The great disk of Milky-Way satellites and cosmological
 sub-structures

Kroupa, Pavel; Theis, Christian; Boily, C. M.

doi:10.1051/0004-6361:20041122

Cited by 367 publications

(516 citation statements)

References 38 publications

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“…Kroupa, Theis & Boily 2005;Pawlowski et al 2012a;Ibata et al 2013) on the grounds that CDM haloes seldom have satellite distributions that are as flattened and showing the same degree of coherent rotation as found in the LG Bahl & Baumgardt 2014;Ibata et al 2014c). Our own analysis of the spatial and kinematic distributions of the satellites around a large sample of SDSS galaxies, returns results that are generally in very good agreement with CDM predictions.…”

Section: Discussion a N D C O N C L U S I O N Ssupporting

confidence: 64%

A new spin on discs of satellite galaxies

Cautun

Wang

Frenk

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We investigate the angular and kinematic distributions of satellite galaxies around a large sample of bright isolated primaries in the spectroscopic and photometric catalogues of the Sloan Digital Sky Survey (SDSS). We detect significant anisotropy in the spatial distribution of satellites. To test whether this anisotropy could be related to the rotating discs of satellites recently found by Ibata et al. in a sample of SDSS galaxies, we repeat and extend their analysis. Ibata et al. found an excess of satellites on opposite sides of their primaries having anticorrelated radial velocities. We find that this excess is sensitive to small changes in the sample selection criteria which can greatly reduce its significance. In addition, we find no evidence for correspondingly correlated velocities for satellites observed on the same side of their primaries, which would be expected for rotating discs of satellites. We conclude that the detection of . We compare our data to the ΛCDM Millennium simulations populated with galaxies according to the semi-analytic model of Guo et al. We find excellent agreement with the spatial distribution of satellites in the SDSS data and the lack of a strong signal from coherent rotation.

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Section: Discussion a N D C O N C L U S I O N Ssupporting

confidence: 64%

A new spin on discs of satellite galaxies

Cautun

Wang

Frenk

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…Applying our approach to the MW and M31 observations results in the same planar distributions as determined by Kroupa et al (2005) and Ibata13, respectively, even though those studies used different identification methods. The good agreement is possibly due to a posteriori selection bias, since those authors may have inadvertently tuned their methods to maximize the significance of the detection.…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 67%

Planes of satellite galaxies: when exceptions are the rule

Cautun¹,

Bose²,

Frenk³

et al. 2015

Mon. Not. R. Astron. Soc.

112

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The detection of planar structures within the satellite systems of both the Milky Way (MW) and Andromeda (M31) has been reported as being in stark contradiction to the predictions of the standard cosmological model (ΛCDM). Given the ambiguity in defining a planar configuration, it is unclear how to interpret the low incidence of the MW and M31 planes in ΛCDM. We investigate the prevalence of satellite planes around galactic mass haloes identified in high resolution cosmological simulations. We find that planar structures are very common, and that ∼10% of ΛCDM haloes have even more prominent planes than those present in the Local Group. While ubiquitous, the planes of satellite galaxies show a large diversity in their properties. This precludes using one or two systems as small scale probes of cosmology, since a large sample of satellite systems is needed to obtain a good measure of the object-to-object variation. This very diversity has been misinterpreted as a discrepancy between the satellite planes observed in the Local Group and ΛCDM predictions. In fact, ∼10% of ΛCDM galactic haloes have planes of satellites that are as infrequent as the MW and M31 planes. The look-elsewhere effect plays an important role in assessing the detection significance of satellite planes and accounting for it leads to overestimating the significance level by a factor of 30 and 100 for the MW and M31 systems, respectively.

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“…The VPOS is thus not only a spatial but also a rotating structure ). Kroupa, Theis & Boily (2005) were the first to argue that the narrow, polar alignment of the 11 brightest "classical" MW satellites is in conflict with the typical distribution of dark matter sub-halos in ΛCDM. Whether the positional alignment of these 11 satellite galaxies is problematic for ΛCDM or not has been challenged since then (e.g.…”

Section: Introductionmentioning

confidence: 99%

The new Milky Way satellites: alignment with the VPOS and predictions for proper motions and velocity dispersions

Pawlowski

McGaugh

Jerjen

2015

Mon. Not. R. Astron. Soc.

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The evidence that stellar systems surrounding the Milky Way (MW) are distributed in a Vast Polar Structure (VPOS) may be observationally biased by satellites detected in surveys of the northern sky. The recent discoveries of more than a dozen new systems in the southern hemisphere thus constitute a critical test of the VPOS phenomenon. We report that the new objects are located close to the original VPOS, with half of the sample having offsets less than 20 kpc. The positions of the new satellite galaxy candidates are so well aligned that the orientation of the revised best-fitting VPOS structure is preserved to within 9 degrees and the VPOS flattening is almost unchanged (31 kpc height). Interestingly, the shortest distance of the VPOS plane from the MW center is now only 2.5 kpc, indicating that the new discoveries balance out the VPOS at the Galactic center. The vast majority of the MW satellites are thus consistent with sharing a similar orbital plane as the Magellanic Clouds, confirming a hypothesis proposed by Kunkel & Demers and Lynden-Bell almost 40 years ago. We predict the absolute proper motions of the new objects assuming they orbit within the VPOS. Independent of the VPOS results we also predict the velocity dispersions of the new systems under three distinct assumptions: that they (i) are dark-matter-free star clusters obeying Newtonian dynamics, (ii) are dwarf satellites lying on empirical scaling relations of galaxies in dark matter halos, and (iii) obey MOND.

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The great disk of Milky-Way satellites and cosmological sub-structures

Cited by 367 publications

References 38 publications

A new spin on discs of satellite galaxies

A new spin on discs of satellite galaxies

Planes of satellite galaxies: when exceptions are the rule

The new Milky Way satellites: alignment with the VPOS and predictions for proper motions and velocity dispersions

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