- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/483/745
- Title:
- NGC 4478 globular clusters
- Short Name:
- J/ApJ/483/745
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate the distance to NGC 4478, a neighbor of the giant Virgo elliptical M87, using the surface brightness fluctuations method on parallel data from the HST WFPC2 camera. The exposures considered were taken through the F814W filter, which approximates the Johnson I, and through the F606W filter, which is effectively a broad V filter. We describe the use of Fourier methods for separation of the fluctuations due to statistical variations in the projected number of stars per pixel (used to determine the distance) from fluctuations from other sources, which include photon noise, foreground stars, cosmic rays, and the variations due to the overall structure of the galaxy. The mean apparent magnitude of stars responsible for the measured fluctuations is m_I_{bar}=29.78+/-0.03, with an additional systematic uncertainty of 0.05mag. Using the latest calibration of Tonry (1997ApJ...475..399T), we obtain a distance of 15.6+/-1.0Mpc, which is consistent with the distance determined through the use of this method in the infrared K band by Pahre & Mould (1994ApJ...433..567P). We discuss the globular cluster (GC) luminosity function and color distribution, based on the ~130 candidates identified in the field. We find a roughly Gaussian luminosity function centered at m_v_=23.82+/-0.38 with {sigma}=1.16+/-0.21. The GC color distribution is also roughly Gaussian, centered at V-I=0.91+/-0.03, with {sigma}=0.20+/-0.03, and it is coincident to within the error bars with the blue peak of the bimodal color distribution found in M87. Comparing our data with recent evaluations of the GC color distribution at two different locations in M87 we find a trend of the red peak disappearing with radial distance. We speculate that this could be understood if the blue portion of the M87 GC population were acquired from its smaller companions. The specific frequency of globular clusters is among the lowest for elliptical galaxies, comparable only to the value found in M32. In both cases this may be a result of tidal truncation by a giant neighbor. This further indicates that clusters have been stripped from NGC 4478 by M87 and likely now are part of its globular cluster population.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1533
- Title:
- NGC 5128 globular clusters
- Short Name:
- J/ApJ/705/1533
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An objective classification of the globular clusters (GCs) of NGC 5128 has been carried out by using a model-based approach of cluster analysis. The set of observable parameters includes structural parameters, spectroscopically determined Lick indices and radial velocities from the literature. The optimum set of parameters for this type of analysis is selected through a modified technique of principal component analysis, which differs from the classical one in the sense that it takes into consideration the effects of outliers present in the data. Then a mixture model based approach has been used to classify the GCs into groups. The efficiency of the techniques used is tested through the comparison of the misclassification probabilities with those obtained using the K-means clustering technique. On the basis of the above classification scheme three coherent groups of GCs have been found. We propose that the clusters of one group originated in the original cluster formation event that coincided with the formation of the elliptical galaxy, and that the clusters of the two other groups are of external origin, from tidally stripped dwarf galaxies on random orbits around NGC 5128 for one group, and from an accreted spiral galaxy for the other.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/37
- Title:
- NGC 4365 globular clusters
- Short Name:
- J/MNRAS/420/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Analysis of the globular cluster (GC) system of the giant elliptical (E3) galaxy NGC 4365, from eight Hubble Space Telescope/Advanced Camera for Surveys pointings and a wide-field Subaru/Suprime-Cam image, is presented. Using magnitude, colour and size criteria, we obtain a catalogue of GC candidates. We also measure the photometric properties of the galaxy starlight, including a new measure of the effective radius.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/1485
- Title:
- NGC 3923 globular clusters
- Short Name:
- J/MNRAS/421/1485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents further results from our spectroscopic study of the globular cluster (GC) system of the group elliptical NGC 3923. From observations made with the GMOS instrument on the Gemini South Telescope, an additional 50 GC and ultra-compact dwarf (UCD) candidates have been spectroscopically confirmed as members of the NGC 3923 system. When the recessional velocities of these GCs are combined with the 29 GC velocities reported previously, a total sample of 79 GC/UCD velocities is produced. This sample extends to over 6-arcmin (>6Re~30kpc) from the centre of NGC 3923 and is used to study the dynamics of the GC system and the dark matter content of NGC 3923.
