TY - JOUR
T1 - Central rotations of Milky Way globular clusters
AU - Fabricius, Maximilian H.
AU - Noyola, Eva
AU - Rukdee, Surangkhana
AU - Saglia, Roberto P.
AU - Bender, Ralf
AU - Hopp, Ulrich
AU - Thomas, Jens
AU - Opitsch, Michael
AU - Williams, Michael J.
PY - 2014/6/1
Y1 - 2014/6/1
N2 - Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements.
AB - Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements.
KW - general -stars
KW - globular clusters
KW - imaging spectroscopy
KW - kinematics and dynamics - techniques
UR - http://www.scopus.com/inward/record.url?scp=84901364470&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/787/2/L26
DO - 10.1088/2041-8205/787/2/L26
M3 - Article
AN - SCOPUS:84901364470
SN - 2041-8205
VL - 787
SP - 1
EP - 6
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L26
ER -