Forthcoming astrometric missions such as the Gaia satellite will bring to the fore the problem of estimating the enclosed mass from a set of positions, radial velocities and proper motions of tracer stars. Here, we show how to construct the tracer mass estimator when the proper motion data are available in addition to the usual line-of-sight velocity data. Notably, the mass estimators do not require any assumption on the anisotropy, as it is naturally incorporated through the different components of proper motions. In addition, the separate treatment of the proper motions and the line-of-sight velocities is desirable because they are observationally independent and thus the propagation of the combined uncertainties is rather straightforward. The extension to projected data is also sketched, together with a possible application of measuring the masses of Galactic globular clusters.
The GAIA satellite will provide unprecedented phase-space information for our Galaxy and enable a new era of Galactic dynamics. We may soon see successful realizations of Galactoseismology, i.e., inferring the characteristics of the Galactic potential and sub-structure from a dynamical analysis of observed perturbations in the gas or stellar disk of the Milky Way. Here, we argue that to maximally take advantage of the GAIA data and other complementary surveys, it is necessary to build comprehensive models for both the stars and the gas. We outline several key morphological puzzles of the Galac…
The final astrometric data from the Gaia mission will transform our view of the stellar content of the Galaxy, particularly when complemented with spectroscopic surveys providing stellar parameters, line-of-sight kinematics and elemental abundances. Analyses with Gaia DR1 are already demonstrating the insight gained and the promise of what is to come with future Gaia releases. I present a brief overview of results and puzzles from recent Galactic Archaeology surveys for context, focusing on the Galactic discs.
The astro-photometric parameters of the open star cluster Dolidze 41, which located in the constellation of Cygnus, have been investigated using the Gaia-ESO DR2 large Survey merging with the near Infrared Two Micron All Sky Survey 2MASS database. The radial density distribution (limited, core and tidal radii), color-magnitude diagrams, the galactocentric coordinates, distances, color excess, and age of Dolidze 41 are presented. Thanks to Gaia DR2 astrometry, which help us to define the membership of the cluster stars easily. The luminosity & mass functions, the entire luminosity & mass, and t…
Stellar clusters are important for astrophysics in many ways, for instance as optimal tracers of the Galactic populations to which they belong or as one of the best test bench for stellar evolutionary models. Gaia DR1, with TGAS, is just skimming the wealth of exquisite information we are expecting from the more advanced catalogues, but already offers good opportunities and indicates the vast potentialities. Gaia results can be efficiently complemented by ground-based data, in particular by large spectroscopic and photometric surveys. Examples of some scientific results of the Gaia-ESO survey …
This contribution to the Stellar Clusters & Associations: A RIA Workshop on Gaia deals with surveys of stars, in particular spectroscopic surveys, with attention to their impact on cluster studies, and their connectionwith Gaia. I review some of the scientific reasons why we want large spectroscopic surveys, what requirements these put on the instrumentation. Then I turn to a review of the current and future instrumentation that will enable us to complement Gaia's excellent distances and proper motions with the desired ground-based spectroscopy to obtain additional radial velocities and elemen…
We model the formation of the Galactic stellar halo via the accretion of satellite galaxies onto a time-dependent semi-cosmological galactic potential. Our goal is to characterize the substructure left by these accretion events in a close manner to what may be possible with the {\it Gaia} mission. We have created a synthetic {\it Gaia} Solar Neighbourhood catalogue by convolving the 6D phase-space coordinates of stellar particles from our disrupted satellites with the latest estimates of the {\it Gaia} measurement errors, and included realistic background contamination due to the Galactic disc…
We perform realistic simulations of the Sun's birth cluster in order to predict the current distribution of solar siblings in the Galaxy. We study the possibility of finding the solar siblings in the Gaia catalogue by using only positional and kinematic information. We find that the number of solar siblings predicted to be observed by Gaia will be around 100 in the most optimistic case, and that a phase space only search in the Gaia catalogue will be extremely difficult. It is therefore mandatory to combine the chemical tagging technique with phase space selection criteria in order to have any…
