- ID:
- ivo://CDS.VizieR/J/ApJ/769/87
- Title:
- Kinematics of halo red giants
- Short Name:
- J/ApJ/769/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the kinematics and orbital properties of a sample of red giants in the halo system of the Milky Way that are thought to have formed in globular clusters based on their anomalously strong UV/blue CN bands. The orbital parameters of the CN-strong halo stars are compared to those of the inner- and outer-halo populations as described by Carollo et al. (2007Natur.450.1020C, 2010ApJ...712..692C), and to the orbital parameters of globular clusters with well-studied Galactic orbits. The CN-strong field stars and the globular clusters both exhibit kinematics and orbital properties similar to the inner-halo population, indicating that stripped or destroyed globular clusters could be a significant source of inner-halo field stars, and suggesting that both the CN-strong stars and the majority of globular clusters are primarily associated with this population.
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- ID:
- ivo://CDS.VizieR/J/AJ/108/1016
- Title:
- Kinematics of local RR lyrae stars. I.
- Short Name:
- J/AJ/108/1016
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the structure and formation history of the galaxy, we have obtained low-to-moderate dispersion spectra of 302 nearby RR Lyrae variables of Bailey type "ab". We derived abundances, typically accurate to 0.15-0.20dex and calibrated to the Zinn & West (1984ApJS...55...45Z) globular cluster metallicity scale, from the pseudo-equivalent widths of the Ca II K, Hdelta, Hgamma, and Hbeta lines. Radial velocities accurate to between 2 and 30km/s were obtained from the spectra and from the literature. Distances accurate to between 5% and 20% were derived from published apparent magnitudes and Burstein & Heiles (1982AJ.....87.1165B) reddenings. The metallicity distribution of the RR Lyrae stars peaks at [Fe/H]_K_ =~ -1.5, and is narrower than that of the Ryan & Norris (1991AJ....101.1865R) subdwarfs, as expected since the most metal-rich and metal-poor progenitors preferentially appear as stable red and blue horizontal branch stars, rather than as RR Lyrae. The metal-rich tail of the RR Lyrae distribution extends to [Fe/H]_K_{approx}0, and a qualitative analysis of the distribution of distances from the galactic plane shows that the stars in this tail (i.e., [Fe/H]_K_>-1.0) are more concentrated to the plane than the more metal-poor stars. The abundance distribution of the local RR Lyrae stars is in excellent agreement with the changing abundance distributions of distant RR Lyrae stars as a function of galactocentric distance, as derived by Suntzeff et al. (1991ApJ...367..528S), who ascribed this change to systematic variations in horizontal branch morphology (probably age variations) with galactocentric distance. The abundance distribution of the local RR Lyrae stars also agrees well with those of the distant RR Lyrae stars as a function of distance from the galactic plane. There is no evidence for an abundance gradient in this direction, suggesting that gaseous dissipation did not play a major role in the formation of the outer halo.
- ID:
- ivo://CDS.VizieR/J/ApJS/96/175
- Title:
- Kinematics of Metal-Poor Stars. I.
