- ID:
- ivo://CDS.VizieR/J/A+A/565/A121
- Title:
- Abundances of 47 Tuc turn-off stars
- Short Name:
- J/A+A/565/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cluster 47 Tuc is among the most metal-rich Galactic globular clusters and its metallicity is similar to that of metal-poor disc stars and open clusters. Like other globular clusters, it displays variations in the abundances of elements lighter than Si, which is generally interpreted as evidence of the presence of multiple stellar populations. We aim to determine abundances of Li, O, and Na in a sample of of 110 turn-off (TO) stars, in order to study the evolution of light elements in this cluster and to put our results in perspective with observations of other globular and open clusters, as well as with field stars. We use medium resolution spectra obtained with the GIRAFFE spectrograph at the ESO 8.2m Kueyen VLT telescope and use state of the art 1D model atmospheres and NLTE line transfer to determine the abundances. We also employ CO^5^BOLD hydrodynamical simulations to assess the impact of stellar granulation on the line formation and inferred abundances.
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- ID:
- ivo://CDS.VizieR/J/ApJ/667/911
- Title:
- Abundances on the main sequence of {omega} Cen
- Short Name:
- J/ApJ/667/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundance ratios of carbon, nitrogen, and strontium relative to iron, calculated using spectrum synthesis techniques, are given for a sample of main-sequence and turnoff stars that belong to the globular cluster omega Centauri. The variations of carbon, nitrogen, and/or strontium show several different abundance patterns as a function of [Fe/H]. The source of the enhancements/depletions in carbon, nitrogen, and/or strontium may be enrichment from asymptotic giant branch stars of low (1-3M_{sun}_ and intermediate (3-8M_{sun}_ mass. Massive rotating stars that produce excess nitrogen without carbon and oxygen overabundances may also play a role. These abundances enable different contributors to be considered and incorporated into the evolutionary picture of omega Cen.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/168
- Title:
- Abundances & RVs for stars near (or in) NGC6273
- Short Name:
- J/ApJ/836/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent observations have shown that a growing number of the most massive Galactic globular clusters contain multiple populations of stars with different [Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been recognized as a member of this "iron-complex" cluster class, and we provide here a chemical and kinematic analysis of >300 red giant branch and asymptotic giant branch member stars using high-resolution spectra obtained with the Magellan-M2FS and VLT-FLAMES instruments. Multiple lines of evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that ranges from about [Fe/H]=-2 to -1 dex, and may include at least three populations with different [Fe/H] values. The three populations identified here contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars, but a Mg-Al anti-correlation may only be present in stars with [Fe/H]>~-1.65. The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process must have dominated the heavy element enrichment at higher metallicities. A small group of stars with low [{alpha}/Fe] is identified and may have been accreted from a former surrounding field star population. The cluster's large abundance variations are coupled with a complex, extended, and multimodal blue horizontal branch (HB). The HB morphology and chemical abundances suggest that NGC 6273 may have an origin that is similar to {omega} Cen and M54.
- ID:
- ivo://CDS.VizieR/J/AJ/154/155
- Title:
- Abundance variations in the outer halo GC NGC 6229
- Short Name:
- J/AJ/154/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectroscopic data on this cluster, we present a detailed chemical composition analysis of 11 red giant branch members based on high resolution (R~38000), high S/N (>100) spectra obtained with the MMT-Hectochelle instrument. We find the cluster to have a mean heliocentric radial velocity of -138.1_-1.0_^+1.0^ km/s, a small dispersion of 3.8_-0.7_^+1.0^ km/s, and a relatively low (M/L_V_)_{sun}_=0.82_-0.28_^+0.49^. The cluster is moderately metal-poor with <[Fe/H]>=-1.13 dex and a modest dispersion of 0.06 dex. However, 18% (2/11) of the stars in our sample have strongly enhanced [La,Nd/Fe] ratios that are correlated with a small (~0.05 dex) increase in [Fe/H]. NGC 6229 shares several chemical signatures with M75, NGC 1851, and the intermediate metallicity populations of {omega} Cen, which lead us to conclude that NGC 6229 is a lower mass iron-complex cluster. The light elements exhibit the classical (anti-)correlations that extend up to Si, but the cluster possesses a large gap in the O-Na plane that separates first and second generation stars. NGC 6229 also has unusually low [Na,Al/Fe] abundances that are consistent with an accretion origin. A comparison with M54 and other Sagittarius clusters suggests that NGC 6229 could also be the remnant core of a former dwarf spheroidal galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/772/82
- Title:
- A catalog of globular cluster systems
- Short Name:
- J/ApJ/772/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 422 galaxies with published measurements of their globular cluster (GC) populations. Of these, 248 are E galaxies, 93 are S0 galaxies, and 81 are spirals or irregulars. Among various correlations of the total number of GCs with other global galaxy properties, we find that N_GC_ correlates well though nonlinearly with the dynamical mass of the galaxy bulge M_dyn_=4{sigma}_e_^2^R_e_/G, where {sigma}_e_ is the central velocity dispersion and R_e_ the effective radius of the galaxy light profile. We also present updated versions of the GC specific frequency S_N_ and specific mass S_M_ versus host galaxy luminosity and baryonic mass. These graphs exhibit the previously known U-shape: highest S_N_ or S_M_ values occur for either dwarfs or supergiants, but in the midrange of galaxy size (10^9^-10^10^L_{sun}_) the GC numbers fall along a well-defined baseline value of S_N_=~1 or S_M_=0.1, similar among all galaxy types. Along with other recent discussions, we suggest that this trend may represent the effects of feedback, which systematically inhibited early star formation at either very low or very high galaxy mass, but which had its minimum effect for intermediate masses. Our results strongly reinforce recent proposals that GC formation efficiency appears to be most nearly proportional to the galaxy halo mass M_halo_. The mean "absolute" efficiency ratio for GC formation that we derive from the catalog data is M_GCS_/M_halo_=6x10^-5^. We suggest that the galaxy-to-galaxy scatter around this mean value may arise in part because of differences in the relative timing of GC formation versus field-star formation. Finally, we find that an excellent empirical predictor of total GC population for galaxies of all luminosities is N_GC_~(R_e_{sigma}_e_)^1.3^, a result consistent with fundamental plane scaling relations.
