Discovery of an extended horizontal branch in the Large Magellanic Cloud globular cluster NGC 1835

Giusti, C, Cadelano, M, Ferraro, FR, Lanzoni, B, Pallanca, C, Salaris, M, Dalessandro, E, Vesperini, E and Mucciarelli, A (2024) Discovery of an extended horizontal branch in the Large Magellanic Cloud globular cluster NGC 1835. Astronomy and Astrophysics, 686. pp. 1-9. ISSN 0004-6361

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Abstract

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.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Date of acceptance:	27 February 2024
Date of first compliant Open Access:	10 June 2024
Date Deposited:	10 Jun 2024 12:20
Last Modified:	10 Jun 2024 12:30
DOI or ID number:	10.1051/0004-6361/202449438
URI:	https://ljmu-9.eprints-hosting.org/id/eprint/23470

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