The dark matter halo of NGC 1399 – CDM or MOND?

Richtler, T.; Schuberth, Y.; Hilker, M.; Dirsch, B.; Bassino, L. P.; Romanowsky, Aaron J.

doi:10.1051/0004-6361:20078539

Cited by 59 publications

(81 citation statements)

References 32 publications

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“…We compiled a sample of 313 UCDs and GCs in the Fornax cluster with stellar masses above M = 10 6 M (Firth et al 2007;Mieske et al 2002Mieske et al , 2004Dirsch et al 2004;Richtler et al 2008;Schuberth et al 2010), which all are confirmed Fornax members according to their radial velocities. To determine their stellar masses consistently for the full sample, we used their V-band magnitudes and (V − I) colors and calculated their V-band massto-light ratios from the simple stellar population models (SSP) of Maraston (2005).…”

Section: Surface Brightness Analysismentioning

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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Section: Surface Brightness Analysismentioning

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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“…However, the same cannot be said conclusively for all elliptical galaxies. Central galaxies in galaxy clusters such as NGC 6166 (Kelson et al 2002), NGC 1399 (Richtler et al 2008;Schuberth et al 2010), and NGC 3311 (Richtler et al 2011) are embedded in massive dark halos as is the case of bright non-central cluster ellipticals such as NGC 4636 and NGC 4374 in Fornax (Schuberth et al 2006;Napolitano et al 2010). In constrast elliptical galaxies with lower luminosities in sparser environments (NGC 821,3379,4494,4697), whose mass profiles Based on observations taken at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and SECYT (Argentina).…”

Section: Introductionmentioning

confidence: 99%

Kinematic properties of the field elliptical NGC 7507

Salinas

Richtler

Bassino

et al. 2012

A&A

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The dark matter (DM) halos of field elliptical galaxies have not been well-studied and their properties appear controversial in the literature. While some galaxies appear to be nearly devoid of DM, others show clear evidence of its presence. Furthermore, modified Newtonian dynamics (MOND), which has been found to have predictive power in the domain of disk galaxies, has not yet been investigated for isolated elliptical galaxies. We study the kinematics of the isolated elliptical NGC 7507, which has been claimed as a clear example of DM presence in early-type galaxies. We obtained major and minor axis long-slit spectroscopy of NGC 7507 using the Gemini South telescope and deep imaging in Kron-Cousins R and Washington C using the CTIO/MOSAIC camera. Mean velocities, velocity dispersion and higher order moments of the velocity distribution are measured out to ∼90 . The galaxy, although almost circular, has significant rotation along the minor axis and a rapidly declining velocity dispersion along both axes. The velocity dispersion profile is modeled in the context of a spherical Jeans analysis. Models without DM provide an excellent representation of the data with a mass-to-light ratio (M/L) of 3.1 (R-band). The most massive Navarro-Frenk-White (NFW) halo the data allow has a virial mass of only 3.9 +3.1 −2.1 × 10 11 M , although the data are more consistent with models that have a slight radial anisotropy, which implies the galaxy has an even lower DM halo mass of 2.2 +2.0 −1.2 × 10 11 M . Modeling of the h 4 Gauss-Hermite coefficient is inconclusive but seems to be consistent with mild radial anisotropy. A cored logarithmic DM halo with parameters r 0 = 7 kpc and v 0 = 100 km s −1 can also reproduce the observed velocity dispersion profile. The MOND predictions overestimate the velocity dispersion. In conclusion, we cannot easily reproduce the previous findings of a predominance of DM in NGC 7507 within a simple spherical model. DM may be present, but only in conjunction with a strong radial anisotropy, for which there are some indications.

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“…Interestingly, Salinas et al (2011) found that MOND predictions overestimate the observed velocity dispersion (declining profile) for the field elliptical NGC 7507. On the other hand, Richtler et al (2008) found that the central galaxy of the Fornax cluster, NGC 1399 needs a hypothetical dark halo. We note that for both NGC 3379 and NGC 5128 the velocity dispersion shows a declining trend, which starts at ∼200 km s −1 for NGC 3379 and ∼150 km s −1 for NGC 5128.…”

Section: Introductionmentioning

confidence: 99%

Isotropic dynamical models of NGC 4472 (M 49)

Samurovic

2012

A&A

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The dark matter halo of NGC 1399 – CDM or MOND?

Cited by 59 publications

References 32 publications

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

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

Kinematic properties of the field elliptical NGC 7507

Isotropic dynamical models of NGC 4472 (M 49)

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