- ID:
- ivo://CDS.VizieR/J/A+A/623/A80
- Title:
- Open clusters in APOGEE and GALAH surveys
- Short Name:
- J/A+A/623/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are ideal laboratories to investigate a variety of astrophysical topics, from the properties of the Galactic disk to stellar evolutionary models. Knowing their metallicity and possibly detailed chemical abundances is therefore important. However, the number of systems with chemical abundances determined from high resolution spectroscopy is still small. To increase the number of open clusters with radial velocities and chemical abundances determined from high resolution spectroscopy we used publicly available catalogues of surveys in combination with Gaia data. Open cluster stars have been identified in the APOGEE and GALAH spectroscopic surveys by cross-matching their latest data releases with stars for which high-probability astrometric membership has been derived in many clusters on the basis of the Gaia second data release. Radial velocities have been determined for 131 and 14 clusters from APOGEE and GALAH data, respectively. This is the first radial velocity determination from high resolution spectra for 16 systems. Iron abundances have been obtained for 90 and 14 systems from APOGEE and GALAH samples, respectively. To our knowledge 66 of these clusters (57 in APOGEE and 9 in GALAH) do not have previous determinations in the literature. For 90 and 7 clusters in the APOGEE and GALAH samples, respectively, we have also determined average abundances for Na, Mg, Al, Si, Ca, Cr, Mn, and Ni.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/912/162
- Title:
- Open clusters in solar neighborhood
- Short Name:
- J/ApJ/912/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the 3D morphology and kinematics of 13 open clusters (OCs) located within 500pc of the Sun, using Gaia} EDR3 and kinematic data from literature. Members of OCs are identified using the unsupervised machine learning method StarGO, using 5D parameters (X, Y, Z, {mu}_{alpha}cos{delta}, {mu}_{delta}). The OC sample covers an age range of 25Myr-2.65Gyr. We correct the asymmetric distance distribution due to the parallax error using Bayesian inversion. The uncertainty in the corrected distance for a cluster at 500pc is 3.0-6.3pc, depending on the intrinsic spatial distribution of its members. We determine the 3D morphology of the OCs in our sample and fit the spatial distribution of stars within the tidal radius in each cluster with an ellipsoid model. The shapes of the OCs are well-described with oblate spheroids (NGC 2547, NGC 2516, NGC 2451A, NGC 2451B, NGC 2232), prolate spheroids (IC 2602, IC 4665, NGC 2422, Blanco 1, Coma Berenices), or triaxial ellipsoids (IC 2391, NGC 6633, NGC 6774). The semi-major axis of the fitted ellipsoid is parallel to the Galactic plane for most clusters. Elongated filament-like substructures are detected in three young clusters (NGC 2232, NGC 2547, NGC 2451B), while tidal-tail-like substructures (tidal tails) are found in older clusters (NGC 2516, NGC 6633, NGC 6774, Blanco 1, Coma Berenices). Most clusters may be super-virial and expanding. N-body models of rapid gas expulsion with an SFE of ~1/3 are consistent with clusters more massive than 250M_{sun}_, while clusters less massive than 250M_{sun}_ tend to agree with adiabatic gas expulsion models. Only six OCs (NGC 2422, NGC 6633, and NGC 6774, NGC 2232, Blanco 1, Coma Berenices) show clear signs of mass segregation.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A102
- Title:
- 3794 open clusters parameters
- Short Name:
- J/A+A/652/A102
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The structure and evolution of the spiral arms of the Milky Way are basic but long-standing questions in astronomy. Especially the lifetime of spiral arms, it is still a puzzle and has not been well constrained from observations. In this work, we aim to inspect these issues by using a large catalogue of open clusters. We have compiled a catalogue of 3794 OCs based on Gaia EDR3. A majority of them have accurately determined parallaxes, proper motions and radial velocities. The age parameters for these OCs are also collected or calculated. Then, we analysed their distributions on the Galactic plane, the kinematic properties, the vertical distributions and the regressed properties of subsamples of OCs in order to better understand the nearby spiral structure and its evolution. We find evidence that the nearby spiral arms are compatible with a long lived pattern and might have remained approximately stable for the past 80 million years. Especially, the Local Arm where our Sun is currently located in, is also suggested to be long-lived in nature, and probable a major arm segment in the Milky Way. The evolutionary characteristics of nearby spiral arms show that the dynamic spiral mechanism might be not suitable for our Galaxy. Instead, the density wave theory is more consistent with the observational properties.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A116
