TheGaia-ESO Survey: Kinematics of seven Galactic globular clusters

Abstract

The Gaia-ESO survey is a large public spectroscopic survey aimed at investigating the origin and formation history of our Galaxy by collecting spectroscopy of representative samples (about 10 5 Milky Way stars) of all Galactic stellar populations, in the field and in clusters. The survey uses globular clusters as intra-and inter-survey calibrators, deriving stellar atmospheric parameters and abundances of a significant number of stars in clusters, along with radial velocity determinations. We used precise radial velocities of a large number of stars in seven globular clusters (NGC 1851, NGC 2808, NGC 4372, NGC 4833, NGC 5927, NGC 6752, and NGC 7078) to validate pipeline results and to preliminarily investigate the cluster internal kinematics. Radial velocity measurements were extracted from FLAMES/GIRAFFE spectra processed by the survey pipeline as part of the second internal data release of data products to ESO. We complemented our sample with ESO archival data obtained with different instrument configurations. Reliable radial velocity measurements for 1513 bona fide cluster star members were obtained in total. We measured systemic rotation, estimated central velocity dispersions, and present velocity dispersion profiles of all the selected clusters, providing the first velocity dispersion curve and the first estimate of the central velocity dispersion for the cluster NGC 5927. Finally, we explore the possible link between cluster kinematics and other physical parameters. The analysis we present here demonstrates that Gaia-ESO survey data are sufficiently accurate to be used in studies of kinematics of stellar systems and stellar populations in the Milky Way.

TheGaia-ESO Survey: Detailed abundances in the metal-poor globular cluster NGC 4372

“…They find a mean radial velocity of v r = 75.9 ± 0.3 km s −1 and a central velocity dispersion of σ 0 = 4.5 ± 0.3 km s −1 . As part of the Gaia-ESO survey, the kinematics of seven GGCs is present in Lardo et al (2015). Using FLAMES/GIRAFFE they analyzed spectra of more than 100 stars and obtained a mean radial velocity of v r = 75.2 ± 0.4 km s −1 with a velocity dispersion of 3.9 km s −1 , confirming the membership of our objects.…”

A Chemical Composition Survey of the Iron-complex Globular Cluster NGC 6273 (M19)*

“…and±30°for PAo. Compared to the large globular cluster samples presented in Bellazzini et al (2012), Kimmig et al (2015), and Lardo et al (2015), NGC 6273 exhibits relatively strong rotation. NGC 6273ʼs large A rot.…”

“…Additional velocity measurements inside ∼0 2-0 5 and the application of more sophisticated models are likely to find a true σ o >12 kms 1 . We estimate that the cluster's true Arot./σ o ratio is ∼0.30-0.35, which is typical for massive elliptical metal-poor globular clusters (e.g., see Bellazzini et al 2012;Kacharov et al 2014;Kimmig et al 2015;Lardo et al 2015).…”

“…Many globular clusters have been shown to rotate with amplitudes of the order of a few kms 1 (e.g., Côté et al 1995;Lane et al 2009Lane et al , 2010aBellazzini et al 2012;Bianchini et al 2013;Kacharov et al 2014;Kimmig et al 2015;Lardo et al 2015). In Figure 4, we investigated net rotation in NGC 6273 by following a standard technique in which the average radial velocity is calculated for stars on either side of an imaginary line passing through the cluster center.…”

The Strong Rotation of M5 (NGC 5904) as Seen from the MIKiS Survey of Galactic Globular Clusters

“…Indeed, deviations from the sharply truncated King phase space distribution (e.g., see the cases of NGC 1851, as studied by Olszewski et al 2009;Marino et al 2014, NGC 5694 by Correnti et al 2011;Bellazzini et al 2015, and several others, as discussed, e.g., by Carballo-Bello et al 2018), spherical symmetry (e.g., Chen & Chen 2010), and pressure isotropy (e.g., van de Ven et al 2006;Bellini et al 2014Bellini et al , 2017Watkins et al 2015) are found in a growing number of GGCs. Also the observational evidence of systemic rotation is increasing (e.g., Anderson & King 2003;Lane et al 2009Lane et al , 2010Bellazzini et al 2012;Bianchini et al 2013;Fabricius et al 2014;Kacharov et al 2014;Kimmig et al 2015;Lardo et al 2015;Bellini et al 2017;Boberg et al 2017;Cordero et al 2017;Ferraro et al 2018b;Kamann et al 2018), possibly suggesting that, when properly surveyed, the majority of GCs rotate at some level. In particular, Ferraro et al (2018b) investigated the intermediate/external region of 11 clusters, demonstrating the presence of internal rotation in almost all of them.…”