The estimation of the main parameters of star clusters is significant in astrophysical studies. The most important aspect of using the Gaia DR2 survey lies in the positions, parallax, and proper motions of cluster stars with homogeneous photometry that make the membership probability determine with high accuracy. In this respect, depending on Gaia DR2 database, an analysis of the open star cluster Melotte 72 is taking place here. It is located at a distance of 2345+/-108 pc with an age of 1.0+/-0.5 Gyr. In studying the radial density profile, the radius is found to be 5.0+/-0.15 arcmin. The reddening, the luminosity and mass functions, the total mass of the cluster, and the galactic geometrical distances (X_Sun, Y_Sun, Z_Sun), and the distance from the galactic center (R_g ) have been estimated as well. Our study has shown a dynamical relaxation behavior of Melotte 72.
This paper presents a deep investigation of two open clusters, Haffner 22 and Melotte 71, using astrometric and photometric data from Gaia EDR3. We identified 382 and 597 most probable cluster members with membership probability higher than 50 percent. Mean proper motion in RA and DEC are estimated as -1.63 and 2.889 respectively for Haffner 22 and -2.398 and 4.210 for Melotte 71. A comparison of observed CMDs with theoretical isochrones leads to an age of 2.25 and 1.27 Gyr for these clusters. The distances 2.88 and 2.28 kpc based on parallax are comparable with the values derived by isochrone…
In this article, we present a morphological study of the well-known extended sized open clusters in the sky, Melotte 22 (Pleiades) and Melotte 25 (Hyades) with J, H, and Ks regions due to Gaia DR2 and PPMXL catalogues. Based on proper motions of these clusters, we extract our candidates and hence constructing fitting isochrones with Solar metallicity Z = 0.019, log (age) = 8.2 +- 0.05 for Melotte 22, and metallicity Z = 0.024, log (age) = 8.9 +- 0.10 for Melotte 25. Some photometric parameters are estimated, e.g. cluster heliocentric distances are 135 +- 3.6 and 47.51 +- 2.15 pc respectively, …
Archival Vilnius CCD photometric observations are presented for the heavily reddened star cluster Melotte 105, resulting in colour-magnitude diagrams and spectral class estimates. There is considerable lack of agreement between studies for reddening, age, and distance for this cluster explaining why the archival data are being made available by this paper. The derived reddening E(B-V =0.34 +/- 0.04 mag and the distance V-M =12.9 +/- 0.3 mag directly from the Vilnius photometry. The Gaia Data Release 2 (DR2) and Vilnius photometric data of the cluster were used to estimate the structural parame…
Ultraviolet (UV) wavelength observations have made a significant contribution to our understanding of hot stellar populations of star clusters. Multi-wavelength spectral energy distributions (SEDs) of stars, including ultraviolet observations, have proven to be an excellent tool for discovering unresolved hot companions in exotic stars such as blue straggler stars (BSS), thereby providing helpful clues to constrain their formation mechanisms. Melotte 66 is a 3.4 Gyr old open cluster located at a distance of 4810 pc. We identify the cluster members by applying the ML-MOC algorithm on Gaia EDR3 …
Blue straggler stars (BSS) are well studied in globular clusters but their systematic study with secure membership determination is lacking in open clusters. We use Gaia DR2 data to determine accurate stellar membership for four intermediate-age open clusters, Melotte 66, NGC 2158, NGC 2506 and NGC 6819, and three old open clusters, Berkeley 39, NGC 188 and NGC 6791, to subsequently study their BSS populations. The BSS radial distributions of five clusters, Melotte 66, NGC 188, NGC 2158, NGC 2506, and NGC 6791, show bimodal distributions, placing them with Family II globular clusters which are…
In this note I show how the recently suggested membership of the open cluster Gaia 1 to the Galactic thick disk is based on incorrect assumptions about the structure of the disk itself, and neglect well-known observational evidences on the disk warp and flare.
