The ESO-VLT MIKiS survey reloaded: velocity dispersion profile and rotation curve of NGC 1904

Silvia Leanza*, Cristina Pallanca, Francesco R. Ferraro, Barbara Lanzoni, Emanuele Dalessandro, Livia Origlia, Alessio Mucciarelli, Elena Valenti, Maria Tiongco, Anna Lisa Varri, Enrico Vesperini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We present an investigation of the internal kinematic properties of M79 (NGC 1904). Our study is based on radial velocity measurements obtained from the ESO-VLT Multi-Instrument Kinematic Survey (MIKiS) of Galactic globular clusters for more than 1700 individual stars distributed between ∼ 0.3′′ and 770′′ (∼ 14 three-dimensional half-mass radii), from the center. Our analysis reveals the presence of ordered line-of-sight rotation with a rotation axis almost aligned along the East-West direction and a velocity peak of 1.5 km s−1 at ∼ 70′′ from the rotation axis. The velocity dispersion profile is well described by the same King model that best fits the projected density distribution, with a constant central plateau at σ0 ∼ 6 km s−1. To investigate the cluster rotation in the plane
of the sky, we have analyzed the proper motions provided by the Gaia EDR3, finding a signature of rotation with a maximum amplitude of ∼ 2.0 km s−1 at ∼ 80′′ from the cluster center. Analyzing the three-dimensional velocity distribution, for a sub-sample of 130 stars, we confirm the presence of
systemic rotation and find a rotation axis inclination angle of 37◦ with respect to the line-of-sight. As a final result, the comparison of the observed rotation curves with the results of a representative N-body simulation of a rotating star cluster shows that the present-day kinematic properties of NGC 1904 are consistent with those of a dynamically old system that has lost a significant fraction of its initial angular momentum.
Original languageEnglish
Article number186
Pages (from-to)1-21
Number of pages21
JournalAstrophysical Journal
Volume929
Issue number2
DOIs
Publication statusPublished - 27 Apr 2022

Keywords

  • astro-ph.GA
  • astro-ph.SR

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