- ID:
- ivo://CDS.VizieR/J/AJ/112/545
- Title:
- Proton capture chains in globular clusters. I.
- Short Name:
- J/AJ/112/545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sodium abundances have been derived for 130 giant stars in the globular cluster M13 from spectra of the Na I doublet at {lambda}5682 and 5685A obtained using the KPNO 4-m Hydra fiber positioner and bench spectrograph. Magnesium abundances have also been obtained for the brightest 98 stars in the sample from the nearby Mg I line at {lambda}5711A. The stars observed in M13 range from the faintest at M_V_~+1.0 and log(g)~2.6 up to the tip of the giant branch, and include 18 stars on the asymptotic giant branch. Among the lower luminosity giants, the sodium abundances have a large star-to-star range, approximately from -0.3<=[Na/Fe]<=+0.5. However, the sodium abundances of the most luminous giants (Mv<-1.7) are usually high; typically, [Na/Fe]>=+0.3, with a much smaller star-to-star scatter. The asymptotic giant branch stars have smaller sodium abundances on average than do the red giant branch tip stars. The spread in [Na/Fe] ratios is larger in M13 than it is among halo field giants of comparable metallicity; M13 contains many more stars with high [Na/Fe] ratios than can be found in the field, even at relatively low luminosities on the giant branch. Magnesium is uniformly overabundant ([Mg/Fe]~+0.3) in all stars with a low sodium abundance, but the [Mg/Fe] ratio ranges from approximately -0.3 to +0.3 in stars with a high sodium abundance. These sodium and magnesium abundance variations in M13 are discussed in the context of proton capture and deep mixing hypotheses. In addition to the CN and ON hydrogen burning chains previously discussed in the literature, the NeNa and MgAl burning chains have also contributed to the abundance mixture observed in M13 giants. At least some of the products of proton capture chains have been produced in situ in the giants, and brought to the surface, most probably via deep mixing. Evidence in support of the occurrence of proton capture nucleosynthesis and deep mixing among M13 stars includes (1) the absence of sodium-poor stars at the red giant tip, (2) the fact that asymptotic branch stars have lower sodium abundances on average than do stars near the red giant tip, and (3) the existence of a positive correlation between sodium and nitrogen abundances as well as a partial anti-correlation of sodium and magnesium abundances.
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- ID:
- ivo://CDS.VizieR/J/ApJ/454/788
- Title:
- Radial velocities and BV photometry of NGC 3201
- Short Name:
- J/ApJ/454/788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BV CCD frames have been used to derive surface brightness profiles for NGC 3201 which extend out to ~18'. A total of 857 radial velocities with median precision ~1km/s for 399 member giants have been used to trace the velocity dispersion profile out to 32.1' (the approximate tidal radius determined from fits of single-mass, isotropic King-Michie models to the cluster surface brightness profiles). The median difference in radial velocity for stars on either side of an imaginary axis stepped through the cluster in 1 deg increments shows a statistically significant maximum amplitude of 1.22+/-0.25km/s. We discuss several possible explanations of this result, including (1) cluster rotation, (2) preferential stripping of stars on prograde orbits near the limiting radius, (3) the projection of the cluster space velocity onto the plane of the sky, and (4) a slight drift in the velocity zero point. It is difficult to unambiguously identify the primary cause of the observed structure in the velocity field, however, and we suspect that all of the above processes may play a role. The BV surface brightness profiles and radial velocities have been modeled with both single- and multimass King-Michie models and nonparametric techniques. The corresponding density profiles and M/L profiles show good agreement over the interval 1.5<~R<~10pc, and both approaches suggest a steady rise in M/L with distance from the cluster center. Due to the low cluster luminosity we are unable to place useful constraints on the anisotropy of M/L_B~M/L_V~2.0+/-0.2 for the multimass and nonparametric models, compared to ~1.65+/-0.15 for models having equal-mass stars. Our best-fit, multimass models have mass function slopes of x~0.75+/-0.25, consistent with recent findings that the form of the mass function depends on the position relative to the potential of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/674/857