- Title:
- Open clusters within 1.8 kpc of the Sun
- Short Name:
- J/A+A/593/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on an almost complete sample of Galactic open star clusters within 1.8kpc, we perform a comprehensive statistical analysis of various cluster parameters like spatial position, age, size, mass and extinction in order to understand the general properties of the open cluster system in the Galaxy and the Galactic structure. Based on the distribution of 1241 open clusters about the Galactic plane and in different age bins, we find the average Galactic scale height as Zh=60+/-2pc for the youngest cluster population having Age<700Myr, however, it increases up to 64+/-2pc when we also include older population of clusters. The solar offset is found to be 6.2+/-1.1pc above the formal Galactic plane. We derive a local mass density of {rho}_0_=0.090+/-0.005M_{sun}_/pc^3^ and found a negligibly small amount of dark matter in the solar neighbourhood. The reddening in the direction of clusters suggests a strong correlation with their vertical distance from the Galactic plane having a respective slope of dE(B-V)/dz=0.40+/-0.04 and 0.42+/-0.05 mag/kpc below and above the GP. We observe a linear mass-radius and mass-age relations in the open clusters and derive a slope of dR/d(logM)=2.08+/-0.10 and d(logM)/d(logT)=-0.36+/-0.05,respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/L186
- Title:
- Orbital eccentricities of 31535 G-dwarfs
- Short Name:
- J/ApJ/725/L186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test four competing models that aim to explain the nature of stars in spiral galaxies that are well away (>1kpc) from the midplane, the so-called thick disk: the stars may have gotten there through orbital migration, through satellite mergers and accretion, or through heating of pre-existing thin disk stars. The eccentricity distribution of thick disk stars has recently been proposed as a diagnostic to differentiate between these mechanisms. Drawing on SDSS-DR7, we have assembled a sample of 31535 G-dwarfs with six-dimensional phase-space information and metallicities and have derived the orbital eccentricities for them.
- ID:
- ivo://CDS.VizieR/I/348
- Title:
- Orbital parameters in Milky-Way-like potentials
- Short Name:
- I/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital parameters, such as eccentricity and maximum vertical excursion, of stars in the Milky Way are an important tool for understanding its dynamics and evolution, but calculation of such parameters usually relies on computationally-expensive numerical orbit integration. We present and test a fast method for estimating these parameters using an application of the Sackel fudge, used previously for the estimation of action-angle variables. We show that the method is highly accurate, to a level of <1% in eccentricity, over a large range of relevant orbits and in different Milky Way-like potentials, and demonstrate its validity by estimating the eccentricity distribution of the RAVE-TGAS data set and comparing it to that from orbit integration. Using the method, the orbital characteristics of the ~7 million Gaia DR2 stars with radial velocity measurements are computed with Monte Carlo sampled errors in ~116 hours of parallelised cpu time, at a speed that we estimate to be ~3 to 4 orders of magnitude faster than using numerical orbit integration. We demonstrate using this catalogue that Gaia DR2 samples a large range of orbits in the solar vicinity, down to those with r_peri_<~2.5kpc, and out to r_ap_>~13kpc. We also show that many of the features present in orbital parameter space have a low mean zmax, suggesting that they likely result from disk dynamical effects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/2479
- Title:
- Orbital parameters of globular clusters
- Short Name:
- J/MNRAS/474/2479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the effects of collisional dynamics on the formation and detectability of cold tidal streams. A semi-analytical model for the evolution of the stellar mass function was implemented and coupled to a fast stellar stream simulation code, as well as the synthetic cluster evolution code EMACSS for the mass evolution as a function of a globular cluster orbit. We find that the increase in the average mass of the escaping stars for clusters close to dissolution has a major effect on the observable stream surface density. As an example, we show that Palomar 5 would have undetectable streams (in an SDSS-like survey) if it was currently three times more massive, despite the fact that a more massive cluster loses stars at a higher rate. This bias due to the preferential escape of low-mass stars is an alternative explanation for the absence of tails near massive clusters, than a dark matter halo associated with the cluster. We explore the orbits of a large sample of Milky Way globular clusters and derive their initial masses and remaining mass fraction. Using properties of known tidal tails, we explore regions of parameter space that favour the detectability of a stream. A list of high-probability candidates is discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/19
