- ID:
- ivo://CDS.VizieR/J/PAZh/33/643
- Title:
- Kinematics of Sco-Cen OB Association
- Short Name:
- J/PAZh/33/643
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A fine structure related to the kinematic peculiarities of three components of the Scorpius-Centaurus association (LCC = Lower Centaurus-Crux, UCL = Upper Centaurus-Lupus, and US = Upper Scorpius) has been revealed in the UV-velocity distribution of Gould Belt stars. We have been able to identify the most likely members of these groups by applying the method of analyzing the two-dimensional probability density function of stellar UV velocities that we developed. A kinematic analysis of the identified structural components has shown that, in general, the center-of-mass motion of the LCC, UCL, and US groups follows the motion characteristic of the Gould Belt, notably its expansion. The entire Scorpius-Centaurus complex is shown to possess a proper expansion with an angular velocity parameter of 46+/-8km/s/kpc for the kinematic center with l_0_=-40{deg} and R_0_=110pc found. Based on this velocity, we have estimated the characteristic expansion time of the complex to be 21+/-4Myr. The proper rotation velocity of the Scorpius-Centaurus complex is lower in magnitude, is determined less reliably, and depends markedly on the data quality.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2369
- Title:
- Kinematics of young associations/clusters
- Short Name:
- J/MNRAS/402/2369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young isolated radio-quiet neutron stars are still hot enough to be detectable at X-ray and optical wavelengths due to their thermal emission and can hence probe cooling curves. An identification of their birth sites can constrain their age. For that reason, we try to identify the parent associations for four of the so-called Magnificent Seven neutron stars for which proper motion and distance estimates are available. We are tracing back in time each neutron star and possible birth association centre to find close encounters. The associated time of the encounter expresses the kinematic age of the neutron star which can be compared to its characteristic spin-down age. Owing to observational uncertainties in the input data, we use Monte Carlo simulations and evaluate the outcome of our calculations statistically. RX J1856.5-3754 most probably originated from the Upper Scorpius association about 0.3Myr ago. RX J0720.4-3125 was either born in the young local association TW Hydrae about 0.4Myr ago or in Trumpler 10 0.5Myr in the past. Also RX J1605.3+3249 and RBS 1223 seem to come from a nearby young association such as the Scorpius-Centraurus complex or the extended Corona-Australis association. For RBS 1223 also a birth in Scutum OB2 is possible. We also give constraints on the observables as well as on the radial velocity of the neutron star. Given the birth association, its age and the flight time of the neutron star, we estimate the mass of the progenitor star. Some of the potential supernovae were located very nearby (<100pc) and thus should have contributed to the 10Be and 60Fe material found in the Earth's crust. In addition, we reinvestigate the previously suggested neutron star/runaway pair PSR B1929+10/zeta Ophiuchi and conclude that it is very likely that both objects were ejected during the same supernova event.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/100
- Title:
- Kinematic structure of the Galactic Center S cluster
- Short Name:
- J/ApJ/896/100
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high-velocity S cluster and orbit the supermassive black hole Sgr A* at the center of the Milky Way. For 39 of them, orbital elements are known; for the remainder, we know proper motions. The distribution of the inclinations and the proper motion flight directions deviate significantly from a uniform distribution, which one expects if the orientation of the orbits are random. Across the central arcseconds, the S-cluster stars are arranged in two almost edge-on disks that are located at a position angle approximately +/-45{deg} with respect to the Galactic plane. The angular momentum vectors for stars in each disk point in both directions, i.e., the stars in a given disk rotate in opposite ways. The poles of this structure are located only about 25{deg} from the line of sight. This structure may be the result of a resonance process that started with the formation of the young B-dwarf stars in the cluster about 6Myr ago. Alternatively, it indicated the presence of a disturber at a distance from the center comparable to the distance of the compact stellar association IRS 13.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A34
- Title:
- KMOS O-type star detection in Tr 16-SE
- Short Name:
