- ID:
- ivo://CDS.VizieR/J/A+A/603/A37
- Title:
- 4 globular clusters RGB and AGB stars
- Short Name:
- J/A+A/603/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic studies have demonstrated that nearly all Galactic globular clusters (GCs) harbour multiple stellar populations with different chemical compositions. Moreover, colour-magnitude diagrams based exclusively on Stroemgrem photometry have allowed us to identify and characterise multiple populations along the RGB of a large number of clusters. In this paper we show for the first time that Stroemgren photometry is also very efficient at identifying multiple populations along the AGB, and demonstrate that the AGB of M3, M92, NGC362, NGC1851, and NGC6752 are not consistent with a single stellar population. We also provide a catalogue of RGB and AGB stars photometrically identified in these clusters for further spectroscopic follow-up studies. We combined photometry and elemental abundances from the literature for RGB and AGB stars in NGC6752 where the presence of multiple populations along the AGB has been widely debated. We find that, while the MS, SGB, and RGB host three stellar populations with different helium and light element abundances, only two populations of AGB stars are present in the cluster. These results are consistent with standard evolutionary theory.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/559/812
- Title:
- Globular cluster system in M87
- Short Name:
- J/ApJ/559/812
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive database of kinematic, photometric, and positional information for 352 objects in the field of M87 (NGC 4486), the central giant elliptical galaxy in the Virgo Cluster; the majority of the tracers are globular clusters associated with that galaxy. New kinematic information comes from multislit observations with the Multi-Object Spectrograph (MOS) of the Canada-France-Hawaii Telescope (CFHT), an investigation that has added 96 new velocities to and confirmed many of the earlier values in a preexisting data set of 256 velocities published elsewhere. The photometry, consisting of magnitudes and colors in the Washington (T_1_, C-T_1_) system, is based on CCD observations made at the Cerro Tololo Inter-American Observatory (CTIO) and the Kitt Peak National Observatory (KPNO).
- ID:
- ivo://CDS.VizieR/J/ApJ/513/733
- Title:
- Globular cluster system in M87
- Short Name:
- J/ApJ/513/733
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 1057 globular cluster candidates in a WFPC2 image of the inner region of M87. The globular cluster luminosity function (GCLF) can be well fitted by a Gaussian profile with a mean value of m^0^_V_=23.67+/-0.07mag and {sigma}=1.39+/-0.06mag. The GCLF in five radial bins is found to be statistically the same at all points, showing no clear evidence of dynamical destruction processes based on the luminosity function (LF). Similarly, there is no obvious trend between the half-light radius of the clusters and the galactocentric distance. The core radius of the globular cluster density distribution is R_c_=56", considerably larger than the core of the stellar component (R_c_=6.8"). The mean color of the cluster candidates is V-I=1.09mag, which corresponds to an average metallicity of Fe/H=-0.74dex. The color distribution is bimodal everywhere, with a blue peak at V-I=0.95mag and a red peak at V-I=1.20mag. The red population is only 0.1mag bluer than the underlying galaxy, indicating that these clusters formed late in the metal-enrichment history of the galaxy and were possibly created in a burst of star/cluster formation 3-6Gyr after the blue population. We also find that both the red and the blue cluster distributions have a more elliptical shape (Hubble type E3.5) than the nearly spherical galaxy. The average half-light radius of the clusters is ~2.5pc, which is comparable to the 3pc average effective radius of the Milky Way clusters, although the red clusters are ~20% smaller than the blue ones.
- ID:
- ivo://CDS.VizieR/J/A+A/455/453
- Title:
- Globular Cluster System of NGC5846
- Short Name:
- J/A+A/455/453
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5846 is a giant elliptical galaxy with a previously well studied globular cluster system (GCS), known to have a bimodal colour distribution with a remarkably high red fraction. Here we revisit the central galaxy regions searching for new globular cluster (GC) candidates, and measure magnitudes, colours and sizes for them. We also search for their X-ray counterparts. Methods: We use archival Hubble Space Telescope WFPC2 images, from which we modelled and subtracted the host light distribution to increase the available sample of GCs. We performed photometry on the central objects, and measured sizes and coordinates for the entire GC system known in this galaxy. Results: We detect two dozen previously unknown GC candidates in the central reg ions. Reliable sizes are obtained for about 60 GCs; their typical effective radii are in the range 3-5pc. The largest clusters are located in the central regions. We find 7 X-ray counterparts to GCs, most of them in the central region. They are among the most luminous X-ray sources in NGC 5846. They are also optically luminous, compact and belong to the red subpopulation. Conclusions: The GCS of NGC 5846 is composed of relatively luminous X-ray sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/3706
- Title:
- Globular cluster 47 Tuc Chandra studies
- Short Name:
- J/MNRAS/472/3706
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combined Chandra ACIS observations of the globular cluster 47 Tucanae (47 Tuc) from 2000, 2002 and 2014-2015 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2.79 arcsec) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chromospherically active BY Dra or W UMa variables identified by Albrow et al. We present alternative positions derived from two methods, centroiding and image reconstruction, for faint, crowded sources. We are able to extract X-ray spectra of the recently discovered MSPs 47 Tuc aa, 47 Tuc ab, the newly timed MSP 47 Tuc Z, and the newly resolved MSPs 47 Tuc S and 47 Tuc F. Generally, they are well fitted by blackbody or neutron star atmosphere models, with temperatures, luminosities and emitting radii similar to those of other known MSPs in 47 Tuc, though 47 Tuc aa and 47 Tuc ab reach lower X-ray luminosities. We limit X-ray emission from the full surface of the rapidly spinning (542 Hz) MSP 47 Tuc aa, and use this limit to put an upper bound for amplitude of r-mode oscillations in this pulsar as {alpha}<2.5x10^-9^ and constrain the shape of the r-mode instability window.