- Short Name:
- J/ApJS/96/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the kinematic properties of a sample of 1936 Galactic stars, selected without kinematic bias, and with abundances [Fe/H] <= -0.6. The stars selected for this study all have measured radial velocities, and the majority have abundances determined from spectroscopic and narrow-/intermediate-band photometric techniques. In contrast to previous examinations of the kinematics of the metal-poor stars in the Galaxy, our sample contains large numbers of stars that are located at distances in excess of 1 kpc from the Galactic plane. Thus, a much clearer picture of the nature of the metal-deficient populations in the Galaxy can now be drawn. Our present data can be well described in terms of a two-component kinematic model consisting of a thick disk, rotating at roughly 200 km/s (independent of metal abundance), and an essentially nonrotating halo. The kinematics of these two components suggest a very broad overlap in metallicity; the thick disk is shown to possess an extremely metal-weak tail, extending to abundances even lower than previously reported, down to at least [Fe/H] ~ -2.0. A "minimal-assumptions" maximum-likelihood model is used to show that below [Fe/H] = -1.5 roughly 30% of stars in the solar neighbourhood can be kinematically associated with the thick disk. Over the metallicity interval -1.6 <= [Fe/H] <= -1.0, the thick-disk proportion rises to 60%. This fraction is only slightly smaller than contribution of thick-disk stars derived by Morrison, Flynn, and Freeman in the same metallicity interval (80%). Our confirmation that significant numbers of stars with thick-disk-like kinematics exist in the solar neighbourhood at arbitrarily low metal abundance suggests that previous disagreements about the correlation of population rotation velocities and metal abundance (e.g. Sandage & Fouts vs. Norris) may be due primarily to the selection criteria employed, and the resulting different contribution of metal-weak thick-disk stars to the respective data sets. The non-Gaussian nature of the velocity distribution of extremely metal-poor stars ([Fe/H] <= -1.5) in the directions of the Galactic poles reported by previous workers can also be understood as a consequence of the overlap between a cold metal-weak thick-disk population and a hot halo population. A maximum-likelihood technique has been developed in order to estimate the velocity ellipsoids of the thick-disk and halo components of the Galaxy. From the 349 stars in our sample with -1.0 <= [Fe/H] <= -0.6 and |z| <= 1 kpc, the velocity ellipsoid of the thick disk is (sigma_U, sigma_V, sigma_W) = (63 +/- 7, 42 +/- 4, 38 +/- 4) km/s. These values are in remarkably good accord with the predicted thick-disk velocity ellipsoid obtained by Quinn, Hernquist, and Fullagar from simulations of a satellite-merger formation scenario. Based on this velocity ellipsoid, a radial scale length for thick-disk stars of h_R = 4.7 +/- 0.5 kpc is obtained, larger than reported by Morrison, and similar to the value obtained for the old-disk population. However, the apparent equality of sigma_V and sigma_W is evidence that the thick disk is kinematically distinct from the old-disk population, where sigma_V:sigma_W ~ 2^{1/2}:1. We find a substantially smaller asymmetric-drift velocity gradient for presumed thick-disk stars (delta Vrot/delta |z| = -13 +/- 6 km/s/kpc) than reported by Majewski (delta Vrot/delta |z| = -21 +/- 1 km/s/kpc). From 887 stars in our sample with [Fe/H] <= -1.5 the local velocity ellipsoid of the halo is (sigma_r, sigma_phi, sigma_theta) = (153 +/- 10, 93 +/- 18, 107 +/- 7) km/s, that is, strongly radially peaked, as indicated by previous studies. We find little difference in the velocity ellipsoids of this sample when it is split into two roughly equal pieces with -2.2 <= [Fe/H] <= -1.5 and [Fe/H] <= -2.2, which indicates a lack of radial metallicity gradient in the halo, as found from studies of the Galactic globular cluster system. The velocity ellipsoid obtained from the small number of stars in our sample with Galactocentric distances r > 10 kpc (N = 61) is (sigma_r, sigma_phi, sigma_theta) = (115 +/- 18, 138 +/- 78, 110 +/- 24) km/s, much less radially elongated than found for the local sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/317/460
- Title:
- Kinematics of Mira stars
- Short Name:
- J/MNRAS/317/460
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The space motions of Mira variables are derived from radial velocities, Hipparcos (<I/239>) proper motions and a period-luminosity relation. The previously known dependence of Mira kinematics on the period of pulsation is confirmed and refined. In addition, it is found that Miras with periods in the range 145-200d in the general Solar neighbourhood have a net radial outward motion from the Galactic Centre of 75+/-18km/s. This, together with a lag behind the circular velocity of Galactic rotation of 98+/-19km/s, is interpreted as evidence for an elongation of their orbits, with their major axes aligned at an angle of ~17{deg} with the Sun-Galactic Centre line, towards positive Galactic longitudes. This concentration seems to be a continuation to the Solar circle and beyond of the bar-like structure of the Galactic bulge, with the orbits of some local Miras probably penetrating into the bulge. These conclusions are not sensitive to the distance scale adopted. A further analysis is given of the short-period (SP) red group of Miras discussed in companion papers in this series. In Appendix A the mean radial velocities and other data for 842 oxygen-rich Mira-like variables are tabulated. These velocities were derived from published optical and radio observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1103
