BSEC Method for Unveiling Open Clusters and its Application to Gaia DR3: 83 New Clusters

Simple though admittedly speculative considerations explain why most of our galaxy’s stellar nurseries are highly fragile but a few survive for a remarkably long time.

The selection of known members of star clusters as BRITE targets is highly preferable. The given apparent visual magnitude limit for the targets, can be immediately transformed into a distance limit of about 750 pc around the Sun depending on the absolute magnitude. For a spectral type of A0, we are, for example, limited to about 65 pc only. With the help of WEBDA (http://www.univie.ac.at/webda), we have found 60 possible candidates which are true members of star clusters (including associations). The membership offers the opportunity to use the results from a detailed cluster analysis “for free”. This includes the determination of the age, the distance, the reddening, the overall metallicity and thus the mass with a high accuracy. These are very valuable starting parameters for any detailed astrophysical study of an individual object. Star clusters Why are they unique? Open clusters and associations (denoted as “star clusters” in the following) are physically related groups of stars held together by mutual gravitational attraction. Therefore, they populate a limited region of space, which is typically much smaller than their distance from the Sun, so that the members are all approximately at the same distance. They are believed to originate from large cosmic gas and dust clouds (diffuse nebulae) in the Milky Way, and to continue to orbit the galaxy through the disk. In many clouds visible as bright diffuse nebulae, star formation still takes place, so that we can observe the birth of new young star clusters. This process of formation takes only a considerably short time (a few Myrs) compared to the lifetime of the cluster, so that all member stars are of similar age. Also, as all the stars in a cluster formed from the same diffuse nebula, they all have similar initial chemical composition. Hence, star clusters are of great interest for scientists: • The cluster members are all at about the same distance from the Sun. 176 Cluster and Association Members • They have the same age within approximately a few million years compared to the cluster age (up to a few billion years). • The chemical composition of cluster members is quite homogeneous. Open cluster metallicities range from about −1.0 to +0.6 dex compared to the Sun. The determination of distance, age and metallicity is, in general, not straightforward for galactic field stars. Star clusters on the other hand represent samples of stars of constant age and homogeneous chemical composition, suited for the study of processes linked to stellar structure and evolution. They allow to fix lines or loci in several important astrophysical diagrams such as the color-magnitude diagram (CMD), or the Hertzsprung-Russell diagram (HRD). Comparing the “standard” HRD, derived from nearby stars with sufficiently well known distances, or the theory of stellar evolution with the measured CMD of star clusters, provides a considerably good method to determine the distance of star clusters. Comparing their HRDs with stellar theory provides a reasonable way to estimate the age of star clusters. BRITE target stars as members of star clusters For a given apparent magnitude limit of targets stars (V =4mag) we can immediately calculate the distance limit for different absolute magnitudes. At maximum (not taking reddening into account) MV =−6mag (early O) we can reach 1000pc whereas the distance significantly decreases to 65 pc for a star with MV =+0mag (A0). With the help of WEBDA (http://www.univie.ac.at/webda), a highly efficient and successful database for the study of star clusters in the Milky Way and the Small Magellanic Cloud, it is possible to extract and retrieve all needed information. The database includes about 3.4 million individual measurements in most photometric systems in which cluster stars have been observed, spectroscopic observations, astrometric data, various kinds of supplementary information, and an extensive bibliography. Taking a distance limit of 750 pc, we find in WEBDA about 220 star clusters which are closer than this value. Including the members of associations, we find about 60 potential BRITE target stars which are members of a star cluster. Why to observe members of star clusters? From kinematic (proper motions as well as radial velocities) and photometric studies we are able to establish the membership of a star to a corresponding

High-precision proper motions and radial velocities of 1046 stars are used to determine member stars using three-dimensional (3D) kinematics for open cluster NGC 188 based on the density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm. By implementing this algorithm, 472 member stars in the cluster are obtained with 3D kinematics. The color-magnitude diagram (CMD) of the 472 member stars using 3D kinematics shows a well-defined main sequence and a red giant branch, which indicate that the DBSCAN clustering algorithm is very effective for membership determination. The DBSCAN clustering algorithm can effectively select probable member stars in 3D kinematic space without any assumption about the distribution of the cluster or field stars. Analysis results show that the CMD of member stars is significantly clearer than the one based on 2D kinematics, which allows us to better constrain the cluster members and estimate their physical parameters. Using the 472 member stars, the average absolute proper motion and radial velocity are determined to be (PMα, PMδ) = (−2.58 ± 0.22, +0.17 ± 0.18) mas yr−1 and Vr = −42.35 ± 0.05 km s−1, respectively. Our values are in good agreement with values derived by other authors.

