Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Battaglia, G.; Taibi, S.; Thomas, G. F.; Fritz, T. K.

doi:10.48550/arxiv.2106.08819

Cited by 13 publications

(36 citation statements)

References 140 publications

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“…In order to highlight Boo I's population among field stars, this procedure is performed on a photometric sample of 1 square degree centered on the satellite for which all stars with a CMD membership probability below 1% and a Pristine metallicity above −1.0 are discarded. The systemic PM obtained is similar to those of Battaglia et al (2021) and McConnachie & Venn (2020) with µ * α = −0.39 ± 0.02 mas yr −1 and µ δ = −1.07 ± 0.01 mas yr −1 . The resulting PM membership probabilities are folded in Eq.…”

Section: Dynamical Analysissupporting

confidence: 73%

“…Combining the elongation of the satellite, the detection of both a systemic velocity and metallicity gradient, the α elements abundance from previous studies and the low pericenter of the satellite as derived by Battaglia et al (2021) suggests that Boo I could have been more massive that it is today and that the satellite is currently significantly affected by tidal interactions with the MW.…”

Section: Discussionmentioning

confidence: 72%

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The Pristine Dwarf-Galaxy survey -- IV. Probing the outskirts of the dwarf galaxy Boötes I

Longeard¹,

Jablonka²,

Arentsen³

et al. 2021

Preprint

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We present a new spectroscopic study of the dwarf galaxy Bootes I (Boo I) with data from the Anglo-Australian Telescope and its AAOmega spectrograph together with the Two Degree Field multi-object system. We observed 36 high-probability Boo I stars selected using Gaia Early Data Release 3 proper motions and photometric metallicities from the Pristine survey. Out of those, 29 are found to be Boo I's stars, resulting in an excellent success rate of 80% at finding new members. Our analysis uses a new pipeline developed to estimate radial velocities and equivalent widths of the calcium triplet lines from Gaussian and Voigt line profile fits. The metallicities of 18 members are derived, including 3 extremely metal-poor stars ([Fe/H] < −3.0), which translates into an exceptional success rate of 25% at finding them with the combination of Pristine and Gaia. Using the large spatial extent of our new members that spans up to 4.1 half-light radii and spectroscopy from the literature, we are able to detect a systemic velocity gradient of 0.15 ± 0.10 km s −1 arcmin −1 and a small but resolved metallicity gradient of −0.007 ± 0.003 dex arcmin −1 . Finally, we show that Boo I is more elongated than previously thought with an ellipticity of = 0.68 ± 0.15. Its velocity and metallicity gradients as well as its elongation suggest that Boo I may have been affected by tides, a result supported by direct dynamical modelling.

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Section: Dynamical Analysissupporting

confidence: 73%

Section: Discussionmentioning

confidence: 72%

The Pristine Dwarf-Galaxy survey -- IV. Probing the outskirts of the dwarf galaxy Boötes I

Longeard¹,

Jablonka²,

Arentsen³

et al. 2021

Preprint

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“…Here we focus on the "ghostly" dwarf galaxy, Crater II, found recently to be orbiting the Milky Way at a radius of 117 kpc currently (Torrealba et al 2016), with a half-light radius of 1.1 kpc and with a relatively small pericenter, so that that significant tidal stripping is assumed to be likely, perhaps resulting in 90% reduction in the its mass, with the possible presence of tidal distortion seen (Ji et al 2021), consistent with the most recent GAIA based pericenter estimate of only 18 +14 −10 kpc (Fritz et al 2018;Battaglia et al 2021), well within the measured virial radius of the MW halo (Sanders, Evans & Dehnen 2018).…”

Section: Introductionsupporting

confidence: 76%

Understanding the "Feeble Giant" Crater II with tidally stretched Wave Dark Matter

