scholarly journals Extended halo of NGC 2682 (M 67) from Gaia DR2

2019 ◽  
Vol 627 ◽  
pp. A119 ◽  
Author(s):  
R. Carrera ◽  
M. Pasquato ◽  
A. Vallenari ◽  
L. Balaguer-Núñez ◽  
T. Cantat-Gaudin ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Open Cluster ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Galactic Disc ◽  
The Past ◽  
External Perturbations ◽  
Galactic Potential ◽  
Gaia Dr2

Context. NGC 2682 is a nearby open cluster that is approximately 3.5 Gyr old. Dynamically, most open clusters are expected to dissolve on shorter timescales of ≈1 Gyr. That it has survived until now means that NGC 2682 was likely much more massive in the past and is bound to have an interesting dynamical history. Aims. We investigate the spatial distribution of the stars in NGC 2682 to constrain dynamical evolution of the cluster. We particularly focus on the marginally bound stars in the cluster outskirts. Methods. We used Gaia DR2 data to identify NGC 2682 members up to a distance of ∼150 pc (10°). The two methods Clusterix and UPMASK were applied to this end. We estimated distances to obtain 3D stellar positions using a Bayesian approach to parallax inversion, with an appropriate prior for star clusters. We calculated the orbit of NGC 2682 using the GRAVPOT16 software. Results. The cluster extends up to 200′ (50 pc), which implies that its size is at least twice as large as previously believed. This exceeds the cluster Hill sphere based on the Galactic potential at the distance of NGC 2682. Conclusion. The extra-tidal stars in NGC 2682 may originate from external perturbations such as disc-shocking or dynamical evaporation from two-body relaxation. The former origin is plausible given the orbit of NGC 2682, which crossed the Galactic disc ≈40 Myr ago.

scholarly journals New star clusters discovered towards the Galactic bulge direction using Gaia DR2

2021 ◽  
Vol 502 (1) ◽  
pp. L90-L94
Author(s):  
F A Ferreira ◽  
W J B Corradi ◽  
F F S Maia ◽  
M S Angelo ◽  
J F C Santos
Keyword(s):  
Spatial Distribution ◽  
Star Clusters ◽  
Open Clusters ◽  
Systematic Search ◽  
Joint Analysis ◽  
The Sun ◽  
Galactic Bulge ◽  
Gaia Dr2

ABSTRACT We report the discovery of 34 new open clusters and candidates as a result of a systematic search carried out in 200 adjacent fields of 1 × 1 deg2 area projected towards the Galactic bulge, using Gaia DR2 data. The objects were identified and characterized by a joint analysis of their photometric, kinematic, and spatial distribution that has been consistently used and proved to be effective in our previous works. The discoveries were validated by cross-referencing the objects position and astrometric parameters with the available literature. Besides their coordinates and astrometric parameters, we also provide sizes, ages, distances, and reddening for the discovered objects. In particular, 32 clusters are closer than 2 kpc from the Sun, which represents an increment of nearly $39{{\ \rm per\ cent}}$ of objects with astrophysical parameters determined in the nearby inner disc. Although these objects fill an important gap in the open clusters distribution along the Sagittarius arm, this arm, traced by known clusters, appears to be interrupted, which may be an artefact due to the incompleteness of the cluster census.

scholarly journals Survival rates of planets in open clusters: the Pleiades, Hyades, and Praesepe clusters

2019 ◽  
Vol 624 ◽  
pp. A110 ◽  
Author(s):  
M. S. Fujii ◽  
Y. Hori
Keyword(s):  
Open Cluster ◽  
Survival Rates ◽  
Giant Planet ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Major Axis ◽  
Open Clusters ◽  
Semi Major Axis ◽  
Embedded Clusters ◽  
Host Stars