We live in an age where an enormous amount of astrometric, photometric, asteroseismic, and spectroscopic data of Milky Way stars are being acquired, many orders of magnitude larger than about a decade ago. Thanks to the Gaia astrometric mission and followup ground-based spectroscopic surveys in the next 5-10 years about 10-20 Million stars will have accurate 6D kinematics and chemical composition measurements. KEPLER-2, PLATO, and TESS will provide asteroseismic ages for a good fraction of those. In this article we outline some outstanding problems concerning the formation and evolution of the…
The European Space Agency's Gaia space telescope, launched in 2013, aims to measure the positions, parallaxes, and proper motions of a billion stars in our Galaxy and throughout the Local Group. In doing so it will include hundreds of thousands of young stars in star forming regions, star clusters and OB associations. This will provide us with an unprecedented view of the role of dynamics in the star formation process and the evolution of young star clusters. Data from this ambitious mission is expected very soon, with the first data release scheduled for 2016. This review discusses the curren…
Gaia, the European Space Agency spacecraft successfully launched on 19 December 2013, entered into nominal science operations on 18 July 2014 after a few months of commissioning, and has been scanning the sky to a faint limit of G = 20.7 mag since then. Gaia is expected to observe more than a hundred thousand RR Lyrae stars in the Galactic halo and bulge (most of which will be new discoveries), and to provide parallax measurements with about 10 μas uncertainty for those brighter than <V>$\sim$ 12-13 mag. Status and activities of the spacecraft since launch are briefly reviewed with emphasis on…
The luminosity function (LF) for stars is here fitted by a Schechter function and by a Gamma probability density function. The dependence of the number of stars on the distance, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter and Gamma LFs. Three astrophysical applications for stars are provided: deduction of the parameters at low distances, behavior of the average absolute magnitude with distance, and the location of the photometric maximum as a function of the selected flux. The use of the truncated LFs allows to model the Ma…
The body of photometric and astrometric data on stars in the Galaxy has been growing very fast in recent years (Hipparcos/Tycho, OGLE-3, 2-Mass, DENIS, UCAC2, SDSS, RAVE, Pan Starrs, Hermes, ...) and in two years ESA will launch the Gaia satellite, which will measure astrometric data of unprecedented precision for a billion stars. On account of our position within the Galaxy and the complex observational biases that are built into most catalogues, dynamical models of the Galaxy are a prerequisite full exploitation of these catalogues. On account of the enormous detail in which we can observe t…
We investigate of the systems of proper motions of stars in the ground-based catalogues HSOY, UCAC5, GPS1 and PMA derived by combining with the Gaia DR1 space data. Assuming the systematic differences of stellar proper motions of two catalogues to be caused by the mutual solid-body rotation and glide of the coordinate systems produced by the data of the catalogues under comparison, we analyse the components of the mutual rotation vector and displacement of the origins of these systems. The equatorial components of the vector of mutual rotation velocity of the compared coordinate systems, as we…
We predict the distinctive three dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10~kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous halo stars. At large distances of 20-100 kpc, unbound HVSs are much more common than runaways; radial velocities easily distinguish both from indigenous halo stars. Comparisons of the predictions with existing observations are encouraging. Although the models fail to match observations of solar-type …
We present results from the analysis of 401 RR Lyrae stars (RRLs) belonging to the field of the Milky Way (MW). For a fraction of them multi-band ($V$, $K_{\rm s}$, $W1$) photometry, metal abundances, extinction values and pulsation periods are available in the literature and accurate trigonometric parallaxes measured by the Gaia mission alongside Gaia $G$-band time-series photometry have become available with the Gaia second data release (DR2) on 2018 April 25. Using a Bayesian fitting approach we derive new near-, mid-infrared period-absolute magnitude-metallicity ($PMZ$) relations and new a…
