Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations ) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399. We have obtained 477 new medium-resolution spectra (of these, 292 are spectra from 265 individual GCs, 241 of which are not in the previous data set). with the VLT FORS 2 and Gemini South GMOS multi-object spectrographs. We revise velocities for the old spectra and measure velocities for the new spectra, using the same templates to obtain an homogeneously treated data set. Our entire sample now comprises velocities for almost 700 GCs with projected galactocentric radii between 6 and 100 kpc. In addition, we use velocities of GCs at larger distances published elsewhere. Combining the kinematic data with wide-field photometric Washington data, we study the kinematics of the metal-poor and metal-rich subpopulations. We discuss in detail the velocity dispersions of subsamples and perform spherical Jeans modelling. The most important results are: the red GCs resemble the stellar field population of NGC 1399 in the region of overlap. The blue GCs behave kinematically more erratic. Both subpopulations are kinematically distinct and do not show a smooth transition. It is not possible to find a common dark halo which reproduces simultaneously the properties of both red and blue GCs. Some velocities of blue GCs are only to be explained by orbits with very large apogalactic distances, thus indicating a contamination with GCs which belong to the entire Fornax cluster rather than to NGC 1399. Also, stripped GCs from nearby elliptical galaxies, particularly NGC 1404, may contaminate the blue sample. We argue in favour of a scenario in which the majority of the blue cluster population has been accreted during the assembly of the Fornax cluster. The red cluster population shares the dynamical history of the galaxy itself. Therefore we recommend to use a dark halo based on the red GCs alone. The dark halo which fits best is marginally less massive than the halo quoted previously. The comparison with X-ray analyses is satisfactory in the inner regions, but without showing evidence for a transition from a galaxy to a cluster halo, as suggested by X-ray work.

We present a photometric investigation of the globular cluster population of NGC 1399, the central galaxy in the Fornax cluster, in Washington C and Kron R filters within a field of 36 0 Â 36 0 , corresponding to about 200 Â 200 kpc at the Fornax distance. This is the largest area around this galaxy ever studied with CCD photometry. The cluster system of NGC 1399 is found to extend farther than 100 kpc away from the galaxy. The color distribution exhibits a pronounced bimodality. Within a radial distance of about 55 kpc, the red clusters are more strongly concentrated toward the center than the blue clusters. At larger radii, the surface density profiles of the clusters are indistinguishable and match well the distribution of the galaxy light. Over the entire radial distance range, the surface brightness profile of NGC 1399 can be very well fitted by a power law with an exponent of À1.85 and a core radius of 3>3. No steepening of the luminosity profile can be detected at large radii. We suggest that the power-law profile of NGC 1399 results from the galaxy being embedded in a large dark matter halo, which prevents the stellar density profile from steepening outward. The cluster system contains 6450 AE 700 clusters and the specific frequency is found to be 5.1 AE 1.2 in the V band. While NGC 1399 shows a pronounced color gradient the nearby comparison galaxy NGC 1404 does not show such a gradient. Using simple assumptions about the underlying population that formed during the same star formation event as the globular clusters, we present a model in which we use radially changing local specific frequencies for the red and blue subpopulations to fit the observations. We find that within 7 0 the required specific frequency of the blue clusters alone is a factor of approximately 3 larger than that of the red ones. Outside this radius, however, both populations have the same high local specific frequency of around 8 and 13 (blue and red clusters, respectively).

We present a Washington C and Kron-Cousins R photometric study of the globular cluster system of NGC 1399, the central galaxy of the Fornax cluster. A large areal coverage of 1 square degree around NGC 1399 is achieved with three adjoining fields of the MOSAIC II Imager at the CTIO 4-m telescope. Working on such a large field, we can perform the first indicative determination of the total size of the NGC 1399 globular cluster system. The estimated angular extent, measured from the NGC 1399 centre and up to a limiting radius where the areal density of blue globular clusters falls to 30 per cent of the background level, is 45 ± 5 arcmin, which corresponds to 220−275 kpc at the Fornax distance. The bimodal colour distribution of this globular cluster system, as well as the different radial distribution of blue and red clusters, up to these large distances from the parent galaxy, are confirmed. The azimuthal globular cluster distribution exhibits asymmetries that might be understood in terms of tidal stripping of globulars from NGC 1387, a nearby galaxy. The good agreement between the areal density profile of blue clusters and a projected dark-matter NFW density profile is emphasized.

