- ID:
- ivo://CDS.VizieR/J/A+A/637/A98
- Title:
- Globular cluster escapees in the Galactic halo
- Short Name:
- J/A+A/637/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A long-lasting open question in the field of Galactic archeology refers to the size of the contribution from former globular cluster (GC) stars to the formation of the stellar halo of the Milky Way. We contribute to answering this important question by establishing observational links between the present-day halo field star population and GCs. To this end, we combined astrometric information such as space motions and parallaxes from the second data release of the Gaia mission (Gaia DR2) with spectroscopic radial velocities and metallicities ([Fe/H]) from the Sloan Digital Sky Survey (SDSS-IV, DR14) to end up with a seven-dimensional chemodynamical information space for more than 3x10^5^ stars. Moreover, from our previous study, we incorporated the sample of halo giant stars with a distinct chemical signature (strong CN bandheads) that resembles the light-elements anomaly otherwise only seen in the second generation of globular cluster stellar populations. Using three different tagging techniques -- among which is the exploration of conservative integrals of motion -- we are able to establish unique associations between 151 extratidal stars in the neighborhood of eight GCs, which coincide with earlier findings of stellar envelopes beyond the tidal radius and even beyond (out to several tens of tidal radii). In addition, we trace the possible origin of about 62% of the sample of CN-strong giants to their potential host clusters. We find a connection between several of the involved GCs and the Gaia-Enceladus and Sequoia merger events. By establishing kinematic and chemical connections between 17 CN-strong stars and their surrounding fields, we identify co- moving groups of stars at the same [Fe/H] with a possible cluster origin. Some of these associations contain RR Lyrae variables, which allows meaningful distance inferences to be made. From these, we find strong evidence that four CN-strong stars and their associates are connected to the Sagittarius stream whilst their tightly confined [Fe/H] may hint to a birth site in M 54, the massive cluster in Sagittarius' core remnant. Finally, by employing the counts of CN-strong and bona-fide CN-normal giants from our novel sample, we provide tentative estimates for the fraction of first-generation cluster stars among all stars lost to the halo. In the immediate cluster vicinity, this value amounts to 50.0+/-16.7% while the associations in the halo field rather imply 80.2-5.2+4.9%. We speculate that -- if proven real by spectroscopic follow-up -- the disparity between these numbers could indicate a major contribution of low- mass clusters to the overall number of stars escaped to the halo or could alternatively suggest strong mass loss from the first generation during early cluster dissolution.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/1075
- Title:
- Globular cluster in nearby dwarf galaxies. II
- Short Name:
- J/MNRAS/396/1075
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) in order to test the suggested external origin of the latter and the conditions at which GC self-enrichment can operate. Using luminosities and structural parameters of nGCs in low-mass (mainly late-type) dwarf galaxies from Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) imaging, we derive the present-day escape velocities (Vesc) of stellar ejecta to reach the cluster tidal radius and compare them with those of EHB-GCs.
- 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/A+AS/112/439
- Title:
- Globular cluster NGC 5286
- Short Name:
- J/A+AS/112/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of photoelectrically calibrated CCD BVRI photometry of 1391 stars in the globular cluster NGC 5286.
- 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.