Classical Cepheids in open clusters are key ingredients for stellar population studies and the characterization of variable stars, as they are tracers of young and massive populations and of recent star formation episodes. Cluster Cepheids are of particular importance since they can be age dated by using the cluster's stellar population to obtain the Cepheid period-luminosity-age relation. In this contribution, we present the preliminary results of an all-sky search for classical Cepheids in Galactic open clusters by taking advantage of the unprecedented astrometric precision of the second dat…
In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals $5300<T_{eff} < 7300$ K, $\log g > 4$ (cgs) and $0.3<(B-V)_0<0.8$ mag, respectively. Stars with relative trigonometric parallax errors $σ_π/π\leq0.01$ were preferred from Gaia DR2 data for the estimation of their $M_V$ absolute magnitudes.…
Context. Currently galactic exploration is being revolutionized by a flow of new data: Gaia provides measurements of stellar distances and kinematics; growing numbers of spectroscopic surveys provide values of stellar atmospheric parameters and abundances of elements; and Kepler and K2 missions provide asteroseismic information for an increasing number of stars. Aims. In this work we aim to determine stellar distances and ages using Gaia and spectrophotometric data in a consistent way. We estimate precisions of age and distance determinations with Gaia end-of-mission and TGAS parallax precisio…
In this paper we revisit the problem of identifying bona fide cluster Cepheids by performing an all-sky search for Cepheids associated with open clusters and making use of state-of-the-art catalogued information for both Cepheids and clusters, based on the unparalleled astrometric precision of the second and early third data releases of the Gaia satellite. We determine membership probabilities by following a Bayesian approach using spatial and kinematic information of the potential cluster-Cepheid pairs. We confirm 19 Cepheid-cluster associations considered in previous studies as bona-fide, an…
We present MINESweeper, a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry to model isochrones and spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition to stellar parameters such as Teff, log(g), [Fe/H], [a/Fe], and radial velocity. MINESweeper employs a Bayesian framework and can easily incorporate a variety of priors, including Gaia parallaxes. Mock data are fit in order to demonstrate how the precision of derived parameters depends on evolutionary phase and SNR. We then fit a selection of data i…
This study presents the multi-wavelength investigation of the absolute magnitudes and colours of the red clump (RC) stars selected from APOGEE and GALAH DR2 combined catalogue which is complemented with {\it Gaia} DR2 astrometric data and multi-wavelength photometric data of {\it GALEX} GR6/7, SDSS DR7, {\it Gaia} DR2, 2MASS and {\it WISE} sky surveys. The analyses are centred on the different distance estimation methods using {\it Gaia} trigonometric parallaxes, (1/$\varpi$) and Bayes statistics, and chemically defined Galactic disc populations on [$α$/Fe]$\times$[Fe/H] plane. Such investigat…
Young massive stars in the halo are assumed to be runaway stars from the Galactic disk. Possible ejection scenarios are binary supernova ejections (BSE) or dynamical ejections from star clusters (DE). Hypervelocity stars (HVSs) are extreme runaway stars that are potentially unbound from the Galaxy. Powerful acceleration mechanisms such as the tidal disruption of a binary system by a supermassive black hole (SMBH) are required to produce them. Therefore, HVSs are believed to originate in the Galactic center (GC), the only place known to host an SMBH. The second Gaia data release (DR2) offers th…
Open clusters and associations are groups of young stars, respectively bound and unbound, that share the same origin and disperse over time into the galactic field. As such, their formation and evolution are the key to understand the origin and properties of galactic stellar populations. Moreover, since their members have about the same age, they are ideal laboratories to study the properties of young stars and constrain stellar evolution theories. In this contribution, I present our current knowledge on open clusters and associations. I focus on the methods used to derive the statistical prop…
The nearest stars provide a fundamental constraint for our understanding of stellar physics and the Galaxy. The nearby sample serves as an anchor where all objects can be studied and understood with precise data. This work is an update of the 10 pc sample published by Reylé et al. (2021) that used the unprecedented high precision parallax measurements from the early third data release of the astrometric space mission Gaia. We review this census, all updates being related to close binaries, brown dwarfs and exoplanets. We provide a new catalogue of 541 stars, brown dwarfs, and exoplanets in 336…
