (∼37), while the shaded region represents the range of values obtained when isotopic fractionation effects are taken into account. In the right panel, this line is extended to 4 kpc for comparative purposes. In the left panel, all the s… view at source ↗
Figure 11
Figure 11. Figure 11: 12C/13C ratios measured in external galaxies. The purple dashed line indicates the value derived in this work (∼37), while the shaded region represents the range of values obtained when isotopic fractionation effects are taken into account. Lines without symbols indicate parameter ranges reported in the literature, as opposed to individual measurements shown as symbols. Values are taken from the literatur… view at source ↗

Review history (2 revisions) →

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Chemistry of Dark Molecular Clouds

    astro-ph.GA 2026-07 unverdicted novelty 2.0

    A comprehensive review arguing that the chemically rich cores TMC-1 CP and L1544 are representative molecular-cloud laboratories, and that complex organic molecule production is largely insensitive to metallicity.

Reference graph

Works this paper leans on

139 extracted references · 139 canonical work pages · cited by 1 Pith paper

  1. [1]

    H., Johansson, L

    Aalto, S., Black, J. H., Johansson, L. E. B., & Booth, R. S. 1991b, A&A, 249, 323 Aalto,S.,Booth,R.S.,Black,J.H.,&Johansson,L.E.B.1995,A&A,300,369

    work page 1995

  2. [2]

    2015, A&A, 579, A101

    Aladro, R., Martín, S., Riquelme, D., et al. 2015, A&A, 579, A101

    work page 2015

  3. [3]

    2013, A&A, 549, A39

    Aladro, R., Viti, S., Bayet, E., et al. 2013, A&A, 549, A39

    work page 2013

  4. [4]

    J., Kroto, H

    Alexander, A. J., Kroto, H. W., & Walton, D. R. M. 1976, Journal of Molecular Spectroscopy, 62, 175

    work page 1976

  5. [5]

    P., et al

    Araki, M., Sanz-Novo, M., Endres, C. P., et al. 2026, Nature Astronomy [arXiv:2511.23299]

    work page arXiv 2026

  6. [6]

    & Thielemann, F.-K

    Arcones, A. & Thielemann, F.-K. 2023, A&A Rev., 31, 1 Armijos-Abendaño, J., Banda-Barragán, W. E., Martín-Pintado, J., et al. 2020, MNRAS, 499, 4918

    work page 2023

  7. [7]

    L., Barnes, A., et al

    Battersby, C., Walker, D. L., Barnes, A., et al. 2025, ApJ, 984, 156

    work page 2025

  8. [8]

    Belloche, A., Müller, H. S. P., Garrod, R. T., & Menten, K. M. 2016, A&A, 587, A91

    work page 2016

  9. [9]

    Belloche, A., Müller, H. S. P., Menten, K. M., Schilke, P., & Comito, C. 2013, A&A, 559, A47

    work page 2013

  10. [10]

    2026, A&A, 707, A242

    Berni, L., Palla, M., Magrini, L., & Spina, L. 2026, A&A, 707, A242

    work page 2026

  11. [11]

    V., Werk, J

    Bish, H. V., Werk, J. K., Prochaska, J. X., et al. 2019, ApJ, 882, 76

    work page 2019

  12. [12]

    2004, Journal of Molecular Spectroscopy, 225, 145 Böhm, L

    Bizzocchi, L., Degli Esposti, C., & Botschwina, P. 2004, Journal of Molecular Spectroscopy, 225, 145 Böhm, L. M., Jacob, A. M., Wyrowski, F., et al. 2026, A&A, 705, A80 Boogert,A. C.A., Ehrenfreund,P., Gerakines,P. A.,et al.2000,A&A, 353,349

    work page 2004

  13. [13]

    Boreiko, R. T. & Betz, A. L. 1991, ApJ, 380, L27

    work page 1991

  14. [14]

    B., Milone, A

    Botelho, R. B., Milone, A. d. C., Meléndez, J., et al. 2020, MNRAS, 499, 2196 Brünken, S., Belloche, A., Martín, S., Verheyen, L., & Menten, K. M. 2010, A&A, 516, A109

    work page 2020

  15. [15]

    M., Burbidge, G

    Burbidge, E. M., Burbidge, G. R., Fowler, W. A., & Hoyle, F. 1957, Reviews of Modern Physics, 29, 547

    work page 1957

  16. [16]

    P., et al

    Butterworth, J., Viti, S., Van der Werf, P. P., et al. 2024, A&A, 686, A31

    work page 2024

  17. [17]