Context. In clustered environments, stellar encounters can liberate planets from their host stars via close encounters. Although the detection probability of planets suggests that the planet population in open clusters resembles that in the field, only a few dozen planet-hosting stars have been discovered in open clusters. Aims. We explore the survival rates of planets against stellar encounters in open clusters similar to the Pleiades, Hyades, and Praesepe and embedded clusters. Methods. We performed a series of N-body simulations of high-density and low-density open clusters, open clusters that grow via mergers of subclusters, and embedded clusters. We semi-analytically calculated the survival rate of planets in star clusters up to ~1 Gyr using relative velocities, masses, and impact parameters of intruding stars. Results. Less than 1.5% of close-in planets within 1 AU and at most 7% of planets with 1–10 AU are ejected by stellar encounters in clustered environments after the dynamical evolution of star clusters. If a planet population from 0.01–100 AU in an open cluster initially follows the probability distribution function of exoplanets with semi-major axis (ap) between 0.03 and 3 AU in the field discovered by RV surveys (∝ ap−0.6), the PDF of surviving planets beyond ~10 AU in open clusters can be slightly modified to ∝ ap−0.76. The production rate of free-floating planets (FFPs) per star is 0.0096–0.18, where we have assumed that all the stars initially have one giant planet with a mass of 1–13 MJup in a circular orbit. The expected frequency of FFPs is compatible with the upper limit on that of FFPs indicated by recent microlensing surveys. Our survival rates of planets in open clusters suggest that planets within 10 AU around FGKM-type stars are rich in relatively-young (≲10–100 Myr for open clusters and ~1–10 Myr for embedded clusters), less massive open clusters, which are promising targets for planet searches.

scholarly journals Hunting for open clusters in Gaia DR2: 582 new open clusters in the Galactic disc

2020 ◽  
Vol 635 ◽  
pp. A45 ◽  
Author(s):  
A. Castro-Ginard ◽  
C. Jordi ◽  
X. Luri ◽  
J. Álvarez Cid-Fuentes ◽  
L. Casamiquela ◽  
...  
Keyword(s):  
Machine Learning ◽  
Big Data ◽  
Clustering Algorithm ◽  
Open Cluster ◽  
Open Clusters ◽  
Galactic Disc ◽  
Data Environment ◽  
Blind Search ◽  
Tidal Tails ◽  
Gaia Dr2

Context. Open clusters are key targets for studies of Galaxy structure and evolution, and stellar physics. Since the Gaia data release 2 (DR2), the discovery of undetected clusters has shown that previous surveys were incomplete. Aims. Our aim is to exploit the Big Data capabilities of machine learning to detect new open clusters in Gaia DR2, and to complete the open cluster sample to enable further studies of the Galactic disc. Methods. We use a machine-learning based methodology to systematically search the Galactic disc for overdensities in the astrometric space and identify the open clusters using photometric information. First, we used an unsupervised clustering algorithm, DBSCAN, to blindly search for these overdensities in Gaia DR2 (l, b, ϖ, μα*, μδ), and then we used a deep learning artificial neural network trained on colour–magnitude diagrams to identify isochrone patterns in these overdensities, and to confirm them as open clusters. Results. We find 582 new open clusters distributed along the Galactic disc in the region |b| < 20°. We detect substructure in complex regions, and identify the tidal tails of a disrupting cluster UBC 274 of ∼3 Gyr located at ∼2 kpc. Conclusions. Adapting the mentioned methodology to a Big Data environment allows us to target the search using the physical properties of open clusters instead of being driven by computational limitations. This blind search for open clusters in the Galactic disc increases the number of known open clusters by 45%.

scholarly journals Reanalysis of nearby open clusters using Gaia DR1/TGAS and HSOY

2018 ◽  
Vol 615 ◽  
pp. A12 ◽  
Author(s):  
Steffi X. Yen ◽  
Sabine Reffert ◽  
Elena Schilbach ◽  
Siegfried Röser ◽  
Nina V. Kharchenko ◽  
...  
Keyword(s):  
Milky Way ◽  
Open Cluster ◽  
Star Clusters ◽  
Open Clusters ◽  
Parameter Estimates ◽  
Cluster Membership ◽  
Fitting Procedure ◽  
Cluster Data ◽  
The Galaxy ◽  
Automatic Tool