We present wide-field, ground-based Johnson-Cousins UBVRI photometry for 48 Galactic globular clusters based on almost 90000 public and proprietary images. The photometry is calibrated with the latest transformations obtained in the framework of our secondary standard project, with typical internal and external uncertainties of order a few millimagnitudes. These data provide a bridge between existing small-area, high-precision HST photometry and all sky-catalogues from large surveys like Gaia, SDSS, or LSST. For many clusters, we present the first publicly available photometry in some of the f…
This paper presents a deep investigation of two open clusters, Haffner 22 and Melotte 71, using astrometric and photometric data from Gaia EDR3. We identified 382 and 597 most probable cluster members with membership probability higher than 50 percent. Mean proper motion in RA and DEC are estimated as -1.63 and 2.889 respectively for Haffner 22 and -2.398 and 4.210 for Melotte 71. A comparison of observed CMDs with theoretical isochrones leads to an age of 2.25 and 1.27 Gyr for these clusters. The distances 2.88 and 2.28 kpc based on parallax are comparable with the values derived by isochrone…
The vast majority of Gaia DR1 Tycho-Gaia astrometric solution (TGAS) stars are located within a distance of 1200 pc from the Sun and up to 600 pc within the Galactic plane. Complete usage of their parallaxes is possible only if their reddening and interstellar extinction are known. We obtained those from a comparison of the eight most accurate and complete 3D maps of reddening and extinction in the considered space. We analyzed the statistics of the maps and their differences in the cells of $20\times20\times20$ pc in the whole considered space. The comparison of the maps in the cells outside …
Estimator forensics for the wide-binary gravity test: the eccentricity-triple coupling manufactures a pseudo-signal, and a pre-registered protocol for Gaia DR4
The main goal of Galactic Archaeology is understanding the formation and evolution of the basic Galactic components. This requires sophisticated chemo-dynamical modeling, where disc asymmetries (e.g., perturbations from the central bar, spirals arms, and infalling satellites) and non-equilibrium processes are taken into account self-consistently. Here we discuss the current status of Galactic chemo-dynamical modeling and focus on a recent hybrid technique, which helps circumvent traditional problems with chemical enrichment and star formation encountered in fully self-consistent cosmological s…
With the help of Gaia data, it is noted that in addition to the core components, there are low-density outer halo components in the extended region of open clusters. To study the extended structure beyond the core radius of the cluster ($\sim$ 10 pc), based on Gaia EDR3 data, taking up to 50 pc as the searching radius, we use the pyUPMASK algorithm to re-determine the member stars of the open cluster within 1-2 kpc. We obtain the member stars of 256 open clusters, especially those located in the outer halo region of open clusters. Furthermore, we find that most open clusters' radial density pr…
The structural and dynamical properties of star clusters are generally derived by means of the comparison between steady-state analytic models and the available observables. With the aim of studying the biases of this approach, we fitted different analytic models to simulated observations obtained from a suite of direct N-body simulations of star clusters in different stages of their evolution and under different levels of tidal stress to derive mass, mass function and degree of anisotropy. We find that masses can be under/over-estimated up to 50% depending on the degree of relaxation reached …
We present an investigation of NGC 2158 using Gaia-DR2 data. We identified 800 most likely cluster members with membership probability higher than 90%. The mean proper motions of this object are determined as (mu_{x}=-0.203 \pm 0.003, mu_{y}=-1.99 \pm 0.004) mas yr^{-1}. The limiting radius, log(age), and distance of the cluster are obtained as 23.5 arcmin, 9.38 \pm 0.04 Gyr and 4.69 \pm 0.22 kpc, respectively. The overall mass function slope (0.93 \pm 0.14) is flatter than the Salpeter value (1.35) within the mass range 1.17-1.44 M_\odot. This cluster also shows the mass-segregation effect an…
The $Λ$CDM cosmological scenario predicts that our Galaxy should contain hundreds of stellar streams at 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-Lz and Lperp-Lz, or spaces of orbital/velocity parameters. By means of high-resolution, dissipationless N-body simul…
