Clumpy streams in a smooth dark halo: the case of Palomar 5

Mastrobuono-Battisti, Alessandra; Matteo, P. Di; Montuori, M.; Haywood, M.

doi:10.1051/0004-6361/201219563

Cited by 28 publications

(28 citation statements)

References 26 publications

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“…The star counts along the stream can have smallscale bumps and dips (see e.g. Küpper et al 2010;Yoon et al 2011;Mastrobuono-Battisti et al 2012), while the across-stream profile can become broader or narrower due to a range of effects, including distance variation, epicyclic feathering, interactions with small substructure and differential orbital plane precession (Koposov et al 2010;Erkal & Belokurov 2015a;Amorisco 2015;Erkal et al 2016a;Amorisco et al 2016).…”

Section: Non-parametric Stream Modelingmentioning

confidence: 99%

“…The epicyclic overdensities have been studied extensively in the literature (see e.g. Combes et al 1999;Capuzzo Dolcetta et al 2005;Küpper et al 2008Küpper et al , 2010Mastrobuono-Battisti et al 2012;Amorisco 2015) and are the result of the similarity of the orbits of the unbound stars. As further confirmation, these observed peaks are closely aligned with the peaks seen in our simulation at φ1 = −0.7 • , +0.6 • (Fig.…”

Section: Putting the Puzzle Togethermentioning

confidence: 99%

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A sharper view of Pal 5's tails: discovery of stream perturbations with a novel non-parametric technique

Erkal

Koposov

Belokurov

2017

Monthly Notices of the Royal Astronomical Society

128

161

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Only in the Milky Way is it possible to conduct an experiment which uses stellar streams to detect low-mass dark matter subhaloes. In smooth and static host potentials, tidal tails of disrupting satellites appear highly symmetric. However, perturbations from dark subhaloes, as well as from GMCs and the Milky Way bar, can induce density fluctuations that destroy this symmetry. Motivated by the recent release of unprecedentedly deep and wide imaging data around the Pal 5 stellar stream, we develop a new probabilistic, adaptive and non-parametric technique which allows us to bring the cluster's tidal tails into clear focus. Strikingly, we uncover a stream whose density exhibits visible changes on a variety of angular scales. We detect significant bumps and dips, both narrow and broad: two peaks on either side of the progenitor, each only a fraction of a degree across, and two gaps, ∼ 2 • and ∼ 9 • wide, the latter accompanied by a gargantuan lump of debris. This largest density feature results in a pronounced inter-tail asymmetry which cannot be made consistent with an unperturbed stream according to a suite of simulations we have produced. We conjecture that the sharp peaks around Pal 5 are epicyclic overdensities, while the two dips are consistent with impacts by subhaloes. Assuming an age of 3.4 Gyr for Pal 5, these two gaps would correspond to the characteristic size of gaps created by subhaloes in the mass range of 10 6 − 10 7 M and 10 7 − 10 8 M respectively. In addition to dark substructure, we find that the bar of the Milky Way can plausibly produce the asymmetric density seen in Pal 5 and that GMCs could cause the smaller gap.

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Section: Non-parametric Stream Modelingmentioning

confidence: 99%

Section: Putting the Puzzle Togethermentioning

confidence: 99%

A sharper view of Pal 5's tails: discovery of stream perturbations with a novel non-parametric technique

Erkal

Koposov

Belokurov

2017

Monthly Notices of the Royal Astronomical Society

128

161

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“…Apart from external perturbations, Newtonian simulations never produce such asymmetries. They can of course produce small length asymmetries, with a longer or shorter leading arm, due to the different orbital velocities of escaped stars when the orbit of the cluster is eccentric (Montuori et al 2007;Mastrobuono-Battisti et al 2012). However, the Newtonian orbits necessary to reproduce the Pal 5 stream never produce large asymmetries.…”

Section: Simulating the Palomar 5 Stream In Mondmentioning

confidence: 99%

Stellar streams as gravitational experiments

Thomas

Famaey

Ibata

et al. 2018

A&A

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Kinematically cold tidal streams of globular clusters (GC) are excellent tracers of the Galactic gravitational potential at moderate Galactocentric distances, and can also be used as probes of the law of gravity on Galactic scales. Here, we compare for the first time the generation of such streams in Newtonian and Milgromian gravity (MOND). We first compute analytical results to investigate the expected shape of the GC gravitational potential in both frameworks, and we then run N-body simulations with the Phantom of Ramses code. We find that the GCs tend to become lopsided in MOND. This is a consequence of the external field effect which breaks the strong equivalence principle. When the GC is filling its tidal radius the lopsidedness generates a strongly asymmetric tidal stream. In Newtonian dynamics, such markedly asymmetric streams can in general only be the consequence of interactions with dark matter subhalos, giant molecular clouds, or interaction with the Galactic bar. In these Newtonian cases, the asymmetry is the consequence of a very large gap in the stream, whilst in MOND it is a true asymmetry. This should thus allow us in the future to distinguish these different scenarios by making deep observations of the environment of the asymmetric stellar stream of Palomar 5. Moreover, our simulations indicate that the high internal velocity dispersion of Palomar 5 for its small stellar mass would be natural in MOND.

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“…These are armlets shed during recent pericentre passages. Their shape is a consequence of the orbital properties of the member stars (e.g., Küpper et al 2012;Mastrobuono-Battisti et al 2012;Amorisco 2015), and is unrelated to external disturbances. Panels Figure 2 shows 1-d density profiles for a selection of the streams displayed in Fig.…”

Section: Example Streamsmentioning

confidence: 99%

Gaps in globular cluster streams: giant molecular clouds can cause them too

Amorisco

Gómez

Vegetti

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

101

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As a result of their internal dynamical coherence, thin stellar streams formed by disrupting globular clusters (GCs) can act as detectors of dark matter (DM) substructure in the Galactic halo. Perturbations induced by close flybys amplify into detectable density gaps, providing a probe both of the abundance and of the masses of DM subhaloes. Here, we use N-body simulations to show that the Galactic population of giant molecular clouds (GMCs) can also produce gaps (and clumps) in GC streams, and so may confuse the detection of DM subhaloes. We explore the cases of streams analogous to the observed Palomar 5 and GD1 systems, quantifying the expected incidence of structure caused by GMC perturbations. Deep observations should detect such disturbances regardless of the substructure content of the Milky Way's halo. Detailed modelling will be needed to demonstrate that any detected gaps or clumps were produced by DM subhaloes rather than by molecular clouds.

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Clumpy streams in a smooth dark halo: the case of Palomar 5

Cited by 28 publications

References 26 publications

A sharper view of Pal 5's tails: discovery of stream perturbations with a novel non-parametric technique

A sharper view of Pal 5's tails: discovery of stream perturbations with a novel non-parametric technique

Stellar streams as gravitational experiments

Gaps in globular cluster streams: giant molecular clouds can cause them too

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