A new spin on discs of satellite galaxies

Cautun, Marius; Wang, Wenting; Frenk, Carlos S.; Sawala, Till

doi:10.1093/mnras/stv490

Cited by 52 publications

(59 citation statements)

References 51 publications

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“…Cautun et al (2015) studied the flattening of the satellite distribution around isolated central galaxies in the SDSS, as viewed on the plane of the sky, finding good agreement between data and cosmological simulations. Using a similar approach, Ibata et al (2015) claimed a higher degree of flattening in their data, but their conclusions may be affected by systematics (see Cautun et al 2015, for a discussion of this study). The expected signature of planar rotation has been investigated by considering the velocity correlation of satellite pairs observed on opposite sides of the host galaxy.…”

mentioning

confidence: 85%

Planes of satellite galaxies: when exceptions are the rule

Cautun¹,

Bose²,

Frenk³

et al. 2015

Mon. Not. R. Astron. Soc.

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103

114

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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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mentioning

confidence: 85%

Planes of satellite galaxies: when exceptions are the rule

Cautun¹,

Bose²,

Frenk³

et al. 2015

Mon. Not. R. Astron. Soc.

Self Cite

103

114

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show abstract

“…While the velocity anti-correlation signal itself was confirmed by other studies, its interpretation as evidence for rotating planes of satellites has been challenged. 43,44 Two main concerns are that (1) the signal is less strong if satellite galaxies at larger radii from the hosts are included in the analysis, and that (2) no overabundance of velocity anti-correlation is found for larger opening angles. Both criticisms deviate from the originally intended analogy with the GPoA system.…”

Section: Statistical Approachesmentioning

confidence: 99%

The planes of satellite galaxies problem, suggested solutions, and open questions

2018

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Satellite galaxies of the Milky Way and of the Andromeda galaxy have been found to preferentially align in significantly flattened planes of satellite galaxies, and available velocity measurements are indicative of a preference of satellites in those structures to co-orbit. There is increasing evidence that such kinematically correlated satellite planes are also present around more distant hosts. Detailed comparisons show that similarly anisotropic phase-space distributions of sub-halos are exceedingly rare in cosmological simulations based on the ΛCDM paradigm. Analogs to the observed systems have frequencies of ≤ 0.5 per cent in such simulations. In contrast to other small-scale problems, the satellite planes issue is not strongly affected by baryonic processes because the distribution of sub-halos on scales of hundreds of kpc is dominated by gravitational effects. This makes the satellite planes one of the most serious small-scale problem for ΛCDM. This review summarizes the observational evidence for planes of satellite galaxies in the Local Group and beyond, and provides an overview of how they compare to cosmological simulations. It also discusses scenarios which aim at explaining the coherence of satellite positions and orbits, and why they all are currently unable to satisfactorily resolve the issue. 1:17 WSPC/INSTRUCTION FILE review 2 Marcel S. Pawlowski successes do not constitute proof of correctness, 2, 3 and science strives to probe the limitations of its models by pushing to test them in novel ways. In particular when expanded beyond its initial scope of applicability, a model is most thoroughly tested and opportunities for refinement or revision can be identified. For ΛCDM -developed to fit the large-scale structure and evolution of the Universe (on scales of many Mpc to Gpc) -such a novel domain of applicability is the regime of galaxies and their satellite galaxy systems (on scales of hundreds of kpc and below). Due to the non-linearity of ΛCDM on those scales, model predictions are made via numerical simulations. These evolve an initially almost homogenious matter distribution forward in time, simulating the formation and evolution of structure in the cosmos until the present day. This implies an important caveat for tests in this regime: not the model itself is tested directly, but its realisation via numerical simulations.Our best observational knowledge of the smallest galaxies stems from observation of the ≈ 50 and 40 known dwarf Spheroidal (dSph) satellite galaxies of our Milky Way (MW) and the neighboring Andromeda galaxy (M31), respectively. Together with ≈ 15 more isolated dwarf galaxies, they make up the Local Group of galaxies, covering a volume of approximately 1 Mpc in radius. Comparisons of cosmological simulations of dark matter halos resembling those expected to host the MW and M31 with the observed systems have revealed a number of small-scale problems of ΛCDM. 4 Among the best known issues are the Missing Satellites Problem, the Core-Cusp Problem, and the Too-Big-to-Fail problem...

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“…Conn et al 2013;Shaya & Tully E-mail: shi.shao@durham.ac.uk 2013; Tully et al 2015), with many of their members showing correlated line-of-sight velocities that potentially a indicate co-rotating configuration (Ibata et al 2013;Müller et al 2018;Hodkinson & Scholtz 2019). Farther afield, Cautun et al (2015a) have shown that external galaxies also have anisotropic satellite distributions.…”

Section: Introductionmentioning

confidence: 99%

“…The plane of satellites most likely reflects the connection between a galaxy and its cosmic web. Multiple satellites are accreted along the same filament (Libeskind et al 2005;Buck et al 2015) which leads to a significant population of corotating satellites (Libeskind et al 2009;Lovell et al 2011;Cautun et al 2015a). Correlated satellite orbits can arise from the accretion of dwarf galaxy groups (e.g.…”

Section: Introductionmentioning

confidence: 99%

Evolution of galactic planes of satellites in the eagle simulation

Shao

Cautun

Frenk

2019

Monthly Notices of the Royal Astronomical Society

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We study the formation of planes of dwarf galaxies around Milky Way (MW)-mass haloes in the EAGLE galaxy formation simulation. We focus on satellite systems similar to the one in the MW: spatially thin or with a large fraction of members orbiting in the same plane. To characterise the latter, we introduce a robust method to identify the subsets of satellites that have the most co-planar orbits. Out of the 11 MW classical dwarf satellites, 8 have highly clustered orbital planes whose poles are contained within a 22 • opening angle centred around (l, b) = (182 • , −2 • ). This configuration stands out when compared to both isotropic and typical ΛCDM satellite distributions. Purely flattened satellite systems are short-lived chance associations and persist for less than 1 Gyr. In contrast, satellite subsets that share roughly the same orbital plane are longer lived, with half of the MW-like systems being at least 4 Gyrs old. On average, satellite systems were flatter in the past, with a minimum in their minor-to-major axes ratio about 9 Gyrs ago, which is the typical infall time of the classical satellites. MWlike satellite distributions have on average always been flatter than the overall population of satellites in MW-mass haloes and, in particular, they correspond to systems with a high degree of anisotropic accretion of satellites. We also show that torques induced by the aspherical mass distribution of the host halo channel some satellite orbits into the host's equatorial plane, enhancing the fraction of satellites with co-planar orbits. In fact, the orbital poles of co-planar satellites are tightly aligned with the minor axis of the host halo.

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A new spin on discs of satellite galaxies

Cited by 52 publications

References 51 publications

Planes of satellite galaxies: when exceptions are the rule

Planes of satellite galaxies: when exceptions are the rule

The planes of satellite galaxies problem, suggested solutions, and open questions

Evolution of galactic planes of satellites in the eagle simulation

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