The astro-photometric parameters of the open star cluster Dolidze 41, which located in the constellation of Cygnus, have been investigated using the Gaia-ESO DR2 large Survey merging with the near Infrared Two Micron All Sky Survey 2MASS database. The radial density distribution (limited, core and tidal radii), color-magnitude diagrams, the galactocentric coordinates, distances, color excess, and age of Dolidze 41 are presented. Thanks to Gaia DR2 astrometry, which help us to define the membership of the cluster stars easily. The luminosity & mass functions, the entire luminosity & mass, and t…
The publication of the Gaia Data Release 2 (Gaia DR2) opens a new era in Astronomy. It includes precise astrometric data (positions, proper motions and parallaxes) for more than $1.3$ billion sources, mostly stars. To analyse such a vast amount of new data, the use of data mining techniques and machine learning algorithms are mandatory. The search for Open Clusters, groups of stars that were born and move together, located in the disk, is a great example for the application of these techniques. Our aim is to develop a method to automatically explore the data space, requiring minimal manual int…
We have derived accurate distances to Galactic globular clusters by combining data from the Gaia Early Data Release 3 with distances based on Hubble Space telescope HST data and literature based distances. We determine distances either directly from the Gaia EDR3 parallaxes, or kinematically by combining line-of-sight velocity dispersion profiles with Gaia EDR3 and HST based proper motion velocity dispersion profiles. We furthermore calculate cluster distances from fitting nearby subdwarfs, whose absolute luminosities we determine from their Gaia EDR3 parallaxes, to globular cluster main-seque…
Here, we conducted a photometric and astrometric study of two open stellar clusters Dolidze-18 and Ruprecht-70, which have not been photometrically studied before. The most important thing for using Gaia (DR2) database lies in the positions, parallax, and proper motions, which make us split cluster members from the field ones and get precise astrophysical parameters. On studying the radial density profiles of these clusters, the actual sizes are estimated and found larger using Gaia. From the color-magnitude diagrams and theoretical isochrones, we simultaneously determined the ages, distance m…
We provide new values of the orbital parameters of 152 globular clusters, which are calculated using the new mean proper motions obtained from the Gaia EDR3 catalog data. The orbits were integrated 5 Gyr back in an axisymmetric three-component potential with a spherical bulge, disk component, and spherical dark halo in the Navarro-Frenk-White form, which we refined using the rotation curve of objects with large galactocentric distances up to 200 kpc. The obtained orbital parameters were compared with the orbital parameters of the same globular clusters calculated earlier in the same gravitatio…
The Gaia Data Release 2 (DR2) provided an unprecedented volume of precise astrometric and excellent photometric data. In terms of data mining the Gaia catalogue, machine learning methods have shown to be a powerful tool, for instance in the search for unknown stellar structures. Particularly, supervised and unsupervised learning methods combined together significantly improves the detection rate of open clusters. We systematically scan Gaia DR2 in a region covering the Galactic anticentre and the Perseus arm $(120 \leq l \leq 205$ and $-10 \leq b \leq 10)$, with the goal of finding any open cl…
Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the sub-milliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. In this study we aim to a establish list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. We compile a list of thousands of known or putative clusters from the l…
The astrometric satellite Gaia recently released part of its third data set, which provides a good opportunity to hunt for more open clusters in the Milky Way. In this work, we conduct a blind search for open clusters in the Galactic disk using a sample-based clustering search method with high spatial resolution, which is especially suited to finding hidden targets. In addition to confirming 1930 previously known open clusters and 82 known globular clusters, 704 new stellar clusters are proposed as potential open clusters at Galactic latitudes of $|$b$|$ < 20 {deg}. For each of these new open …
The improvements in the precision of the published data in \textit{Gaia} EDR3 with respect to \textit{Gaia} DR2, particularly for parallaxes and proper motions, offer the opportunity to increase the number of known open clusters in the Milky Way by detecting farther and fainter objects that have so far go unnoticed. Our aim is to keep completing the open cluster census in the Milky Way with the detection of new stellar groups in the Galactic disc. We use \textit{Gaia} EDR3 up to magnitude $G = 18$ mag, increasing in one unit the magnitude limit and therefore the search volume explored in our p…