- Title:
- Kinematics of Orion Nebula Cluster
- Short Name:
- J/ApJ/697/1103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a kinematic study of the Orion Nebula Cluster (ONC) based upon RVs measured by multifiber echelle spectroscopy at the 6.5m MMT and Magellan telescopes. Velocities are reported for 1613 stars, with multi-epoch data for 727 objects as part of our continuing effort to detect and analyze spectroscopic binaries (SBs). We confirm and extend the results of Furesz et al. (2008, Cat. J/ApJ/676/1109), showing that the ONC is not relaxed, consistent with its youth, and that the stars generally follow the position-velocity structure of the moderate density gas in the region, traced by ^13^CO. The additional RVs we have measured enable us to probe some discrepancies between stellar and gaseous structure which can be attributed to binary motion and the inclusion of nonmembers in our kinematic sample. Our multi-epoch data allow us to identify 89 SBs; more will be found as we continue monitoring. Our results reinforce the idea that the ONC is a cluster in formation, and thus provide a valuable testing ground for theory.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A94
- Title:
- Kinematics of the Gamma Vel cluster
- Short Name:
- J/A+A/563/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A key science goal of the Gaia-ESO survey (GES) at the VLT is to use the kinematics of low-mass stars in young clusters and star forming regions to probe their dynamical histories and how they populate the field as they become unbound. The clustering of low-mass stars around the massive Wolf-Rayet binary system {gamma}^2^ Velorum was one of the first GES targets. Targets were selected from colour-magnitude diagrams and intermediate resolution spectroscopy was used to derive radial velocities and assess membership from the strength of the LiI 6708{AA} line. The radial velocity distribution was analysed using a maximum likelihood technique that accounts for unresolved binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/110/463
- Title:
- Kinematics of the Shapley supercluster
- Short Name:
- J/AJ/110/463
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new analysis of the kinematics of the Shapley supercluster based on radial velocities for 1087 galaxies in the clusters A3558 (Shapley 8), A3528 (Klemola 21), A3532 (Klemola 22), A3530, A3556 (SC 1321-314), A3559 (CE 1327-292), A3560, A3562, SC 1329-314 and in the intercluster region of the core of the supercluster, of which 367 are new measurements. We also present accurate positions from APM and MAMA scans of the ESO/SERC Southern Sky Survey photographic plates. We obtain new velocity dispersions and estimate the masses of the member clusters, evaluating dynamical models of the supercluster. The supercluster is found to be significantly flattened. We find that for Omega_0=0.3, H_0=75km/s/Mpc, the gravitational pull of the supercluster may account for up to 25% of the peculiar velocity of the Local Group required to explain the dipole anisotropy of the Cosmic Microwave Background radiation, in which case the mass of the supercluster would be dominated by intercluster dark matter. This fractional contribution would be considerably higher for combinations of significantly lower values of Omega_0 and higher values of H_0.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/497
- Title:
- Kinematics of W UMa-type binaries
- Short Name:
- J/MNRAS/357/497
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The kinematics of 129 W Ursae Majoris type binaries (W UMas) were studied. The sample is heterogeneous with different orbits and physically different components from F to K spectral-type main-sequence stars. The computed U, V, W space velocities indicate that the sample is also heterogeneous in velocity space.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/202
- Title:
- Kinematic study of the Leo II dwarf galaxy
- Short Name:
- J/ApJ/836/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a large spectroscopic survey of 336 red giants in the direction of the Leo II dwarf galaxy using Hectochelle on the Multiple Mirror Telescope, and we conclude that 175 of them are members based on their radial velocities and surface gravities. Of this set, 40 stars have never before been observed spectroscopically. The systemic velocity of the dwarf is 78.3+/-0.6km/s with a velocity dispersion of 7.4+/-0.4km/s. We identify one star beyond the tidal radius of Leo II but find no signatures of uniform rotation, kinematic asymmetries, or streams. The stars show a strong metallicity gradient of -1.53+/-0.10dex/kpc and have a mean metallicity of -1.70+/-0.02dex.