Context.Data from theGaiasatellite are revolutionising our understanding of the Milky Way. With every new data release, there is a need to update the census of open clusters.Aims.We aim to conduct a blind, all-sky search for open clusters using 729 million sources fromGaiaDR3 down to magnitudeG ∼ 20, creating a homogeneous catalogue of clusters including many new objects.Methods.We used the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm to recover clusters. We validated our clusters using a statistical density test and a Bayesian convolutional neural network for colour-magnitude diagram classification. We inferred basic astrometric parameters, ages, extinctions, and distances for the clusters in the catalogue.Results.We recovered 7167 clusters, 2387 of which are candidate new objects and 4782 of which crossmatch to objects in the literature, including 134 globular clusters. A more stringent cut of our catalogue contains 4105 highly reliable clusters, 739 of which are new. Owing to the scope of our methodology, we are able to tentatively suggest that many of the clusters we are unable to detect may not be real, including 1152 clusters from the Milky Way Star Cluster (MWSC) catalogue that should have been detectable inGaiadata. Our cluster membership lists include many new members and often include tidal tails. Our catalogue’s distribution traces the galactic warp, the spiral arm structure, and the dust distribution of the Milky Way. While much of the content of our catalogue contains bound open and globular clusters, as many as a few thousand of our clusters are more compatible with unbound moving groups, which we will classify in an upcoming work.Conclusions.We have conducted the largest search for open clusters to date, producing a single homogeneous star cluster catalogue which we make available with this paper.

Context. The Galactic globular cluster system is incompletely known, especially in the low-latitude regions of the Galactic bulge and disk. We report the physical characterisation of 12 star clusters in the Milky Way, most of which are explored here for the first time. Aims. Our primary aim is determining their main physical parameters, such as reddening, extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), and distances, in order to reveal the physical nature of these clusters. Methods. We study the clusters using optical and near-infrared (NIR) datasets. In particular, we use the Gaia Early Data Release 3 (EDR3) PMs in order to perform a PM decontamination procedure and build final catalogues with probable members. We match the Gaia EDR3 with the VISTA Variables in the Vía Láctea extended (VVVX) survey and the Two Micron All-Sky survey (2MASS) in the NIR, in order to construct complete NIR and optical colour-magnitude diagrams (CMDs) and investigate the clusters properties. Results. The extinctions are evaluated using existing reddening maps. We find ranges spanning 0.09 ≲ AKs ≲ 0.86 mag and 0.89 ≲ AG ≲ 4.72 mag in the NIR and optical, respectively. Adopting standard intrinsic red clump (RC) magnitudes and extinction values, we first obtain the distance modulus for each cluster and thereafter their heliocentric distances, which range from about 4 to 20 kpc. Therefore, we are able to place these clusters at 3 ≲ RG ≲ 14 kpc from the Galactic centre. The best PARSEC isochrone fit yields a metallicity range of −1.8 < [Fe/H] < +0.3 and an approximate age range of 2 < age < 14 Gyr. Finally, we find that all clusters have low luminosities, with −6.9 < MV < −3.5 mag. Conclusions. Based on our photometric analysis, we find both open clusters (OCs) and globular clusters (GCs) in our sample. In particular, we confirm the OC nature for Kronberger 100, while we classify Patchick 125 as a metal-poor GC, Ferrero 54 as a metal-rich GC, and ESO 92-18 as a possible old OC or young GC. The classification as GC candidates is also suggested for Kronberger 99, Patchick 122, Patchick 126, Riddle 15, FSR 190, and Gaia 2. We also conclude that Kronberger 119 and Kronberger 143 might be either old OCs or young GCs.

We present our study on the membership and age determination of M67 (NGC 2682), one of the oldest open clusters known to date. Proper motions and parallax of stars collected in the Gaia Early Data Release 3 are used to derive the cluster members by employing the Hierarchical Density-Based Spatial Clustering of Applications with Noise algorithm, which is further improved upon using a Gaussian Mixture Model. We calculate the position of the cluster centre and the parallax to be α = 08h51m24s±1m33s, δ = 11°49’12"±0°22’48" and 1.1497±0.06 mas respectively. The proper motion of the cluster is obtained to be μa = −10.96 ± 0.20 mas/yr and μs = −2.90 ± 0.19 mas/yr. Subsequently, we perform an isochrone fitting to the Color-Magnitude Diagram (CMD) of M67 source members by using the Automated Stellar Cluster Analysis tool (ASteCA). Our findings estimate the log age, metallicity (z), reddening (EB–V ), and distance modulus (m – M)0 to be 9.630 ± 0.033 log-years, 0.01865 ± 0.001, 0.037 ± 0.008, and 9.409 ± 0.031 respectively.

