- ID:
- ivo://CDS.VizieR/J/MNRAS/416/155
- Title:
- Globular clusters in five early-type galaxies
- Short Name:
- J/MNRAS/416/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present deep high-quality photometry of globular cluster systems (GCSs) belonging to five early-type galaxies, covering a range of mass and environment. Photometric data were obtained with the Gemini North and Gemini South telescopes in the filter passbands g', r' and i'. The combination of these filters with good seeing conditions allows an excellent separation between globular cluster (GC) candidates and unresolved field objects.
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1312. Globular clusters in M87
- ID:
- ivo://CDS.VizieR/J/AJ/106/493
- Title:
- Globular clusters in M87
- Short Name:
- J/AJ/106/493
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep integrated Washington CCD photometry of the extremely populous globular cluster system of NGC 4486 (M87) in Virgo. The metallicities of 407 of the best candidates with T1 < 22 have been estimated from the (C-T1) color. These values are internally precise to ~0.15dex and accurate to ~0.25dex. The mean metallicity of the globular clusters is [Fe/H] = -0.86dex, with a formal standard error of the mean of 0.03dex but a more realistic uncertainty of about 0.2dex. This value is higher than that of the corresponding means of the globular clusters in the Galaxy and M31, but similar to those of the globular clusters in NGC 1399 and NGC 5128, as expected from the relative parent galaxy luminosities. Approximately 10% of the clusters exceed solar abundance, similar to the case for the globular clusters in NGC 1399 and NGC 5128. As found by Couture et al. [ApJS, 73, 671 (1990)], there is a large metallicity dispersion at any radius, with a sigma ~ 0.65dex. However, in contrast to their result and that of previous small-field CCD studies, the globular clusters display a marked gradient in both mean (M-T1) and (C-T1) color with galactocentric distance. The mean metallicity decreases by some 0.6dex over the radial extent of the cluster sample. This result is consistent with the early photographic study by Strom et al. [ApJ, 245, 416 (1981)]. The metallicity distribution function is remarkably similar to that of NGC 1399 found by Ostrov et al. [AJ, 105, 1762 (1993)] using the same technique. The two central cluster ellipticals show significant peaks at very similar metallicities, indicating similar formation and enrichment histories. We also find that this structure in the metallicity distribution function persists to radii where the halo light is dominated by the cD envelope.
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1965
- Title:
- Globular clusters in M104
- Short Name:
- J/MNRAS/401/1965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Images from the Hubble Space Telescope Advanced Camera for surveys are used to carry out a new photometric study of the globular clusters (GCs) in M104, the Sombrero galaxy. The primary focus of our study is the characteristic distribution function of linear sizes [size distribution function (SDF)] of the GCs. We measure the effective radii for 652 clusters with point spread function-convolved King and Wilson dynamical model fits. The SDF is remarkably similar to those measured for other large galaxies of all types, adding strong support to the view that it is a 'universal' feature of GC systems. We use the Sombrero and Milky Way data and the formation models of Baumgardt & Kroupa (2007MNRAS.380.1589B) to develop a more general interpretation of the SDF for GCs.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1043
- Title:
- Globular clusters in M31 and the Galaxy
- Short Name:
- J/AJ/140/1043
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way system and the Andromeda galaxy experienced radically different evolutionary histories. Nevertheless, it is found that these two galaxies ended up with globular cluster systems in which individual clusters have indistinguishable distributions of half-light radii. Furthermore, globulars in both M31 and the Galaxy are found to have radii that are independent of their luminosities. In this respect, globular clusters differ drastically from early-type galaxies in which half-light radius and luminosity are tightly correlated. Metal-rich globular clusters in M31 occupy a slightly larger volume than do those in the Galaxy. The specific globular cluster frequency in the Andromeda galaxy is found to be significantly higher than it is in the Milky Way system. The present discussion is based on the 107 Galactic globular clusters, and 200 putative globulars in M31, for which UBV photometry was available.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/L55
- Title:
- Globular clusters in M31 from K-band photometry
- Short Name:
- J/MNRAS/392/L55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relationship between low-mass X-ray binaries (LMXBs) and globular clusters (GCs) using United Kingdom Infrared Telescope (UKIRT) observations of M31 and existing Chandra, XMM-Newton and ROSAT catalogues. By fitting King models to these data, we have estimated the structural parameters and stellar collision rates of 239 of its GCs. We show a highly significant trend between the presence of a LMXB and the stellar collision rate of a cluster. The stellar collision rate is found to be a stronger predictor of which clusters will host LMXBs than the host cluster mass. We argue that our results show that the stellar collision rate of the clusters is the fundamental parameter related to the production LMXBs. This is consistent with the formation of LMXBs through dynamical interactions with little direct dependence on the neutron star retention fraction or cluster mass.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/879
- Title:
- Globular clusters in nearby dwarf galaxies
- Short Name:
- J/MNRAS/392/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the old globular cluster (GC) population of 68 faint (M_V_>−16mag) dwarf galaxies located in the halo regions of nearby (<~12Mpc) loose galaxy groups and in the field environment based on archival Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) images in F606W and F814W filters.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/123
- Title:
- Globular clusters in NGC 474 from CFHT obs.
- Short Name:
- J/ApJ/835/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters (GCs) are some of the most visible tracers of the merging and accretion histories of galaxy halos. Metal-poor GCs, in particular, are thought to arrive in massive galaxies largely through dry, minor merging events, but it is rare to see a direct connection between GCs and visible stellar streams. NGC 474 is a post-merger early-type galaxy with dramatic fine structures made of concentric shells and radial streams that have been more clearly revealed by deep imaging. We present a study of GCs in NGC 474 to better establish the relationship between merger-induced fine structure and the GC system. We find that many GCs are superimposed on visible streams and shells, and about 35% of GCs outside 3R_e,galaxy_ are located in regions of fine structure. The spatial correlation between GCs and fine structure is significant at the 99.9% level, which shows that this correlation is not coincidental. The colors of GCs on fine structures are mostly blue, and we also find an intermediate-color population that is dominant in the central region and that will likely passively evolve to have colors consistent with a traditional metal-rich GC population. The association of the blue GCs with fine structures is direct confirmation that many metal-poor GCs are accreted onto massive galaxy halos through merging events and that the progenitors of these mergers are sub-L^*^ galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/87
- Title:
- Globular clusters of M60 with HST
- Short Name:
- J/ApJ/760/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present g and z photometry and size estimates for globular clusters (GCs) in the massive Virgo elliptical NGC 4649 (M60) using a five-pointing Hubble Space Telescope/Advanced Camera for Surveys mosaic. The metal-poor GCs show a monotonic negative metallicity gradient of -0.43+/-0.10dex per dex in radius over the full radial range of the data, out to ~24kpc. There is evidence for substantial color substructure among the metal-rich GCs. The metal-poor GCs have typical sizes ~0.4pc larger than the metal-rich GCs out to large galactocentric distances (>~20kpc), favoring an intrinsic explanation for the size difference rather than projection effects. There is no clear relation between half-light radius and galactocentric distance beyond ~15kpc, suggesting that the sizes of GCs are not generically set by tidal limitation. Finally, we identify ~20 candidate ultracompact dwarfs that extend down to surprisingly faint absolute magnitudes (M_z_~-8.5), and may bridge the gap between this class and "extended clusters" in the Local Group. Three of the brighter candidates have published radial velocities and can be confirmed as bona fide ultracompact dwarfs; follow-up spectroscopy will determine the nature of the remainder of the candidates.
1319. 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.
