- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1995
- Title:
- Deep uVI photometry of NGC2419
- Short Name:
- J/MNRAS/431/1995
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate wide-field uVI photometry of the remote and massive Galactic globular cluster NGC 2419, aimed at searching for the u-V colour spread along the red giant branch (RGB) which is generally interpreted as the photometric signature of the presence of multiple populations in globular clusters. Focusing on the RGB stars in the magnitude range 19.8<=V<=22.0, we find that (i) the u-V, u-I and the V-I spreads about the RGB ridge line are significantly larger than that expected from observational errors, accurately quantified by means of extensive artificial stars experiments, (ii) the intrinsic colour spreads in u-V and u-I are larger than in V-I, and (iii) the stars lying to the blue of the RGB ridge line in u-V and u-I are significantly more concentrated towards the cluster centre than those lying to the red of that line. All the above observational facts can be interpreted in a scenario where a sizable fraction of cluster stars belong to a second generation heavily enriched in helium. Finally, we find that bright RGB stars (17.5<V<19.0) having [Mg/Fe]<0.0 lie preferentially on the red side of the cluster RGB, while those having [Mg/Fe]>0.0 lie preferentially on the blue side.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2492
- Title:
- {Delta}a observations of 3 globular clusters
- Short Name:
- J/MNRAS/443/2492
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters are main astrophysical laboratories to test and modify evolutionary models. Thought to be rather homogeneous in their local elemental distribution of members, results suggest a wide variety of chemical peculiarities. Besides different main sequences, believed to be caused by different helium abundances, peculiarities of blue horizontal-branch stars and on the red giant branch were found. This whole zoo of peculiar objects has to be explained in the context of stellar formation and evolution. The tool of {Delta}a photometry is employed in order to detect peculiar stars in the whole spectral range. This three filter narrow-band system measures the flux distribution in the region from 4900 to 5600{AA} in order to find any peculiarities around 5200{AA}. It is highly efficient to detect classical chemically peculiar stars of the upper main sequence, Be/Ae, shell and metal-weak objects in the Milky Way and Magellanic Clouds. We present {Delta}a photometry of 2266 stars from 109 individual frames for three globular clusters (NGC 104, NGC 6205, and NGC 7099). A comparison with published abundances, for three horizontal-branch stars, only, yields an excellent agreement. According to the 3{sigma} detection limit of each globular cluster, about 3 percent of the stars lie in abnormal regions in the diagnostic diagrams. The first observations of three widely different aggregates give very promising results, which will serve as a solid basis for follow-up observations including photometric as well as spectroscopic studies.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A138
- Title:
- Detailed chemical abundances in the GlC NGC 362
- Short Name:
- J/A+A/557/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained FLAMES GIRAFFE+UVES spectra for both first and second-generation red giant branch (RGB) stars in the globular cluster (GC) NGC 362 and used them to derive abundances of 21 atomic species for a sample of 92 stars. The surveyed elements include proton-capture (O, Na, Mg, Al, Si), alpha-capture (Ca, Ti), Fe-peak (Sc, V, Mn, Co, Ni, Cu), and neutron-capture elements (Y, Zr, Ba, La, Ce, Nd, Eu, Dy). The analysis is fully consistent with that presented for twenty GCs in previous papers of this series. Stars in NGC 362 seem to be clustered into two discrete groups along the Na-O anti-correlation, with a gap at [O/Na]~0dex. Na-rich, second generation stars show a trend to be more centrally concentrated, although the level of confidence is not very high. When compared to the classical second-parameter twin NGC 288, with similar metallicity, but different horizontal branch type and much lower total mass, the proton-capture processing in stars of NGC 362 seems to be more extreme, confirming previous analysis. We discovered the presence of a secondary RGB sequence, redder than the bulk of the RGB: a preliminary estimate shows that this sequence comprises about 6% of RGB stars. Our spectroscopic data and literature photometry indicate that this sequence is populated almost exclusively by giants rich in Ba, and probably rich in all s-process elements, as found in other clusters. In this regards, NGC 362 joins previously studied GCs like NGC 1851, NGC 6656 (M 22), and NGC 7089 (M 2).