We report 541 new open cluster candidates in Gaia EDR3 through revisiting the cluster results from an earlier analysis of the Gaia DR2, which revealed nearly a thousand open cluster candidates in the solar neighborhood (mostly d < 3 kpc) resideing at Galactic latitudes |b| < 20 degrees. A subsequent comparison with lists of known clusters shows a large increases of the cluster samples within 2 kpc from the Sun. We assign membership probabilities to the stars through the open source pyUPMASK algorithm, and also estimate the physical parameters through isochrone fitting for each candidate. Most …
In Gaia DR2, the unprecedented high-precision level reached in sub-mas for astrometry and mmag for photometry. Using cluster members identified with these astrometry and photometry in Gaia DR2, we can obtain a reliable determination of cluster properties. However, because of the shortcoming of Gaia spectroscopic observation in dealing with densely crowded cluster region, the number of radial velocity and metallicity for cluster member stars from Gaia DR2 is still lacking. In this study, we aim to improve the cluster properties by combining the LAMOST spectra. In particular, we provide the list…
We report the serendipitous discovery of three new open clusters, named UFMG 1, UFMG 2 and UFMG 3 in the field of the intermediate-age cluster NGC 5999, by using Gaia DR2 data. A colour-magnitude filter tailored for a proper selection of main-sequence stars and red clump giants turned evident the presence of NGC 5999 and these three new stellar groups in proper motion space. Their structural parameters were derived from King-profile fittings over their projected stellar distributions and isochrone fits were performed on the clusters cleaned colour-magnitude diagrams built with Gaia bands to de…
The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G~12 mag. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or UCAC4 proper motions, and TGAS parallaxes. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/MCMC technique to fit stellar isochrones to the observed 2MASS JHK$…
The estimation of the main parameters of star clusters is a very important target in astrophysical studies. Many of the open clusters listed in known catalogs have insuffcient astrometric parameters. Improving the observations and analysis methods proved that some of them are not true clusters. The most important aspect of using the Gaia survey lies in the positions, parallax, and proper motions for the cluster stars with the homogeneous photometry, which makes the membership candidates precisely determined. In this respect, several photometric parameters of the open star cluster Kronberger 60…
We present orbits and their properties for 152 globular clusters of the Milky Way galaxy obtained using average Gaia DR2 proper motions and other astrometric data from the list of Vasiliev (2019). For orbit integrating we have used the axisymmetric model of the Galactic potential based on the Navarro-Frenk-White dark halo, and modified by Bajkova and Bobylev (2016) using circular velocities of Galactic objects in wide region of Galactocentric distances (up to 200 kpc) from Bhattacharjee et.al. (2014) catalog. Based on the analysis of the obtained orbits, we have modified the composition of the…
Tidally stripped galaxy nuclei and luminous globular clusters (GCs) are important tracers of the halos and assembly histories of nearby galaxies, but are difficult to reliably identify with typical ground-based imaging data. In this paper we present a new method to find these massive star clusters using Gaia DR2, focusing on the massive elliptical galaxy Centaurus A (Cen A). We show that stripped nuclei and globular clusters are partially resolved by Gaia at the distance of Cen A, showing characteristic astrometric and photometric signatures. We use this selection method to produce a list of 6…
In this paper we revisit the problem of identifying bona fide cluster Cepheids by performing an all-sky search for Cepheids associated with open clusters and making use of state-of-the-art catalogued information for both Cepheids and clusters, based on the unparalleled astrometric precision of the second and early third data releases of the Gaia satellite. We determine membership probabilities by following a Bayesian approach using spatial and kinematic information of the potential cluster-Cepheid pairs. We confirm 19 Cepheid-cluster associations considered in previous studies as bona-fide, an…
We use Gaia DR2 data to show that the globular cluster NGC5634 is physically associated with an arm of the Sagittarius Stream, the huge system of tidal tails created by the ongoing disruption of the Sagittarius dwarf spheroidal galaxy (Sgr dSph). Two additional arms of the Stream are also detected along the same line of sight, at different distances. We show that the Sgr Stream stars surrounding NGC5634 are more metal-poor, on average, than those found in the more distant Stream arm lying behind the cluster and in the main body of Sgr~dSph, confirming that a significant metallicity (and, presu…
