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.

Investigation of the nearby open clusters with Gaia DR2 data

2019 ◽  
Vol 14 (S351) ◽  
pp. 502-506
Author(s):  
Anton F. Seleznev ◽  
Vladimir M. Danilov ◽  
Giovanni Carraro
Keyword(s):  
Three Dimensional ◽  
Open Clusters ◽  
Dimensional Structure ◽  
Proper Motions ◽  
Membership Probability ◽  
First Results ◽  
Alpha Persei ◽  
Mass Functions ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractGaia DR2 catalog provides a unique possibility to study the three-dimensional structure and the three-dimensional velocity field of the nearby open clusters. We can either select stars with a maximum membership probability and the most accurate values for the proper motions, parallaxes, and the radial velocities, or study these clusters statistically using overwhelmingly large areas of sky of tens by tens degrees. The second approach allows us to reveal the extensive outer parts of the clusters - a corona and the tidal tails and to study the luminosity and mass functions of these clusters. We present the first results of the investigation of several nearby open clusters, including Pleiades, Alpha Persei, Ruprecht 147.

scholarly journals Investigating dynamical properties of evolved Galactic open clusters

2019 ◽  
Vol 624 ◽  
pp. A8 ◽  
Author(s):  
M. S. Angelo ◽  
J. F. C. Santos ◽  
W. J. B. Corradi ◽  
F. F. S. Maia
Keyword(s):  
Open Cluster ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Long Term Evolution ◽  
Open Clusters ◽  
Evolutionary Stage ◽  
Proper Motions ◽  
Stellar Content ◽  
Term Evolution

Context. The stellar content of Galactic open clusters is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of open clusters are called open cluster remnants. These are sparsely populated structures that can barely be distinguished from the field. Aims. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as remnants or remnant candidates. We employed parameters that are intimately associated with the dynamical evolution: age, limiting radius, stellar mass, and velocity dispersion. The sample also includes 7 objects that are catalogued as dynamically evolved open clusters for comparison purposes. Methods. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the Gaia DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes (μα, μδ, ϖ) for stars in the objects’ areas. The luminosity and mass functions and total masses for most open cluster remnants are derived here for the first time. Our analysis used predictions of N-body simulations to estimate the initial number of stars of the remnants from their dissolution timescales. Results. The investigated open cluster remnants present masses (M) and velocity dispersions (σv) within well-defined ranges: M between ∼10−40 M⊙ and σv between ∼1−7 km s−1. Some objects in the remnant sample have a limiting radius Rlim ≲ 2 pc, which means that they are more compact than the investigated open clusters; other remnants have Rlim between ∼2−7 pc, which is comparable to the open clusters. We suggest that cluster NGC 2180 (previously classified as an open cluster) is entering a remnant evolutionary stage. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Conclusions. We conclude that the open cluster remnants we studied are in fact remnants of initially very populous open clusters (N0 ∼ 103−104 stars). The outcome of the long-term evolution is to bring the final residues of the open clusters to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.

scholarly journals Discovery and astrophysical properties of Galactic open clusters in dense stellar fields using Gaia DR2

2020 ◽  
Vol 496 (2) ◽  
pp. 2021-2038
Author(s):  
F A Ferreira ◽  
W J B Corradi ◽  
F F S Maia ◽  
M S Angelo ◽  
J F C Santos
Keyword(s):  
Milky Way ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Open Clusters ◽  
Galactic Latitude ◽  
Galactic Disc ◽  
New Findings ◽  
Low Latitudes ◽  
First Time ◽  
Gaia Dr2

ABSTRACT We report the discovery of 25 new open clusters resulting from a search in dense low Galactic latitude fields. We also provide, for the first time, structural and astrophysical parameters for the new findings and 34 other recently discovered open clusters using Gaia Data Release 2 (DR2) data. The candidates were confirmed by jointly inspecting the vector point diagrams and spatial distribution. The discoveries were validated by matching near known objects and comparing their mean astrometric parameters with the available literature. A decontamination algorithm was applied to the three-dimensional astrometric space to derive membership likelihoods for clusters stars. By rejecting stars with low membership likelihoods, we built decontaminated colour–magnitude diagrams and derived the clusters astrophysical parameters by isochrone fitting. The structural parameters were also derived by King-profile fittings over the stellar distributions. The investigated clusters are mainly located within 3 kpc from the Sun, with ages ranging from 30 Myr to 3.2 Gyr and reddening limited to E(B − V) = 2.5. On average, our cluster sample presents less concentrated structures than Gaia DR2 confirmed clusters, since the derived core radii are larger while the tidal radii are not significantly different. Most of them are located in the IV quadrant of the Galactic disc at low latitudes, therefore, they are immersed in dense fields characteristic of the inner Milky Way.

