- ID:
- ivo://CDS.VizieR/J/A+A/622/A191
- Title:
- 885 globular cluster giants abundances
- Short Name:
- J/A+A/622/A191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to provide abundances of a large set of light and neutron-capture elements homogeneously analyzed that cover a wide range of metallicity to constrain globular cluster (GC) formation and evolution models. We analyzed a large sample of 885 GCs giants from the SDSS~IV-Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. We used the Cannon results to separate the red giant branch and asymptotic giant branch stars, not only allowing for a refinement of surface gravity from isochrones, but also providing an independent H-band spectroscopic method to distinguish stellar evolutionary status in clusters. We then used the Brussels Automatic Code for Characterizing High accUracy Spectra (BACCHUS) to derive metallicity, microturbulence, macroturbulence, many light-element abundances, and the neutron-capture elements Nd and Ce for the first time from the APOGEE GCs data. Our independent analysis helped us to diagnose issues regarding the standard analysis of the APOGEE DR14 for low-metallicity GC stars. Furthermore, while we confirm most of the known correlations and anticorrelation trends (Na-O, Mg-Al, C-N), we discover that some stars within our most metal-poor clusters show an extreme Mg depletion and some Si enhancement. At the same time, these stars show some relative Al depletion, displaying a turnover in the Mg-Al diagram. These stars suggest that Al has been partially depleted in their progenitors by very hot proton-capture nucleosynthetic processes. Furthermore, we attempted to quantitatively correlate the spread of Al abundances with the global properties of GCs. We find an anticorrelation of the Al spread against clusters metallicity and luminosity, but the data do not allow us to find clear evidence of a dependence of N against metallicity in the more metal-poor clusters. Large and homogeneously analyzed samples from ongoing spectroscopic surveys unveil unseen chemical details for many clusters, including a turnover in the Mg-Al anticorrelation, thus yielding new constrains for GCs formation/evolution models.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/245/5
- Title:
- Globular cluster intrinsic iron abundance spreads
- Short Name:
- J/ApJS/245/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an up-to-date catalog of intrinsic iron abundance spreads in the 55 Milky Way globular clusters (GCs) for which sufficiently precise spectroscopic measurements are available. Our method combines multiple data sets when possible to improve the statistics, taking into account the fact that different methods and instruments can lead to systematically offset metallicities. Only high spectral resolution (R>14000) studies that measure the equivalent widths of individual iron lines are found to have uncertainties on the metallicities of the individual stars that can be calibrated sufficiently well for the intrinsic dispersion to be separated cleanly from a random measurement error. The median intrinsic iron spread is found to be 0.045dex, which is small but unambiguously measured to be nonzero in most cases. There is large variation between clusters, but more luminous GCs, above 10^5^L_{sun}_, have increasingly large iron spreads on average; no trend between the iron spread and metallicity is found.
- ID:
- ivo://CDS.VizieR/J/other/NewA/88.J1607
- Title:
- Globular cluster NGC 6397 variable stars
- Short Name:
- J/other/NewA/88.
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a new time-series VI CCD photometry of the globular cluster NGC 6397, from which we obtained and analysed the light curves of 35 variables carefully identified in the cluster field. We assessed the membership of the variables with an astrometric analysis based on Gaia DR2 data. The cluster colour-magnitude diagram was differentially de- reddened and cleaned of non members, which allowed us to fit isochrones for [Fe/H]=-2.0dex in the range 13.0-13.5Gyr, for a mean reddening E(B-V)=0.19, and a distance of 2.5kpc. This distance was confirmed using the period-luminosity relation for the cluster's five SX Phoenicis variables (V10, V11, V15, V21, and V23) present among its blue stragglers, yielding 2.24+/-0.13kpc. We also modelled the light curves of four eclipsing binaries (V4, V5, V7, and V8), and gave the parameters of the systems; the contact binaries V7 and V8 have distances consistent with that of the cluster. NGC 6397 appears to harbour no RR Lyrae stars, being its horizontal branch remarkably blue, much like that of its analogous cluster, M10. To match the blue tail of the horizontal branch population, models of 0.64-0.66M_{sun}_ with mass loss at the RGB are required, indicating rather thin shell masses for horizontal branch stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/159
- Title:
- Globular cluster populations in S4G galaxies
- Short Name:
- J/ApJ/799/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3.6{mu}m images of 97 early-type galaxies, we develop and verify methodology to measure globular cluster populations from the S^4^G survey images. We find that (1) the ratio, T_N_, of the number of clusters, N_CL_, to parent galaxy stellar mass, M_*_, rises weakly with M_*_ for early-type galaxies with M_*_>10^10^M_{sun}_ when we calculate galaxy masses using a universal stellar initial mass function (IMF) but that the dependence of T_N_ on M_*_ is removed entirely once we correct for the recently uncovered systematic variation of IMF with M_*_; and (2) for M_*_<10^10^M_{sun}_, there is no trend between N_CL_ and M_*_, the scatter in T_N_is significantly larger (approaching two orders of magnitude), and there is evidence to support a previous, independent suggestion of two families of galaxies. The behavior of N_CL_ in the lower-mass systems is more difficult to measure because these systems are inherently cluster-poor, but our results may add to previous evidence that large variations in cluster formation and destruction efficiencies are to be found among low-mass galaxies. The average fraction of stellar mass in clusters is ~0.0014 for M_*_>10^10^M_{sun}_ and can be as large as ~0.02 for less massive galaxies. These are the first results from the S^4^G sample of galaxies and will be enhanced by the sample of early-type galaxies now being added to S^4^G and complemented by the study of later-type galaxies within S^4^G.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/99
- Title:
- Globular cluster populations in S4G galaxies. II.