- ID:
- ivo://CDS.VizieR/J/A+AS/132/255
- Title:
- A catalogue of Mg_2_ indices
- Short Name:
- J/A+AS/132/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of published absorption-line Mg_2_ index measurements of galaxies and globular clusters. The catalogue consists in four tables and is maintained up-to-date in the database HYPERCAT (http://www-obs.univ-lyon1.fr/~prugniel/cgi-bin/hypercat/). The measurements are listed together with the references to the original articles where the data were published. A coded description of the observations is provided. Compiled raw data are aperture- corrected and, when it is possible, transformed to the homogeneous system. The zeropoints and re-scaling of errors are provided. The catalogue gather in total 3706 measurements for 1409 objects from 70 datasets. Total of 46 different publications were used to compile the catalogue. This catalogue will be updated. Check at the above given URL for recent version.
- ID:
- ivo://CDS.VizieR/J/ApJS/221/13
- Title:
- ACS Fornax Cluster Survey. XI. GC candidates
- Short Name:
- J/ApJS/221/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present catalogs of globular cluster (GC) candidates for 43 galaxies from the ACS Fornax Cluster survey, a program designed to carry out imaging of early-type members of the Fornax cluster using the Advanded Camera for Surveys (ACS) on board the Hubble Space Telescope. The procedure to select bona fide GC candidates from the full list of detections is based on model-based clustering methods, similar to those adopted for a survey of 100 galaxies in the Virgo cluster, the ACS Virgo Cluster Survey. For each detected source, we measure its position, magnitudes in the F475W (~Sloan g) and F850LP (~Sloan z) bandpasses, half-light radii obtained by fitting point-spread function-convolved King models to the observed light distribution, and an estimate of the probability {rho}_GC_ that each cataloged source is a GC. These measurements are presented for 9136 sources, of which 6275 have {rho}_GC_>=0.5, and are thus likely GCs.
- ID:
- ivo://CDS.VizieR/J/AJ/133/1658
- Title:
- ACS survey of galactic globular clusters
- Short Name:
- J/AJ/133/1658
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a large Advanced Camera for Surveys (ACS) survey of Galactic globular clusters. This Hubble Space Telescope (HST) Treasury project is designed to obtain photometry with S/N (signal-to-noise ratio) >~10 for main-sequence stars with masses >~0.2M_{sun}_ in a sample of globulars using the ACS Wide Field Channel. Here we focus on clusters without previous HST imaging data. These include NGC 5466, NGC 6779, NGC 5053, NGC 6144, Palomar 2, E3, Lynga 7, Palomar 1, and NGC 6366. Our color-magnitude diagrams (CMDs) extend reliably from the horizontal branch to as much as 7 mag fainter than the main-sequence turnoff and represent the deepest CMDs published to date for these clusters. Using fiducial sequences for three standard clusters (M92, NGC 6752, and 47 Tuc) with well-known metallicities and distances, we perform main-sequence fitting on the target clusters in order to obtain estimates of their distances and reddenings. These comparisons, along with fitting the cluster main sequences to theoretical isochrones, yield ages for the target clusters. We find that the majority of the clusters have ages that are consistent with the standard clusters at their metallicities. The exceptions are E3, which appears ~2Gyr younger than 47 Tuc, and Pal 1, which could be as much as 8Gyr younger than 47 Tuc.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/279
- Title:
- ACS Virgo Cluster Survey. III. M87
- Short Name:
- J/ApJ/613/279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ACIS instrument on board the Chandra X-Ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87, the giant elliptical galaxy near the dynamical center of the Virgo Cluster. These images - with a total exposure time of 154 ks - are the deepest X-ray observations yet obtained of M87. We identify 174 X-ray point sources, of which 150 are likely LMXBs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/L6
- Title:
- AGB and RGB stars in {omega} Cen
- Short Name:
- J/MNRAS/416/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We herein determine the average integrated mass-loss from stars belonging to the dominant metal-poor population ([Fe/H]~-1.7) of the Galactic globular cluster {omega} Centauri (NGC 5139) during their red giant and horizontal branch (HB) evolution.
