Isolated ellipticals and their globular cluster systems

Salinas, R.; Richtler, T.

doi:10.1051/0004-6361/201220231

Cited by 25 publications

(37 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…There is now strong evidence that the majority of metal-poor clusters (which dominate the GCSs of giant ellipticals) have been accreted through the accretion of dwarf galaxies (see Richtler 2013, for a recent review). One would, therefore, expect that isolated ellipticals have poorer GCSs, and for most of the investigated galaxies this is indeed the case (Spitler et al 2008;Lane et al 2013;Caso et al 2013). However, the galaxy sample of Cho et al (2012) suggests that the role of the environment is minor in comparison to the host galaxy mass as parameter.…”

Section: Introductionmentioning

confidence: 80%

“…The work by Hau & Forbes (2006) is an important source for data regarding the central kinematics of IEs. A&A 574, A21 (2015) Many present morphologies with the signature of mergers that are highly visible (see also Tal et al 2009;Lane et al 2013). Others, even without obvious visible disturbances, show intermediate ages through their dynamics.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Isolated elliptical galaxies and their globular cluster systems

Richtler¹,

Salinas²,

Hilker³

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

Context. Rich globular cluster systems, particularly the metal-poor part of them, are thought to be the visible manifestations of longterm accretion processes. The invisible part is the dark matter halo, which may show some correspondence to the globular cluster system. It is therefore interesting to investigate the globular cluster systems of isolated elliptical galaxies, which supposedly have not experienced extended accretion. Aims. We investigate the globular cluster system of the isolated elliptical NGC 7796, present new photometry of the galaxy, and use published kinematical data to constrain the dark matter content. Methods. Deep images in B and R, obtained with the VIsible MultiObject Spectrograph (VIMOS) at the VLT, form the data base. We performed photometry with DAOPHOT and constructed a spherical photometric model. We present isotropic and anisotropic Jeans-models and give a morphological description of the companion dwarf galaxy. Results. The globular cluster system has about 2000 members, so it is not as rich as those of giant ellipticals in galaxy clusters with a comparable stellar mass, but richer than many cluster systems of other isolated ellipticals. The colour distribution of globular clusters is bimodal, which does not necessarily mean a metallicity bimodality. The kinematic literature data are somewhat inconclusive. The velocity dispersion in the inner parts can be reproduced without dark matter under isotropy. Radially anisotropic models need a low stellar mass-to-light ratio, which would contrast with the old age of the galaxy. A MONDian model is supported by X-ray analysis and previous dynamical modelling, but better data are necessary for a confirmation. The dwarf companion galaxy NGC 7796-1 exhibits tidal tails, multiple nuclei, and very boxy isophotes. Conclusions. NGC 7796 is an old, massive isolated elliptical galaxy with no indications of later major star formation events as seen frequently in other isolated ellipticals. Its relatively rich globular cluster system shows that isolation does not always mean a poor cluster system. The properties of the dwarf companion might indicate a dwarf-dwarf merger.

show abstract

Section: Introductionmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Isolated elliptical galaxies and their globular cluster systems

Richtler¹,

Salinas²,

Hilker³

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…Milgrom (2012) recently showed, that the isolated ellipticals NGC 720 and 1521 are consistent with the MONDian phenomonology. Both are late merger remnants (as is the case with many isolated ellipticals; Tal et al 2009;Lane et al 2013) with lower M/L-values than for old, metal-rich elliptical galaxies. So it not only seems that the MONDian phenomenology extends to elliptical galaxies (or in other words, that elliptical galaxies fall onto the same baryonic Tully-Fisher relation as disk galaxies), but also that from the ΛCDM point of view, the dark matter content depends somehow on the M/L values of the stellar population, which would be intriguing.…”