- Title:
- Orphan stream high-resolution spectroscopic study
- Short Name:
- J/ApJ/784/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high-resolution spectroscopic study on the Orphan stream for five stream candidates, observed with the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Clay telescope. The targets were selected from the low-resolution catalog of Casey et al. (2013ApJ...764...39C): three high-probability members, one medium, and one low-probability stream candidate were observed. Our analysis indicates that the low- and medium-probability targets are metal-rich field stars. The remaining three high-probability targets range over ~1 dex in metallicity, and are chemically distinct compared to the other two targets and all standard stars: low [{alpha}/Fe] abundance ratios are observed, and lower limits are ascertained for [Ba/Y], which sit well above the Milky Way trend. These chemical signatures demonstrate that the undiscovered parent system is unequivocally a dwarf spheroidal galaxy, consistent with dynamical constraints inferred from the stream width and arc. As such, we firmly exclude the proposed association between NGC 2419 and the Orphan stream. A wide range in metallicities adds to the similarities between the Orphan stream and Segue 1, although the low [{alpha}/Fe] abundance ratios in the Orphan stream are in tension with the high [{alpha}/Fe] values observed in Segue 1. Open questions remain before Segue 1 could possibly be claimed as the "parent" of the Orphan stream. The parent system could well remain undiscovered in the southern sky.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A78
- Title:
- Orphan stream RR Lyrae and non-variables
- Short Name:
- J/A+A/648/A78
- Date:
- 07 Dec 2021 13:05:58
- Publisher:
- CDS
- Description:
- We present a chemo-dynamical study of the Orphan stellar stream using a catalog of RR Lyrae pulsating variable stars for which photometric, astrometric, and spectroscopic data are available. Employing low-resolution spectra from the Sloan Digital Sky Survey (SDSS), we determined line-of-sight velocities for individual exposures and derived the systemic velocities of the RR Lyrae stars. In combination with the stars' spectroscopic metallicities and Gaia EDR3 astrometry, we investigated the northern part of the Orphan stream. In our probabilistic approach, we found 20 single mode RR Lyrae variables likely associated with the Orphan stream based on their positions, proper motions, and distances. The acquired sample permitted us to expand our search to nonvariable stars in the SDSS dataset, utilizing line-of-sight velocities determined by the SDSS. We found 54 additional nonvariable stars linked to the Orphan stream. The metallicity distribution for the identified red giant branch stars and blue horizontal branch stars is, on average, -2.13+/-0.05dex and -1.87+/-0.14dex, with dispersions of 0.23 and 0.43dex, respectively. The metallicity distribution of the RR Lyrae variables peaks at -1.80+/-0.06dex and a dispersion of 0.25dex. Using the collected stellar sample, we investigated a possible link between the ultra-faint dwarf galaxy Grus II and the Orphan stream. Based on their kinematics, we found that both the stream RR Lyrae and Grus II are on a prograde orbit with similar orbital properties, although the large uncertainties on the dynamical properties render an unambiguous claim of connection difficult. At the same time, the chemical analysis strongly weakens the connection between both. We argue that Grus II in combination with the Orphan stream would have to exhibit a strong inverse metallicity gradient, which to date has not been detected in any Local Group system.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/2216
- Title:
- Outer bulge O-rich Mira's JHKL photometry
- Short Name:
- J/MNRAS/455/2216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report periods and JHKL observations for 643 oxygen-rich Mira variables found in two outer bulge fields at b=-7{deg} and l=+/-8{deg} and combine these with data on 8057 inner bulge Miras from the OGLE, Macho and 2MASS surveys, which are concentrated closer to the Galactic centre. Distance moduli are estimated for all these stars. Evidence is given showing that the bulge structure is a function of age. The longer period Miras (LogP>2.6, age~5Gyr and younger) show clear evidence of a bar structure inclined to the line of sight in both the inner and outer regions. The distribution of the shorter period (metal-rich globular cluster age) Miras, appears spheroidal in the outer bulge. In the inner region these old stars are also distributed differently from the younger ones and possibly suggest a more complex structure. These data suggest a distance to the galactic centre R_0_, of 8.9kpc, with an estimated uncertainty of ~0.4kpc. The possible effect of helium enrichment on our conclusions is discussed.