- ID:
- ivo://CDS.VizieR/J/PASP/109/883
- Title:
- Globular metallicity scale. I.
- Short Name:
- J/PASP/109/883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained 2640 CCD spectra with resolution ~4{AA} in the region 7250-9000{AA} for 976 stars lying near the red giant branches in color-magnitude diagrams of 52 Galactic globular clusters. Radial velocities of ~16km/s accuracy per star determined from the spectra are combined with other criteria to assess quantitative membership probabilities. Measurements of the equivalent widths of the infrared calcium triplet lines yield a relative metal-abundance ranking with a precision that compares favorably to other techniques. Regressions between our system and those of others are derived. Our reduction procedures are discussed in detail, and the resultant catalog of derived velocities and equivalent widths is presented. The metal abundances derived from these data will be the subject of a future paper. (c) Astronomical Society of the Pacific
357. Globulars in M31
- ID:
- ivo://CDS.VizieR/J/AJ/114/1488
- Title:
- Globulars in M31
- Short Name:
- J/AJ/114/1488
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep (V=~27) V- and I-band stellar photometry of G302 and G312, two globular star clusters in the halo of M31. These data were obtained using the Hubble Space Telescope's Wide Field/Planetary Camera 2. We find iron abundances of [Fe/H]=-1.85+/-0.12 for G302 and [Fe/H]=-0.56+/-0.03 for G312, consistent with spectroscopic measurements. The color-magnitude diagrams for each cluster show no evidence for an intermediate-aged population of stars, or a second parameter effect in the morphology of the horizontal branch. G302 shows no evidence for a color gradient but the inner regions of G312 are bluer than the outer regions. G312 shows no evidence of ellipticity or an extended halo of stars. G302 has a projected ellipticity of {epsilon}=0.195+/-0.012 with the projected major axis oriented towards the center of M31. G302 also shows evidence of an extended asymmetric stellar halo extending to at least twice the fitted Michie-King tidal radius. The amount of mass beyond the tidal radius of G302 is consistent with the stellar escape rates which have been predicted by N-body simulations of globular clusters in the Galactic tidal field. (c) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/AJ/137/383
- Title:
- Globulars in PGC 6510, PGC 10922, PGC 4287
- Short Name:
- J/AJ/137/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the globular cluster (GC) systems of four early-type poststarburst galaxies using deep g- and I-band images from the Advanced Camera for Surveys aboard the Hubble Space Telescope. All the galaxies feature shells distributed around their main bodies and are thus likely merger remnants. The color distribution of the GCs in all four galaxies shows a broad peak centered on g-I~1.4, while PGC 6240 and PGC 42871 show a significant number of GCs with g-I~1.0.
359. Globulars of M81
- ID:
- ivo://CDS.VizieR/J/AJ/109/1055
- Title:
- Globulars of M81
- Short Name:
- J/AJ/109/1055
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained photometric BVR, morphological, and astrometric information on 3774 objects located within a 25' radius of M81. This catalogue is complete for 15 <= V <= 21; it is used here to identify globular cluster candidates in M81 and as a database for a statistical analysis of the system as a whole. The M81 globular cluster system is revealed as a strong surface density excess of ~70 objects within an 11 kpc galactocentric radius. The total population is estimated at N_T = 210 +/- 30 globulars. The spatial, (B-V), and (V-R) distributions are very similar to those of the Milky Way and of M31. Small but significant systematic errors in Madore et al.'s [AJ, 106, 2243 (1993)] photometry could be responsible for an overestimate of the Cepheid distance to M81 [(m-M)0 = 27.8] and we propose a revised modulus of (m-M)0 = 27.5 +/- 0.3. The globular cluster luminosity function then reaches its maximum at M_V* = -7.5 +/- 0.4, as it does in the galaxy and in M31. There is suggestive evidence that 13 +/- 5 objects are globulars seen through the disk of M81; spectroscopy or high-resolution imaging will resolve this issue. Using the (B-R)0 index to trace [Fe/H], we notice a weak dependence of mean metallicity on galactocentric distance, as observed in the galaxy and in M31. This result argues in favour of in situ globular formation during the continuous collapse and self-enrichment of an early-type spiral host.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/199
- Title:
- Globulars with X-ray sources in NGC 5128
- Short Name:
- J/ApJ/682/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We detect 353 X-ray point sources, mostly low-mass X-ray binaries (LMXBs), in four Chandra observations of Centaurus A (NGC 5128), the nearest giant early-type galaxy, and correlate this point-source population with the largest available ensemble of confirmed and likely globular clusters (GCs) associated with this galaxy. Of the X-ray sources, 31 are coincident with 30 GCs that are confirmed members of the galaxy by radial velocity measurement (two X-ray sources match one GC within our search radius), while one X-ray source coincides with a GC resolved by Hubble Space Telescope (HST) images. Another 36 X-ray point sources match probable, but spectroscopically unconfirmed, GC candidates.