- Short Name:
- J/ApJ/818/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3.6 and 4.5{mu}m images of 73 late-type, edge-on galaxies from the S^4^G survey, we compare the richness of the globular cluster populations of these galaxies to those of early-type galaxies that we measured previously. In general, the galaxies presented here fill in the distribution for galaxies with lower stellar mass, M_*_, specifically log(M_{star}_/M_{sun})<10, overlap the results for early-type galaxies of similar masses, and, by doing so, strengthen the case for a dependence of the number of globular clusters per 10^9^M_{sun}_ of galaxy stellar mass, T_N_, on M_*_. For 8.5<log(M_{star}_/M_{sun})<10.5 we find the relationship can be satisfactorily described as T_N_=(M_{star}_/10^6.7^)^-0.56^ when M_*_ is expressed in solar masses. The functional form of the relationship is only weakly constrained, and extrapolation outside this range is not advised. Our late-type galaxies, in contrast to our early types, do not show the tendency for low-mass galaxies to split into two T_N_ families. Using these results and a galaxy stellar mass function from the literature, we calculate that, in a volume-limited, local universe sample, clusters are most likely to be found around fairly massive galaxies (M_*_~10^10.8^M_{sun}_) and present a fitting function for the volume number density of clusters as a function of parent-galaxy stellar mass. We find no correlation between T_N_ and large-scale environment, but we do find a tendency for galaxies of fixed M_*_ to have larger T_N_ if they have converted a larger proportion of their baryons into stars.
- ID:
- ivo://CDS.VizieR/J/A+A/309/116
- Title:
- 10 globular cluster ROSAT observations
- Short Name:
- J/A+A/309/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray observations of ten globular clusters observed with the ROSAT PSPC. The clusters were chosen to have large core radii and to be nearby. Three clusters contain X-ray sources which are probably associated with the cluster. One is the previously discovered X-ray transient H1825-331 in NGC 6652. The other two, in NGC 6366 and NGC 6809, are new members of the class of low-luminosity sources, with luminosities in the region of 10^32^erg/s. Upper limits can be placed on the source temperatures of both sources, making them similar to sources found in other globular clusters by ROSAT.
- ID:
- ivo://CDS.VizieR/J/AZh/96/267
- Title:
- Globular clusters abundances and kinematics
- Short Name:
- J/AZh/96/267
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- For the catalog, we compiled the abundances of 28 chemical elements: alpha-elements (O, Mg, Si, Ca, Ti), carbon, iron-peak elements(Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), slow and rapid neutron-capture elements (Sr, Y, Zr, Mo, Ba, La, Ce, Nd, Eu, Dy) and three odd-Z elements(Na, Al, K) in the stars of 69 globular clusters. The data are taken from 101 papers published from 1986 to 2018. The abundances of chemical elements in stars of the clusters in almost all the used papers are determined from high-resolution spectra obtained mainly for the atmospheres of red giants. The spectra are analyzed with the local thermodynamic equilibrium approximation.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2114
- Title:
- Globular clusters around NGC 1399
- Short Name:
- J/AJ/127/2114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities of 468 globular clusters around NGC 1399, the central galaxy in the Fornax cluster, have been obtained with FORS2 and the Mask Exchange Unit (MXU) at the ESO Very Large Telescope. This is the largest sample of globular cluster velocities around any galaxy obtained so far. The mean velocity uncertainty is 50km/s. This data sample is accurate and large enough to be used in studies of the mass distribution of NGC 1399 and the properties of its globular cluster system. Here we describe the observations and the reduction procedure, and we discuss the uncertainties of the resulting velocities. The complete sample of cluster velocities that is used in a dynamical study of NGC 1399 is tabulated. A subsample is compared with previously published values.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4956
- Title:
- Globular clusters around NGC 1407
- Short Name:
- J/AJ/137/4956
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 1407 is the central elliptical in a nearby evolved group of galaxies apparently destined to become a galaxy cluster core. We use the kinematics of globular clusters (GCs) to probe the dynamics and mass profile of the group's center, out to a radius of 60kpc (~10 galaxy effective radii)-the most extended data set to date around an early-type galaxy. This sample consists of 172 GC line-of-sight velocities, most of them newly obtained using Keck/DEIMOS, with a few additional objects identified as dwarf-globular transition objects or as intragroup GCs.
- ID:
- ivo://CDS.VizieR/J/PAZh/29/253
- Title:
- Globular clusters as gravitational lenses
- Short Name:
- J/PAZh/29/253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We argue that globular clusters (GCs) are good candidates for gravitational lenses in explaining quasar-galaxy associations. The catalog of associations (Bukhmastova, 2001, Cat. <J/AZh/78/675>) compiled from the LEDA catalog of galaxies (Paturel, 1997A&AS..124..109P) and from the catalog of quasars (Veron-Cetty and Vero, 1998, see Cat. <VII/235>) is used. Based on the new catalog, we show that one might expect an increased number of GCs around irregular galaxies of types 9 and 10 from the hypothesis that distant compact sources are gravitationally lensed by GCs in the halos of foreground galaxies. The King model is used to determine the central surface densities of 135 GCs in the Milky Way. The distribution of GCs in central surface density was found to be lognormal.
