HST proper motions on the far side of the Galactic bar-data
Abstract
This is the third paper in a series that attempts to observe a clear signature of the Galactic bar/bulge using kinematic observations of the bulge stellar populations in low foreground extinction windows. We report on the detection of ~100 000 new proper motions in four fields covering the far side of the Galactic bar/bulge, at negative longitudes. Our proper motions have been obtained using observations from the Advance Camera for Surveys (ACS), on board of the Hubble Space Telescope (HST), with a time-baseline of 8-9 years, which has produced accuracies better than 0.5 mas yr-1 for a significant fraction of the stellar populations with F814W < 23 mag. Interestingly, as shown in previous works, the Hess diagrams show a strikingly similar proper motion distribution to fields closer to the Galactic center and consistent with an old stellar population. The observed kinematics point to a significant bulge rotation, which seems to predominate even in fields as far as l ≃ -8°, and is also reflected in the changes of the velocity ellipsoid in the l, b plane as a function of distance.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2023
- DOI:
- 10.1093/mnras/stad1911
- Bibcode:
- 2023MNRAS.524..224S
- Keywords:
-
- methods: data analysis;
- Galaxy: bulge;
- Galaxy: kinematics and dynamics;
- Galaxy: stellar content