The Globular Cluster System of NGC 1399. I. A Wide-Field Photometric Study

By B. Dirsch, T. Richtler, Doug Geisler, J. Forte, L. Bassino, W. Gieren. 2003

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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′ × 36′, corresponding to about 200 × 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 -1.85 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 ± 700 clusters and the specific frequency is found to be 5.1 ± 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′ 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).

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5a5bd794f927d2fd79baa31e20978b50e587948a

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Citations in the corpus

Galaxy threshing and the origin of ultra-compact dwarf galaxies in the Fornax cluster (2003, background): “Moreover, they are observed to be within 30 arcmin of the central dominant galaxy in Fornax, NGC 1399, and are distributed as large radii as this galaxy’s globular cluster system (extending out to a radius of 100 kpc at least; Dirsch et al. 2003).”
Extragalactic Globular Clusters and Galaxy Formation (2006, methodology): “When corrected, the SN value for this galaxy was revised downward by a factor of two, from SN ∼ 12 to 5− 6 (Ostrov et al. 1998; Dirsch et al. 2003).”
The SLUGGS Survey: kinematics for over 2500 globular clusters in 12 early-type galaxies (2012, background): “…have been found in galaxies of all morphological type and they extend beyond the detectable galaxy diffuse light, probing galactocentric distances ≥10Reff , where there are only few other gravitational constrains (Rhode & Zepf 2001, 2004; Dirsch et al. 2003; Tamura et al. 2006; Forbes et al. 2011).”
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters (2005, background): “We note that Ostrov et al. (1998) and Dirsch et al. (2003) described the bright clusters in NGC 1399 as displaying a unimodal color distribution, whereas Strader et al. (2005) state that the blue clusters in M87 follow a color/luminosity trend.”
The ACS Virgo Cluster Survey. X. Half-Light Radii of Globular Clusters in Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for Distance Estimation (2005, background): “…spatial distributions, with the latter having a more extended spatial distribution (Kissler-Patig et al. 1997; Lee, Kim & Geisler 1998; Côté et al. 2001; Dirsch et al. 2003).15 Likewise, the dependence of 〈rh〉 14 For NGC 4697, which is not a member of the Virgo Cluster and hence does not appear…”
WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, background): “The possible convergence of the GC color-magnitude distribution to a unimodal distribution at the bright end has been previously discussed in other galaxies by Ostrov, Forte, & Geisler (1998), Dirsch et al. (2003), Harris et al. (2006), Romanowsky et al. (2009), and Forbes et al. (2011).”
Globular Clusters in Virgo Ellipticals: Unexpected Results for Giants and Dwarfs from Advanced Camera for Surveys Imaging (2005, background): “Similar bright, intermediate-color GCs have also been found in NGC 1399 (Dirsch et al. 2003), NGC 4636 (Dirsch et al. 2005), and NGC 1407 (Cenarro et al. 2006); they appear to be a common feature of gEs.”
Globular cluster systems in nearby dwarf galaxies – III. Formation efficiencies of old globular clusters (2010, background): “…limits, adequate spatial coverage etc.) from the literature (Ashman & Zepf 1998; Rhode & Zepf 2001, 2003, 2004; Forbes et al. 2001; Forte et al. 2001; Dirsch et al. 2003, 2005; Gómez & Richtler 2004; Bassino et al. 2006b,a, 2008; Harris et al. 2006; Tamura et al. 2006a,b; Rhode et al. 2007).”