J/A+A/703/A199 M3DIS. II. CEMP abundances (Eitner+, 2025)
M3DIS - A grid of 3D radiation-hydrodynamics stellar atmosphere models for
stellar surveys. II. Carbon-enhanced metal-poor stars.
Eitner P., Bergemann M., Hoppe R., Storm N., Lipatova V., Glover S.C.O.,
Klessen R.S., Nordlund A., Popovas A.
<Astron. Astrophys. 703, A199 (2025)>
=2025A&A...703A.199E 2025A&A...703A.199E (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Abundances ; Stars, metal-deficient
Keywords: hydrodynamics - radiative transfer - stars: abundances -
stars: atmospheres - Galaxy: evolution - Galaxy: halo
Abstract:
Understanding the origin and evolution of carbon-enhanced metal-poor
(CEMP) stars is key to tracing the early chemical enrichment of the
Galaxy. In this work, we investigate how physically realistic 3D
radiation-hydrodynamics (RHD), carbon-enhanced model atmospheres
affect the inferred carbon abundances in CEMP stars, and assess the
implications for their classification and for the Galactic chemical
evolution (GCE). We pay particular attention to the systematic biases
introduced by traditional 1D hydrostatic equilibrium (HE) models.
We use the M3DIS code to compute 3D RHD model atmospheres for
main-sequence and sub-giant stars spanning a wide range of
metallicities and carbon enhancements. Synthetic spectra of the CH
G-band are calculated using full 3D radiative transfer, and compared
to spectra from classical 1D HE MARCS models. We derive abundance
corrections and apply them to a large literature sample of metal-poor
stars from the SAGA database to quantify systematic effects on the
carbon abundance distribution and CEMP classification.
Our new 3D CEMP models predict significantly cooler upper atmospheric
layers than present in 1D HE models, resulting in stronger CH
absorption and lower inferred carbon abundances by up to -0.9dex at
the lowest metallicities. Carbon enhancement in the atmosphere itself
increases molecular opacities and leads to radiative re-heating, which
partly offsets the adiabatic cooling in 3D models and reduces the
magnitude of 3D-1D abundance corrections. Applying these corrections
lowers the CEMP fraction by up to 20% below [Fe/H]=-3, and furthermore
alters the relative contribution of CEMP sub-classes. In particular,
the fraction of CEMP-no stars increases while the number of stars
classified as CEMP-r/s decreases, owing to the downward revision of
absolute carbon abundances. These changes bring the Galactic carbon
abundance distribution into better agreement with GCE models that
assume a contribution from faint supernovae of 20%. Physically
realistic model atmospheres are thus essential for reliable
reconstruction of the early chemical enrichment history of the Galaxy.
Description:
Selected stars from the SAGA database. For each star, [C/Fe]
abundances from the dataset are corrected for 3D effects using 3D RHD
M3DIS models. See paper. Object ID, references, stellar parameters,
and 1D [C/Fe] abundances are obtained using the online tool available
at http://sagadatabase.jp/Retrieval/db.cgi.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
abund.dat 89 1745 Carbon abundances of selected targets from the SAGA
database, 3D corrected using 3D RHD M3DIS models
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Byte-by-byte Description of file: abund.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Object Object ID
27- 61 A35 --- Refs List of references
63- 66 I4 K Teff [4000/7949] Effective temperature
68- 71 F4.2 [cm/s2] logg [2.7/5.1] Log10 surface gravity
73- 77 F5.2 --- [Fe/H] Mettalicity, [Fe/H]
79- 83 F5.2 --- [C/Fe]1D Abundance [C/Fe] (1D)
85- 89 F5.2 --- [C/Fe]3D Abundance [C/Fe] (3D corrected)
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Acknowledgements:
Philipp Eitner, eitner(at)mpia.de, Maria Bergemann, bergemann(at)mpia.de
References:
Eitner et al., Paper I 2024A&A...688A..52E 2024A&A...688A..52E
(End) Patricia Vannier [CDS] 29-Sep-2025