    & Ceccarelli, C

    Caselli, P. & Ceccarelli, C. 2012, A&A Rev., 20, 56

    work page 2012

  18. [18]

    2003, ApJ, 586, L133

    Chabrier, G. 2003, ApJ, 586, L133

    work page 2003

  19. [19]

    1991, International Journal of Infrared and Millimeter Waves, 12, 987

    Chen, W., Bocquet, R., Wlodarczak, G., & Boucher, D. 1991, International Journal of Infrared and Millimeter Waves, 12, 987

    work page 1991

  20. [20]

    M., et al

    Chen, Z., Do, T., Ghez, A. M., et al. 2023, ApJ, 944, 79

    work page 2023

  21. [21]

    2008, A&A, 479, L9

    Chiappini, C., Ekström, S., Meynet, G., et al. 2008, A&A, 479, L9

    work page 2008

  22. [22]

    M., et al

    Colzi, L., Fontani, F., Rivilla, V. M., et al. 2018, MNRAS, 478, 3693

    work page 2018

  23. [23]

    2024, A&A, 690, A121

    Colzi, L., Martín-Pintado, J., Zeng, S., et al. 2024, A&A, 690, A121

    work page 2024

  24. [24]

    Colzi, L., Sipilä, O., Roueff, E., Caselli, P., & Fontani, F. 2020, A&A, 640, A51 Creswell,R.A.,Winnewisser,G.,&Gerry,M.C.L.1977,JournalofMolecular Spectroscopy, 65, 420 Danielson,A.L.R.,Swinbank,A.M.,Smail,I.,etal.2013,MNRAS,436,2793 De Marchi, G., Habel, N., Meixner, M., et al. 2025, ApJ, 992, 203 de Zafra, R. L. 1971, ApJ, 170, 165

    work page 2020

  25. [25]

    DeLeon, R. L. & Muenter, J. S. 1985, J. Chem. Phys., 82, 1702

    work page 1985

  26. [26]

    2020, ApJ, 901, L28

    Do, T., David Martinez, G., Kerzendorf, W., et al. 2020, ApJ, 901, L28

    work page 2020

  27. [27]

    M., Vermariën, G., Viti, S., et al

    Dutkowska, K. M., Vermariën, G., Viti, S., et al. 2025, A&A, 703, A46

    work page 2025

  28. [28]

    J., Stark, A

    Encrenaz, P. J., Stark, A. A., Combes, F., & Wilson, R. W. 1979, A&A, 78, L1

    work page 1979

  29. [29]

    P., Schlemmer, S., Schilke, P., Stutzki, J., & Müller, H

    Endres, C. P., Schlemmer, S., Schilke, P., Stutzki, J., & Müller, H. S. P. 2016, Journal of Molecular Spectroscopy, 327, 95

    work page 2016

  30. [30]

    2020, MNRAS, 494, 396

    Feldmeier-Krause, A., Kerzendorf, W., Do, T., et al. 2020, MNRAS, 494, 396

    work page 2020

  31. [31]

    Fomalont, E. B. & Weliachew, L. 1973, ApJ, 181, 781

    work page 1973

  32. [32]

    Friske, J. K. S. & Schönrich, R. 2025, A&A, 701, A140

    work page 2025

  33. [33]

    Gardner, F. F. & Whiteoak, J. B. 1979, MNRAS, 188, 331

    work page 1979

  34. [34]

    Gardner, F. F. & Whiteoak, J. B. 1982, MNRAS, 199, 23P Gerhard,O.2011,MemoriedellaSocietaAstronomicaItalianaSupplementi,18, 185 Giesen,T.F.,Harding,M.E.,Gauss,J.,Grabow,J.-U.,&Müller,H.S.P.2020a, Journal of Molecular Spectroscopy, 371, 111303

    work page 1982

  35. [35]

    2018, ApJ, 853, 171

    Ginsburg, A., Bally, J., Barnes, A., et al. 2018, ApJ, 853, 171

    work page 2018

  36. [36]

    Goldsmith, P. F. & Langer, W. D. 1999, ApJ, 517, 209

    work page 1999

  37. [37]

    Goldsmith, P. F. & Linke, R. A. 1981, ApJ, 245, 482

    work page 1981

  38. [38]

    2015, MNRAS, 450, 2094

    Grieco, V., Matteucci, F., Ryde, N., Schultheis, M., & Uttenthaler, S. 2015, MNRAS, 450, 2094

    work page 2015

  39. [39]

    1985, A&A, 149, 195

    Guesten, R., Henkel, C., & Batrla, W. 1985, A&A, 149, 195

    work page 1985

  40. [40]