It is well known that there are few open clusters (OCs) in the high-latitude region of the Milky Way galaxy, because most star formation takes place in the thin disk. It is therefore crucial to look for high Galactic latitude OCs, in order to understand OCs and the Galactic parts outside the plane well. This work looks for high Galactic latitude OCs in Gaia Early Data Release 3, and determines their basic parameters from color–magnitude diagrams (CMDs) if the main sequence is included in CMDs. The friend-of-friend method is applied to the determination of the membership of stars. Star groups with more than 20 bright (G < 18 mag) stars are taken as OC candidates, and these candidates are finally verified by the observed CMDs including stars fainter than 18 mag in the G band. After crossmatching with previous catalogs, 56 new OC candidates are found in the high Galactic latitude region with ∣b∣ ≥ 25°, in which 35 have somewhat clear CMDs and are suggested as newly discovered OCs. Finally, eight of the new OCs are confirmed again by the pyUPMASK technique. The new sample increases the total number of known high Galactic latitude OC candidates significantly. The distance modulus, color excess, metallicity, age, and binary fraction of 35 newly discovered OCs are determined by fitting their observed CMDs to the ASPS stellar population models. All the results are included in the new star cluster catalog, LISC, as its second part (LISC II).

Context. Globular clusters (GCs) are the oldest objects known in the Milky Way, so each discovery of a new GC is astrophysically important. In the inner Galactic bulge regions these objects are difficult to find due to extreme crowding and extinction. However, recent near-IR surveys have discovered a number of new bulge GC candidates that need to be further investigated. Aims. Our main objective is to use public data from the Gaia mission, the VISTA Variables in the Via Lactea (VVV) survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer to measure the physical parameters of Minni 48, a new candidate globular star cluster located in the inner bulge of the Milky Way at l = 359.35 deg, b = 2.79 deg. The specific goals are to measure its main astrophysical parameters, such as size, proper motions, metallicity, reddening and extinction, distance, total luminosity, and age. Methods. Even though there is a bright foreground star contaminating the field, this cluster appears quite bright in near- and mid-IR images. The size of Minni 48 is derived from the cluster radial density profile, while its reddening and extinction are estimated from optical and near-IR reddening maps. We obtain statistically decontaminated optical and near-IR colour-magnitude diagrams (CMDs) for this cluster. Mean cluster proper motions are measured from Gaia data. The heliocentric cluster distance is determined from both the red clump (RC) and the red giant branch (RGB) tip magnitudes in the near-IR CMD, while the cluster metallicity is estimated from the RGB slope and the fit to theoretical stellar isochrones. Results. The size of this GC is found to be r = 6′±1′, and the reddening and extinction values are E(J − Ks) = 0.60 ± 0.05 mag, AG = 3.23 ± 0.10 mag, and AKs = 0.45 ± 0.05 mag. The resulting mean cluster proper motions are μα = −3.5 ± 0.5 mas yr−1 and μδ = −6.0 ± 0.5 mas yr−1. We also study the RR Lyrae stars recognized in the field, and we argue that they are not members of this GC. The magnitude of the RC in the near-IR CMD yields an accurate distance modulus estimate of (m − M)0 = 14.61 mag, equivalent to a distance D = 8.4 ± 1.0 kpc. Such a distance is consistent with the optical distance estimate, (m − M)0 = 14.67 mag, D = 8.6 ± 1.0 kpc, as well as with the distance estimated using the tip of the RGB, (m − M)0 = 14.45 mag, D = 7.8 ± 1.0 kpc. We also derive a cluster metallicity of [Fe/H] = − 0.20 ± 0.30 dex. Adopting these values of metallicity and distance, a good fit to the PARSEC stellar isochrones is obtained in all CMDs using Age = 10 ± 2 Gyr. The total absolute magnitude of this GC is estimated to be MKs = −9.04 ± 0.66 mag. Conclusions. Based on its position, kinematics, metallicity, and age, we conclude that Minni 48 is a genuine GC, similar to other well-known metal-rich bulge GCs. It is located at a projected galactocentric angular distance of 2.9 deg, equivalent to 0.4 kpc, situating this cluster as one of the closest GCs to the Galactic centre currently known.

