- 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.
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Search Results
- 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.
- 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/AJ/140/2101
- Title:
- NGC 5128 globular clusters photometry
- Short Name:
- J/AJ/140/2101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometry for 323 of the globular clusters in NGC 5128 (Centaurus A), measured for the first time in the g'r'i'z' filter system. The color indices are calibrated directly to standard stars in the g'r'i'z' system and are used to establish the fiducial mean colors for the blue and red (low and high metallicity) globular cluster sequences. We also use previously published spectroscopically measured abundances to establish the conversion between the most metallicity-sensitive colors ((g'-r')_0_,(g'-i')_0_) and metallicity, [Fe/H].
- ID:
- ivo://CDS.VizieR/J/AJ/134/494
- Title:
- NGC 5128 globular clusters UBVRICMT1 phot. & RV
- Short Name:
- J/AJ/134/494
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new kinematic and dynamic study of the halo of the giant elliptical galaxy NGC 5128 is presented. From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae, the rotation amplitude, rotation axis, velocity dispersion, and total dynamical mass are determined for the halo of NGC 5128.
1747. NGC 5523 H-band image
- ID:
- ivo://CDS.VizieR/J/A+A/598/A119
- Title:
- NGC 5523 H-band image
- Short Name:
- J/A+A/598/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multi-band images of the very isolated spiral galaxy NGC 5523 show a number of unusual features consistent with NGC 5523 having experienced a significant merger: (1) Near-infrared (NIR) images from the Spitzer Space Telescope (SST) and the WIYN 3.5-m Multi-band images of the very isolated spiral galaxy NGC 5523 show a number of unusual features consistent with NGC 5523 having experienced a significant merger: (1) Near-infrared (NIR) images from the Spitzer Space Telescope (SST) and the WIYN 3.5-m telescope reveal a nucleated bulge-like structure embedded in a spiral disk. (2) The bulge is offset by ~1.8kpc from a brightness minimum at the center of the optically bright inner disk. (3) A tidal stream, possibly associated with an ongoing satellite interaction, extends from the nucleated bulge along the disk. We interpret these properties as the results of one or more non-disruptive mergers between NGC 5523 and companion galaxies or satellites, raising the possibility that some galaxies become isolated because they have merged with former companions.
1748. NGC 1741 HST photometry
- ID:
- ivo://CDS.VizieR/J/AJ/117/1708
- Title:
- NGC 1741 HST photometry
- Short Name:
- J/AJ/117/1708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope (HST) Faint Object Camera (FOC) ultraviolet (UV) and WFPC2 optical images in conjunction with UV spectroscopic observations taken with the Goddard High Resolution Spectrograph to examine the star formation history and properties of the interacting galaxy system NGC 1741 in the Hickson Compact Group 31. The high spatial resolution afforded by HST has allowed us to identify a large number of starburst knots, or "superstar clusters" (SSCs), in the starburst regions of this system. Photometry of these SSCs in the UV and optical bands indicates that most of these objects have ages of a few Myr, with a few up to ~100Myr, and masses between 10^4^ and 10^6^M_{sun}_. The estimated age is confirmed by a spectral synthesis analysis of one knot for which we have obtained a UV spectrum. The V-band luminosity function of the SSCs is well represented by a power law {Phi}(L)~L^-{alpha}^ with an index of -1.85, with no evidence of a turnover brighter than the completeness limit. These properties are in good agreement with those found for SSCs in other starburst galaxies. Our results support the suggestion that some of these SSCs may be extremely young globular clusters formed in a relatively recent starburst episode that has been triggered by a merger event.
- ID:
- ivo://CDS.VizieR/J/AJ/146/57
- Title:
- NGC 6402. I. BV photometry
- Short Name:
- J/AJ/146/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV photometry of the Galactic globular cluster NGC 6402 (M14), based on 65 V frames and 67 B frames, reaching two magnitudes below the turnoff level. This represents, to the best of our knowledge, the deepest color-magnitude diagram (CMD) of NGC 6402 available in the literature. Statistical decontamination of field stars as well as differential reddening corrections are performed in order to derive a precise ridgeline and hence physical parameters of the cluster. We discuss previous attempts at deriving a reddening value for the cluster, and argue in favor of a value E(B-V)=0.57+/-0.02, which is significantly higher than indicated by either the Burstein & Heiles or Schlegel et al. (corrected according to Bonifacio et al.) interstellar dust maps. Differential reddening across the face of the cluster, which we find to be present at the level of {Delta}E(B-V){approx}0.17mag, is taken into account in our analysis. We measure several metallicity indicators based on the position of the red giant branch (RGB) in the cluster CMD. These give a metallicity of [Fe/H]=-1.38+/-0.07 on the Zinn & West scale and [Fe/H]=-1.28+/-0.08 on the new Carretta et al. (UVES) scale. We also provide measurements of other important photometric parameters for this cluster, including the position of the RGB luminosity function "bump" and the horizontal branch morphology. We compare the NGC 6402 ridgeline with that of NGC 5904 (M5) derived by Sandquist et al., and find evidence that NGC 6402 and M5 have approximately the same age to within the uncertainties, although the possibility that M14 may be slightly older cannot be ruled out.
1750. NGC 3923 MegaCam image
- ID:
- ivo://CDS.VizieR/J/A+A/588/A77
- Title:
- NGC 3923 MegaCam image
- Short Name:
- J/A+A/588/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The elliptical galaxy NGC 3923 is known to be surrounded by a number of stellar shells, probable remnants of an accreted galaxy. Despite its uniqueness, the deepest images of its outskirts come from the 1980s. On the basis of the modified Newtonian dynamics (MOND), it has recently been predicted that a new shell lies in this region. We obtain the deepest image ever of the galaxy, map the tidal features in it, and search for the predicted shell. The image of the galaxy was taken by the MegaCam camera at the Canada-France-Hawaii Telescope in the g'-band. It reached the surface-brightness limit of 29mag/arcsec^2^. In addition, we reanalyzed an archival HST image of the galaxy.
