Study Of Globular Cluster Systems Research Articles

The Brazil–Argentina Gemini Group for the Study of Globular Cluster Systems (BAGGs GCs): FLAMINGOS-2 and GMOS Data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC 1395. This is the first step of a long-term Brazilian–Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and K s), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC 1395.

Extragalactic Globular Cluster Systems in the Near-IR

Extragalactic Globular Clusters are useful tracers of galaxy formation and evolution. Photometric studies of globular cluster systems beyond the Local Group are still the most popular method to investigate their physical properties, such as their ages and metallicities. However, the limitations of optical photometry are well known. The better wavelength sampling of the underlying cluster's SED using K-band photometry combined with optical passbands allows us to create colors which reduce the age-metallicity degeneracy to the largest extent. Here we report on the very first results of our near-IR photometric survey of globular cluster systems in early-type galaxies outside the Local Group.

A Comparative Study of Globular Cluster Systems in UGC 9799 and NGC 1129

We present a preliminary analysis of HST-WFPC2 observations of globular cluster systems in the two brightest galaxies, UGC 9799 (cD) and NGC 1129 (non-cD), located in the center of rich clusters.

New Insights from [ITAL]HST[/ITAL] Studies of Globular Cluster Systems. I. Colors, Distances, and Specific Frequencies of 28 Elliptical Galaxies

We present an analysis of the globular cluster systems of 28 elliptical galaxies using archival WFPC2 images in the V and I-bands. The V-I color distributions of at least 50% of the galaxies appear to be bimodal {\it at the present level of photometric accuracy}. We argue that this is indicative of multiple epochs of cluster formation early in the history of these galaxies, possibly due to mergers. We also present the first evidence of bimodality in low luminosity galaxies and discuss its implication on formation scenarios. The mean color of the 28 cluster systems studied by us is V-I = 1.04$\pm$0.04 (0.01) mag corresponding to a mean metallicity of Fe/H = -1.0$\pm$0.19 (0.04). We find that the turnover magnitudes of the globular cluster luminosity functions (GCLF) of our sample are in excellent agreement with the distance measurements using other methods and conclude that the accuracy of the GCLF is at least as good as the surface brightness fluctuation method. The absolute magnitude of the turnover luminosity of the GCLF is M$_V^0$ = -7.41 (0.03) in V and M$_I^0$ = -8.46 (0.03) in I. The mean local specific frequency of our sample of elliptical galaxies within the WFPC2 field-of-view is 2.4$\pm$1.8 (0.4), considerably higher than the 1.0$\pm$0.6 (0.1) derived for a comparable sample of S0s in a similar analysis. It shows no obvious correlation with metallicity, host galaxy mass or membership in a galaxy cluster. The median size of clusters in all galaxies appears to be remarkably constant at $\sim$2.4 pc. We suggest that in the future it might be possible to use the sizes of clusters in the inner regions of galaxies as a simple geometrical distance indicator.

Globular Cluster Systems in Galaxies

The study of globular cluster systems is very important. Because these systems are so old, their investigation is a form of archeo-astronomy whereby a slow and, at times, tedious gathering of fragmentary data laboriously uncovers the skeleton of early galactic structures. Our theories and our imagination can then try to put some flesh on these bones in attempts to visualize what these early inhabitants of the Universe might have looked like.