We use Gaia DR2 systemic proper motions of 45 satellite galaxies to constrain the mass of the Milky Way using the scale free mass estimator of Watkins et al. (2010). We first determine the anisotropy parameter $β$, and the tracer satellites' radial density index $γ$ to be $β$=$-0.67^{+0.45}_{-0.62}$ and $γ=2.11\pm0.23$. When we exclude possible former satellites of the Large Magellanic Cloud, the anisotropy changes to $β$=$-0.21^{+0.37}_{-0.51}$. We find that the index of the Milky Way's gravitational potential $α$, which is dependent on the mass itself, is the parameter with the largest impac…
As we enter a golden age for studies of internal kinematics and dynamics of Galactic globular clusters (GCs), it is timely to assess the performance of modelling techniques in recovering the mass, mass profile, and other dynamical properties of GCs. Here, we compare different mass-modelling techniques (distribution-function (DF)-based models, Jeans models, and a grid of N-body models) by applying them to mock observations from a star-by-star N-body simulation of the GC M 4 by Heggie. The mocks mimic existing and anticipated data for GCs: surface brightness or number density profiles, local ste…
We explore the vicinity of the Milky Way through the use of spectro-photometric data from the Sloan Digital Sky Survey and high-quality proper motions derived from multi-epoch positions extracted from the Guide Star Catalogue II database. In order to identify and characterise streams as relics of the Milky Way formation, we start with classifying, select, and study $2417$ subdwarfs with $\rm{[Fe/H] < -1.5}$ up to $3$ kpc away from the Sun as tracers of the local halo system. Then, through phase-space analysis, we find statistical evidence of five discrete kinematic overdensities among $67$ of …
The study of the kinematics of globular clusters (GCs) offers the possibility of unveiling their long term evolution and uncovering their yet unknown formation mechanism. Gaia DR2 has strongly revitalized this field and enabled the exploration of the 6D phase-space properties of Milky Way GCs, thanks to precision astrometry. However, to fully leverage on the power of precision astrometry, a thorough investigations of the data is required. In this contribution, we show that the study of the mean radial proper motion profiles of GCs offers an ideal benchmark to assess the presence of systematics…
The velocity anisotropy parameter, beta, is a measure of the kinematic state of orbits in the stellar halo which holds promise for constraining the merger history of the Milky Way (MW). We determine global trends for beta as a function of radius from three suites of simulations, including accretion only and cosmological hydrodynamic simulations. We find that both types of simulations are consistent and predict strong radial anisotropy (<beta>~0.7) for Galactocentric radii greater than 10 kpc. Previous observations of beta for the MW's stellar halo claim a detection of an isotropic or tangentia…
The spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs) are established using re-estimated trigonometric parallaxes of {\it Gaia} DR3. The data sample of 1,587 CVs in this study is claimed to be suitable for Galactic model parameter estimation as the distances are based on trigonometric parallaxes and the {\it Gaia} DR3 photometric completeness limits were taken into account when the sample was created. According to the analysis, the scale height of All CVs increases from 248$\pm$2 to 430$\pm$4 pc towards shorter periods near the lower limit o…
The nearest stars provide a fundamental constraint for our understanding of stellar physics and the Galaxy. The nearby sample serves as an anchor where all objects can be seen and understood with precise data. This work is triggered by the most recent data release of the astrometric space mission Gaia and uses its unprecedented high precision parallax measurements to review the census of objects within 10 pc. The first aim of this work was to compile all stars and brown dwarfs within 10 pc observable by Gaia, and compare it with the Gaia Catalogue of Nearby Stars as a quality assurance test. W…
The orbits, atmospheric parameters, chemical abundances, and ages of individual stars in the Milky Way provide the most comprehensive illustration of galaxy formation available. The Tycho-Gaia Astrometric Solution (TGAS) will deliver astrometric parameters for the largest ever sample of Milky Way stars, though its full potential cannot be realized without the addition of complementary spectroscopy. Among existing spectroscopic surveys, the RAdial Velocity Experiment (RAVE) has the largest overlap with TGAS ($\gtrsim$200,000 stars). We present a data-driven re-analysis of 520,781 RAVE spectra u…
Photometric metallicity of Galactic RR Lyrae stars in the Gaia DR3 era