- ID:
- ivo://CDS.VizieR/J/A+A/372/85
- Title:
- Detected sources at 12{mu}m in 47 Tuc
- Short Name:
- J/A+A/372/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present paper investigates the properties of the dust mass loss in stars populating the giant branch of the globular cluster 47 Tuc, by combining ISOCAM and DENIS data. Raster maps of 5 fields covering areas ranging from 4x4 to 15x15arcmin^2^ at different distances from the center of the cluster have been obtained with ISOCAM at 11.5{mu}m (LW10 filter). The covered fields include most of the red variables known in this cluster. A detection threshold of about 0.2 mJy is achieved, allowing us to detect giant stars at 11.5{mu}m all the way down to the horizontal branch. No dust-enshrouded asymptotic giant branch stars have been found in the observed fields, contrary to the situation encountered in LMC/SMC globular clusters with larger turnoff masses. The color index [12]-[2] (based on the ISO 11.5{mu}m flux and on the DENIS K_S_ magnitude) is used as a diagnostic of dust emission (and hence dust mass loss). Its evolution with luminosity along the giant branch reveals that dust mass loss is only present in V3 (the only cluster Mira variable observed in the present study) and in V18, a star presenting intermittent variability. This conclusion confirms the importance of stellar pulsations in the dust formation and ensuing mass loss.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/1443
- Title:
- 2dF study of globular clusters in NGC 5128
- Short Name:
- J/MNRAS/386/1443
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a spectroscopic study of globular clusters (GCs) in the nearest giant elliptical NGC 5128 using the 2dF facility at the Anglo-Australian Telescope. We obtained integrated optical spectra for a total of 254 GCs, 79 of which are newly confirmed on the basis of their radial velocities and spectra. In addition, we obtained an integrated spectrum of the galaxy starlight along the southern major axis.
- ID:
- ivo://CDS.VizieR/J/AJ/143/70
- Title:
- Differential reddening in Milky Way globulars
- Short Name:
- J/AJ/143/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive photometric studies of the globular clusters located toward the center of the Milky Way have been historically neglected. The presence of patchy differential reddening in front of these clusters has proven to be a significant obstacle to their detailed study. We present here a well defined and reasonably homogeneous photometric database for 25 of the brightest Galactic globular clusters located in the direction of the inner Galaxy. These data were obtained in the B, V, and I bands using the Magellan 6.5m Telescope and the Hubble Space Telescope. A new technique is extensively used in this paper to map the differential reddening in the individual cluster fields, and to produce cleaner, dereddened color-magnitude diagrams for all the clusters in the database. Subsequent papers will detail the astrophysical analysis of the cluster populations, and the properties of the obscuring material along the clusters' lines of sight.
- ID:
- ivo://CDS.VizieR/J/A+A/432/851
- Title:
- Distance of 72 Galactic globular clusters
- Short Name:
- J/A+A/432/851
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present distance modulus and reddening determinations for 72 Galactic globular clusters from the homogeneous photometric database of Piotto et al. (2002, cat. <J/A+A/391/945>), calibrated to the HST flight F439W and F555W bands. The distances have been determined by comparison with theoretical absolute magnitudes of the ZAHB. For low and intermediate metallicity clusters, we have estimated the apparent Zero Age Horizontal Branch (ZAHB) magnitude from the RR Lyrae level. For metal rich clusters, the ZAHB magnitude was obtained from the fainter envelope of the red HB. Reddenings have been estimated by comparison of the HST colour-magnitude diagrams (CMD) with ground CMDs of template clusters with low reddening. The homogeneity of both the photometric data and the adopted methodological approach allowed us to obtain highly accurate relative cluster distances and reddenings. Our results are also compared with recent compilations in the literature. Description:
- ID:
- ivo://CDS.VizieR/J/A+A/619/A13
- Title:
- 28 distant globular clusters CaT metallicities
- Short Name:
- J/A+A/619/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an earlier paper we presented the first part of a project to obtain metallicities and radial velocities of Galactic globular clusters from multiobject spectroscopy of their member stars using the ESO Very Large Telescope. In this paper we add metallicities and radial velocities for a new sample of 28 globular clusters, including in particular globular clusters in the MW halo and the Galactic bulge. Together with our previous results, this study brings the number of globular clusters with homogeneous measurements to ~69% of those listed in the W. Harris' catalogue. As in our previous work, we have used the CaII triplet lines to derive metallicities and radial velocities. For most of the clusters in this study, this is the first analysis based on spectroscopy of individual member stars. The metallicities derived from the CaII triplet are then compared to the results of our parallel study based on spectral fitting in the optical region and the implications for different calibrations of the CaII triplet line strengths are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/347/251
- Title:
- Dynamics of Globular Cluster M15
- Short Name:
- J/ApJ/347/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The velocity dispersion as a function of radius in the globular cluster M15 is derived from measurements of 120 individual stars between 0.1' and 4.6' of the cluster center, and from the integrated light of the central cusp. The stellar measurements, with an individual accuracy of 1 km/s, indicate a mean cluster velocity of -107.1+/-0.9 km/s, and a mean velocity dispersion of 9.0+/-0.6 km/s. The velocity dispersion inside 1' varies with radius. The dispersion of the 27 stars within 20" is 14.2+/-1.9 km/s, while that of the 30 stars between 0.5' and 1.2' is 8.4+/-1.4 km/s. The cusp itself appears to have a dispersion of at least 25 km/s. Except for its greater velocity broadening, the spectrum of the integrated light of the cusp is indistinguishable from that formed by superposition of the individual M15 giant spectra, demonstrating that the excess light at the center is due primarily to the normal M15 population. The increase of the dispersion toward the center is not consistent with truncated isothermal (King-Michie) models, for which the velocity dispersion is nearly constant within a few core radii and then falls steeply beyond. The observed behaviour is difficult to reconcile as well with current post-core collapse models, which are also isothermal and whose central energy sources are modest. It is indicative of a nonthermal energy distribution with substantial heating in the central regions; this is consistent with a central black hole of about 1000 M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/106/1508
- Title:
- Dynamics of globular cluster NGC 362
- Short Name:
- J/AJ/106/1508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we have examined the internal dynamics of the globular cluster NGC 362 using a combination of V-band CCD images and echelle spectra of the member red giants. A V-band surface brightness profile (SBP) was constructed from the CCD images, and, after it was determined that the cluster is not post core-collapse, fit with single- and multi-pass King-Michie (KM) models. We found that for small values of the mass function slope, x, anisotropic models were favored while for steeper mass functions isotropic orbits provided superior fits. The total cluster luminosity is 1.70 +/- 0.1 x 10^5 L(Vsun) [assumes (m-M)0 = 14.77]. A total of 285 stellar spectra were obtained of 215 stars for radial velocity determinations. Three stars were obvious nonmembers and four showed strong evidence for radial velocity variations; these latter stars are probably members of binary systems with periods less than a few years. The true cluster binary fraction was determined from simulations to be 0.15 for circular orbits or 0.27 for orbits with a distribution function f(e) = e (e is eccentricity). This relatively high binary detection frequency may indicate that NGC 362 is overabundant in binaries compared to other clusters. The 208 remaining stellar velocities showed no sign of rotation and had kinematics which were incompatible with KM models having isotropic orbits and luminosity profiles consistent with the SBP. Therefore, the best agreement with both the kinematic data and the SBP were for shallow mass functions x = 0.0-0.5 and intermediate amounts of anisotropy in the velocity dispersion tensor. In this best-fit range, the derived cluster mass is M = 2.5-3.5x10^5 Msun for a global mass-to-light ratio of M/L(V) = 1.5-2.0 Msun/L(Vsun). This low value for x is in disagreement with the correlation between x and the height above the Galactic disk seen for a sample of other clusters. The results are also different from the sharp turnup in the low mass end of mass functions derived from the deep luminosity functions of three other globular clusters.