- J/A+A/648/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carina Nebula harbors a large population of high-mass stars, including at least 75 O-type and Wolf-Rayet (WR) stars, but the current census is not complete since further high-mass stars may be hidden in or behind the dense dark clouds that pervade the association. With the aim of identifying optically obscured O- and early B-type stars in the Carina Nebula, we performed the first infrared spectroscopic study of stars in the optically obscured stellar cluster Tr 16-SE, located behind a dark dust lane south of {eta} Car. We used the integral-field spectrograph KMOS at the ESO VLT to obtain H- and K-band spectra with a resolution of R~4000 ({Delta}{lambda}~5{AA}) for 45 out of the 47 possible OB candidate stars in Tr 16-SE, and we derived spectral types for these stars. We find 15 stars in Tr 16-SE with spectral types between O5 and B2 (i.e. high-mass stars with M>=8M_{sun}_), only two of which were known before. An additional nine stars are classified as (Ae)Be stars, i.e. intermediate-mass pre-main sequence stars, and most of the remaining targets show clear signatures of being late-type stars and are thus most likely foreground stars or background giants unrelated to the Carina Nebula. Our estimates of the stellar luminosities suggest that nine of the 15 O- and early B-type stars are members of Tr 16-SE, whereas the other six seem to be background objects. Our study increases the number of spectroscopically identified high-mass stars (M>=8M_{sun}_) in Tr 16-SE from two to nine and shows that Tr 16-SE is one of the larger clusters in the Carina Nebula. Our identification of three new stars with spectral types between O5 and O7 and four new stars with spectral types O9 to B1 significantly increases the number of spectroscopically identified O-type stars in the Carina Nebula.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/822
- Title:
- LAMOST candidate members of star clusters
- Short Name:
- J/MNRAS/448/822
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) stellar parameter pipeline at Peking University - LSP3, developed and implemented for the determinations of radial velocity Vr and stellar atmospheric parameters (effective temperature Teff, surface gravity logg, metallicity [Fe/H]) for the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC). We describe the algorithms of LSP3 and examine the accuracy of parameters yielded by it. The precision and accuracy of parameters yielded are investigated by comparing results of multi-epoch observations and of candidate members of open and globular clusters, with photometric calibration, as well as with independent determinations available from a number of external data bases, including the PASTEL archive, the APOGEE, SDSS and RAVE surveys, as well as those released in the LAMOST DR1. The uncertainties of LSP3 parameters are characterized and quantified as a function of the spectral signal-to-noise ratio (SNR) and stellar atmospheric parameters. We conclude that the current implementation of LSP3 has achieved an accuracy of 5.0km/s, 150K, 0.25dex, 0.15dex for the radial velocity, effective temperature, surface gravity and metallicity, respectively, for LSS-GAC spectra of FGK stars of SNRs per pixel higher than 10. The LSP3 has been applied to over a million LSS-GAC spectra collected hitherto. Stellar parameters yielded by the LSP3 will be released to the general public following the data policy of LAMOST, together with estimates of the interstellar extinction E(B-V) and stellar distances, deduced by combining spectroscopic and multiband photometric measurements using a variety of techniques.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/65
- Title:
- LAMOST K giants in Galactic halo substructures
- Short Name:
- J/ApJ/880/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a large halo K-giant sample by combining the positions, distances, radial velocities, and metallicities of over 13000 LAMOST DR5 halo K giants with the Gaia DR2 proper motions, which covers a Galactocentric distance range of 5-120kpc. Using a position-velocity clustering estimator (the 6Distance), we statistically quantify the presence of position-velocity substructure at high significance: K giants have more close pairs in position-velocity space than a smooth stellar halo. We find that the amount of substructure in the halo increases with increasing distance and metallicity. With a percolation algorithm named friends-of-friends to identify groups, we identify members belonging to Sagittarius (Sgr) Streams, Monoceros Ring, Virgo Overdensity, Hercules-Aquila Cloud, Orphan Streams, and other unknown substructures and find that the Sgr streams account for a large part of grouped stars beyond 20kpc and enhance the increase of substructure with distance and metallicity. For the first time, we identify spectroscopic members of Monoceros Ring in the southern and northern Galactic hemispheres, which presents a rotation of about 185km/s and a mean metallicity of -0.66dex.
- ID:
- ivo://CDS.VizieR/J/AJ/152/45
- Title:
- LAMOST survey of star clusters in M31. II.
