- ID:
- ivo://CDS.VizieR/J/A+A/345/471
- Title:
- Memberships of open clusters
- Short Name:
- J/A+A/345/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New memberships, mean parallaxes and proper motions of all 9 open clusters closer than 300pc (except the Hyades) and 9 rich clusters between 300 and 500pc have been computed using Hipparcos (Cat. <I/239>) data. Precisions, ranging from 0.2 to 0.5mas for parallaxes and 0.1 to 0.5mas/yr for proper motions, are of great interest for calibrating photometric parallaxes as well as for kinematical studies. Careful investigations of possible biases have been performed and no evidence of significant systematic errors on the mean cluster parallaxes has been found. The distances and proper motions of 32 more distant clusters, which may be used statistically, are also indicated.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/631/A166
- Title:
- Members of 5 cluster in Ori OB1a association
- Short Name:
- J/A+A/631/A166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13Myr old. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with 10% precision. While four of the clusters have ages between 11 and 13Myr, the ASCC 20 cluster stands out at an age of 21+/-3Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21Myr old population on the younger parts of the complex, including their formation.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1065
- Title:
- Members of the Sculptor dwarf spheroidal galaxy
- Short Name:
- J/AJ/130/1065
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy are presented. Our aims were to obtain an accurate map of the outer structure of Sculptor and to determine the level of interaction between this system and the Galaxy. Photometry was obtained in two colors down to the magnitude limits of V=20 and I=19, covering a 3.1{deg}x3.1{deg} area centered on Sculptor.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/11
- Title:
- Member stars in the MW satellite Tucana III
- Short Name:
- J/ApJ/838/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v_hel_=-102.3+/-0.4(stat.)+/-2.0(sys.)km/s, a velocity dispersion of 0.1_-0.1_^+0.7^km/s, and a mean metallicity of [Fe/H]=-2.42_-0.08_^+0.07^. The upper limit on the velocity dispersion is {sigma}<1.5km/s at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0x10^4^M_{sun}_. We cannot rule out mass-to-light ratios as large as 240M_{sun}_/L_{sun}_ for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V=15.7 that is the brightest known member star of an ultra-faint satellite.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A21
- Title:
- Merging galaxies (mis)alignments
- Short Name:
- J/A+A/582/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spatially resolved stellar and/or ionized gas kinematic properties for a sample of 103 interacting galaxies, tracing all merger stages: close companions, pairs with morphological signatures of interaction, and coalesced merger remnants. In order to distinguish kinematic properties caused by a merger event from those driven by internal processes, we compare our galaxies with a control sample of 80 non-interacting galaxies. We measure for both the stellar and the ionized gas components the major (projected) kinematic position angles (PA_kin_, approaching and receding) directly from the velocity distributions with no assumptions on the internal motions. This method also allow us to derive the deviations of the kinematic PAs from a straight line ({delta}PA_kin_). We find that around half of the interacting objects show morpho-kinematic PA misalignments that cannot be found in the control sample. In particular, we observe those misalignments in galaxies with morphological signatures of interaction. On the other hand, the level of alignment between the approaching and receding sides for both samples is similar, with most of the galaxies displaying small misalignments. Radial deviations of the kinematic PA orientation from a straight line in the stellar component measured by {delta}PA_kin_ are large for both samples. However, for a large fraction of interacting galaxies the ionized gas {delta}PA_kin_ is larger than the typical values derived from isolated galaxies (48%), indicating that this parameter is a good indicator to trace the impact of interaction and mergers in the internal motions of galaxies. By comparing the stellar and ionized gas kinematic PA, we find that 42% (28/66) of the interacting galaxies have misalignments larger than 16{deg}, compared to 10% from the control sample. Our results show the impact of interactions in the motion of stellar and ionized gas as well as the wide the variety of their spatially resolved kinematic distributions. This study also provides a local Universe benchmark for kinematic studies in merging galaxies at high redshift.
- ID:
- ivo://CDS.VizieR/J/A+AS/110/177
- Title:
- Mesure de vitesses radiales. VII.
- Short Name:
- J/A+AS/110/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We publish 734 radial velocities of stars distributed in 28 fields of 4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot et al. 1990 and 1992), using the Fehrenbach objective prism method.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A15
- Title:
- Metallicity and kinematics in Galactic bar
- Short Name:
- J/A+A/563/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observe red clump stars in four fields along the Galactic bar major axis (l=10{deg}, -6{deg}, 6{deg} and b=0{deg}, plus a field at l=0{deg}, b=1{deg}) with low-resolution spectroscopy from FLAMES/GIRAFFE (setup LR08) at the VLT, observing around the CaII triplet. We developed robust methods to extract radial velocity and metallicity estimates from these low signal-to-noise spectra. Results have been derived by fixing atmospheric parameters typical of a red clump star (Teff=4750K, logg=2.5). For some targets, the metallicity could not be derived.