We use the data from Gaia Early Data Release 3 (EDR3) to study the kinematic properties of Milky Way globular clusters. We measure the mean parallaxes and proper motions (PM) for 170 clusters, determine the PM dispersion profiles for more than 100 clusters, uncover rotation signatures in more than 20 objects, and find evidence for radial or tangential PM anisotropy in a dozen richest clusters. At the same time, we use the selection of cluster members to explore the reliability and limitations of the Gaia catalogue itself. We find that the formal uncertainties on parallax and PM are underestima…
NGC 288 is a Galactic globular cluster having observed extra tidal structure, without confirmed tidal tails. $Gaia$ DR2 provides photometric and astrometric data for many of the stars in NGC 288 and its extra tidal structure. To compare with $Gaia$ data, we simulate an $N$-body model of a star cluster with the same orbit as NGC 288 in a Milky Way potential. The simulation shows that the cluster forms tidal tails that are compressed along the cluster's orbit when it is at apocentre and are expected to be a diffuse bipolar structure. In this letter, we present a comparison between the simulation…
Although previous searches for star clusters have been very successful, many clusters are likely still omitted, especially at high Galactic latitude regions. In this work, based on the astrometry of Gaia EDR3, we searched nearby (parallax > 0.8 mas) all-sky regions, obtaining 886 star clusters, of which 270 candidates have not been cataloged before. At the same time, we have presented the physical parameters of the clusters by fitting theoretical isochrones to their optical magnitudes. More halo members and expanding structures in many star clusters were also found. Most of the new objects are…
In this paper, we present astrophysical parameters of the open cluster King 13 based on the VI CCD and 2MASS JHKs photometric data. This is a poorly studied cluster, for which new results have been found in the present work. To identify probable members, we use proper motion data from Gaia DR2 catalogue. The mean proper motion of the cluster is determined as -2.8 \pm 0.2 and -0.88 \pm 0.14 mas yr{-1} and cluster extent is derived as 3'.2. Using color-magnitude diagrams, we estimate the age and distance of the cluster as 510 \pm 60 Myr and 3.84 \pm 0.15 kpc respectively. Interstellar reddening …
Embedded clusters are groups of stars which have not dispersed yet the residual of the parental cloud where they were born so getting precise distances and properties of these groups turns out to be an essential task. We present results for five embedded clusters: [DBS2003]5, [DBS2003]60, [DBS2003]98, [DBS2003]116 and [DBS2003]117. Results come from a combination of deep CCD UBVI photometry suitable to identify blue faint stars and infrared information from available surveys. In turn photometry was linked with proper motions and parallaxes from Gaia DR2. Each object was treated in a multi-spac…
The recent exquisite Gaia astrometric, photometric, and radial velocity (RV) measurements resulted in a substantial advancement for the determination of the orbits for old star clusters, including the oldest Milky Way globular clusters (MW GCs). The main goal of this paper is to use the Gaia DR3 and the VVVX measurements to obtain the orbits for nearly a dozen new Galactic GC candidates that have been poorly studied or previously unexplored. We use the Gaia DR3 and VVVX databases to identify bonafide members of the Galactic GC candidates: VVV-CL160, Patchick122, Patchick125, Patchick126, Kronb…
We review the implications of the Gaia Data Release 2 catalogue for studying the dynamics of Milky Way globular clusters, focusing on two separate topics. The first one is the analysis of the full 6-dimensional phase-space distribution of the entire population of Milky Way globular clusters: their mean proper motions (PM) can be measured with an exquisite precision (down to 0.05 mas/yr, including systematic errors). Using these data, and a suitable ansatz for the steady-state distribution function (DF) of the cluster population, we then determine simultaneously the best-fit parameters of this …
In this study, we carried out CCD UBV photometry of eight open clusters, ASCC 115, Collinder 421, NGC 6793, NGC 7031, NGC 7039, NGC 7086, Roslund 1, Stock 21, and determined their reddening, metallicity, distance, age, and mass functions. We used new Gaia Data Release 2 (DR2) astrometric data to separate cluster member stars from the field stars and obtain precise structural and astrophysical parameters. To identify cluster member stars we utilized an unsupervised membership assignment code (UPMASK), which is based on the photometric and astrometric data. The density distributions for the open…
