- ID:
- ivo://CDS.VizieR/J/MNRAS/396/1075
- Title:
- Globular cluster in nearby dwarf galaxies. II
- Short Name:
- J/MNRAS/396/1075
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) in order to test the suggested external origin of the latter and the conditions at which GC self-enrichment can operate. Using luminosities and structural parameters of nGCs in low-mass (mainly late-type) dwarf galaxies from Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) imaging, we derive the present-day escape velocities (Vesc) of stellar ejecta to reach the cluster tidal radius and compare them with those of EHB-GCs.
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- ID:
- ivo://CDS.VizieR/J/ApJ/799/159
- Title:
- Globular cluster populations in S4G galaxies
- Short Name:
- J/ApJ/799/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3.6{mu}m images of 97 early-type galaxies, we develop and verify methodology to measure globular cluster populations from the S^4^G survey images. We find that (1) the ratio, T_N_, of the number of clusters, N_CL_, to parent galaxy stellar mass, M_*_, rises weakly with M_*_ for early-type galaxies with M_*_>10^10^M_{sun}_ when we calculate galaxy masses using a universal stellar initial mass function (IMF) but that the dependence of T_N_ on M_*_ is removed entirely once we correct for the recently uncovered systematic variation of IMF with M_*_; and (2) for M_*_<10^10^M_{sun}_, there is no trend between N_CL_ and M_*_, the scatter in T_N_is significantly larger (approaching two orders of magnitude), and there is evidence to support a previous, independent suggestion of two families of galaxies. The behavior of N_CL_ in the lower-mass systems is more difficult to measure because these systems are inherently cluster-poor, but our results may add to previous evidence that large variations in cluster formation and destruction efficiencies are to be found among low-mass galaxies. The average fraction of stellar mass in clusters is ~0.0014 for M_*_>10^10^M_{sun}_ and can be as large as ~0.02 for less massive galaxies. These are the first results from the S^4^G sample of galaxies and will be enhanced by the sample of early-type galaxies now being added to S^4^G and complemented by the study of later-type galaxies within S^4^G.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/99
- Title:
- Globular cluster populations in S4G galaxies. II.
- Short Name:
- J/ApJ/818/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 3.6 and 4.5{mu}m images of 73 late-type, edge-on galaxies from the S^4^G survey, we compare the richness of the globular cluster populations of these galaxies to those of early-type galaxies that we measured previously. In general, the galaxies presented here fill in the distribution for galaxies with lower stellar mass, M_*_, specifically log(M_{star}_/M_{sun})<10, overlap the results for early-type galaxies of similar masses, and, by doing so, strengthen the case for a dependence of the number of globular clusters per 10^9^M_{sun}_ of galaxy stellar mass, T_N_, on M_*_. For 8.5<log(M_{star}_/M_{sun})<10.5 we find the relationship can be satisfactorily described as T_N_=(M_{star}_/10^6.7^)^-0.56^ when M_*_ is expressed in solar masses. The functional form of the relationship is only weakly constrained, and extrapolation outside this range is not advised. Our late-type galaxies, in contrast to our early types, do not show the tendency for low-mass galaxies to split into two T_N_ families. Using these results and a galaxy stellar mass function from the literature, we calculate that, in a volume-limited, local universe sample, clusters are most likely to be found around fairly massive galaxies (M_*_~10^10.8^M_{sun}_) and present a fitting function for the volume number density of clusters as a function of parent-galaxy stellar mass. We find no correlation between T_N_ and large-scale environment, but we do find a tendency for galaxies of fixed M_*_ to have larger T_N_ if they have converted a larger proportion of their baryons into stars.
- ID:
- ivo://CDS.VizieR/J/AJ/105/1762
- Title:
- Globular clusters around NGC 1399
- Short Name:
- J/AJ/105/1762
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained integrated Washington photometry (C,M,T1) of globular cluster candidates in the field of NGC 1399. This galaxy, the dominant object in the Fornax cluster, shares with NGC 4486 (M87) the property of possessing one of the largest known specific frequencies of globulars. Conflicting evidence on the presence of a B-V color gradient as a function of galactocentric distance has been reported for this cluster system. Here we investigate the existence of a gradient using the C-T1 index, which is twice as metallicity sensitive as B-V. A small gradient is detected. This color gradient, in the sense that outer clusters are bluer, amounts to approx. 0.1 mag in C-T1 over a galactocentric range from about 0.5 to 3.5 arcmin, corresponding to a difference of approx. 0.2 dex in metallicity. This confirms qualitatively the B-V gradient suggested by Bridges et al. [AJ, 101, 469 (1991)]. Photometry for 420 globular cluster candidates is presented. Metal abundances internally precise to approx. 0.25 dex and accurate to approx. 0.3 dex have been obtained for some 250 of the best candidates, after statistically subtracting a field contamination estimated at 30%. The mean abundance of -0.9 +/- 0.2 confirms previous indications that the NGC 1399 globular cluster system is, on average, significantly more metal rich than that of the Galaxy, as expected from the relative parent galaxy luminosities. Approximately 10% of the clusters exceed solar abundance, similar to the case for NGC 5128. The signature of possible globular cluster formation in mergers, as suggested by Ashman and Zepf [ApJ, 384, 50 (1992)], is found in the distinct peaks in the metallicity distribution function. However, their prediction (based on a simple theory designed only for application to normal elliptical galaxies and not the more complicated cD galaxies represented by NGC 1399) that the color difference between the clusters and the background halo light monotonically increases with radius is not borne out by the observations. The difference decreases with radius from the center to approx. 2 arcmin; beyond this radius, the difference does appear to increase, however. At all radii, the mean globular cluster abundance is some 0.25-0.5 dex more metal poor than that of the background halo.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2114
