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We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC 3115, observed as part of the ongoing wide-field imaging survey VEGAS, carried out with the 2.6 m VST telescope. We used deep g and i observations of NGC 3115, a well-studied lenticular galaxy that is covered excellently well in the scientific literature. This is fundamental to test the methodologies, verify the results, and probe the capabilities of the VEGAS-SSS. Leveraging the large field of view of the VST allowed us to accurately study the distribution and properties of SSSs as a function of galactocentric distance, well beyond ~20 galaxy effective radii, in a way that is rarely possible. Our analysis of colors, magnitudes, and sizes of SSS candidates confirms the results from existing studies, some of which were carried out with 8-10 m class telescopes, and further extends them to previously unreached galactocentric distances with similar accuracy. In particular, we find a color bimodality for the GC population and a de Vaucouleurs r1/4 profile for the surface density of GCs similar to the galaxy light profile. The radial color gradient of blue and red GCs previously found, for instance, by the SLUGGS survey with Subaru and Keck data, is further extended out to the largest galactocentric radii inspected, ~65 kpc. In addition, the surface density profiles of blue and red GCs taken separately are well approximated by a r1/4 density profile, with the fraction of blue GCs being slightly larger at larger radii. We do not find hints of a trend for the red GC subpopulation and for the GC turnover magnitude to vary with radius, but we observe a ~0.2 mag difference in the turnover magnitude of the blue and red GC subpopulations. Finally, from inspecting SSS sizes and colors, we obtain a list of ultracompact dwarf galaxies and GC candidates suitable for future spectroscopic follow-up. In conclusion, our study shows i) the reliability of the methodologies developed to study SSSs in the field of bright early-type galaxies; and ii) the great potential of the VEGAS survey to produce original results on SSSs science, mainly thanks to the wide-field imaging adopted. Full Table 3 is only available at the CDS via anonymous ftp to "http://cdsarc.u-strasbg.fr" (ftp://130.79.128.5) or via "http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A14"

We present a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with Hubble Space Telescope and Chandra high resolution, allow us to constrain the LMXB formation scenarios in elliptical galaxies. We confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to > 5R(eff) of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L(X) > 10(39) erg s(-1) shows no variability, which may indicate a superposition of multiple LMXBs in these systems.

We present a comprehensive high spatial-resolution imaging study of globular clusters (GCs) in NGC1399, the central giant elliptical cD galaxy in the Fornax galaxy cluster, conducted with HST/ACS. Using a novel technique to construct drizzled PSF libraries for HST/ACS data, we accurately determine the fidelity of GC structural parameter measurements from detailed artificial star cluster experiments. The measurement of rh for the major fraction of the NGC1399 GC system reveals a trend of increasing rh versus galactocentric distance, Rgal, out to about 10 kpc and a flat relation beyond. This trend is very similar for blue and red GCs which are found to have a mean size ratio of rh(red)/rh(blue)=0.82+/-0.11 at all galactocentric radii from the core regions of the galaxy out to ~40 kpc. This suggests that the size difference between blue and red GCs is due to internal mechanisms related to the evolution of their constituent stellar populations. Modeling the mass density profile of NGC1399 shows that additional external dynamical mechanisms are required to limit the GC size in the galaxy halo regions to rh~2 pc. We suggest that this may be realized by an exotic GC orbit distribution function, an extended dark matter halo, and/or tidal stress induced by the increased stochasticity in the dwarf halo substructure at larger Rgal. We match our GC rh measurements with radial velocity data from the literature and find that compact GCs show a significantly smaller line-of-sight velocity dispersion, =225+/-25 km/s, than their extended counterparts, =317+/-21 km/s. Considering the weaker statistical correlation in the GC rh-color and the GC rh-Rgal relations, the more significant GC size-dynamics relation appears to be astrophysically more relevant and hints at the dominant influence of the GC orbit distribution function on the evolution of GC structural parameters., Comment: 22 pages, 17 figures, accepted for publication in The Astrophysical Journal, a high-quality PDF version is available at http://www.astro.puc.cl/~tpuzia/PUC/Home.html