This research presents unsupervised machine learning and statistical methods to identify and analyze tidal tails in open star clusters using data from the Gaia DR3 catalog. We aim to identify member stars and to detect and analyze tidal tails in five open clusters, BH 164, Alessi 2, NGC 2281, NGC 2354, and M67, of ages between 60 Myr and 4 Gyr. These clusters were selected based on the previous evidence of extended tidal structures. We utilized machine learning algorithms such as Density-based Spatial Clustering of Applications with Noise (DBSCAN) and principal component analysis (PCA), along with statistical methods to analyze the kinematic, photometric, and astrometric properties of stars. Key characteristics of tidal tails, including radial velocity, the color-magnitude diagram, and spatial projections in the tangent plane beyond the cluster's Jacobi radius (r_J), were used to detect them. We used N-body simulations to visualize and compare the observables with real data. Further analysis was done on the detected cluster and tail stars to study their internal dynamics and populations, including the binary fraction. We also applied the residual velocity method to detect rotational patterns in the clusters and their tails. We identified tidal tails in all five clusters, with detected tails extending farther in some clusters and containing significantly more stars than previously reported (tails ranging from 40 to 100 pc, one to four times their r_J, with 100-200 tail stars). The luminosity functions of the tails and their parent clusters were generally consistent, and tails lacked massive stars. In general, the binary fraction was found to be higher in the tidal tails. Significant rotation was detected in M67 and NGC 2281 for the first time.

Although they are the main constituents of the Galactic disk population, for half of the open clusters in the Milky Way reported in the literature nothing is known except the raw position and an approximate size. The main goal of this study is to determine a full set of uniform spatial, structural, kinematic, and astrophysical parameters for as many known open clusters as possible. On the basis of stellar data from PPMXL and 2MASS, we used a dedicated data-processing pipeline to determine kinematic and photometric membership probabilities for stars in a cluster region. For an input list of 3784 targets from the literature, we confirm that 3006 are real objects, the vast majority of them are open clusters, but associations and globular clusters are also present. For each confirmed object we determined the exact position of the cluster centre, the apparent size, proper motion, distance, colour excess, and age. For about 1500 clusters, these basic astrophysical parameters have been determined for the first time. For the bulk of the clusters we also derived the tidal radius. We estimated additionally average radial velocities for more than 30% of the confirmed clusters. The present sample (called MWSC) reaches both the central parts of the Milky Way and its outer regions. It is almost complete up to 1.8 kpc from the Sun and also covers neighbouring spiral arms. However, for a small subset of the oldest open clusters ($\log t \gtrsim 9$) we found some evidence of incompleteness within about 1 kpc from the Sun.

view Abstract Citations (43) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Young Globular Clusters in the Milky Way: ARP 2 Buonanno, R. ; Corsi, C. E. ; Pecci, F. Fusi ; Richer, H. B. ; Fahlman, G. G. Abstract We have obtained the first B,V CCD color-magnitude diagram (CMD) of the galactic globular cluster Arp 2. About 1600 stars have been measured between the tip of the red giant branch at V approximately 15.5 and V approximately 23.5, about two magnitudes below the main sequence turnoff. A centrally concentrated population of blue stragglers has been detected. The slope of the red giant branch and the overall CMD morphology are consistent with that of a metal-poor cluster, with (Fe/H) = -1.84 +/- 0.25. A preliminary spectroscopic measurement based on the Ca II triplet yields (Fe/H) = -1.73 +/- 0.05. The comparison of the CMD of Arp 2 with that of other clusters favors a value more metal-poor than that indicated by the Ca II triplet. In this respect, Arp 2 is similar to Ruprecht 106. Differential ages between Arp 2 and a number of reference clusters are obtained from the vertical age parameter, deltaHBTO and the horizontal age parameter, delta(B-V)RGBTO By requiring both age estimators to give consistent results, we find that Arp 2 is approximately 3 Gyr younger than the group of the metal-poor clusters and slightly older than Ruprecht 106. The detection of young metal-poor clusters (Fe/H) less than or = -1.8) implies a complex scenario for the origin of the galactic halo, possibly involving interactions with satellite galaxies and their cluster systems. Publication: The Astronomical Journal Pub Date: February 1995 DOI: 10.1086/117308 Bibcode: 1995AJ....109..650B Keywords: Chronology; Color-Magnitude Diagram; Globular Clusters; Milky Way Galaxy; Astronomical Spectroscopy; Blue Stars; Charge Coupled Devices; Galactic Clusters; Galactic Halos; Interacting Galaxies; Metallicity; Morphology; Red Giant Stars; Astronomy; GLOBULAR CLUSTERS: INDIVIDUAL: ARP 2 full text sources ADS | data products SIMBAD (19) CDS (1)