Using data from Gaia DR2, we study the radial number density profiles of the Galactic globular cluster sample. Proper motions are used for accurate membership selection, especially crucial in the cluster outskirts. Due to the severe crowding in the centres, the Gaia data is supplemented by literature data from HST and surface brightness measurements, where available. This results in 81 clusters with a complete density profile covering the full tidal radius (and beyond) for each cluster. We model the density profiles using a set of single-mass models ranging from King and Wilson models to gener…
Blanco 1, a 100Myr open cluster in the solar neighborhood, is well known for its two 50pc-long tidal tails. Taking Blanco 1 as a reference, we find evidence of early-stage tidal disruption in two other open clusters of ~120Myr: the Pleiades and NGC 2516, via Gaia EDR3 data. These two clusters have a total mass of 2-6 times that of Blanco 1. Despite having a similar age as Blanco 1, the Pleiades and NGC 2516 have a larger fraction of their members bound: 86% of their mass is inside the tidal radius, versus 63% for Blanco 1. However, a correlation between Blanco 1's 50pc-long tidal tails and the…
We determine the color excesses, photometric distances, ages, astrometric parallaxes and proper motions for 94 open clusters in the northern part of the Milky Way. We estimate the color excesses and photometric distances based on the data from IPHAS photometric survey of the northern Galactic plane using individual total-to-selective extinction ratios R_r=A_r/E_(r-i) for each cluster computed via the color-difference method based on IPHAS r, i, and H_alpha-band, 2MASS J, H, and K_s-band, WISE W1-band, and Pan-STARRS i, z, and y-band data. The inferred R_r values vary significantly from cluster…
The Gaia mission promises to deliver precision astrometry at an unprecedented level, heralding a new era for discerning the kinematic and spatial coordinates of stars in our Galaxy. Here, we present a new technique for estimating the age of tidally disrupted globular cluster streams using the proper motions and parallaxes of tracer stars. We evolve the collisional dynamics of globular clusters within the evolving potential of a Milky Way-like halo extracted from a cosmological $Λ$CDM simulation and analyze the resultant streams as they would be observed by Gaia. The simulations sample a variet…
There is a growing interest in the automated characterization of open clusters using data from the Gaia mission. This work evidences the importance of choosing an appropriate sampling radius (the radius of the circular region around the cluster used to extract the data) and the usefulness of additional multiband photometry in order to achieve accurate results. We address this issue using as a case study the cluster Alessi-Teutsch 9. The optimal sampling is determined by counting the number of assigned members at different sampling radii. By using this strategy with data from Gaia EDR3 and with…
Line-of-sight kinematic studies indicate that many Galactic globular clusters have a significant degree of internal rotation. However, three-dimensional kinematics from a combination of proper motions and line-of-sight velocities are needed to unveil the role of angular momentum in the formation and evolution of these old stellar systems. Here we present the first quantitative study of internal rotation on the plane-of-the-sky for a large sample of globular clusters using proper motions from Gaia DR2. We detect signatures of rotation in the tangential component of proper motions for 11 out of …
Open clusters are groups of stars that form at the same time, making them an ideal laboratory to test theories of star formation, stellar evolution, and dynamics in the Milky Way disk. However, the utility of an open cluster can be limited by the accuracy and completeness of its known members. Here, we employ a "top-down" technique, {\it extreme deconvolution gaussian mixture models} (XDGMM), to extract and evaluate known open clusters from Gaia DR2 by fitting the distribution of stellar parallax and proper motion along a line-of-sight. Extreme deconvolution techniques can recover the intrinsi…
Stars form in spatially and temporarily correlated star formation events (CSFEs) and the dynamical processes within these "embedded clusters" leave imprints in the stellar populations in galactic fields. Such imprints are correlations in phase space (e.g. gravitationally bound star clusters, tidal streams), in the binary properties of stars and in the present-day stellar mass functions in the surviving clusters. The dynamical processes include expulsion of massive stars from cluster cores, disruption of CSFEs due to residual gas expulsion and energy-equipartition driven evaporation of stars fr…
