Origins and Interpretation of Tidal Debris

Johnston, Kathryn V.

doi:10.1007/978-3-319-19336-6_6

Cited by 5 publications

(1 citation statement)

References 73 publications

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“…Stars also retain memory of their origin in the way they move. For example as a galaxy gets torn apart by the tidal forces of a larger system like the Milky Way, the stripped stars continue to follow similar trajectories as their progenitor system (Johnston et al 1996, Johnston 1998. This implies that if the Milky Way halo is the result of the mergers of many different objects, their stars should define streams that crisscross the whole Galaxy ).…”

Section: Introductionmentioning

confidence: 99%

Streams, Substructures, and the Early History of the Milky Way

Helmi

2020

Annu. Rev. Astron. Astrophys.

327

169

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The advent of the second data release of the Gaia mission, in combination with data from large spectroscopic surveys, is revolutionizing our understanding of the Galaxy. Thanks to these transformational data sets and the knowledge accumulated thus far, a new, more mature picture of the evolution of the early Milky Way is currently emerging. ▪ Two of the traditional Galactic components, namely, the stellar halo and the thick disk, appear to be intimately linked: Stars with halo-like kinematics originate in similar proportions from a heated (thick) disk and from a debris from a system named Gaia-Enceladus. Gaia-Enceladus was the last big merger event experienced by the Milky Way and was completed around 10 Gyr ago. The puffed-up stars now present in the halo as a consequence of the merger have thus exposed the existence of a disk component at z ∼ 1.8. This is likely related to the previously known metal-weak thick disk and may be traceable to metallicities [Fe/H] [Formula: see text] −4. As importantly, there is evidence that the merger with Gaia-Enceladus triggered star formation in the early Milky Way, plausibly leading to the appearance of the thick disk as we know it. ▪ Other merger events have been characterized better, and new ones have been uncovered. These include, for example, the Helmi streams, Sequoia, and Thamnos, which add to the list of those discovered in wide-field photometric surveys, such as the Sagittarius streams. Current knowledge of their progenitors’ properties, star formation, and chemical evolutionary histories is still incomplete. ▪ Debris from different objects shows different degrees of overlap in phase-space. This sometimes confusing situation can be improved by determining membership probabilities via quantitative statistical methods. A task for the next few years will be to use ongoing and planned spectroscopic surveys for chemical labeling and to disentangle events from one another using dimensions other than phase-space, metallicity, or [α/Fe]. ▪ These large surveys will also provide line-of-sight velocities missing for faint stars in Gaia releases and more accurate distance determinations for distant objects, which in combination with other surveys could also lead to more accurate age dating. The resulting samples of stars will cover a much wider volume of the Galaxy, allowing, for example, the linking of kinematic substructures found in the inner halo to spatial overdensities in the outer halo. ▪ All the results obtained so far are in line with the expectations of current cosmological models. Nonetheless, tailored hydrodynamical simulations to reproduce in detail the properties of the merger debris, as well as constrained cosmological simulations of the Milky Way, are needed. Such simulations will undoubtedly unravel more connections between the different Galactic components and their substructures, and will aid in pushing our knowledge of the assembly of the Milky Way to the earliest times. Expected final online publication date for the Annual Review of Astronomy, Volume 58 is August 18, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Section: Introductionmentioning

confidence: 99%

Streams, Substructures, and the Early History of the Milky Way

Helmi

2020

Annu. Rev. Astron. Astrophys.

327

169

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On the fast track: Rapid construction of stellar stream paths

Starkman

Bovy

Webb

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Stellar streams are sensitive probes of the Galactic potential. The likelihood of a stream model given stream data is often assessed using simulations. However, comparing to simulations is challenging when even the stream paths can be hard to quantify. Here we present a novel application of Self-Organizing Maps and first-order Kalman Filters to reconstruct a stream’s path, propagating measurement errors and data sparsity into the stream path uncertainty. The technique is Galactic-model independent, non-parametric, and works on phase-wrapped streams. With this technique, we can uniformly analyze and compare data with simulations, enabling both comparison of simulation techniques and ensemble analysis with stream tracks of many stellar streams. Our method is implemented in the public Python package TrackStream , available at https://github.com/nstarman/trackstream.

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The dark side of FIRE: predicting the population of dark matter subhaloes around Milky Way-mass galaxies

Barry

Wetzel

Chapman

et al. 2023

Monthly Notices of the Royal Astronomical Society

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A variety of observational campaigns seek to test dark-matter models by measuring dark-matter subhaloes at low masses. Despite their predicted lack of stars, these subhaloes may be detectable through gravitational lensing or via their gravitational perturbations on stellar streams. To set measurable expectations for subhalo populations within ΛCDM, we examine 11 Milky Way (MW)-mass haloes from the FIRE-2 baryonic simulations, quantifying the counts and orbital fluxes for subhaloes with properties relevant to stellar stream interactions: masses down to 106 M⊙, distances ≲ 50 kpc of the galactic center, across z = 0 − 1 (tlookback = 0 − 8 Gyr). We provide fits to our results and their dependence on subhalo mass, distance, and lookback time, for use in (semi)analytic models. A typical MW-mass halo contains ≈16 subhaloes >107 M⊙ (≈1 subhalo >108 M⊙) within 50 kpc at z ≈ 0. We compare our results with dark-matter-only versions of the same simulations: because they lack a central galaxy potential, they overpredict subhalo counts by 2 − 10 ×, more so at smaller distances. Subhalo counts around a given MW-mass galaxy declined over time, being ≈10 × higher at z = 1 than at z ≈ 0. Subhaloes have nearly isotropic orbital velocity distributions at z ≈ 0. Across our simulations, we also identified 4 analogs of Large Magellanic Cloud satellite passages; these analogs enhance subhalo counts by 1.4 − 2.1 times, significantly increasing the expected subhalo population around the MW today. Our results imply an interaction rate of ∼5 per Gyr for a stream like GD-1, sufficient to make subhalo-stream interactions a promising method of measuring dark subhaloes.

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Origins and Interpretation of Tidal Debris

Cited by 5 publications

References 73 publications

Streams, Substructures, and the Early History of the Milky Way

Streams, Substructures, and the Early History of the Milky Way

On the fast track: Rapid construction of stellar stream paths

The dark side of FIRE: predicting the population of dark matter subhaloes around Milky Way-mass galaxies

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