- Short Name:
- J/AJ/152/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We select from Paper I a sample of 306 massive star clusters observed with the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33, and determine their metallicities, ages, and masses. Metallicities and ages are estimated by fitting the observed integrated spectra with stellar synthesis population (SSP) models with a pixel-to-pixel spectral fitting technique. Ages for most young clusters are also derived by fitting the multi-band photometric measurements with model spectral energy distributions (SEDs). The estimated cluster ages span a wide range, from several million years to the age of the universe. The numbers of clusters younger and older than 1Gyr are, respectively, 46 and 260. With ages and metallicities determined, cluster masses are then estimated by comparing the multi-band photometric measurements with SSP model SEDs. The derived masses range from ~10^3^ to ~10^7^M_{Sun}_, peaking at ~10^4.3^ and ~10^5.7^M_{Sun}_ for young (<1Gyr) and old (>1Gyr) clusters, respectively. Our estimated metallicities, ages, and masses are in good agreement with available literature values. Old clusters richer than [Fe/H]~-0.7dex have a wide range of ages. Those poorer than [Fe/H]~-0.7dex seem to be composed of two groups, as previously found for Galactic globular clusters-one of the oldest ages with all values of metallicity down to ~-2dex and another with metallicity increasing with decreasing age. The old clusters in the inner disk of M31 (0-30kpc) show a clear metallicity gradient measured at -0.038+/-0.023dex/kpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/2220
- Title:
- Larson relations in massive clumps
- Short Name:
- J/MNRAS/477/2220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We tested the validity of the three Larson relations in a sample of 213 massive clumps selected from the Herschel infrared Galactic Plane (Hi-GAL) survey, also using data from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey of 3-mm emission lines. The clumps are divided into five evolutionary stages so that we can also discuss the Larson relations as a function of evolution. We show that this ensemble does not follow the three Larson relations, regardless of the clump's evolutionary phase. A consequence of this breakdown is that the dependence of the virial parameter {alpha}_vir_ on mass (and radius) is only a function of the gravitational energy, independent of the kinetic energy of the system; thus, {alpha}_vir_ is not a good descriptor of clump dynamics. Our results suggest that clumps with clear signatures of infall motions are statistically indistinguishable from clumps with no such signatures. The observed non-thermal motions are not necessarily ascribed to turbulence acting to sustain the gravity, but they might be a result of the gravitational collapse at the clump scales. This seems to be particularly true for the most massive (M>=1000M_{sun}_) clumps in the sample, where exceptionally high magnetic fields might not be enough to stabilize the collapse.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/455
- Title:
- LH 47 UVBRI photometry
- Short Name:
- J/A+AS/123/455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 3 lists the final photometric data of our observations. The UBVRI observations were done with the 1.54m Danish telescope at ESO on October 3rd and 4th, 1992. The CCD was ESO#28, a TEK 1024x1024 with a pixel size of 24mue corresponding to 0.377" per pixel. The total field of view is 6.4'x6.4'. A standard reduction was done with MIDAS and IRAF, the photometry was performed with DAOPHOT within IRAF. The images of Oct 4th have been calibrated using the calibration field around PG 0231+051 (Landolt 1992, Cat. <II/183>). The images of Oct 3rd have then been adopted to the system of Oct 4th. The final Table 3 lists 4613 stars with V and B-V information. In addition U-B is available for 1159 of these stars, V-R for 3519 and V-I for 2854 stars. Table 4 gives those stars from our field of view which are present in the MACS (Magellanic Catalogue of Stars; Tucholke et al. 1996, Cat. <I/221>). The table contains the MACS Id., our x and y position and our UBV photometry, and right ascension and declination from the MACS. These stars may serve to calculate an exact position for every star from Table 3 or to define a coordinate grid for comparison with other observations, such as radio or X-ray data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/L39
- Title:
- Lindsay 1 spectroscopy for 34 targets
- Short Name:
- J/MNRAS/465/L39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lindsay 1 is an intermediate-age (~=8Gyr) massive cluster in the Small Magellanic Cloud. Using VLT FORS2 spectra of 16 probable cluster members on the lower red giant branch of the cluster, we measure CN and CH band strengths (at ~=3883 and 4300{AA}, respectively), along with carbon and nitrogen abundances and find that a sub-population of stars has significant nitrogen enrichment. A lack of spread in carbon abundances excludes evolutionary mixing as the source of this enrichment, so we conclude that this is evidence of multiple populations. Therefore, Lindsay 1 is the youngest cluster to show such variations, implying that the process triggering the onset of multiple populations must operate until at least redshift ~1.