    K., Reid, M

    Hachisuka, K., Choi, Y. K., Reid, M. J., et al. 2015, ApJ, 800, 2

    work page 2015

  41. [41]

    T., Woolf, N

    Halfen, D. T., Woolf, N. J., & Ziurys, L. M. 2017, ApJ, 845, 158

    work page 2017

  42. [42]

    H., et al

    Helmi, A., Babusiaux, C., Koppelman, H. H., et al. 2018, Nature, 563, 85

    work page 2018

  43. [43]

    2014, A&A, 565, A3

    Henkel, C., Asiri, H., Ao, Y., et al. 2014, A&A, 565, A3

    work page 2014

  44. [44]

    Henkel, C., Guesten, R., & Gardner, F. F. 1985, A&A, 143, 148

    work page 1985

  45. [45]

    1993, A&A, 268, L17

    Henkel, C., Mauersberger, R., Wiklind, T., et al. 1993, A&A, 268, L17

    work page 1993

  46. [46]

    M., & Wilson, T

    Henkel, C., Walmsley, C. M., & Wilson, T. L. 1980, A&A, 82, 41

    work page 1980

  47. [47]

    L., & Bieging, J

    Henkel, C., Wilson, T. L., & Bieging, J. 1982, A&A, 109, 344

    work page 1982

  48. [48]

    L., Walmsley, C

    Henkel, C., Wilson, T. L., Walmsley, C. M., & Pauls, T. 1983, A&A, 127, 388 Henley,D.B.,Shelton,R.L.,Kwak,K.,Joung,M.R.,&MacLow,M.-M.2010, ApJ, 723, 935 Henshaw,J.D.,Barnes,A.T.,Battersby,C.,etal.2023,inAstronomicalSociety of the Pacific Conference Series, Vol. 534, Protostars and Planets VII, ed. S. Inutsuka, Y. Aikawa, T. Muto, K. Tomida, & M. Tamura, 83

    work page 1983

  49. [49]

    & van Dishoeck, E

    Herbst, E. & van Dishoeck, E. F. 2009, ARA&A, 47, 427

    work page 2009

  50. [50]

    K., Thiel, V., Henkel, C., et al

    Humire, P. K., Thiel, V., Henkel, C., et al. 2020, A&A, 642, A222

    work page 2020

  51. [51]

    A., Gilmore, G., & Irwin, M

    Ibata, R. A., Gilmore, G., & Irwin, M. J. 1994, Nature, 370, 194

    work page 1994

  52. [52]

    M., Menten, K

    Jacob, A. M., Menten, K. M., Wiesemeyer, H., et al. 2020, A&A, 640, A125

    work page 2020

  53. [53]

    2011, MNRAS, 418, 1753 Jiménez-Serra, I., Martín-Pintado, J., Rivilla, V

    Jiang, X., Wang, J., & Gu, Q. 2011, MNRAS, 418, 1753 Jiménez-Serra, I., Martín-Pintado, J., Rivilla, V. M., et al. 2020, Astrobiology, 20, 1048 Jiménez-Serra, I., Rodríguez-Almeida, L. F., Martín-Pintado, J., et al. 2022, A&A, 663, A181 Jiménez-Serra, I., Viti, S., Quénard, D., & Holdship, J. 2018, ApJ, 862, 128

    work page 2011

  54. [54]

    Johansson, L. E. B., Olofsson, H., Hjalmarson, A., Gredel, R., & Black, J. H. 1994, A&A, 291, 89 Jones,P.A.,Burton,M.G.,Cunningham,M.R.,etal.2012,MNRAS,419,2961

    work page 1994

  55. [55]

    Karakas, A. I. & Lattanzio, J. C. 2014, PASA, 31, e030

    work page 2014

  56. [56]

    1998, ApJ, 494, L107 Article number, page 15 A&A proofs:manuscript no

    Keene, J., Schilke, P., Kooi, J., et al. 1998, ApJ, 494, L107 Article number, page 15 A&A proofs:manuscript no. main

    work page 1998

  57. [57]

    1998, PASJ, 50, 309

    Kikumoto, T., Taniguchi, Y., Nakai, N., et al. 1998, PASJ, 50, 309

    work page 1998

  58. [58]

    I., & Lugaro, M

    Kobayashi, C., Karakas, A. I., & Lugaro, M. 2020, ApJ, 900, 179

    work page 2020

  59. [59]

    2022, MNRAS, 510, 1894

    Kovtyukh, V., Lemasle, B., Bono, G., et al. 2022, MNRAS, 510, 1894

    work page 2022

  60. [60]