Context. The census of the globular clusters (GCs) in the Milky Way is still a work in progress. The advent of new deep surveys has made it possible to discover many new star clusters both in the Galactic disk and bulge, but many of these new candidates have not yet been studied in detail, leaving a veil on their true physical nature. Aims. We explore the nature of 19 new GC candidates in the Galactic bulge by analysing their colour–magnitude diagrams (CMDs) in the near-infrared (NIR) using the VISTA Variables in the Via Láctea Survey (VVV) database. We estimate their main astrophysical parameters: reddening and extinction, distance, total luminosity, mean cluster proper motions (PMs), metallicity, and age. Methods. We obtain the cluster catalogues including the likely cluster members by applying a decontamination procedure on the observed CMDs based on the vector PM diagrams from VIRAC2. We adopt NIR reddening maps in order to calculate the reddening and extinction for each cluster, and then estimate the distance moduli and heliocentric distances. Metallicities and ages are evaluated by fitting theoretical stellar isochrones. We also calculate their luminosities in comparison with known Galactic GCs. Results. We estimate a wide reddening range of 0.25 ⩽ E(J − Ks)⩽2.0 mag and extinction 0.11 ⩽ AKs ⩽ 0.86 mag for the sample clusters, as expected in the bulge regions. The range of heliocentric distances is 6.8 ⩽ D ⩽ 11.4 kpc. This allows us to place these clusters between 0.56 and 3.25 kpc from the Galactic centre, assuming R⊙ = 8.2 kpc. Also, their PMs are kinematically similar to the typical motion of the Galactic bulge, apart from VVV-CL160, which shows different PMs. We also derive their metallicities and ages, finding −1.40⩽ [Fe/H] ⩽ 0.0 dex and t ≈ 8 − 13 Gyr respectively. The luminosities are calculated both in Ks- and V-bands, recovering −3.4 ⩽ MV ⩽ −7.5. We also examine the possible RR Lyrae members found in the cluster fields. Conclusions. Based on their positions, kinematics, metallicities, and ages, and comparing our results with the literature, we conclude that nine candidates are real GCs, seven need more observations to be fully confirmed as GCs, and three candidates are discarded as GCs and appear to be younger open clusters.

Blue Straggler Stars (BSSs) are one of the keys to understand in a better way how stars evolve and interact with each other in different star clusters. They appear to be hotter and brighter than the Main Sequence Turn Off Point (MSTO) and, therefore, they should have evolved off the Main-Sequence branch. We properly select, for Open Clusters (OCs) and Globular Clusters (GCs), star cluster members based on proper motions and parallaxes provided by Gaia Data Release 3 (DR3). Using isochrones models and selection criteria from previous studies, we select and classify stars as BSS, Yellow Straggler Stars and Red Stragglers Stars (evolved BSSs). We identify BSSs to be present in all our GCs and in 42/129 (∼ 33 %) of studied OCs. We counted a total of 4399 BSSs; 434 (∼ 10 %) located in OCs and 3965 (90 %) located in GCs. Clusters younger than ∼ 500 Myr do not show the presence of BSSs in our sample. We obtain astrophysical parameters from 3 different methods (color–temperature relations, isochrone–fitting models and parameters from Gaia DR3 spectra) such as the effective temperature Teff, star mass M, and surface gravity log(g). We find values for BSS Teff to be ∼ (6800 ± 585) K in GCs and ∼ (7570 ± 1400) K in OCs; and an average mass of ⟨MBSS⟩ = (1.75 ± 0.45) M⊙ in OCs and ⟨MBSS⟩ = (1.02 ± 0.1) M⊙ in GCs. For every BSS, we compute the difference of the BSS mass and the MSTO mass of its parent cluster, normalized by the MSTO mass, and called it Me based on previous studies. This parameter is classified as low–Me (Me &lt; 0.5, BSS likely formed through mass-transfer) and high–Me (0.5 &lt; Me &lt; 1.0, BSS likely formed through mergers). For OCs we find a percentage 81.34 % high–Me and 18.66 % low–Me. For GCs, we find 94.25 % low–Me and 5.25 % high–Me. Comparing Me against the BSS age obtained with isochrone modes, we were able to detect: i) GC BSSs that are most likely to be formed through collisions show a “boost” in their percentage/fraction for stars with an age ∼ 1 − 2 Gyr, in agreement with reported age for core-collapse events in GCs found in previous studies; ii) a double sequence for GC BSSs, where we conclude that these sequences correspond to a pre merger/closer-binary interaction and post merger/closer-binary interaction of BSS formation

