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Start Over Subject proper motions Content Level Research
251. HSTPROMO cat. VI. Improved analysis of NGC362
ID:
ivo://CDS.VizieR/J/ApJ/861/99
Title:
HSTPROMO cat. VI. Improved analysis of NGC362
Short Name:
J/ApJ/861/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an improved data-reduction technique to obtain high-precision proper motions (PMs) of globular clusters (GCs) using Hubble Space Telescope data. The new reduction is superior to the one presented in the first paper of this series for the faintest sources in very crowded fields. We choose the GC NGC 362 as a benchmark to test our new procedures. We measure PMs of 117450 sources in the field, showing that we are able to obtain a PM precision better than 10{mu}as/yr for bright stars. We make use of this new PM catalog of NGC 362 to study the cluster's internal kinematics. We investigate the velocity dispersion profiles of the multiple stellar populations hosted by NGC 362 and find new pieces of information on the kinematics of first- and second- generation stars. We analyze the level of energy equipartition of the cluster and find direct evidence for its post-core-collapsed state from kinematic arguments alone. We refine the dynamical mass of the blue stragglers (BSs) and study possible kinematic differences between BSs formed by collisions and mass transfer. We also measure no significant cluster rotation in the plane of the sky. Finally, we measure the absolute PM of NGC 362 and of the background stars belonging to the Small Magellanic Cloud, finding a good agreement with previous estimates in the literature. We make the PM catalog publicly available.
252. HSTPROMO I. Observations and NGC7078 results
ID:
ivo://CDS.VizieR/J/ApJ/797/115
Title:
HSTPROMO I. Observations and NGC7078 results
Short Name:
J/ApJ/797/115
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first study of high-precision internal proper motions (PMs) in a large sample of globular clusters, based on Hubble Space Telescope (HST) data obtained over the past decade with the ACS/WFC, ACS/HRC, and WFC3/UVIS instruments. We determine PMs for over 1.3 million stars in the central regions of 22 clusters, with a median number of ~60000 stars per cluster. These PMs have the potential to significantly advance our understanding of the internal kinematics of globular clusters by extending past line-of-sight (LOS) velocity measurements to two- or three-dimensional velocities, lower stellar masses, and larger sample sizes. We describe the reduction pipeline that we developed to derive homogeneous PMs from the very heterogeneous archival data. We demonstrate the quality of the measurements through extensive Monte Carlo simulations. We also discuss the PM errors introduced by various systematic effects and the techniques that we have developed to correct or remove them to the extent possible. We provide in electronic form the catalog for NGC 7078 (M 15), which consists of 77837 stars in the central 2.4'. We validate the catalog by comparison with existing PM measurements and LOS velocities and use it to study the dependence of the velocity dispersion on radius, stellar magnitude (or mass) along the main sequence, and direction in the plane of the sky (radial or tangential).
253. HST proper-motions of M4 main-sequence stars
ID:
ivo://CDS.VizieR/J/AJ/127/2771
Title:
HST proper-motions of M4 main-sequence stars
Short Name:
J/AJ/127/2771
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new results from a photometric study of the main-sequence stars in M4 (NGC 6121=C1620-264), the closest globular cluster to the Sun. Multifield, multiepoch observations at approximately 1, 2, and 6 core radii were obtained with WFPC2 on the Hubble Space Telescope through either the F606W filter or the F555W (V) and F814W (I) filters. The multi-epoch observations allowed us to clean the data on the basis of proper motion and thus separate cluster from field stars or extragalactic objects.
