| Issue |
A&A
Volume 686, June 2024
|
|
|---|---|---|
| Article Number | A6 | |
| Number of page(s) | 9 | |
| Section | Galactic structure, stellar clusters and populations | |
| DOI | https://doi.org/10.1051/0004-6361/202449438 | |
| Published online | 24 May 2024 | |
Discovery of an extended horizontal branch in the Large Magellanic Cloud globular cluster NGC 1835⋆
1
Dipartimento di Fisica & Astronomia, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
e-mail: camilla.giusti3@unibo.it
2
INAF – Astrophysics and Space Science Observatory Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
3
Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF, UK
4
Dept. of Astronomy, Indiana University, Bloomington, 47401 IN, USA
Received:
31
January
2024
Accepted:
27
February
2024
We present a high-angular-resolution multi-wavelength study of the massive globular cluster NGC 1835 in the Large Magellanic Cloud. Thanks to a combination of optical and near-ultraviolet images acquired with the WFC3 on board the HST, we performed a detailed inspection of the stellar population in this stellar system, adopting a ‘UV-guided search’ to optimize the detection of relatively hot stars. This allowed us to discover a remarkably extended horizontal branch (HB): it spans more than 4.5 mag in both the optical and the near-ultraviolet bands, and its colour (temperature) ranges from the region redder than the instability strip up to effective temperatures of 30 000 K. This is the first time that such a feature has been detected in an extragalactic cluster, demonstrating that the physical conditions responsible for the formation of extended HBs are ubiquitous. The HB of NGC 1835 includes a remarkably large population of RR Lyrae (67 confirmed variables and 52 new candidates). The acquired dataset was also used to redetermine the cluster distance modulus, reddening, and absolute age: (m − M)0 = 18.58, E(B − V) = 0.08, and t = 12.5 Gyr.
Key words: Hertzsprung–Russell and C–M diagrams / stars: horizontal-branch / globular clusters: general / Magellanic Clouds
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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