SECOND-GENERATION STELLAR DISKS IN DENSE STAR CLUSTERS AND CLUSTER ELLIPTICITIES

Journal Article · Fri May 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/823/1/61· OSTI ID:22663026

Mastrobuono-Battisti, Alessandra; Perets, Hagai B. ^[1]

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1. Physics Department, Technion—Israel Institute of Technology, Haifa, Israel 32000 (Israel)

Globular clusters (GCs) and nuclear star clusters (NSCs) are typically composed of several stellar populations, characterized by different chemical compositions. Different populations show different ages in NSCs, but not necessarily in GCs. The youngest populations in NSCs appear to reside in disk-like structures as observed in our Galaxy and in M31. Gas infall followed by formation of second-generation (SG) stars in GCs may similarly form disk-like structures in the clusters nuclei. Here we explore this possibility and follow the long-term evolution of stellar disks embedded in GCs, and study their effects on the evolution of the clusters. We study disks with different masses by means of detailed N-body simulations and explore their morphological and kinematic signatures on the GC structures. We find that as a SG disk relaxes, the old, first-generation stellar population flattens and becomes more radially anisotropic, making the GC structure become more elliptical. The SG stellar population is characterized by a lower velocity dispersion and a higher rotational velocity compared with the primordial older population. The strength of these kinematic signatures depends both on the relaxation time of the system and on the fractional mass of the SG disk. We therefore conclude that SG populations formed in flattened configurations will give rise to two systematic trends: (1) a positive correlation between GC ellipticity and fraction of SG population and (2) a positive correlation between GC relaxation time and ellipticity. Therefore, GC ellipticities and rotation could be related to the formation of SG stars and their initial configuration.

• OSTI ID: 22663026
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 823; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
COMPARATIVE EVALUATIONS
CORRELATIONS
DISPERSIONS
GALAXIES
GALAXY CLUSTERS
GALAXY NUCLEI
MASS
RELAXATION TIME
ROTATION
SIMULATION
STAR CLUSTERS
STARS
VELOCITY