254. HST VI photometry and proper motions in NGC 6528
ID:
ivo://CDS.VizieR/J/A+A/385/67
Title:
HST VI photometry and proper motions in NGC 6528
Short Name:
J/A+A/385/67
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using two epochs of HST/WFPC2 images of the metal-rich globular cluster NGC 6528 we derive the proper motions of the stars and use them to separate the stars belonging to NGC 6528 from those of the Galactic bulge. The stellar sequences in the resulting colour-magnitude diagram for the cluster are significantly better determined than in previously published data. From comparison of the colour-magnitude diagram with the fiducial line for NGC 6553 from Zoccali et al. (2001AJ....121.2638Z) we conclude that the two globular clusters have the same age. Further, using alpha-enhanced stellar isochrones, NGC 6528 is found to have an age of 11+/-2Gyr. This fitting of isochrones also give that the cluster is 7.2kpc away from us. From the measured velocities both the proper motion of the cluster and the velocity dispersion in the Galactic bulge are found. NGC 6528 is found to have a proper motion relative to the Galactic bulge of <mu_l_>=0.006 and <mu_b_>=0.044 arcsec per century. Using stars with 14<V_555_<19 (i.e. the red giant branch and horizontal branch) we find, for the Galactic bulge, sigma_l_=0.33+/-0.03 and sigma_b_=0.25+/-0.02 arcsec per century. This give sigma_l/sigma_b=1.32+/-0.16, consistent both with previous proper motion studies of K giants in the Galactic bulge as well as with predictions by models of the kinematics of bulge stars.
255. HST VI photometry of HD 97950 cluster members stars
ID:
ivo://CDS.VizieR/J/ApJ/764/73
Title:
HST VI photometry of HD 97950 cluster members stars
Short Name:
J/ApJ/764/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep Hubble Space Telescope/Wide Field and Planetary Camera 2 photometry of the young HD 97950 star cluster in the giant H II region NGC 3603. The data were obtained in 1997 and 2007 permitting us to derive membership based on proper motions of the stars. Our data are consistent with an age of 1 Myr for the HD 97950 cluster. A possible age spread, if present in the cluster, appears to be small. The global slope of the incompleteness-corrected mass function for member stars within 60" is {Gamma}=-0.88+/-0.15, which is flatter than the value of a Salpeter slope of -1.35. The radially varying mass function shows pronounced mass segregation ranging from slopes of -0.26 +/-0.32 in the inner 5" to -0.94+/-0.36 in the outermost annulus (40"-60"). Stars more massive than 50M_{sun}_ are found only in the cluster center. The {Lambda} minimum spanning tree technique confirms significant mass segregation down to 30M_{sun}_. The dependence of {Lambda} on mass, i.e., that high-mass stars are more segregated than low-mass stars, and the (weak) dependence of the velocity dispersion on stellar mass might imply that the mass segregation is dynamical in origin. While primordial segregation cannot be excluded, the properties of the mass segregation indicate that dynamical mass segregation may have been the dominant process for segregation of high-mass stars.
256. Hyades brown dwarfs and very low mass stars
ID:
ivo://CDS.VizieR/J/A+A/481/661
Title:
Hyades brown dwarfs and very low mass stars
Short Name:
J/A+A/481/661
Date:
21 Oct 2021
Publisher:
CDS
Description:
We conducted a search for brown dwarfs (BDs) and very low mass (VLM) stars in the 625Myr-old Hyades cluster in order to derive the cluster's mass function across the stellar-substellar boundary. We performed a deep (I=23, z=22.5) photometric survey over 16deg^2^ around the cluster center and followed up with K-band photometry to measure the proper motion of candidate members and with optical and near-IR spectroscopy of probable BD and VLM members.
257. Hyades cluster: motion, membership, and distance
ID:
ivo://CDS.VizieR/J/AJ/80/379
Title:
Hyades cluster: motion, membership, and distance
Short Name:
J/AJ/80/379
Date:
21 Oct 2021
Publisher:
CDS
Description:
New absolute proper motions referred directly to external galaxies, photographic photometry, and cluster membership probabilities have been determined for over 600 faint stars in the Hyades region. These have been used to investigate the Hyades convergent point and distance. A detailed review of the foundations of the convergent-point method, its applicability to the Hyades, the several mathematical variations of the method, and its possible role in producing the apparent discrepancy between previous Hyades proper motion results and "secondary" Hyades distance indicators, has been carried out. The convergent-point method, as applied to the Hyades, is entirely valid, and cannot be the source of any significant error in the Hyades distance. Systematic errors in meridian circle proper motions are implicated as the cause of the observed Hyades distance discrepancy. The convergent-point analysis of the new absolute Hyades proper motions represents the first Hyades distance determination independent of all meridian circle proper motion systems. The resulting Hyades distance modulus is m-M=3.42, significantly greater than all previous values from proper motions, and in agreement with predictions of the Hyades distance from stellar structure theory, and with the results of "secondary" distance indicators. Incorporating this value, the most likely value of the mean Hyades distance modulus from all sources is m-M=3.29+/-0.08. The quoted error represents a larger and more realistic estimate of the true errors than has been previously stated. Significant effects of the increased Hyades distance on the cosmic distance scale and other questions of general astronomical importance are briefly discussed.
