Hubble Space Telescope survey of Magellanic Cloud star clusters

Photometry and astrometry of 113 clusters and early results^⋆

¹ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Univ. di Padova, Vicolo dell’Osservatorio 3, Padova 35122, Italy
e-mail: antonino.milone@unipd.it
² Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova 35122, Italy
³ Istituto Nazionale di Astrofisica – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, Firenze 50125, Italy
⁴ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, Roma, Italy
⁵ Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218, USA
⁶ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁸ School of Mathematics and Physics, The University of Queensland, St. Lucia, QLD 4072, Australia
⁹ Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Circuito exterior, Ciudad de Mexico 04510, Mexico
¹⁰ Departament de Fisica, EEBE, Universitat Politecnica de Catalunya, Av. Eduard Maristany 16, 08019 Barcelona, Spain
¹¹ School of Mathematical and Physical Sciences, Macquarie University, Balaclava Road, Sydney, NSW 2109, Australia
¹² Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Balaclava Road, Sydney, NSW 2109, Australia
¹³ Department of Astronomy, China West Normal University, 1 ShiDa Road, 637002 Nanchong, PR China
¹⁴ School of Physics and Astronomy, Sun Yat-sen University, Daxue Road, Zhuhai 519082, PR China
¹⁵ Department of Astronomy, Indiana University, Bloomington, IN 47401, USA
¹⁶ Dipartimento di Fisica e Astronomia Augusto Righi, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy

Received: 23 August 2022
Accepted: 13 December 2022

Abstract

In the past few years, we have undertaken an extensive investigation of star clusters and their stellar populations in the Large and Small Magellanic Clouds (LMC and SMC) based on archival images collected with the Hubble Space Telescope. We present photometry and astrometry of stars in 101 fields observed with the Wide Field Channel of the Advanced Camera for Surveys and the Ultraviolet and Visual Channel and the Near-Infrared Channel of Wide Field Camera 3. These fields comprise 113 star clusters. We provide differential-reddening maps for those clusters with significant reddening variations across the field of view. We illustrate various scientific outcomes that arise from the early inspection of the photometric catalogs. In particular, we provide new insights into the extended main-sequence turnoff (eMSTO) phenomenon: (i) We detected eMSTOs in two clusters, KMHK 361 and NGC 265, which had no previous evidence of multiple populations. This finding corroborates the conclusion that the eMSTO is a widespread phenomenon among clusters younger than ∼2 Gyr. (ii) The homogeneous color-magnitude diagrams (CMDs) of 19 LMC clusters reveal that the distribution of stars along the eMSTO depends on cluster age. (iii) We discovered a new feature along the eMSTO of NGC 1783, which consists of a distinct group of stars on the red side of the eMSTO in CMDs composed of UV filters. Furthermore, we derived the proper motions of stars in the fields of view of clusters with multi-epoch images. Proper motions allowed us to separate the bulk of bright field stars from cluster members and investigate the internal kinematics of stellar populations in various LMC and SMC fields. As an example, we analyze the field around NGC 346 to disentangle the motions of its stellar populations, including NGC 364 and BS 90, young and pre-main-sequence stars in the star-forming region associated with NGC 346, and young and old field stellar populations of the SMC. Based on these results and the fields around five additional clusters, we find that young SMC stars exhibit elongated proper-motion distributions that point toward the LMC, thus providing new evidence for a kinematic connection between the LMC and SMC.