Context. Open clusters have long been used to gain insights into the structure, composition, and evolution of the Galaxy. With the large amount of stellar data available for many clusters in the Gaia era, new techniques must be developed for analyzing open clusters, as visual inspection of cluster color-magnitude diagrams is no longer feasible. An automatic tool will be required to analyze large samples of open clusters. Aims. We seek to develop an automatic isochrone-fitting procedure to consistently determine cluster membership and the fundamental cluster parameters. Methods. Our cluster characterization pipeline first determined cluster membership with precise astrometry, primarily from TGAS and HSOY. With initial cluster members established, isochrones were fitted, using a χ2 minimization, to the cluster photometry in order to determine cluster mean distances, ages, and reddening. Cluster membership was also refined based on the stellar photometry. We used multiband photometry, which includes ASCC-2.5 BV, 2MASS JHKs, and Gaia G band. Results. We present parameter estimates for all 24 clusters closer than 333 pc as determined by the Catalogue of Open Cluster Data and the Milky Way Star Clusters catalog. We find that our parameters are consistent to those in the Milky Way Star Clusters catalog. Conclusions. We demonstrate that it is feasible to develop an automated pipeline that determines cluster parameters and membership reliably. After additional modifications, our pipeline will be able to use Gaia DR2 as input, leading to better cluster memberships and more accurate cluster parameters for a much larger number of clusters.

scholarly journals A Gaia DR2 view of the open cluster population in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A93 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
C. Jordi ◽  
A. Vallenari ◽  
A. Bragaglia ◽  
L. Balaguer-Núñez ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Number Of Clusters ◽  
History Of ◽  
Gaia Dr2

Context. 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 submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

scholarly journals Open cluster remnants in low-density Galactic fields

2009 ◽  
Vol 5 (S266) ◽  
pp. 487-490
Author(s):  
D. B. Pavani ◽  
L. O. Kerber ◽  
E. Bica ◽  
W. J. Maciel
Keyword(s):  
Galactic Disk ◽  
Information Source ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Theoretical Models ◽  
Open Clusters ◽  
Low Density ◽  
Statistical Tool ◽  
General Picture ◽  
Disk Evolution

AbstractOpen cluster remnants (OCRs) are fundamental objects to investigate open cluster dissolution processes (e.g., Bica et al. 2001; Carraro 2002; Pavani et al. 2003; Carraro et al. 2007; Pavani & Bica 2007). They are defined as poorly populated concentrations of stars, with enough members to show evolutionary sequences in colour–magnitude diagrams (CMDs) as a result of the dynamical evolution of an initially more massive physical system. An OCR is intrinsically poorly populated, which makes its differentiation from field-star fluctuations difficult. Among the possible approaches to establish the nature of OCRs, we adopted CMD analysis combined with a robust statistical tool applied to 2mass data. In addition, photometry is the main information source available for possible OCRs (POCRs). We developed a statistical diagnostic tool to analyse the CMDs of POCRs and verify them as physical systems, explore membership probabilityies taking into account field contamination and derive age, distance and reddening values in a self-consistent way. We present the results of our analysis of 88 POCRs that are part of a larger sample that is widely distributed across the sky, with a significant density contrast of bright stars compared to the Galactic field. The 88 objects are projected onto low-density Galactic fields, at relatively high latitudes (|b| > 15°). Studies of larger POCR samples will provide a better understanding of OCR properties and constraints for theoretical models, including new insights into the evolution of open clusters and their dissolution rates. The results of this ongoing survey will provide a general picture of these fossil stellar systems and their connection to Galactic-disk evolution.

scholarly journals Star clusters as tracers of galactic subsystems

1993 ◽  
Vol 153 ◽  
pp. 323-324
Author(s):  
B. Barbuy ◽  
E. Bica ◽  
S. Ortolani
Keyword(s):  
Spatial Distribution ◽  
Galaxy Formation ◽  
Formation Process ◽  
Globular Clusters ◽  
Star Clusters ◽  
Open Clusters ◽  
Horizontal Branch ◽  
The Galaxy ◽  
Magnitude Difference

We have obtained CCD BVRI colour-magnitude diagrams for a series of disk globular clusters, improving parameters and detecting a new one: Lyngå 7. Using the magnitude difference between turn-off and horizontal branch Δ(TO-HB) as an age discriminator, and their spatial distribution we compare old disk open clusters, young halo globular clusters, and metal-rich disk globular clusters, obtaining clues to the Galaxy formation process.

scholarly journals Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm

2019 ◽  
Vol 488 (2) ◽  
pp. 1635-1651 ◽  
Author(s):  
M S Angelo ◽  
A E Piatti ◽  
W S Dias ◽  
F F S Maia
Keyword(s):  
Structural Parameters ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Mass Star ◽  
Proper Motions ◽  
Concentration Parameter ◽  
Low Mass ◽  
Gaia Dr2 ◽  
Spiral Arm