scholarly journals Photo-evaporation of close-in gas giants orbiting around G and M stars

2019 ◽  
Vol 624 ◽  
pp. A101 ◽  
Author(s):  
Daniele Locci ◽  
Cesare Cecchi-Pestellini ◽  
Giuseppina Micela
Keyword(s):  
Extreme Ultraviolet ◽  
Dynamical Evolution ◽  
High Energy ◽  
Electron Content ◽  
Mass Star ◽  
X Rays ◽  
Atmospheric Escape ◽  
Low Mass ◽  
M Stars ◽  
The Stability

Context. X-rays and extreme ultraviolet radiation impacting a gas produce a variety of effects that, depending on the electron content, may provide significant heating of the illuminated region. In a planetary atmosphere of solar composition, stellar high energy radiation can heat the gas to very high temperatures and this could affect the stability of planetary atmospheres, in particular for close-in planets. Aims. We investigate the variations with stellar age in the occurring frequency of gas giant planets orbiting G and M stars, taking into account that the high energy luminosity of a low mass star evolves in time, both in intensity and hardness. Methods. Using the energy-limited escape approach we investigated the effects induced by the atmospheric mass loss on giant exoplanet distribution that is initially flat, at several distances from the parent star. We followed the dynamical evolution of the planet atmosphere, tracking the departures from the initial profile due to the atmospheric escape, until it reaches the final mass-radius configuration. Results. We find that a significant fraction of low mass Jupiter-like planets orbiting with periods lower than ~3.5 days either vaporize during the first billion years or lose a relevant part of their atmospheres. The planetary initial mass profile is significantly distorted; in particular, the frequency of occurrence of gas giants, less massive than 2 MJ, around young stars can be considerably greater than their occurrence around older stellar counterparts.

scholarly journals A wide survey for circumstellar disks in the Lupus complex

2020 ◽  
Vol 642 ◽  
pp. A86
Author(s):  
P. S. Teixeira ◽  
A. Scholz ◽  
J. Alves
Keyword(s):  
Three Dimensional ◽  
Circumstellar Disks ◽  
Young Stellar Objects ◽  
Dimensional Structure ◽  
Spectral Energy ◽  
Mass Star ◽  
Nearby Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Low Mass

Previous star formation studies have, out of necessity, often defined a population of young stars confined to the proximity of a molecular cloud. Gaia allows us to examine a wider, three-dimensional structure of nearby star forming regions, leading to a new understanding of their history. We present a wide-area survey covering 494 deg2 of the Lupus complex, a prototypical low-mass star forming region. Our survey includes all known molecular clouds in this region as well as parts of the Upper Scorpius and Upper Centaurus Lupus (UCL) groups of the Sco-Cen complex. We combine Gaia DR2 proper motions and parallaxes as well as ALLWISE mid-infrared photometry to select young stellar objects (YSOs) with disks. The YSO ages are inferred from Gaia color-magnitude diagrams, and their evolutionary stages from the slope of the spectral energy distributions. We find 98 new disk-bearing sources. Our new sample includes objects with ages ranging from 1 to 15 Myr and masses ranging from 0.05 to 0.5 M⊙, and consists of 56 sources with thick disks and 42 sources with anemic disks. While the youngest members are concentrated in the clouds and at distances of 160 pc, there is a distributed population of slightly older stars that overlap in proper motion, spatial distribution, distance, and age with the Lupus and UCL groups. The spatial and kinematic properties of the new disk-bearing YSOs indicate that Lupus and UCL are not distinct groups. Our new sample comprises some of the nearest disks to Earth at these ages, and thus provides an important target for follow-up studies of disks and accretion in very low mass stars, for example with ALMA and ESO-VLT X-shooter.

