- ID:
- ivo://CDS.VizieR/J/ApJ/710/1032
- Title:
- Proper motions in {omega} Cen
- Short Name:
- J/ApJ/710/1032
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze data from the Hubble Space Telescope's (HST) Advanced Camera for Surveys of the globular cluster (GC) Omega Cen. We construct a photometric catalog of 1.2x10^6^ stars over a 10'x10' central field down to below B_F435W_=25 (M~0.35M_{sun}_). The 2.5 to 4 year baseline between observations yields a catalog of some 10^5^ proper motions over a smaller area, with 53382 "high-quality" measurements in a central R<~2' field. Artificial-star tests characterize the photometric incompleteness. We determine the cluster center to ~1" accuracy from star counts using two different methods, one based on isodensity contours and the other on "pie slices." We independently confirm the result by determining also the kinematical center of the HST proper motions, as well as the center of unresolved light seen in Two Micron All Sky Survey data. All results agree to within their 1"-2" levels of uncertainty. The proper-motion dispersion of the cluster increases gradually inward, but there is no variation in kinematics with position within the central ~15": there is no dispersion cusp and no stars with unusually high velocities. We measure for the first time in any GC the variation in internal kinematics along the main sequence.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/360/472
- Title:
- Proper motions in omega Centauri
- Short Name:
- J/A+A/360/472
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables present the photometric and astrometric results of an extensive proper motion study of the globular cluster omega Centauri: information on the photographic plates used, variability analysis, astrometric data for 9847 stars, membership determination and surface density profile, cluster proper motion dispersions and systematics and cross-references with star-numbers used by Norris et al. (1997ApJ...487L.187N) and Lynga (1996A&AS..115..297L).
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/3401
- Title:
- Proper motions of blue stragglers in 38 GC
- Short Name:
- J/MNRAS/462/3401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new blue straggler star (BSS) catalogues in 38 Milky Way globular clusters (GCs) based on multipassband and multi-epoch treasury survey data from the Hubble Space Telescope. We measure precise astrometry and relative proper motions of stars in all target clusters and performed a subsequent cluster membership selection. We study the accuracy of our proper-motion measurements using estimates of central velocity dispersions and find very good agreement with previous studies in the literature. Finally, we present a homogeneous BSS selection method, that expands the classic BSS selection parameter space to more evolved BSS evolutionary stages. We apply this method to the proper-motion cleaned GC star catalogues in order to define proper-motion cleaned BSS catalogues in all 38 GCs, which we make publicly available to enable further study and follow-up observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/2832
- Title:
- Proper motions of Milky Way globular clusters
- Short Name:
- J/MNRAS/484/2832
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Gaia Data Release 2 to determine the mean proper motions for 150 Milky Way globular clusters (almost the entire known population), with a typical uncertainty of 0.05mas/yr limited mainly by systematic errors. Combining them with distance and line-of-sight velocity measurements from the literature, we analyse the distribution of globular clusters in the 6D phase space, using both position/velocity and action/angle coordinates. The population of clusters in the central 10kpc has a mean rotational velocity reaching 50-80km/s, and a nearly isotropic velocity dispersion 100-120km/s, while in the outer galaxy, the cluster orbits are strongly radially anisotropic. We confirm a concentration of clusters at high radial action in the outer region of the Galaxy. Finally, we explore a range of equilibrium distribution function-based models for the entire globular cluster system, and the information they provide about the potential of the Milky Way. The dynamics of clusters is best described by models with the circular velocity between 10 and 50kpc staying in the range 210-240km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/420/612
- Title:
- Proper motions & radial velocities in M22
- Short Name:
- J/ApJ/420/612
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distance to the globular cluster M22 is reexamined from new radial-velocity data and revised proper motions. Proper motions are rederived for 672 stars in the field of M22 using plate constant solutions from which stars of large proper motions have been removed, to reduce systematic errors which depend on coordinates. Radial velocities good to 1km/s have been obtained for 130 members of the globular cluster M22. The mean radial velocity is -148.8+/-0.8km/s. The radial velocity dispersion is 6.6+/-0.8km/s in the mean, and shows little if any dependence on distance from the cluster center over a 3'-7' annulus. Ignoring the small effect of rotation, a mass-to-light ratio M/L_V=0.85+/-0.15 in solar units is derived. The lack of stars moving faster than the escape velocity suggests strongly that a value M/L_V~1 applies to the cluster as a whole. This value is among the lowest observed for any globular cluster. Rotation is evident in both proper motions and radial velocities, and its position angle is in reasonable agreement with the major axis of the cluster's elongation. Its amplitude diminishes with radius, from ~6km/s for 1'<=r<= 3', to ~3km/s for 3'<=r<=7'. Rotation must be carefully modeled to determine an accurate distance to the cluster. From the simple approximation that the velocity dispersion is unaffected in the directions perpendicular to the streaming motion, a comparison of the dispersions in proper motion with those in radial velocity leads to a preliminary estimate for the distance of 2.6+/-0.3kpc, and a horizontal-branch magnitude M_V=0.71+/-0.27, using the reddening value E(B-V)=0.42 from M22 BHB stars.
- ID:
- ivo://CDS.VizieR/J/A+AS/104/161
- Title:
- Proper motion study of M 3
- Short Name:
- J/A+AS/104/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/3711
- Title:
- Proper motion study of M55 stars
- Short Name:
- J/MNRAS/414/3711
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived the absolute proper motion (PM) of the globular cluster M55 using a large set of CCD images collected with the du Pont telescope between 1997 and 2008. We find (pmRAcosDE, pmDE)=(-3.31+/-0.10, -9.14+/-0.15)mas/yr relative to background galaxies. Membership status was determined for 16945 stars with 14<V<21 from the central part of the cluster.
- ID:
- ivo://CDS.VizieR/VII/271
- Title:
- Properties of Galactic Globular Clusters
- Short Name:
- VII/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled 560 recent measurements from the literature of distances of Galactic globular clusters and found revised distance estimates for 154 of the 157 clusters in the McMaster catalogue [Harris, 2010 edition, Cat. VII/202]. We find a trough in the X-distribution at the Galactic centre, and symmetries corresponding to the structure of the bar. These features indicate a distance, R_0_=7.4+/-0.2(stat)+/-0.2(sys)kpc, only a little higher than Bica et al.'s (2006, Cat. J/A+A/450/105) estimate.
- ID:
- ivo://CDS.VizieR/J/A+A/450/105
- Title:
- Properties of 153 Galactic globular clusters
- Short Name:
- J/A+A/450/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Updated data of the 153 Galactic globular clusters are used to readdress fundamental parameters of the Milky Way, such as the distance of the Sun to the Galactic centre, the bulge and halo structural parameters, and cluster destruction rates. We build a reduced sample that has been decontaminated of all the clusters younger than 10Gyrs and of those with retrograde orbits and/or evidence of relation to dwarf galaxies. The reduced sample contains 116 globular clusters that are tested for whether they were formed in the primordial collapse.
- ID:
- ivo://CDS.VizieR/J/AJ/155/183
- Title:
- Properties of variables in the NGC 1846 field
- Short Name:
- J/AJ/155/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of {delta} Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single {delta} Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of {delta} Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its {delta} Sct population.
