Pith Number

pith:UE4XU3CW

pith:2026:UE4XU3CWOE64I23GH2IDPRQ4SD

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The ${}^{13}\mathrm{CO}(2{-}1)/^{12}\mathrm{CO}(2{-}1)$ Line Ratio from 100 Molecular Clouds in the Large Magellanic Cloud

Adam Leroy, Dia Kalra, Erik Rosolowsky, Remy Indebetouw

Molecular clouds in the Large Magellanic Cloud show a median 13CO/12CO line ratio of 0.078 that rises with active star formation.

arxiv:2605.17024 v1 · 2026-05-16 · astro-ph.GA

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Claims

C1strongest claim

We measure a median line ratio of 13CO(2-1)/12CO(2-1) = 0.078 with 68% of the sample falling between 0.058 and 0.107. A regression analysis confirms a nearly linear relationship across two orders of magnitude in line luminosity. Moreover, we find that the inclusion of (L_FIR) from Young Stellar Objects as a predictor variable of the line ratio significantly improves the quality of the fit, with clouds hosting IR-bright YSOs having relatively brighter 13CO emission. This analysis indicates that active star forming molecular clouds have different internal conditions than more quiescent clouds.

C2weakest assumption

The regression analysis treats FIR luminosity from identified YSOs as an independent predictor of the line ratio without significant contamination from other variables such as cloud mass, metallicity gradients, or observational selection effects; this premise is invoked in the abstract when stating that inclusion of L_FIR significantly improves the fit.

C3one line summary

Observational study of 100 LMC GMCs finds median 13CO(2-1)/12CO(2-1) line ratio of 0.078, nearly linear with luminosity, and higher in clouds hosting IR-bright young stellar objects.

References

239 extracted · 239 resolved · 133 Pith anchors

[1] K., Hughes, A., Liu, D., et al · doi:10.3847/1538-4365/abec80

[2] Little Things · doi:10.1088/0004-6256/144/5/134

[3] THINGS: The HI Nearby Galaxy Survey · doi:10.1088/0004-6256/136/6/2563

[4] A Molecular Star Formation Law in the Atomic Gas Dominated Regime in Nearby Galaxies · doi:10.1088/0004-6256/142/2/37

[5] 2024, A&A, 691, A163, doi: 10.1051/0004-6361/202449944 · doi:10.1051/0004-6361/202449944

Receipt and verification

First computed	2026-05-20T00:03:36.491796Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

a1397a6c56713dc46b663e9037c61c90eb747749a0d5afa8277a8ccb3f6cd344

Aliases

arxiv: 2605.17024 · arxiv_version: 2605.17024v1 · doi: 10.48550/arxiv.2605.17024 · pith_short_12: UE4XU3CWOE64 · pith_short_16: UE4XU3CWOE64I23G · pith_short_8: UE4XU3CW

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Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/UE4XU3CWOE64I23GH2IDPRQ4SD \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: a1397a6c56713dc46b663e9037c61c90eb747749a0d5afa8277a8ccb3f6cd344

Canonical record JSON

{
  "metadata": {
    "abstract_canon_sha256": "b13aa794603e0f9c4255a1b22979738b673a9fbfddd836d320c612d53a2b6e4f",
    "cross_cats_sorted": [],
    "license": "http://creativecommons.org/licenses/by-nc-sa/4.0/",
    "primary_cat": "astro-ph.GA",
    "submitted_at": "2026-05-16T14:53:41Z",
    "title_canon_sha256": "06b2390aa92043f0b02972a772662af5e62578cc1632d1691401082ee22acc2f"
  },
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  "source": {
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    "kind": "arxiv",
    "version": 1
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}