Globular cluster candidates within the Fornax Cluster: Intracluster globulars?

Bassino, L. P.; Cellone, S. A.; Forte, J. C.; Dirsch, B.

doi:10.1051/0004-6361:20021810

Cited by 47 publications

(54 citation statements)

References 52 publications

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“…3.3.1 below. Another source of contamination to the list of GC candidates of NGC 1427A is contamination from possible Fornax intracluster globulars (Bassino et al 2003) and the GC population of NGC 1399 which is thought to extend to large distances (Dirsch et al 2003). We discuss this in Sect.…”

Section: Contamination and Gc Numbersmentioning

confidence: 99%

The old globular cluster system of the dIrr galaxy NGC 1427A in the Fornax cluster

Georgiev

Hilker²,

Puzia

et al. 2006

A&A

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We present a study of the old globular cluster (GC) population of the dwarf irregular galaxy NGC 1427A using multi-wavelength VLT observations in U, B, V, I, H α and J bands under excellent observing conditions. We applied color and size selection criteria to select old GC candidates and made use of archival ACS images taken with the Hubble Space Telescope to reject contaminating background sources and blended objects from the GC candidates' list. The H α observations were used to check for contamination due to compact, highly reddened young star clusters whose colors and sizes could mimic those of old GCs. After accounting for contamination we obtain a total number of 38 ± 8 GC candidates with colors consistent with an old (∼10 Gyr) and metal-poor (Z < 0.4 × Z ) population as judged by simple stellar population models. Our contamination analysis indicates that the density distribution of GCs in the outskirts of the Fornax central cD galaxy NGC 1399 may not be spherically symmetric. We derive a present-day specific frequency S N of 1.6 for NGC 1427A, a value significantly larger than what is observed in the Local Group dwarf irregular galaxies and comparable with the values found for the same galaxy types in the Virgo and Fornax clusters. Assuming a universal globular cluster luminosity function turnover magnitude, we derive a distance modulus to NGC 1427A of 31.01 ± 0.21 mag which places it ∼3.2 ± 2.5 (statistic) ± 1.6 (systematic) Mpc in front of the Fornax central cD galaxy NGC 1399. The implications of this result for the relationship between NGC 1427A and the cluster environment are briefly discussed.

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Section: Contamination and Gc Numbersmentioning

confidence: 99%

The old globular cluster system of the dIrr galaxy NGC 1427A in the Fornax cluster

Georgiev

Hilker²,

Puzia

et al. 2006

A&A

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“…However, for large ensembles of UCDs there is no estimator yet, which can distinguish between both UCD formation channels and thus constrain their fractions among a UCD population. A&A 586, A102 (2016) The Fornax cluster, in particular, its central galaxy NGC 1399, has a well-studied UCD and globular cluster population (Dirsch et al , 2004Bassino et al 2003Bassino et al , 2006Schuberth et al 2010). NGC 1399 hosts ∼6500 globular clusters within 83 kpc (at a distance of 19 Mpc) with a specific frequency of S N = 5.5, making it a good testing ground for GC/UCD populations.…”

Section: Introductionmentioning

confidence: 99%

Globular cluster clustering and tidal features around ultra-compact dwarf galaxies in the halo of NGC 1399

Voggel¹,

Hilker²,

Richtler³

2016

A&A

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We present a novel approach to constrain the formation channels of ultra-compact dwarf galaxies (UCDs). They most probably are an inhomogeneous class of objects, composed of remnants of tidally stripped dwarf elliptical galaxies and star clusters that occupy the high mass end of the globular cluster luminosity function. We use three methods to unravel their nature: 1) we analyzed their surface brightness profiles; 2) we carried out a direct search for tidal features around UCDs; and 3) we compared the spatial distribution of GCs and UCDs in the halo of their host galaxy. Based on FORS2 observations under excellent seeing conditions, we studied the detailed structural composition of a large sample of 97 UCDs in the halo of NGC 1399, the central galaxy of the Fornax cluster, by analyzing their surface brightness profiles. We found that 13 of the UCDs were resolved above the resolution limit of 23 pc and we derived their structural parameters fitting a single Sérsic function. When decomposing their profiles into composite King and Sérsic profiles, we find evidence for faint stellar envelopes at µ =∼ 26 mag arcsec −2 , surrounding the UCDs up to an extension of 90 pc in radius. We also show new evidence for faint asymmetric structures and tidal tail-like features surrounding several of these UCDs, a possible tracer of their origin and assembly history within their host galaxy halos. In particular, we present evidence for the first discovery of a significant tidal tail with an extension of ∼350 pc around UCD-FORS 2. Finally, we studied the local overdensities in the spatial distribution of globular clusters within the halo of NGC 1399 out to 110 kpc to see if they are related to the positions of the UCDs. We found a local overabundance of globular clusters on a scale of ≤1 kpc around UCDs, when we compared it to the distribution of globulars from the host galaxy. This effect is strongest for the metal-poor blue GCs. We discuss how likely it is that these clustered globulars were originally associated with the UCD, either as globular cluster systems of a nucleated dwarf galaxy that was stripped down to its nucleus, or as a surviving member of a merged super star cluster complex.

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“…Half a century ago, van den Bergh (1958) speculated that "about one third of all the globular clusters are of the intergalactic type" and numerous studies since then have lent support to the idea that at least some globular clusters are not gravitationally bound to individual galaxies (e.g., Muzzio et al 1984;White 1987;West et al 1995;Bassino et al 2003;Hilker 2001;Jordán et al 2003;Williams et al 2007;Schuberth et al 2008;Coenda et al 2009;Gregg et al 2009;Lee et al 2010;Peng et al 2011). Little is known at present about the nature or origin of IGCs.…”

Section: Introductionmentioning

confidence: 99%

The globular cluster systems of Abell 1185

West

Jordán

Blakeslee

et al. 2011

A&A

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We examine the properties of a previously discovered population of globular clusters in the heart of the rich galaxy cluster Abell 1185 that might be intergalactic in nature. Deep images obtained with the Advanced Camera for Surveys (ACS) aboard Hubble Space Telescope (HST) confirm the presence of ∼1300 globular clusters brighter than I F814W 27.3 mag in a field devoid of any large galaxies. The luminosities and colors of these objects are found to be similar to those of metal-poor globular clusters observed in many galaxies to date. Although a significant fraction of the detected globular clusters undoubtedly reside in the outer halos of galaxies adjacent to this field, detailed modeling of their distribution suggests that the majority of these objects are likely to be intergalactic, in the sense that they are not gravitationally bound to any individual galaxy. We conclude that the true nature and origin of the globular cluster population in the core of A1185 − galactic residents or intergalactic wanderers − remains uncertain, and suggest how future observation could resolve this ambiguity.

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Globular cluster candidates within the Fornax Cluster: Intracluster globulars?

Cited by 47 publications

References 52 publications

The old globular cluster system of the dIrr galaxy NGC 1427A in the Fornax cluster

The old globular cluster system of the dIrr galaxy NGC 1427A in the Fornax cluster

Globular cluster clustering and tidal features around ultra-compact dwarf galaxies in the halo of NGC 1399

The globular cluster systems of Abell 1185

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