We present a systematic study of the low mass X-ray binary (LMXB) populations of 6 elliptical galaxies, aimed at investigating the detected LMXB − globular cluster (GC) connection. We utilize Chandra archival data to identify 665 X-ray point sources and HST archival data supplemented by ground observations to identify 6173 GCs. Applying rigorous X-ray and optical photometry and conservative matching criteria, we associate 209 LMXBs with red GC (RGC) and 76 LMXBs with blue GCs (BGC), while we find no optical GC counterpart for 258 LMXBs. This is the largest GC−LMXB sample studied so far.We confirm previous reports suggesting that the fraction of GCs associated with LMXBs is ∼ 3 times larger in RGCs than in BGCs, indicating that metallicity is a primary factor in the GC−LMXB formation. While as already known, the brighter (and bigger) GCs have a higher probability to host LMXBs, we find that this optical luminosity (or mass) dependency is stronger in RGCs than in BGCs. We also find that GCs located near the galaxy center have a higher probability to harbor LMXBs compared to those in the outskirts. The radial distributions of GC−LMXBs (for both RGC and BGC) are steeper than those of the whole optical GC sample, but consistent with those of the optical halo light, suggesting that there must be another parameter (in addition to metallicity) governing LMXB formation in GCs. This second parameter must depend on the galacto-centric distance. One possibility is a galacto-centric distance dependent encounter rate.We find no statistically significant difference in the X-ray properties (shape of X-ray luminosity function, L X /L V distribution, X-ray spectra) among RGC−LMXBs, BGC−LMXBs and field−LMXBs. The similarity of the X-ray spectra of BGC−LMXBs and RGC−LMXBs is inconsistent with the irradiationinduced stellar wind model prediction of more absorbed X-ray spectra in -2 -BGC−LMXBs than in RGC−LMXBs. The similarity of the X-ray luminosity functions (XLFs) of GC−LMXBs and field−LMXBs indicates that there is no significant difference in the fraction of BH binaries present in these two populations, in contrast to Galactic LMXBs where BH binaries are not found in GCs. The similar X-ray properties as well as the similar radial distributions of GC−LMXBs and field−LMXBs cannot constrain the hypothesis that all LMXBs were formed in GCs.

We study the kinematics and dynamics of the globular cluster system of NGC 1399, the brightest elliptical galaxy near the center of the Fornax cluster of galaxies. The observational data consists of medium-resolution spectra, obtained at the Very Large Telescope with FORS2 and the Mask Exchange Unit (MXU). Our sample comprises 468 radial velocities in the magnitude range 20 < m R < 23. This is the largest sample of globular cluster velocities around any galaxy obtained so far. Typical velocity uncertainties are 50 km s À1 , significantly improving on earlier samples. The radial range is 2 0 < r < 9 0 , corresponding to 11 kpc to 50 kpc of galactocentric distance. The shape of the velocity distribution of the sample is compatible with being a Gaussian distribution. However, under moderate error selection, a slight asymmetry is visible between high and low radial velocities. We find bright clusters with radial velocities below 800 km s À1 , while they are not found at the corresponding highvelocity side above 2000 km s À1 . There is the possibility that unbound clusters and/or objects in the foreground contaminate the NGC 1399 cluster sample. Under strong error selection, practically no objects are found with velocities lower than 800 km s À1 or higher than 2000 km s À1 . Since the extreme velocities influence the velocity dispersion considerably, uncertainty regarding the exact value of the dispersion remains. With the above velocity limits, we derive a projected velocity dispersion for the total sample of 274 AE 9 km s À1 which within the uncertainties remains constant over the entire radial range. Without any velocity restriction, it increases to 325 km s À1 . Guided by the bimodal color distribution of clusters, we distinguish between red clusters (CÀR > 1:6) and blue clusters (CÀR < 1:6), and find velocity dispersions for these groups of 255 AE 13 and 291 AE 14 km s À1 , respectively, again radially constant. Any possible rotation of either of these cluster populations is below the detection limit, with the exception of a weak signature of rotation for the blue clusters more distant than 6 0 . Spherical models point to a circular velocity of 419 AE 30 km s À1 , assuming isotropy for the red clusters. This value is constant out to 40 kpc. The inferred dark halo potential can be well represented by a logarithmic potential. A halo of the NFW type also provides a good fit to the observations. The orbital structure of the clusters can only be weakly constrained. It is consistent with isotropy for the red clusters and a slight tangential bias for the blue clusters. Some mass profiles derived from X-ray analyses do not agree with a constant circular velocity within our radial range, irrespective of its exact value. Interpreting the extreme low radial velocities as space velocities of bound clusters near their pericentric distances would require an extension of the cluster system of at least 200 kpc. Implications for formation scenarios of the cluster system are briefly commented on.