Section: High Velocity Offsetsmentioning

confidence: 94%

The globular cluster system of NGC 1316

Gómez¹,

Richtler²,

Infante³

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. The merger remnant NGC 1316 (Fornax A) is one of the most important objects regarding the investigation of and thus an important object to study merger-related processes. A recent photometric study used globular clusters in NGC 1316 to constrain its star formation history, but without the knowledge of individual radial velocities. The kinematical properties of the globular cluster system in comparison with the diffuse stellar light might give more insight into the formation of NGC 1316. Of particular interest is the dark matter content. Planetary nebulae in NGC 1316 indicate a massive dark halo, and globular cluster velocities provide independent evidence. Aims. We aim at measuring radial velocities of globular clusters in NGC 1316. We use these kinematical data to investigate the global structure of NGC 1316 and to constrain the dark matter content. Methods. We perform multiobject spectroscopy with VLT/FORS2 and MXU. Out of 562 slits, we extract radial velocities for 177 globular clusters. Moreover, we measure radial velocities of the integrated galaxy light, using slits with a sufficiently bright sky. To these data, we add 20 cluster velocities from the literature. In an appendix, we identify new morphological features of NGC 1316 and its companion galaxy NGC 1317.Results. The GC sample based on radial velocities confirms the colour peaks already found in our photometric study. The bright clusters, which probably have their origin in a 2 Gyr old starburst and younger star formation events, avoid the systemic velocity. A Gaussian velocity distribution is found only for clusters fainter than about m R = 22 mag. The velocity distribution of clusters shows a pronounced peak at 1600 km s −1 . These clusters populate a wide area in the south-western region which we suspect to be a disk population. Globular clusters or subsamples of them do not show a clear rotation signal. This is different from the galaxy light, where rotation along the major axis is discernable out to 3 radius. The kinematic major axis of NGC 1316 is misaligned by about 10• with the photometric major axis, which might indicate a triaxial symmetry. A simple spherical model like that suggested by dynamical analyses of planetary nebulae also reproduces the velocity dispersions of the faint globular clusters. Conclusions. The central dark matter density of the present model resembles a giant elliptical galaxy. This contradicts population properties which indicate spiral galaxies as pre-merger components. Modified Newtonian dynamics (MOND) would provide a solution, but the kinematical complexity of NGC 1316 does not allow a really firm conclusion. However, NGC 1316 might anyway be a problem for a cold dark matter scenario, if the high dark matter density in the inner region is confirmed in future studies.

show abstract

“…Figure 6 (upper panel) contains a comparison between our results with the sample of Cho et al (2012) of ten low-density early-type galaxies and galaxies from the ACS Virgo Cluster Survey (ACSVCS, Peng et al 2008). Additionally, we include the S N of five more isolated or low-density ellipticals, NGC 3585, NGC 5812 (Lane et al 2013), NGC 7507 (Caso et al 2013), NGC 720 (Kartha et al 2014) and NGC 7796 (Richtler et al 2015). Figure 6 (upper left panel) presents S N as a function of stellar mass.…”

Section: Specific Frequency Of Clusters In Low-and High-density Envirmentioning

confidence: 99%

Isolated ellipticals and their globular cluster systems

Salinas

Alabi

Richtler

2015

A&A

Self Cite

View full text Add to dashboard Cite

As tracers of star formation, galaxy assembly, and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS g i observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271, and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of them, but remains inconclusive for the other two. All the studied GCSs are rather poor with a mean specific frequency S N ∼ 1.5, independently of the parent galaxy luminosity. Considering information from previous work as well, it is clear that bimodality and especially the presence of a significant, even dominant, population of blue clusters occurs at even the most isolated systems, which casts doubts on a possible accreted origin of metal-poor clusters, as suggested by some models. Additionally, we discuss the possible existence of ultra-compact dwarfs around the isolated elliptical NGC 3962.

show abstract

Isolated ellipticals and their globular cluster systems

Cited by 25 publications

References 55 publications

Isolated elliptical galaxies and their globular cluster systems

Isolated elliptical galaxies and their globular cluster systems

The globular cluster system of NGC 1316

Isolated ellipticals and their globular cluster systems

Contact Info

Product

Resources

About