- Title:
- Globular clusters around NGC 1399
- Short Name:
- J/AJ/127/2114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities of 468 globular clusters around NGC 1399, the central galaxy in the Fornax cluster, have been obtained with FORS2 and the Mask Exchange Unit (MXU) at the ESO Very Large Telescope. This is the largest sample of globular cluster velocities around any galaxy obtained so far. The mean velocity uncertainty is 50km/s. This data sample is accurate and large enough to be used in studies of the mass distribution of NGC 1399 and the properties of its globular cluster system. Here we describe the observations and the reduction procedure, and we discuss the uncertainties of the resulting velocities. The complete sample of cluster velocities that is used in a dynamical study of NGC 1399 is tabulated. A subsample is compared with previously published values.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4956
- Title:
- Globular clusters around NGC 1407
- Short Name:
- J/AJ/137/4956
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 1407 is the central elliptical in a nearby evolved group of galaxies apparently destined to become a galaxy cluster core. We use the kinematics of globular clusters (GCs) to probe the dynamics and mass profile of the group's center, out to a radius of 60kpc (~10 galaxy effective radii)-the most extended data set to date around an early-type galaxy. This sample consists of 172 GC line-of-sight velocities, most of them newly obtained using Keck/DEIMOS, with a few additional objects identified as dwarf-globular transition objects or as intragroup GCs.
- ID:
- ivo://CDS.VizieR/J/PAZh/33/403
- Title:
- Globular clusters as gravitational lenses
- Short Name:
- J/PAZh/33/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the SDSS catalog, we have found new close quasar-galaxy pairs. We analyze the radial distribution of quasars from pairs around galaxies of different types. We show that the quasars from pairs follow the density profile of halo globular clusters. This is new observational evidence that the quasars projected onto the halos of galaxies are magnified by gravitational lensing by halo globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/L27
- Title:
- Globular clusters in ACSVCS early-type galaxies
- Short Name:
- J/ApJ/773/L27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a determination of the two-dimensional shape parameters of the blue and red globular cluster systems (GCSs) in a large number of elliptical galaxies and lenticular galaxies (early-type galaxies, called ETGs). We use a homogeneous data set of the globular clusters in 23 ETGs obtained from the HST/ACS Virgo Cluster Survey. The position angles of both blue and red GCSs show a correlation with those of the stellar light distribution, showing that the major axes of the GCSs are well aligned with those of their host galaxies. However, the shapes of the red GCSs show a tight correlation with the stellar light distribution as well as with the rotation property of their host galaxies, while the shapes of the blue GCSs do much less. These provide clear geometric evidence that the origins of the blue and red globular clusters are distinct and that ETGs may have dual halos: a blue (metal-poor) halo and a red (metal-rich) halo. These two halos show significant differences in metallicity, structure, and kinematics, indicating that they are formed in two distinguishable ways. The red halos might have formed via dissipational processes with rotation, while the blue halos are through accretion.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/1317
- Title:
- Globular clusters in 3 early-type galaxies
- Short Name:
- J/MNRAS/420/1317
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the age and metallicity distributions of bright globular clusters (GCs) in the candidate intermediate-age early-type galaxies NGC 3610, 584 and 3377 using a combination of new Gemini's Near InfraRed Imager and Spectrometer K'-band imaging and existing optical VI photometry from Hubble Space Telescope data.
- ID:
- ivo://CDS.VizieR/J/AJ/108/2087
- Title:
- Globular Clusters in Ellipticals
- Short Name:
- J/AJ/108/2087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VRI photometry for the globular cluster systems (GCS's) of ten elliptical and S0 galaxies in Virgo and Leo. We find that the V-I color (metallicity) distributions are quite different from galaxy to galaxy. One extreme is represented by NGC 4374 with a narrow, blue distribution. NGC 4472 has a very broad, uniform distribution in color, corresponding to -1.8 < [Fe/H] < +0.47. At the other extreme is NGC 4365, which is weighted towards red colors, and possibly has a peculiar luminosity function. We suggest that this variation of GCS metallicity depends on environment, with formation of high metallicity globular clusters inhibited in higher density environments. We compare color-color plots of the GCS's of these galaxies with the Milky Way GCS and with integrated isochrones. We find good agreement with the galaxies studied here except that the isochrones predict colors which are slightly too bright in the I band for metal-rich clusters. We also consider the radial GC color distributions in these galaxies. We find evidence for a V-I color gradient only in NGC 4374, in the sense of redder clusters toward the center of the galaxy but warn that possible systematic effects must be ruled out with the new data. Lastly, using the surface brightness fluctuation distances to these galaxies, we find supporting evidence for the universality of the globular cluster luminosity function.