- Title:
- Radial velocities and CT1 magnitudes in M60 galaxy
- Short Name:
- J/ApJ/674/857
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocity measurements for globular clusters in M60, a giant elliptical galaxy in the Virgo Cluster. Target globular cluster candidates were selected using Washington photometry based on deep 16'x16' images taken at the KPNO 4m telescope and using VI photometry derived from Hubble Space Telescope WFPC2 archival images. The spectra of the target objects were obtained with the Multi-Object Spectrograph at the Canada-France-Hawaii Telescope. We have measured the radial velocities of 111 objects in the field of M60: 93 globular clusters (72 blue globular clusters with 1.0<=C-T1<1.7, and 21 red globular clusters with 1.7<=C-T1<2.4), 11 foreground stars, six small galaxies, and the nucleus of M60.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/167
- Title:
- Radial velocities and membership in Pal 13
- Short Name:
- J/ApJ/743/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Keck/DEIMOS spectroscopy and Canada-France-Hawaii Telescope/MegaCam photometry for the Milky Way globular cluster Palomar 13. We triple the number of spectroscopically confirmed members, including many repeat velocity measurements. Palomar 13 is the only known globular cluster with possible evidence for dark matter, based on a Keck/High Resolution Echelle Spectrometer 21 star velocity dispersion of {sigma}=2.2+/-0.4km/s. We reproduce this measurement, but demonstrate that it is inflated by unresolved binary stars. For our sample of 61 stars, the velocity dispersion is {sigma}=0.7^+0.6^_-0.5_km/s. Combining our DEIMOS data with literature values, our final velocity dispersion is {sigma}=0.4^+0.4^_-0.3_km/s. We determine a spectroscopic metallicity of [Fe/H]=-1.6+/-0.1 dex, placing a 1{sigma} upper limit of {sigma}_[Fe/H]_~0.2dex on any internal metallicity spread. We determine Palomar 13's total luminosity to be M_V_=-2.8+/-0.4, making it among the least luminous known globular clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/417/597
- Title:
- Radial velocities in 4 globular clusters
- Short Name:
- J/A+A/417/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial and rotation velocity measurements from UVES+VLT high resolution spectra of 61 stars in the blue horizontal branches (HB) of the Galactic globular clusters NGC 1904 (M 79), NGC 2808, NGC 6093 (M 80) and NGC 7078 (M 15). ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
- ID:
- ivo://CDS.VizieR/J/A+A/566/A58
- Title:
- Radial velocities in M3, M13, and M92
- Short Name:
- J/A+A/566/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocity data are presented for three Galactic globular clusters, M3, M13, and M92. The provided catalogues include several hundreds of stars in each cluster that cover a wide range of distances to the cluster centres. Besides the measured radial velocities, the catalogues contain measurement uncertainties, identifiers, world coordinates and variability information for each star. The velocities for stars near the centres of the clusters were obtained using PMAS integral field spectroscopy (IFS). Note that in order to facilitate future variability studies, for each star the individual velocity measurements are provided instead of a single combined velocity. The PMAS data are complemented with velocities reported in various literature studies for stars at larger distances to the centres.