258. Hyades members distances
ID:
ivo://CDS.VizieR/J/A+A/243/386
Title:
Hyades members distances
Short Name:
J/A+A/243/386
Date:
21 Oct 2021
Publisher:
CDS
Description:
Distances for 145 Hyades members in an extended region of the Hyades cluster were derived on the basis of new, highly accurate proper motions obtained from work on the catalogues FK5 and PPM. The cluster membership on the stars has been discussed and a few new candidates are proposed. From a selected subset of our sample we have obtained the convergence point {alpha}=6h30.7m+/-1.7m=97deg41'+/-25', {delta}=5deg59'+/-11'. Combining this point with the mean cluster radial velocity of 39.1km/s by Detweiler et al. (1984AJ.....89.1038D) one find the galactic space velocity (U, V, W)=(-42.02, -20.12, -1.04)km/s. The galactic coordinates of the centre of our sample are (X, Y, Z)=(-44.3, +0.5, -18.2)pc. The distance of this centre from the Sun is 47.9+/-0.8pc corresponding to a modulus m-M=3.40+/-0.04mag. Individual distance moduli, coordinates and velocity residuals per star are given. The Hyades main sequence has been constructed in the range B-V<1.2mag and it is presented analytically as well as by tabular values. The dispersion {sigma}(M_v_)=0.14mag of the absolute magnitudes about the main sequence indicates its high internal accuracy.
259. IC 4665 DANCe
ID:
ivo://CDS.VizieR/J/A+A/631/A57
Title:
IC 4665 DANCe
Short Name:
J/A+A/631/A57
Date:
21 Oct 2021
Publisher:
CDS
Description:
The study of star formation is extremely challenging due to the lack of complete and clean samples of young, nearby clusters, and star forming regions. The recent Gaia DR2 catalogue complemented with the deep, ground based COSMIC DANCe catalogue offers a new database of unprecedented accuracy to revisit the membership of clusters and star forming regions. The 30 Myr open cluster IC 4665 is one of the few well-known clusters of this age and it is an excellent target where to test evolutionary models and study planetary formation. We aim to provide a comprehensive membership analysis of IC 4665 and to study the following properties: empirical isochrones, distance, magnitude distribution, present-day system mass function, and spatial distribution. We use the Gaia DR2 catalogue together with the DANCe catalogue to look for members using a probabilistic model of the distribution of the observable quantities in both the cluster and background populations. We obtain a final list of 819 candidate members which cover a 12.4 magnitude range (7<J<19.4). We find that 50% are new candidates, and we estimate a conservative contamination rate of 20%. This unique sample of members allows us to obtain a present-day system mass function in the range of 0.02-6M_{sun}_, which reveals a number of details not seen in previous studies. In addition, they favour a spherically symmetric spatial distribution for this young open cluster. Our membership analysis represents a significant increase in the quantity and quality (low-contamination) with respect to previous studies. As such, it offers an excellent opportunity to revisit other fundamental parameters such as the age.
260. IC 348 proper motion catalogue
ID:
ivo://CDS.VizieR/J/A+AS/137/305
Title:
IC 348 proper motion catalogue
Short Name:
J/A+AS/137/305
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new proper motion study for about 1400 stars with R<18mag in a one square degree region around the young open cluster IC 348 based on Schmidt plates is presented. With an overall accuracy of about 3mas/yr (2.5mas/yr, respectively for all stars with R<17mag) we have obtained membership probabilities dividing our sample into three groups: foreground stars, cluster stars and background stars. This separation is also supported by the proper motion distribution with respect to the direction of the standard antapex and an increase of mean proper motion cluster membership probabilities with smaller cluster radii. 240 stars of our sample have cluster membership probabilities larger than 80%.