- ID:
- ivo://CDS.VizieR/J/A+A/583/A69
- Title:
- NGC 6139 BV photometry
- Short Name:
- J/A+A/583/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information on globular clusters (GC) formation mechanisms can be gathered by studying the chemical signature of the multiple populations that compose these stellar systems. In particular, we investigate the anti-correlations among O, Na, Al, and Mg to explore the influence of cluster mass and environment on GCs in the Milky Way and in extragalactic systems. We present here the results obtained on NGC 6139, which, on the basis of its horizontal branch morphology, has been proposed to be dominated by first-generation stars. In our extensive study based on high-resolution spectroscopy, the first for this cluster, we found a metallicity of [Fe/H]=-1.579+/-0.015+/-0.058 (rms=0.040dex, 45 bona fide member stars) on the UVES scale defined by our group. The stars in NGC 6139 show a chemical pattern normal for GCs, with a rather extended Na-O (and Mg-Al) anticorrelation. NGC 6139 behaves as expected from its mass and contains a large portion (about two thirds) of second-generation stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/438/3507
- Title:
- NGC 5824 calcium triplet equivalent widths
- Short Name:
- J/MNRAS/438/3507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of the strengths of the calcium triplet absorption lines in the spectra of a large sample of red giant members of the luminous outer Galactic halo globular cluster NGC 5824. The spectra were obtained with the FORS2 and GMOS-S multi-object spectrographs at the VLT and the Gemini-S telescope, respectively. By comparing the line strengths of the NGC 5824 stars with those for red giants in clusters with well-established abundances, we conclude that there is an intrinsic abundance dispersion in NGC 5824 characterized by an inter-quartile range in [Fe/H] of 0.10dex and a total range of ~0.3dex. As for {omega} Cen and M22, the abundance distribution shows a steep rise on the metal-poor side and a shallower decline on the metal-rich side. There is also some indication that the distribution is not unimodal with perhaps three distinct abundance groupings present. NGC 5824 has a further unusual characteristic: the outer surface density profile shows no signs of a tidal cutoff. Instead, the profile has a power-law distribution with cluster stars detected to a radius exceeding 400pc. We postulate that NGC 5824 may be the remnant nuclear star cluster of a now disrupted dwarf galaxy accreted during the formation of the Galaxy's halo. We further speculate that the presence of an intrinsic [Fe/H] spread is the characteristic that distinguishes former nuclear star clusters from other globular clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A129
- Title:
- NGC 2808 central kinematics
- Short Name:
- J/A+A/542/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from ground based VLT/FLAMES spectroscopy in combination with HST data for the globular cluster NGC 2808. The aim of this work is to probe whether this massive cluster hosts an intermediate-mass black hole at its center and to compare the results with the expected value predicted by the M_BH_-{sigma} scaling relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/586/814
- Title:
- NGC 4472 Chandra/HST study
- Short Name:
- J/ApJ/586/814
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a Chandra/Hubble Space Telescope (HST) study of the point sources of the Virgo Cluster giant elliptical galaxy NGC 4472. We identify 144 X-ray point sources outside the nuclear region, 72 of which are located within the HST fields. The optical data show 1102 sources, of which 829 have colors consistent with being globular clusters (with only four in the restricted central 10" region). Thirty matches are found between the two lists - these are likely to be low-mass X-ray binaries (LMXBs) associated with globular clusters, while ~42 of the X-ray sources have no optical counterparts to V<~25 and I<~24, indicating that they are likely to be predominantly LMXBs in the field star population with a small amount of possible contamination from background active galactic nuclei. Thus approximately 40% of the X-ray sources are in globular clusters and 4% of the globular clusters contain X-ray sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/600/716
- Title:
- NGC 5128 Chandra X-ray point sources
- Short Name:
- J/ApJ/600/716
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very Large Telescope images in BVI are used to identify the optical counterparts to bright Chandra X-ray points sources discovered by Kraft and coworkers (2001, Cat. <J/ApJ/560/675>). Of a total of 111 X-ray point sources with L_X_>2x10^36^erg/s present in a 56arcmin^2^ field centered on this galaxy, 58 have optical counterparts. On the basis of the sizes, optical magnitudes, and colors, 20 new globular cluster counterparts of X-ray sources are identified, and three are identified on the basis of their sizes. This brings the total number of globular cluster X-ray sources in this galaxy to 33 and establishes that 30% of the X-ray point sources in NGC 5128 are associated with globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/75
- Title:
- NGC 5824 giant star members from VLT obs.
