J/A+A/707/A86 Omega Cen JWST+HST phot. and proper motions (Ziliotto+, 2026)
A joint JWST and HST view of Omega Centauri:
Multiple stellar populations and their kinematics.
Ziliotto T., Milone A.P., Cordoni G., Marino A.F., Legnardi M.V.,
Dondoglio E., Bortolan E., Muratore F.
<Astron. Astrophys. 707, A86 (2026)>
=2026A&A...707A..86Z 2026A&A...707A..86Z (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, population II ; Photometry, HST ;
Photometry, infrared ; Proper motions
Keywords: globular clusters: general - stars: population II -
stars: abundances - techniques: photometry
Abstract:
We combine F115W and F277W images collected with the Near Infrared
Camera of the James Webb Space Telescope with multiband, multi-epoch
Hubble Space Telescope observations of omega Centauri to investigate
its multiple stellar populations and internal kinematics. Our study
focuses on a region spanning about 0.9 to 2.3 half-light radii from
the cluster center, which is largely unexplored by these telescopes.
Using chromosome maps, we identified the principal populations along
the upper main sequence and among M dwarfs, distinguishing
lower-stream stars chemically akin to first-generation globular
cluster stars with similar metallicities from upper-stream stars
enriched in helium and nitrogen but oxygen poor. Both streams also
host subpopulations with varying metallicities.
We found radially anisotropic motions, with upper-stream stars
exhibiting significantly stronger anisotropy than lower-stream stars.
Subdividing the upper stream into extreme and intermediate
light-element populations revealed a gradient in anisotropy, with
intermediate stars lying between the lower-stream stars and extreme
upper-stream populations. However, metal-rich and metal-poor stars
within each stream show moderate kinematic differences.
The lower-stream stars show a higher angular momentum dispersion
compared to upper-stream stars, and they also exhibit stronger
systemic rotation and proper motion skewness, further highlighting
their kinematic divergence.
Finally, leveraging a mass range of about 0.15 to 0.7 solar masses, we
detected a low degree of energy equipartition for all cluster stars,
which decreases with radial distance from the cluster center.
Description:
Photometry, astrometry, and proper motions for stars in the field
of Omega Centauri.
Chromosome map color indices for lower-MS stars.
Chromosome map color indices for upper-MS stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
photcat.dat 235 114711 Main catalog of photometry and proper motions
chmlowms.dat 57 2199 Chromosome map indices for lower-MS stars
chmupms.dat 57 6152 Chromosome map indices for upper-MS stars
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Byte-by-byte Description of file: photcat.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 mag F277W ?=99.9999 Magnitude in JWST F277W filter
11- 18 F8.6 mag e_F277W ?=9.9999 RMS uncertainty in F277W magnitude
20 I1 --- o_F277W ?=0 Number of measurements in F277W
22- 30 F9.6 mag F115W ?=99.9999 Magnitude in JWST F115W filter
32- 39 F8.6 mag e_F115W ?=9.9999 RMS uncertainty in F115W magnitude
41 I1 --- o_F115W ?=0 Number of measurements in F115W
43- 51 F9.6 mag F814W ?=99.9999 Magnitude in HST F814W filter
53- 60 F8.6 mag e_F814W ?=9.9999 RMS uncertainty in F814W magnitude
62 I1 --- o_F814W ?=0 Number of measurements in F814W
64- 72 F9.6 mag F475W ?=99.9999 Magnitude in HST F475W filter
74- 81 F8.6 mag e_F475W ?=9.9999 RMS uncertainty in F475W magnitude
83 I1 --- o_F475W ?=0 Number of measurements in F475W
85- 93 F9.6 mag F438W ?=99.9999 Magnitude in HST F438W filter
95-102 F8.6 mag e_F438W ?=9.9999 RMS uncertainty in F438W magnitude
104 I1 --- o_F438W ?=0 Number of measurements in F438W
106-114 F9.6 mag F336W ?=99.9999 Magnitude in HST F336W filter
116-123 F8.6 mag e_F336W ?=9.9999 RMS uncertainty in F336W magnitude
125-126 I2 --- o_F336W ?=0 Number of measurements in F336W
128-136 F9.6 mag F275W ?=99.9999 Magnitude in HST F275W filter
138-145 F8.6 mag e_F275W ?=9.9999 RMS uncertainty in F275W magnitude
147-148 I2 --- o_F275W ?=0 Number of measurements in F275W
150-158 F9.6 mag dE(B-V) Differential reddening correction applied
to each star
160-169 F10.6 deg RAdeg Right ascension (ICRS) at Ep=2000
171-180 F10.6 deg DEdeg Declination (ICRS) at Ep=2000
182-191 F10.6 mas/yr pmX ?=-99.999 Proper motion in X direction
193-201 F9.6 mas/yr e_pmX ?=0 Uncertainty in pmx
203-212 F10.6 mas/yr pmY ?=-99.999 Proper motion in Y direction
214-222 F9.6 mas/yr e_pmY ?=0 Uncertainty in pmy
224-225 I2 --- o_pm Number of epochs used for PM
227-235 F9.6 yr TimeBase Time baseline of PM measurement
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Byte-by-byte Description of file: chmlowms.dat chmupms.dat
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Bytes Format Units Label Explanations
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1- 14 F14.10 deg RAdeg Right ascension (ICRS) at Ep=2000
16- 29 F14.10 deg DEdeg Declination (ICRS) at Ep=2000
31- 43 F13.10 mag F475W-F814W Color index F475W-F814W
45- 57 F13.10 mag F115W-F277W Color index F115W-F277W
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Acknowledgements:
From Tuila Ziliotto, tuila.ziliotto(at)noirlab.edu
Based on observations made with the NASA/ESA Hubble Space Telescope and
the James Webb Space Telescope.
(End) Patricia Vannier [CDS] 23-Feb-2026