Halo streams in the solar neighborhood

Klement, Rainer J.

doi:10.1007/s00159-010-0034-0

Cited by 48 publications

(37 citation statements)

References 114 publications

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“…Evidence of spatial and kinematical substructures in the Galactic halo resulting from this process has indeed been found as reviewed by Helmi (2008) and Klement (2010). Elemental abundance ratios of halo stars may also be used to probe this formation process by so-called "chemical tagging" of the "building blocks" (Freeman & Bland-Hawthorn 2002).…”

Section: Introductionmentioning

confidence: 92%

Two distinct halo populations in the solar neighborhood

Nissen

Schuster

2011

A&A

161

167

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Section: Introductionmentioning

confidence: 92%

Two distinct halo populations in the solar neighborhood

Nissen

Schuster

2011

A&A

161

167

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“…Numerous studies in the last 15 yr have suggested that the imprints of past merger events, even if dispersed in configuration space, can still be identified in kinematics-related spaces, such as the energy-angular momentum space (hereafter referred to as E − L z , L z being the z component of the angular momentum for an axisymmetric potential where z is the symmetry axis), the L ⊥ − L z space, where L ⊥ is the angular momentum component in the x − y plane, or spaces of orbital parameters, such as the apocenter-pericenter-angular momentum space (APL) and its projections (Helmi et al 1999(Helmi et al , 2006Helmi & de Zeeuw 2000;Knebe et al 2005;Brown et al 2005;Font et al 2006;Choi et al 2007;Morrison et al 2009;Re Fiorentin et al 2015) -see also Klement (2010), Smith (2016) for two recent and comprehensive reviews.…”

Section: Introductionmentioning

confidence: 99%

On the kinematic detection of accreted streams in theGaiaera: a cautionary tale

Jean-Baptiste

Matteo

Haywood

et al. 2017

A&A

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The ΛCDM cosmological scenario predicts that our Galaxy should contain hundreds of stellar streams in the solar vicinity, fossil relics of the merging history of the Milky Way and more generally of the hierarchical growth of galaxies. Because of the mixing time scales in the inner Galaxy, it has been claimed that these streams should be difficult to detect in configuration space but can still be identifiable in kinematic-related spaces like the energy/angular momenta spaces, E − L z and L ⊥ − L z , or spaces of orbital/velocity parameters. By means of high-resolution, dissipationless N-body simulations containing between 25 × 10 6 and 35 × 10 6 particles, we model the accretion of a series of up to four 1:10 mass ratio satellites then up to eight 1:100 satellites and search systematically for the signature of accretions in these spaces. The novelty of this work with respect to the majority of those already published is our analysis of fully consistent models, where both the satellite(s) and the Milky Way galaxy are "live" systems, which can react to the interaction and experience kinematical heating, tidal effects and dynamical friction (the latter, a process often neglected in previous studies). We find that, in agreement with previous works, all spaces are rich in substructures, but that, contrary to previous works, the origin of these substructures -accreted or in-situ -cannot be determined for the following reasons. In all spaces considered (1) each satellite provides the origin of several independent over-densities; (2) over-densities of multiple satellites overlap; (3) satellites of different masses can produce similar substructures; (4) the overlap between the in-situ and the accreted population is considerable everywhere; and (5) in-situ stars also form substructures in response to the satellite(s') accretion. These points are valid even if the search is restricted to kinematically-selected halo stars only. As we are now entering the "Gaia era", our results warn that extreme caution must be employed before interpreting over-densities in any of those spaces as evidence of relics of accreted satellites. Reconstructing the accretion history of our Galaxy will require a substantial amount of accurate spectroscopic data, that, complemented by the kinematic information, will possibly allow us to (chemically) identify accreted streams and measure their orbital properties.

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“…More attention has been given to the study of the impact of AM redistribution in major mergers than in minor mergers (with mass ratios ≤0.1). This despite the fact that minor mergers are expected to be much more common than major mergers (Fakhouri & Ma 2008) and that many traces of ongoing or past interactions are visible both in the Milky Way (see Klement 2010, for a recent review), our neighbor galaxy Andromeda (Ibata et al 2001;McConnachie et al 2009) and other galaxies in the local Universe (Martinez-Delgado et al 2010). Di pointed out that the AM redistribution during minor mergers also have an impact on the kinematics of stellar disks and may explain the distribution of the orbital eccentricities of stars in the solar neighborhood.…”

Section: Introductionmentioning

confidence: 99%

Minor mergers and their impact on the kinematics of old and young stellar populations in disk galaxies

Matteo

Lehnert

et al. 2011

A&A

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By means of N-body simulations we investigate the impact of minor mergers on the angular momentum and dynamical properties of the merger remnant. Our simulations cover a range of initial orbital characteristics and gas-to-stellar mass fractions (from 0 to 20%), and include star formation and supernova feedback. We confirm and extend previous results by showing that the specific angular momentum of the stellar component always decreases independently of the orbital parameters or morphology of the satellite, and that the decrease in the rotation velocity of the primary galaxy is accompanied by a change in the anisotropy of the orbits. However, the decrease affects only the old stellar population, and not the new population formed from gas during the merging process. This means that the merging process induces an increasing difference in the rotational support of the old and young stellar components, with the old one lagging with respect to the new. Even if our models are not intended specifically to reproduce the Milky Way and its accretion history, we find that, under certain conditions, the modeled rotational lag found is compatible with that observed in the Milky Way disk, thus indicating that minor mergers can be a viable way to produce it. The lag can increase with the vertical distance from the disk midplane, but only if the satellite is accreted along a direct orbit, and in all cases the main contribution to the lag comes from stars originally in the primary disk rather than from stars in the satellite galaxy. We also discuss the possibility of creating counter-rotating stars in the remnant disk, their fraction as a function of the vertical distance from the galaxy midplane, and the cumulative effect of multiple mergers on their creation.

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Halo streams in the solar neighborhood

Cited by 48 publications

References 114 publications

Two distinct halo populations in the solar neighborhood

Two distinct halo populations in the solar neighborhood

On the kinematic detection of accreted streams in theGaiaera: a cautionary tale

Minor mergers and their impact on the kinematics of old and young stellar populations in disk galaxies

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