The outer halo globular cluster system of M31 – II. Kinematics

Veljanoski, J.; Mackey, A. D.; Ferguson, Annette M. N.; Huxor, Avon; Côté, Patrick; Irwin, M. J.; Tanvir, N. R.; Peñarrubia, Jorge; Bernard, Edouard J.; Fardal, Mark A.; Martín, Nicolás F.; McConnachie, Alan W.; Lewis, Geraint F.; Chapman, Scott; Ibata, Rodrigo; Babul, Arif

doi:10.1093/mnras/stu1055

Cited by 100 publications

(244 citation statements)

References 115 publications

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“…So far, seven GCs are discovered along the NWS, and five (PAndAS-04, 09, 10, 11 and 12) of them show a clear correlation of their galactocentric radial velocities with projected radii from M31's centre (see table 4 and figure 11 of Veljanoski et al 2014). In this paper, we assume that these five GCs initially inhabited the progenitor of the NWS and still have the same orbital motion as the NWS.…”

Section: Model and Assumptionmentioning

confidence: 89%

“…Panels (b) and (e) show the simulated LOS velocities. Red circles are the observed velocities of the GCs Veljanoski et al (2014). The spatial distribution of the particles is shown in panels (c) and (f).…”

Section: Summary and Discussionmentioning

confidence: 99%

“…As a result, little is known about the formation history of the c 2016 The Authors Veljanoski et al (2013) reported that a number of GCs appear to spatially coincide with the stellar debris and streams in M31's halo. Veljanoski et al (2014) measured the LOS velocities of these GCs and found that some GCs aligned with the streams exhibited a clear correlation between their positions and LOS velocities. This included five GCs aligned with the NWS.…”

Section: Introductionmentioning

confidence: 99%

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The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Kirihara

Miki

Mori

2017

Monthly Notices of the Royal Astronomical Society

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We examine the nature, possible orbits and physical properties of the progenitor of the North-western stellar stream (NWS) in the halo of the Andromeda galaxy (M31). The progenitor is assumed to be an accreting dwarf galaxy with globular clusters (GCs). It is, in general, difficult to determine the progenitor's orbit precisely because of many necessary parameters. Recently, Veljanoski et al. (2014) reported five GCs whose positions and radial velocities suggest an association with the stream. We use this data to constrain the orbital motions of the progenitor using test-particle simulations. Our simulations split the orbit solutions into two branches according to whether the stream ends up in the foreground or in the background of M31. Upcoming observations that will determine the distance to the NWS will be able to reject one of the two branches. In either case, the solutions require that the pericentric radius of any possible orbit be over 2 kpc. We estimate the efficiency of the tidal disruption and confirm the consistency with the assumption for the progenitor being a dwarf galaxy. The progenitor requires the mass > ∼ 2 × 10 6 M ⊙ and half-light radius > ∼ 30 pc. In addition, N-body simulations successfully reproduce the basic observed features of the NWS and the GCs' line-of-sight velocities.

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Section: Model and Assumptionmentioning

confidence: 89%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Kirihara

Miki

Mori

2017

Monthly Notices of the Royal Astronomical Society

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“…Fardal et al 2013;Cautun et al 2014a,b;González, Kravtsov & Gnedin 2014;Piffl et al 2014;Veljanoski et al 2014, for a compilation of other measurements and discussions of systematic effects see Courteau et al 2014;Wang et al 2015). This results in 2849 MS-II haloes and in 63 COCO haloes in the required mass range.…”

Section: Data a N D S A M P L E S E L E C T I O Nmentioning

confidence: 94%

Planes of satellite galaxies: when exceptions are the rule

Cautun¹,

Bose²,

Frenk³

et al. 2015

Mon. Not. R. Astron. Soc.

100

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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“…Mackey et al (2010) found ∼80% of the GCs to preferentially project onto the various stellar overdensities, suggesting that these objects were brought into the M 31 system by accreted dwarf galaxies, an observation which supports hierarchical formation models. Recent kinematic studies of the M 31 outer halo GC system (Veljanoski et al 2013(Veljanoski et al , 2014 have found various velocity correlations or clustering exhibited by GCs that project along particular stellar debris features. This not only supports the accretion hypothesis but also highlights the power of using GCs as tracers of accretion events.…”

Section: Introductionmentioning

confidence: 99%

The kinematics of globular clusters systems in the outer halos of the Aquarius simulations

Veljanoski

Helmi

2016

A&A

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Stellar halos and globular cluster (GC) systems contain valuable information regarding the assembly history of their host galaxies. Motivated by the detection of a significant rotation signal in the outer halo GC system of M 31, we investigate the likelihood of detecting such a rotation signal in projection, using cosmological simulations. To this end we select subsets of tagged particles in the halos of the Aquarius simulations to represent mock GC systems, and analyse their kinematics. We find that GC systems can exhibit a non-negligible rotation signal provided the associated stellar halo also has a net angular momentum. The ability to detect this rotation signal is highly dependent on the viewing perspective, and the probability of seeing a signal larger than that measured in M 31 ranges from 10% to 90% for the different halos in the Aquarius suite. High values are found from a perspective such that the projected angular momentum of the GC system is within 40 deg of the rotation axis determined via the projected positions and line-of-sight velocities of the GCs. Furthermore, the true 3D angular momentum of the outer stellar halo is relatively well aligned, within 35 deg, with that of the mock GC systems. We argue that the net angular momentum in the mock GC systems arises naturally when the majority of the material is accreted from a preferred direction, namely along the dominant dark matter filament of the large-scale structure that the halos are embedded in. This, together with the favourable edge-on view of M 31's disk suggests that it is not a coincidence that a large rotation signal has been measured for its outer halo GC system.

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The outer halo globular cluster system of M31 – II. Kinematics

Cited by 100 publications

References 115 publications

The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Planes of satellite galaxies: when exceptions are the rule

The kinematics of globular clusters systems in the outer halos of the Aquarius simulations

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