scholarly journals New ultra-cool and brown dwarf candidates in Gaia DR2

2018 ◽  
Vol 619 ◽  
pp. L8 ◽  
Author(s):  
C. Reylé
Keyword(s):  
Brown Dwarfs ◽  
Mass Range ◽  
Solar Neighborhood ◽  
Proper Motions ◽  
Brown Dwarf ◽  
Expected Number ◽  
Data Release ◽  
Low Mass ◽  
Fine Structures ◽  
Gaia Dr2

Context. The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources. The resulting Hertzsprung–Russel diagram reveals fine structures throughout the mass range. Aims. This paper aims to investigate the content of Gaia DR2 at the low-mass end and to characterize ultra-cool and brown dwarfs. Methods. We first retrieved the sample of spectroscopically confirmed ultra-cool and brown dwarfs in Gaia DR2. We used their locus in the precise Hertzsprung–Russel diagram to select new candidates and to investigate their properties. Results. The number of spectroscopically confirmed objects recovered in Gaia DR2 corresponds to 61% and 74% of the expected number of objects with an estimated Gaia magnitude G est ≤ 21.5 and 20.3, respectively. This fills much of the gap to Gaia DR1. Furthermore, Gaia DR2 contains Ȉ13 000 ≥ M7 and 631 new L candidates. A tentative classification suggests that a few hundred of them are young or subdwarf candidates. Their distance distribution shows that the solar neighborhood census is still incomplete. Conclusions. Gaia DR2 offers a great wealth of information on low-mass objects. It provides a homogeneous and precise catalog of candidates that is worthwhile to be further characterized with spectroscopic observations.

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 Fundamental parameters for 45 open clusters with Gaia DR2, an improved extinction correction and a metallicity gradient prior

2020 ◽  
Vol 499 (2) ◽  
pp. 1874-1889
Author(s):  
H Monteiro ◽  
W S Dias ◽  
A Moitinho ◽  
T Cantat-Gaudin ◽  
J R D Lépine ◽  
...  
Keyword(s):  
Maximum Likelihood Method ◽  
Interstellar Extinction ◽  
Substantial Improvement ◽  
Open Clusters ◽  
Likelihood Method ◽  
Proper Motions ◽  
Review Of The Literature ◽  
Fundamental Parameters ◽  
Galactic Abundance ◽  
Gaia Dr2

ABSTRACT Reliable fundamental parameters of open clusters (OCs) such as distance, age, and extinction are key to our understanding of Galactic structure and stellar evolution. In this work, we use Gaia Data Release 2 (DR2) to investigate 45 OCs listed in the New catalogue of optically visible open clusters and candidates (DAML) but with no previous astrometric membership estimation based on Gaia DR2. In the process of selecting targets for this study, we found that some clusters reported as new discoveries in recent papers based on Gaia DR2 were already known clusters listed in DAML. Cluster memberships were determined using a maximum likelihood method applied to Gaia DR2 astrometry. This has allowed us to estimate mean proper motions and mean parallaxes for all investigated clusters. Mean radial velocities were also determined for 12 clusters, 7 of which had no previous published values. We have improved our isochrone fitting code to account for interstellar extinction using an updated extinction polynomial for the Gaia DR2 photometric bandpasses and the Galactic abundance gradient as a prior for metallicity. The updated procedure was validated with a sample of clusters with high-quality [Fe/H] determinations. We then did a critical review of the literature and verified that our cluster parameter determinations represent a substantial improvement over previous values.

scholarly journals The Effects of Radiation Feedback on Early Fragmentation and Stellar Multiplicity

2010 ◽  
Vol 6 (S270) ◽  
pp. 231-234
Author(s):  
Stella S. R. Offner
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
High Mass ◽  
Radiation Hydrodynamics ◽  
Mass Star ◽  
Low Mass ◽  
Effects Of Radiation ◽  
Radiation Feedback

AbstractForming stars emit a significant amount of radiation into their natal environment. While the importance of radiation feedback from high-mass stars is widely accepted, radiation has generally been ignored in simulations of low-mass star formation. I use ORION, an adaptive mesh refinement (AMR) three-dimensional gravito-radiation-hydrodynamics code, to model low-mass star formation in a turbulent molecular cloud. I demonstrate that including radiation feedback has a profound effect on fragmentation and protostellar multiplicity. Although heating is mainly confined within the core envelope, it is sufficient to suppress disk fragmentation that would otherwise result in low-mass companions or brown dwarfs. As a consequence, turbulent fragmentation, not disk fragmentation, is likely the origin of low-mass binaries.

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