    V., Andrievsky, S

    Kovtyukh, V. V., Andrievsky, S. M., Martin, R. P., et al. 2019, MNRAS, 489, 2254

    work page 2019

  61. [61]

    A., & Gilmore, G

    Kroupa, P., Tout, C. A., & Gilmore, G. 1993, MNRAS, 262, 545

    work page 1993

  62. [62]

    1990, A&A, 229, 17

    Kruegel, E., Chini, R., & Steppe, H. 1990, A&A, 229, 17

    work page 1990

  63. [63]

    Langer, W. D. & Penzias, A. A. 1990, ApJ, 357, 477

    work page 1990

  64. [64]

    2022, ApJ, 933, 139

    Li, F., Zhang, Z.-Y., Wang, J., et al. 2022, ApJ, 933, 139

    work page 2022

  65. [65]

    2020, MNRAS, 492, 556

    Li, J., Wang, J., Qiao, H., et al. 2020, MNRAS, 492, 556

    work page 2020

  66. [66]

    1990, A&A, 228, 331

    Loiseau, N., Nakai, N., Sofue, Y., et al. 1990, A&A, 228, 331

    work page 1990

  67. [67]

    Loison, J.-C., Wakelam, V., Gratier, P., & Hickson, K. M. 2020, MNRAS, 498, 4663

    work page 2020

  68. [68]

    2024, A&A, 690, A372

    Luo, G., Colzi, L., Liu, T., et al. 2024, A&A, 690, A372

    work page 2024

  69. [69]

    & Mannucci, F

    Maiolino, R. & Mannucci, F. 2019, A&A Rev., 27, 3

    work page 2019

  70. [70]

    R., Skrutskie, M

    Majewski, S. R., Skrutskie, M. F., Weinberg, M. D., & Ostheimer, J. C. 2003, ApJ, 599, 1082

    work page 2003

  71. [71]

    Mallinson, P. D. & de Zafra, R. L. 1978, Molecular Physics, 36, 827 Margulès, L., Belloche, A., Müller, H. S. P., et al. 2016, A&A, 590, A93 Martín,S.,Aladro,R.,Martín-Pintado,J.,&Mauersberger,R.2010,A&A,522, A62 Martín, S., Mangum, J. G., Harada, N., et al. 2021, A&A, 656, A46 Martín,S.,Martín-Pintado,J.,Blanco-Sánchez,C.,etal.2019a,A&A,631,A159 Martín,S...

    work page 1978

  72. [72]

    S., et al

    Matsunaga, N., Taniguchi, D., Elgueta, S. S., et al. 2023, ApJ, 954, 198

    work page 2023

  73. [73]

    2021, A&A Rev., 29, 5

    Matteucci, F. 2021, A&A Rev., 29, 5

    work page 2021

  74. [74]

    & Henkel, C

    Mauersberger, R. & Henkel, C. 1993, Reviews in Modern Astronomy, 6, 69

    work page 1993

  75. [75]

    S., Walter, F., Bolatto, A

    Meier, D. S., Walter, F., Bolatto, A. D., et al. 2015, ApJ, 801, 63

    work page 2015

  76. [76]

    N., Savage, C., Brewster, M

    Milam, S. N., Savage, C., Brewster, M. A., Ziurys, L. M., & Wyckoff, S. 2005, ApJ, 634, 1126

    work page 2005

  77. [77]

    S., Caffau, E., et al

    Molaro, P., Aguado, D. S., Caffau, E., et al. 2023, A&A, 679, A72 Müller, H. S. P., Belloche, A., Menten, K. M., Comito, C., & Schilke, P. 2008, Journal of Molecular Spectroscopy, 251, 319 Müller, H. S. P., Belloche, A., Xu, L.-H., et al. 2016, A&A, 587, A92 Müller, H. S. P., Schlöder, F., Stutzki, J., & Winnewisser, G. 2005, Journal of Molecular Structur...

    work page 2023

  78. [78]

    2006, A&A, 458, 417

    Muller, S., Guélin, M., Dumke, M., Lucas, R., & Combes, F. 2006, A&A, 458, 417

    work page 2006

  79. [79]

    C., Evans, N

    Myeong, G. C., Evans, N. W., Belokurov, V., Sanders, J. L., & Koposov, S. E. 2018, ApJ, 863, L28

    work page 2018

  80. [80]

    F., Hillier, D

    Najarro, F., Figer, D. F., Hillier, D. J., Geballe, T. R., & Kudritzki, R. P. 2009, ApJ, 691, 1816

    work page 2009

Showing first 80 references.