- ID:
- ivo://CDS.VizieR/J/A+A/462/L9
- Title:
- Radial velocities in NGC 7099
- Short Name:
- J/A+A/462/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A test of Newton's law of gravity in the low acceleration regime using globular clusters is presented and new results for the core collapsed globular cluster NGC 7099 given. The run of the gravitational potential as a function of distance is probed by studying the velocity dispersion profile of the cluster, as derived from a set of 125 radial velocities with accuracy better than 1km/s. The velocity dispersion profile is traced up to ~18pc from the cluster center. The dispersion is found to be maximal at the center, then decrease until 10+/-2pc from the center, well inside the cluster tidal radius of 42pc. After that the dispersion remains basically constant with an average value of 2.2+/-0.3km/s. Assuming a total V magnitude of M(V)=-7.43mag for NGC 7099, the acceleration at 10+/-2pc from the center is 1.1^+0.4_-0.3_{tau}x10^-8^cm/s^2^, where {tau} is the mass-to-light ratio. Thus, for {tau}>~2 typical of globular clusters, the flattening of the velocity dispersion profile occurs for a value of the internal acceleration of gravity that is fully consistent with a_0_=1.2x10^-8^cm/s^2^ observed in galaxies. This new result for NGC 7099 brings to 4 the clusters with velocity dispersion profile probing acceleration below a_0_. All four have been found to have a flat dispersion profile at large radii where the acceleration is below a_0_, thereby mimicking elliptical galaxies qualitatively and quantitatively. Whether this indicates a failure of Newtonian dynamics in the low acceleration limit or some more conventional dynamical effect (e.g., tidal heating) is still unclear. However, the similarities emerging between very different globular clusters, as well as between globular clusters and elliptical galaxies, seem to favor the first of these two possibilities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1137
- Title:
- Radial velocities in NGC 1851
- Short Name:
- J/MNRAS/426/1137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the result of a spectroscopic survey performed in the outskirts of the globular cluster NGC1851 with Visible MultiObject Spectrograph (VIMOS)/Very Large Telescope (VLT) with the medium-resolution grism coupled with the GG475 filter. The spectral coverage is from 5000 to 8000{AA} with a resolution R~580. Target stars have been selected from the photometry of Carballo-Bello et al. (2012MNRAS.419...14C), sampling a wide range in magnitude and colour (16<B<22, 0.6<B-R<2.1). We report the radial velocities of 107 stars in a region between 12 and 33 arcmin around the cluster centre. Observations have been performed during three nights in 2008 October at the Very Large Telescope's (VLT) Unit Telescope 3 (Melipal) at the European Southern Observatory (ESO), Cerro Paranal, Chile, equipped with the VIsible MultiObject Spectrograph (VIMOS). Velocities have been obtained by cross-correlating the spectra of the individual exposures with a GIRAFFE solar spectrum smoothed to the resolution of our targets using the region of the H-alpha line. Typical errors are of about 15km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/6
- Title:
- Radial velocities in {omega} Cen
- Short Name:
- J/ApJ/751/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The multi-object fiber-fed spectrograph AAOmega at the Anglo-Australian Telescope has been used to establish and measure accurate (<=1km/s) radial velocities for a new sample of members in the outer parts of the stellar system {omega} Centauri. The new sample more than doubles the number of known members with precise velocities that lie between 25' and 45' from the cluster center. Combining this sample with earlier work confirms that the line-of-sight velocity dispersion of {omega} Cen remains approximately constant at ~6.5km/s in the outer parts of the cluster, which contain only a small fraction of the total cluster stellar mass. It is argued that the approximately constant velocity dispersion in the outer regions is most likely a consequence of external influences, such as the tidal shock heating that occurs each time {omega} Cen crosses the Galactic plane. There is therefore no requirement to invoke dark matter or non-standard gravitational theories.
- ID:
- ivo://CDS.VizieR/J/A+A/445/503
- Title:
- Radial velocities in Omega Cen (NGC5139)
- Short Name:
- J/A+A/445/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- List of 1966 radial velocity measurements of stars in globular cluster Omega Centauri (NGC 5139) taken with the ARGUS multi-object spectrometer at the CTIO 4m Blanco telescope. All the stars have a B magnitude brighter than 16.5. The median error is less than 2km/s. The stars are numbered using their LID (Leiden Identification Number) from van Leeuwen et.al. (2000, Cat. <J/A+A/360/472>). In a companion paper by van de Ven et al. (2006A&A...445..513V), we correct these radial velocities for the perspective rotation caused by the space motion of the cluster. Additionaly 339 stars where measured. These consist of (i) 87 stars with B-V<0.4, (ii) 252 stars not in the van Leeuwen et al. catalog. We suspect that that many of these stars have an erroneous value for their radial velocity.
