First Phase Space Portrait of a Hierarchical Stellar Structure in the Milky Way

Dalessandro, E, Varri, AL, Tiongco, M, Vesperini, E, Fanelli, C, Mucciarelli, A, Origlia, L, Bellazzini, M, Saracino, S, Oliva, E, Sanna, N, Fabrizio, M and Livernois, A (2021) First Phase Space Portrait of a Hierarchical Stellar Structure in the Milky Way. Astrophysical Journal, 909 (1). ISSN 0004-637X

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Abstract

We present the first detailed observational picture of a possible ongoing massive cluster hierarchical assembly in the Galactic disk as revealed by the analysis of the stellar full phase space (3D positions and kinematics and spectro-photometric properties) of an extended area (6° diameter) surrounding the well-known h and χ Persei double stellar cluster in the Perseus Arm. Gaia-EDR3 shows that the area is populated by seven comoving clusters, three of which were previously unknown, and by an extended and quite massive (M ∼ 105 M⊙) halo. All stars and clusters define a complex structure with evidence of possible mutual interactions in the form of intra-cluster overdensities and/or bridges. They share the same chemical abundances (half-solar metallicity) and age (t ∼ 20 Myr) within a small confidence interval and the stellar density distribution of the surrounding diffuse stellar halo resembles that of a cluster-like stellar system. The combination of these pieces of evidence suggests that stars distributed within a few degrees from h and χ Persei are part of a common, substructured stellar complex that we named LISCA I. Comparison with results obtained through direct N-body simulations suggest that LISCA I may be at an intermediate stage of an ongoing cluster assembly that can eventually evolve in a relatively massive (a few times 105 M⊙) stellar system. We argue that such a cluster formation mechanism may be quite efficient in the Milky Way and disk-like galaxies and, as a consequence, it has a relevant impact on our understanding of cluster formation efficiency as a function of the environment and redshift.

Item Type:	Article
Uncontrolled Keywords:	Astrometry; Astronomy & Astrophysics; Dynamical evolution; Photometry; Physical Sciences; Science & Technology; Star clusters; Science & Technology; Physical Sciences; Astronomy & Astrophysics; Star clusters; Dynamical evolution; Photometry; Astrometry; Astronomy & Astrophysics; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural)
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society; IOP Publishing
Date of acceptance:	7 January 2021
Date of first compliant Open Access:	17 October 2022
Date Deposited:	17 Oct 2022 09:52
Last Modified:	17 Oct 2022 10:15
DOI or ID number:	10.3847/1538-4357/abda43
URI:	https://researchonline.ljmu.ac.uk/id/eprint/17846

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