Abstract The study of dynamical properties of Galactic open clusters (OCs) is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 OCs, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129−SC32, and BH 150, projected against dense stellar fields. In order to do that, we employed Washington CT1 photometry and Gaia DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes. From the derived membership likelihoods, we built decontaminated colour–magnitude diagrams, while structural parameters were obtained from King profiles fitting. Our analysis revealed that they are relatively young OCs (log(t  yr−1) ∼7.3–8.6), placed along the Sagittarius spiral arm, and at different internal dynamical stages. We found that the half-light radius to Jacobi radius ratio, the concentration parameter and the age to relaxation time ratio describe satisfactorily their different stages of dynamical evolution. Those relative more dynamically evolved OCs have apparently experienced more important low-mass star loss.

scholarly journals OCCASO – III. Iron peak and α elements of 18 open clusters. Comparison with chemical evolution models and field stars

2019 ◽  
Vol 490 (2) ◽  
pp. 1821-1842 ◽  
Author(s):  
L Casamiquela ◽  
S Blanco-Cuaresma ◽  
R Carrera ◽  
L Balaguer-Núñez ◽  
C Jordi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Giant Stars ◽  
Stellar Nucleosynthesis ◽  
Solar Abundances ◽  
Red Giant

ABSTRACT The study of open-cluster chemical abundances provides insights on stellar nucleosynthesis processes and on Galactic chemo-dynamical evolution. In this paper we present an extended abundance analysis of 10 species (Fe, Ni, Cr, V, Sc, Si, Ca, Ti, Mg, O) for red giant stars in 18 OCCASO clusters. This represents a homogeneous sample regarding the instrument features, method, line list and solar abundances from confirmed member stars. We perform an extensive comparison with previous results in the literature, and in particular with the Gaia FGK Benchmark stars Arcturus and $\mu$-Leo. We investigate the dependence of [X/Fe] with metallicity, Galactocentric radius (6.5 kpc &lt; RGC &lt; 11 kpc), age (0.3 Gyr &lt; Age &lt; 10 Gyr), and height above the plane (|z| &lt; 1000 pc). We discuss the observational results in the chemo-dynamical framework, and the radial migration impact when comparing with chemical evolution models. We also use APOGEE DR14 data to investigate the differences between the abundance trends in RGC and |z| obtained for clusters and for field stars.

scholarly journals The blue straggler population of the old open cluster Berkeley 17

2019 ◽  
Vol 624 ◽  
pp. A26 ◽  
Author(s):  
Souradeep Bhattacharya ◽  
Kaushar Vaidya ◽  
W. P. Chen ◽  
Giacomo Beccari
Keyword(s):  
Radial Distribution ◽  
Globular Clusters ◽  
Minimum Spanning Tree ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Blue Straggler ◽  
Magnitude Diagram ◽  
First Time ◽  
Giant Branch Stars

Context. Blue straggler stars (BSSs) are observed in Galactic globular clusters and old open clusters. The radial distribution of BSSs has been used to diagnose the dynamical evolution of globular clusters. For the first time, with a reliable sample of BSSs identified with Gaia DR2, we conduct such an analysis for an open cluster. Aims. We aim to identify members, including BSSs, of the oldest known Galactic open cluster Berkeley 17 with the Gaia DR2 proper motions and parallaxes. We study the radial distribution of the BSS population to understand the dynamical evolution of the cluster. Methods. We selected cluster members to populate the colour magnitude diagram in the Gaia filters. Cluster parameters are derived using the brightest members. The BSSs and giant branch stars are identified, and their radial distributions are compared. The segregation of BSSs is also evaluated with respect to the giant branch stars using the minimum spanning tree (MST) analysis. Results. We determine Berkeley 17 to be at 3138.6−352.9+285.5 pc. We find 23 BSS cluster members, only two of which were previously identified. We find a bimodal radial distribution of BSSs supported by findings from the MST method. Conclusions. The bimodal radial distribution of BSSs in Berkeley 17 indicates that they have just started to sink towards the cluster centre, placing Berkeley 17 with globular clusters of intermediate dynamical age. This is the first such determination for an open cluster.

Sign in / Sign up

Export Citation Format

Share Document