JWST imaging of omega Centauri: II. Evidence of a split white dwarf cooling sequence in the near-infrared

Scalco, M ORCID: 0000-0001-8834-3734, Salaris, M ORCID: 0000-0002-2744-1928, Bedin, LR ORCID: 0000-0003-4080-6466, Blouin, S, Vesperini, E, Bergeron, P, Libralato, M, Griggio, M ORCID: 0000-0002-5060-1379, Burgasser, A, Nardiello, D ORCID: 0000-0003-1149-3659, Bellini, A, Anderson, J, Gerasimov, R ORCID: 0000-0003-0398-639X and Apai, D (2025) JWST imaging of omega Centauri: II. Evidence of a split white dwarf cooling sequence in the near-infrared. Astronomy & Astrophysics, 703. ISSN 0004-6361

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Abstract

We present a detailed analysis of the white dwarf (WD) cooling sequence (CS) in omega Centauri based on combined Hubble Space Telescope (HST) and JWST observations. Our analysis confirms the previously reported split-based on HST observations in ultraviolet filters-in the upper part of the WD CS, which is consistent with the presence of two distinct WD populations. We extend its study to a significantly fainter and cooler limit (down to ∼ 8000 K), which corresponds to cooling ages of about 1 Gyr. We used artificial star tests and cooling models to confirm that the split is evidence of two WD populations with different masses and progenitors: one sequence of 'canonical WDs produced by the He-normal progenitors and one sequence of low-mass WDs that originated from the cluster He-rich component. We show that the fraction of WDs from the He-rich component in the outer regions is smaller than that found in the innermost regions. We also studied the kinematics of WDs and show that in the outer regions, the velocity distribution of WDs from He-rich progenitors is slightly radially anisotropic, while that of canonical WDs is slightly tangentially anisotropic. Both the radial variation in the fraction of WDs from the He-rich population and the difference between their velocity distribution and that of canonical WDs are consistent with spatial and kinematic differences previously found for He-rich and He-normal main-sequence stars and are in general agreement with models that predict that He-rich stars form more centrally concentrated than He-normal stars.

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 5101 Astronomical Sciences; 51 Physical Sciences; 5109 Space Sciences; 5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Date of acceptance:	9 October 2025
Date of first compliant Open Access:	22 January 2026
Date Deposited:	22 Jan 2026 11:50
Last Modified:	22 Jan 2026 11:50
DOI or ID number:	10.1051/0004-6361/202557087
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27951

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