- ID:
- ivo://CDS.VizieR/J/MNRAS/494/396
- Title:
- Metallicity distribution in GC
- Short Name:
- J/MNRAS/494/396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present stellar metallicity measurements of more than 600 late-type stars in the central 10pc of the Galactic Centre. Together with our previously published KMOS data, this data set allows us to investigate, for the first time, spatial variations of the nuclear star cluster's metallicity distribution. Using the integral-field spectrograph KMOS (VLT), we observed almost half of the area enclosed by the nuclear star cluster's effective radius. We extract spectra at medium spectral resolution and apply full spectral fitting utilizing the PHOENIX library of synthetic stellar spectra. The stellar metallicities range from [M/H]=-1.25dex to [M/H]>+0.3dex, with most of the stars having supersolar metallicity. We are able to measure an anisotropy of the stellar metallicity distribution. In the Galactic north, the portion of subsolar metallicity stars with [M/H]<0.0dex is more than twice as high as in the Galactic south. One possible explanation for different fractions of subsolar metallicity stars in different parts of the cluster is a recent merger event. We propose to test this hypothesis with high- resolution spectroscopy and by combining the metallicity information with kinematic data.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A55
- Title:
- Metallicity of the {gamma} Vel cluster
- Short Name:
- J/A+A/567/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowledge of the abundance distribution of star forming regions and young clusters is critical to investigate a variety of issues, from triggered star formation and chemical enrichment by nearby supernova explosions to the ability to form planetary systems. In spite of this, detailed abundance studies are currently available for relatively few regions. In this context, we present the analysis of the metallicity of the Gamma Velorum cluster, based on the products distributed in the first internal release of the Gaia-ESO Survey. The Gamma Velorum candidate members have been observed with FLAMES, using both UVES and Giraffe, depending on the target brightness and spectral type. In order to derive a solid metallicity determination for the cluster, membership of the observed stars must be first assessed. To this aim, we use several membership criteria including radial velocities, surface gravity estimates, and the detection of the photospheric lithium line. Out of the 80 targets observed with UVES, we identify 14 high-probability members. We find that the metallicity of the cluster is slightly sub-solar, with a mean [Fe/H]=-0.057+/-0.018dex. Although J08095427-4721419 is one of the high-probability members, its metallicity is significantly larger than the cluster average. We speculate about its origin as the result of recent accretion episodes of rocky bodies of about 60 Msun hydrogen-depleted material from the circumstellar disc.
- ID:
- ivo://CDS.VizieR/J/AJ/108/538
- Title:
- Metal-poor MS stars UBV photometry
- Short Name:
- J/AJ/108/538
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From analysis of a photometrically selected sample of 175 metal-poor field stars with main sequence gravities (hereafter BMPs) and UBV colors blueward of the most metal-poor globular cluster main-sequence turnoffs, 0.15<(B-V)_0_<0.35, and properties of the candidate lists of the HK objective prism survey, we calculate the space density and a suitably defined specific frequency of BMPs within ~2kpc of the Sun. We consider two cases. If we adopt the luminosities and color distribution of globular cluster blue stragglers (hereafter BS) for BMPs, the BMP space density, is ~350kpc^-3^, from which we obtain a specific frequency S(BMP)~8, a value 9 times larger than that of BSs in globular clusters. From this result, we conclude that cluster-type BSs are but a minor component of the field BMPs and that the remainder must be of a different nature. If we adopt luminosities of metal-poor models halfway between the Zero Age Main Sequence and the phase of core hydrogen exhaustion, we obtain a space density of 450(+300,-150)kpc^-3^ and a specific frequency S(BMP)=10(+5,-3). From a subsample of 107 BMPs with available radial velocities we derive a galactic rotation of 128km/s and an isotropic velocity dispersion of {sigma}~90km/s, values intermediate between those of halo and thick-disk populations. From analysis of a larger sample of stars on 0.15<(B-V)0<0.35 binned by a crude line-blanketing parameter, we find that our results are insensitive to adopted BMP selection criteria: none of these subsamples of A- and early F-type stars above the galactic plane possess disk kinematics. The region of the UBV two-color diagram occupied by BMPs could be populated by metal-deficient, main-sequence gravity stars with ages substantially younger than those of the metal-poor halo. Because we cannot imagine how or where the observed local population of BMPs could have been produced within our galaxy during the past 3 to 10Gyr, we suggest that BMPs are the bluest members of metal-poor intermediate-age main sequences accreted, probably, from dwarf spheroidal satellites of the Milky Way during the past 10Gyr. We discuss observational consequences of this suggestion.
