J/A+A/700/A74 Metallicity maps of the Magellanic Clouds (Omkumar+ 2025)
Stroemgren photometric metallicity map of the Magellanic Cloud stars using
Gaia DR3-XP spectra.
Omkumar O.A., Cioni L.M.-R., Subramanian S., de Bruijne J., Nair A., Dias B.
<Astron. Astrophys. 700, A74 (2025)>
=2025A&A...700A..74O 2025A&A...700A..74O (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, supergiant ; Photometry, uvby ;
Abundances, [Fe/H] ; Stars, distances
Keywords: galaxies: abundances - galaxies: evolution - Magellanic Clouds
Abstract:
One key to understanding a galaxy's evolution is studying the
consequences of its past dynamical interactions that have influenced
its shape. By measuring the metallicity distribution of stellar
populations with different ages, one can learn about these
interactions. The Magellanic Clouds, being the nearest pair of
interacting dwarf galaxies with a morphology characterised by
different tidal and kinematic sub-structures as well as a vast range
of stellar populations, represent an excellent place to study the
consequences of dwarf-dwarf galaxy interactions and the interactions
with their large host, the Milky Way.
We aim to determine the metallicities ([Fe/H]) of red giant branch
(old) and supergiant (young) stars covering the entire galaxies,
estimate their radial metallicity gradients, and produce homogeneous
metallicity maps.
We used the XP spectra from Gaia Data Release 3 to calculate synthetic
Stroemgren magnitudes from the application of the GaiaXPy tool and
adopted calibration relations from the literature to estimate the
photometric metallicities. Results. We present photometric metallicity
maps for ∼90000 young stars and ∼270000 old stars within ∼11° of
the Small Magellanic Cloud and ∼20° of the Large Magellanic Cloud
from a homogeneous dataset. We find that the overall radial
metallicity gradients decrease linearly, in agreement with previous
studies. Thanks to the large stellar samples, we could apply
piecewise-regression fitting to derive the gradients within different
radial regions. The catalogues containing the estimated photometric
metallicities from this work are made available at the CDS.
The overall metallicity gradients, traced by young and old stars,
decrease from the centre to the outskirts of both galaxies. However,
they show multiple breakpoints, depicting regions following different
and sometimes opposite trends. These are associated with the structure
of the galaxies and their history of star formation and chemical
evolution but may be influenced by a low number of sources, especially
at the centre (due to crowding) and in the outermost regions.
Description:
Photometric metallicities for ∼90000 young stars and ∼270000 old stars
within ∼11° of the Small Magellanic Cloud and ∼20° of the
Large Magellanic Cloud. Metallicities of old (RGB) stars are derived
from the Calamida et al. (2007ApJ...670..400C 2007ApJ...670..400C) calibration and the
metallicities of the young (supergiant) stars are derived from the
Grebel & Richtler 1992 (1992A&A...253..359H 1992A&A...253..359H) calibration. Estimated
photometric metallicities are recalibrated based on spectroscopic
metallicities from APOGEE-DR17, with associated uncertainties.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lmc-rgb.dat 133 214424 Photometric metallicities for LMC RGB stars
lmc-sgb.dat 133 69020 Photometric metallicities for LMC supergiant stars
smc-rgb.dat 133 57488 Photometric metallicities for SMC RGB stars
smc-sgb.dat 133 20670 Photometric metallicities for SMC supergiant stars
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: [ls]mc-[rs]gb.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Unique source ID from Gaia DR3
21- 35 F15.11 deg RAdeg Right Ascension (ICRS) at Ep=2016.0
37- 51 F15.11 deg DEdeg Declination (ICRS) at Ep=2016.0
53- 59 F7.4 mag vmag Standardised Stroemgren magnitude in v band
61- 67 F7.4 mag bmag Standardised Stroemgren magnitude in b band
69- 75 F7.4 mag ymag Standardised Stroemgren magnitude in y band
77- 86 F10.7 deg Dist-deg Radius from the centre of the LMC in degrees
88- 97 F10.7 kpc Dist-kpc Radius from the centre of the LMC in kpc
99-106 F8.6 mag E(B-V) Reddening values (1)
108-116 F9.7 mag AV Extinction in v band
118-125 F8.5 [-] [Fe/H] Recalibrated photometric metallicity
127-133 F7.5 [-] e_[Fe/H] Recalibrated photometric metallicity
uncertainty ([Fe/H]_err)
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Note (1): Reddening values provided by Skowron et al. (2021ApJS..252...23S 2021ApJS..252...23S,
Cat. J/ApJS/252/23) & Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
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Acknowledgements:
Abinaya O. Omkumar, aomkumar(at)aip.de
(End) Patricia Vannier [CDS] 31-Jul-2025