- Short Name:
- J/ApJ/859/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5824 is a massive Galactic globular cluster suspected to have an intrinsic spread in its iron content, according to the strength of the calcium triplet lines. We present chemical abundances of 117 cluster giant stars using high-resolution spectra acquired with the multi-object spectrograph FLAMES. The metallicity distribution of 87 red giant branch stars is peaked at [Fe/H]=-2.11+/-0.01dex, while that derived from 30 asymptotic giant branch stars is peaked at [Fe/H]=-2.20+/-0.01dex. Both the distributions are compatible with a null spread, indicating that this cluster did not retain the ejecta of supernovae. The small iron abundance offset between the two groups of stars is similar to the abundances already observed among red and asymptotic giant branch stars in other clusters. The lack of intrinsic iron spread rules out the possibility that NGC 5824 is the remnant of a disrupted dwarf galaxy, as previously suggested. We also find evidence of the chemical anomalies usually observed in globular clusters, namely the Na-O and the Mg-Al anticorrelations. In particular, NGC 5824 exhibits a huge range of [Mg/Fe] abundance, observed in only a few metal-poor and/or massive clusters. We conclude that NGC 5824 is a normal globular cluster, without spread in [Fe/H] but with an unusually large spread in [Mg/Fe], possibly due to an efficient self-enrichment driven by massive asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/L36
- Title:
- NGC 5128 globular cluster abundances
- Short Name:
- J/ApJ/773/L36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high-resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high-resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between -1.6 and -0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H]<-0.4 is +0.37+/-0.07, while the average [Ca/Fe] in our Milky Way (MW) and M31 GC samples is +0.29+/-0.09 and +0.24+/-0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the MW or M31. This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the MW. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1624
- Title:
- NGC 1533 globular cluster candidates
- Short Name:
- J/ApJ/671/1624
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use two-band imaging data from the Advanced Camera for Surveys onboard the Hubble Space Telescope for a detailed study of NGC 1533, an SB0 galaxy in the Dorado group surrounded by a ring of HI.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A131
- Title:
- NGC1316 globular cluster candidates photometry
- Short Name:
- J/A+A/543/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of point-like sources around NGC 1316, which forms the photometric database for our paper. This catalogue basically is a selection from a larger photometric database. The selection criteria are specified in the paper. The catalog contains coordinates, R magnitudes with uncertainties, C-R colors and their uncertainties as well as "sharp" and "chi" values from DAOPHOT II. The coordinates are for identification purposes only. Depending on the position, deviations of up to 1 arcsec may occur. See the paper for validity limits of the photometric calibration, particularly for very red colors.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/2208
- Title:
- NGC 4473 globular clusters
- Short Name:
- J/MNRAS/452/2208
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 4473 is a so-called double sigma (2{sigma}) galaxy, i.e. a galaxy with rare, double peaks in its 2D stellar velocity dispersion. Here, we present the globular cluster (GC) kinematics in NGC 4473 out to ~10R_e_ (effective radii) using data from combined Hubble Space Telescope/Advanced Camera for Surveys and Subaru/Suprime-Cam imaging and Keck/Deep Imaging Multi-Object Spectrograph. We find that the 2{sigma} nature of NGC 4473 persists up to 3R_e_, though it becomes misaligned to the photometric major axis. We also observe a significant offset between the stellar and GC rotation amplitudes. This offset can be understood as a co-addition of counter-rotating stars producing little net stellar rotation. We identify a sharp radial transition in the GC kinematics at ~4R_e_ suggesting a well defined kinematically distinct halo. In the inner region (<4R_e_), the blue GCs rotate along the photometric major axis, but in an opposite direction to the galaxy stars and red GCs. In the outer region (>4R_e_), the red GCs rotate in an opposite direction compared to the inner region red GCs, along the photometric major axis, while the blue GCs rotate along an axis intermediate between the major and minor photometric axes. We also find a kinematically distinct population of very red GCs in the inner region with elevated rotation amplitude and velocity dispersion. The multiple kinematic components in NGC 4473 highlight the complex formation and evolutionary history of this 2{sigma} galaxy, as well as a distinct transition between the inner and outer components.