Pozo,

Broadhurst,

Emami

et al. 2021

Preprint

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The unusually large, "feeble dwarf" galaxy Crater II, with its small velocity dispersion, 3 km/s, defies expectations that low mass galaxies should be small and dense. Here we examine its unusual properties in the context of "Wave Dark Matter", combining the latest stellar and velocity dispersion profiles for Crater II, finding a prominent dark core of radius 0.71 +0.09 −0.08 kpc, surrounded by a low density halo, with a visible transition between the core and the halo. This observed behaviour is very similar to the distinctive core-halo profile structure of dark matter as a Bose-Einstein condensate, 𝜓DM, where the ground state forms a prominent soliton core, surrounded by a tenuous halo of interfering waves, with a marked density transition predicted between the soliton and the halo. Crater II conforms well this distinctive 𝜓DM prediction, with consistency found between its large core and low velocity dispersion for a boson mass of 𝑚 𝜓 𝑐 2 (1.9 ± 0.3) × 10 −22 eV. Similar core-halo structure is also apparent in most dwarf spheroidal galaxies (dSph), but with typically smaller cores, 0.25 kpc and higher velocity dispersions, 9km/s. We argue that Crater II may have have been a more typical dSph dwarf that has lost most of its halo mass to tidal stripping in the context of 𝜓DM, resulting in a factor 3 reduction in velocity dispersion causing a threefold expansion of the soliton core, following the inverse scaling between velocity and de Broglie wavelength required by the Uncertainty Principle. This tidal origin for Crater II is supported by its small pericenter of 20 kpc, now established by GAIA, implying significant tidal stripping by the Milky Way.

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“…Particles that initially had very low angular momenta show the strongest enhancement in orbital pole density towards the VPOS normal. However, these angular momenta are inconsistent with the observed dwarf galaxies, as based on Gaia EDR3 proper motions (Battaglia et al 2021). Restricting the analysis to particles of comparably high angular momenta, the orbital pole enhancement all but vanishes.…”

Section: Discussionmentioning

confidence: 65%

“…1 we reproduce the COM shifts (as obtained from figures 4 and 6 in GC21). We subtract the respective distance-dependent values from the Cartesian positions and velocities of the observed MW satellites, for which we adopt the dataset by Battaglia et al (2021) who provide proper motions based on Gaia EDR3. Here and in the following we focus on satellites in the Galactocentric distance range of 50 to 250 kpc, which results in a sample of 31 dwarfs.…”

Section: Effect On Milky Way Satellitesmentioning

confidence: 99%

On the Effect of the Large Magellanic Cloud on the Orbital Poles of Milky Way Satellite Galaxies

Pawlowski,

Oria,

Taibi

et al. 2021

Preprint

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The reflex motion and distortion of the Milky Way (MW) halo caused by the infall of a massive Large Magellanic Cloud (LMC) was shown to result in an excess of orbital poles of dark matter halo particles towards the LMC orbital pole. This was suggested to help explain the observed preference of MW satellite galaxies to co-orbit along the Vast Polar Structure (VPOS), the MW's satellite plane. We test this idea by correcting the positions and velocities of the MW satellites for the Galactocentric-distancedependent shifts inferred from a LMC-infall simulation. While this should substantially reduce the observed clustering of orbital poles if it were mainly caused by the LMC, we instead find that the strong clustering remains preserved. We confirm the initial study's result with our own simulation of an MW-LMC-like interaction, and use it to identify two reasons why this scenario is unable to explain the VPOS: (1) the orbital pole enhancement is very mild (∼ 10%) compared to the substantial observed enhancement (∼ 300%), and (2) it is very sensitive to the specific angular momenta of the simulation particles, with higher angular momentum particles being affected the least. Particles in simulated dark matter halos tend to follow more radial orbits (lower angular momentum), so their orbital poles are more easily affected by small offsets in position and velocity caused by an LMC infall than objects with more tangential velocity (higher angular momentum), such as the observed dwarf galaxies surrounding the MW. The origin of the VPOS thus remains unexplained.

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Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Cited by 13 publications

References 140 publications

The Pristine Dwarf-Galaxy survey -- IV. Probing the outskirts of the dwarf galaxy Boötes I

The Pristine Dwarf-Galaxy survey -- IV. Probing the outskirts of the dwarf galaxy Boötes I

Understanding the "Feeble Giant" Crater II with tidally stretched Wave Dark Matter

On the Effect of the Large Magellanic Cloud on the Orbital Poles of Milky Way Satellite Galaxies

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