University of Delhi（德里大学）；Indian Institute of Astrophysics（印度天体物理研究所）；Inter-University Center for Astronomy and Astrophysics（大学间天文与天体物理中心）；University of Petroleum and Energy Studies（石油与能源大学）
[...] This paper presents a rigorous derivation of a goodness-of-fit statistics for colour-magnitude diagrams (CMD). We discuss the reliability of the underlying assumptions and their validity. We derived the distribution of the sum of squared Mahalanobis distances of stellar data and theoretical isochrone for a generic set of data and models. We applied this to the case of synthetic CMDs constructed to mimic real data of open clusters in the GAIA sample. We analysed the capability of distinguishing among different sets of input physics and parameters that were used to compute the stellar mode…
Stellar masses and ages in Gaia Data Release 4 from the Final Luminosity Age Mass Estimator algorithm
Université Côte d’Azur, Observatoire de la Côte d’Azur（蔚蓝海岸大学，蔚蓝海岸天文台）；LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台 LIRA 实验室，巴黎文理研究大学，索邦大学，巴黎西岱大学，CY 塞尔吉巴黎大学）；Université Rennes, CNRS, IPR (Institut de Physique de Rennes)（雷恩大学，法国国家科学研究中心，雷恩物理研究所）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；Centre national d’études spatiales (CNES)（法国国家空间研究中心）
Estimating a distance by inverting a parallax is only valid in the absence of noise. As most stars in the Gaia catalogue will have non-negligible fractional parallax errors, we must treat distance estimation as a constrained inference problem. Here we investigate the performance of various priors for estimating distances, using a simulated Gaia catalogue of one billion stars. We use three minimalist, isotropic priors, as well an anisotropic prior derived from the observability of stars in a Milky Way model. The two priors that assume a uniform distribution of stars--either in distance or in sp…
The hypervelocity star (HVS) survey conducted at the Multiple Mirror Telescope (MMT) identified 42 B-type stars in the Galactic halo whose radial velocity in the Galactic rest-frame exceeds $+275\,$km$\,$s${}^{-1}$. In order to unravel the nature and origin of those high-velocity outliers, their complete six-dimensional phase space information is needed. To this end, we complemented positions and proper motions from the second data release of {\it Gaia} with revised radial velocities and spectrophotometric distances that are based on a reanalysis of the available MMT spectra of 40 objects usin…
Orbital properties of stars, computed from their six-dimensional phase space measurements and an assumed Galactic potential, are used to understand the structure and evolution of the Galaxy. Stellar actions, computed from orbits, have the attractive quality of being invariant under certain assumptions and are therefore used as quantitative labels of a star's orbit. We report a subtle but important systematic error that is induced in the actions as a consequence of local midplane variations expected for the Milky Way. This error is difficult to model because it is non-Gaussian and bimodal, with…
Decades after their discovery, only four hydrogen-deficient carbon (HdC) stars were known to have no circumstellar dust shell. This is in complete contrast to the $\sim$130 known Galactic HdC stars that are notorious for being heavy dust producers, i.e. the R Coronae Borealis (RCB) stars. Together they form a rare class of supergiant stars that are thought to originate from the merger of CO/He white dwarf binary systems, otherwise known as the double-degenerate scenario. We searched for new dustless HdC (dLHdC) stars. We used primarily the 2MASS and GAIA eDR3 catalogues to select candidates th…
The publication of the Gaia Data Release 2 (Gaia DR2) opens a new era in Astronomy. It includes precise astrometric data (positions, proper motions and parallaxes) for more than $1.3$ billion sources, mostly stars. To analyse such a vast amount of new data, the use of data mining techniques and machine learning algorithms are mandatory. The search for Open Clusters, groups of stars that were born and move together, located in the disk, is a great example for the application of these techniques. Our aim is to develop a method to automatically explore the data space, requiring minimal manual int…
The Gaia mission promises to deliver precision astrometry at an unprecedented level, heralding a new era for discerning the kinematic and spatial coordinates of stars in our Galaxy. Here, we present a new technique for estimating the age of tidally disrupted globular cluster streams using the proper motions and parallaxes of tracer stars. We evolve the collisional dynamics of globular clusters within the evolving potential of a Milky Way-like halo extracted from a cosmological $Λ$CDM simulation and analyze the resultant streams as they would be observed by Gaia. The simulations sample a variet…