view Abstract Citations (104) References (152) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Star Clusters in the Clouds of Magellan van den Bergh, Sidney Abstract Star clusters in the Magellanic Clouds differ from those in the Galaxy in a number of important respects: 1. Both old and young clusters in the Clouds have radii r_h_ that are typically 3-4 times larger than those of their Galactic counterparts. 2. Luminous clusters of all ages in the LMC and the SMC are, on average, significantly more flattened than Galactic clusters. 3. The clouds contain a class of populous star clusters, with masses that are typically an order of magnitude smaller than those of average globulars, but an order of magnitude larger than those of most Galactic open clusters. 4. Many young clusters in the Magellanic Clouds are embedded in rich unbound stellar coronae. Such halos are probably the remnants of the associations in which these clusters were born. Stellar coronae around clusters can survive longer in the Clouds than in the Galaxy because tidal forces are much lower in the LMC and SMC than they are in the Galaxy. 5. The Large Cloud is surrounded by at least seven real globular clusters with ages greater than 10 Gyr (six of which contain RR Lyrae stars), whereas the Small Cloud has only one such companion. These clusters have luminosities and mass-to-light ratios similar to those of Galactic globulars. All six of the Large Cloud globular clusters for which color-magnitude diagrams are available have blue horizontal branches. This may indicate that these objects all have very large ages. Available data do not yet entirely exclude the possibility that these globular clusters belong to a spheroidal halo. 6. The specific globular cluster frequency is found to be S = 0.4 +/- 0.15 for the LMC, and S = 0.3 +/- 0.3 for the SMC. 7. In both the Large Cloud and the Small Cloud old clusters are found to be more widely distributed than are younger clusters. Known old clusters (and nova) (exhibit no concentration to the Bar of the LMC. 8. Both the metal enrichment history and the ages of star clusters indicate that star formation in the SMC got off to a slow start. The large residual gas mass in the Small Cloud also indicates that the Small Cloud never went through an intense prolonged starburst phase. No Large Cloud clusters are presently known with ages between about 3 and 10 Gyr. The end of this hiatus may have coincided with a major burst of star formation in the LMC. 9. The fact that the two largest bursts of star and cluster formation in the LMC appear to have no counterparts in the SMC indicates that the bursts of star formation in the Large Cloud were not triggered by close encounters between the Clouds. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169732 Bibcode: 1991ApJ...369....1V Keywords: Globular Clusters; Magellanic Clouds; Star Clusters; Star Formation; Stellar Evolution; Color-Magnitude Diagram; Early Stars; Elliptical Galaxies; Milky Way Galaxy; Astrophysics; CLUSTERS: GLOBULAR; GALAXIES: MAGELLANIC CLOUDS; GALAXIES: STELLAR CONTENT; STARS: EVOLUTION; STARS: FORMATION full text sources ADS | data products SIMBAD (17) NED (2)

view Abstract Citations (94) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ruprecht 106: A Young Metal-Poor Galactic Globular Cluster Buonanno, R. ; Buscema, G. ; Fusi Pecci, F. ; Richer, H. B. ; Fahlman, G. G. Abstract The first CCD photometric survey in the Galactic globular cluster Ruprecht 106 has been performed. The results show that Ruprecht 106 is a metal-poor cluster with (Fe/H) about -2 located at about 25 kpc from the Galactic center. A sizable, high centrally concentrated population of blue stragglers was detected. Significant differences in the positions of the turnoffs in the color-magnitude diagram are found compared to those in metal-poor clusters. The cluster appears younger than other typical metal-poor Galactic globulars by about 4-5 Gyr; if true, this object would represent the first direct proof of the existence of a significant age spread among old, very metal-poor clusters. Publication: The Astronomical Journal Pub Date: December 1990 DOI: 10.1086/115640 Bibcode: 1990AJ....100.1811B Keywords: Astronomical Photometry; Color-Magnitude Diagram; Galactic Clusters; Globular Clusters; Metallicity; Charge Coupled Devices; Milky Way Galaxy; Ubv Spectra; Astrophysics; CLUSTERS: GLOBULAR full text sources ADS | data products SIMBAD (8) CDS (1)