Distance Uncertainty Research Articles

Extratidal Members of Segue 3 are Rare and Difficult to Confirm

We simulate extratidal members of Segue 3, a sparse, faint, and small, ∼2.6 Gyr halo cluster, and investigate their observational detectability. Using the Gala package to simulate Segue 3's potential tidal tails, we find that the tails are narrow, linear, and around 4°–6° in length: the tails’ position angles and width are most sensitive to the uncertainties in the cluster's distance and mean proper motion. Post-processing the synthetic tail particles to assign realistic observational properties, we infer that Segue 3 would have close to 25 extra-tidal members with G ≤ 23, concentrated ≲1.°33 from the center of the cluster. The 11 candidate extratidal members identified by Fadely and collaborators are comparable in number, but significantly closer to the cluster center (d ∼ 4′) than these simulations predict. This analysis demonstrates the difficulty of identifying extratidal stars in the Milky Way's halo clusters, even in deep photometric surveys.

An Integrated Uncertainty Quantification Framework for Probabilistic Seismic Hazard Analysis

Probabilistic seismic hazard analysis (PSHA) is a tool to quantify the annual rate of exceedance of seismic intensity measure at a location of interest. The present study investigates the uncertainty embedded in three PSHA parameters: magnitude of earthquake, source-to-site distance, and corresponding ground shaking. Although previous researchers have worked to quantify the uncertainty in these hazard parameters, the source-to-site distance uncertainty in PSHA has not been explicitly addressed to acquire more accurate and reliable seismic hazard estimates. This study develops an uncertainty quantification framework for PSHA considering source-to-site distance uncertainty, including interdependency between hazard parameters. To capture this uncertainty, an approach of considering grids in the area seismic source zone is adopted using a geographic information system (GIS) and implementing Latin hypercube sampling (LHS) to quantify the uncertainty of the occurrence of an earthquake at any distance from the site. The interaction of magnitude and source-to-site distance has been investigated using copula theory. As a part of practical implementation, PSHA of Silchar city in Northeast India is taken into consideration due to its tectonic features and high seismicity. This work applies two processes to quantify uncertainty: (1) considering the center point of a grid, and (2) stratified sampling of points within a grid by LHS. The results reveal that on applying LHS (with uncorrelated random events), the hazard increases due to discretization of the area sources, and robust consideration of uncertainty. While, in case of correlated random events, the hazard levels are relatively low. The results are being subjected to verification and are compared with the previous studies to ensure fulfilling specifications and its intended purpose. Structural designers and decision makers can utilize the developed PSHA framework to plan and build new projects and to evaluate the seismic risk of existing infrastructure in a city.

Phase-based reconstruction optimization method for digital holographic measurement of microstructures.

Digital holography has transformative potential in measuring stacked-chip microstructures due to its noninvasive, single-shot, full-field characteristics. However, uncertainties in reconstruction distance inevitably lead to resolving blur and reconstruction distortion. Herein, we propose a phase-based reconstruction optimization method that consists of a phase-evaluation function and a structured surface-characterization model. Our proposed method involves setting a reconstruction distance range, obtaining phase information using sliced numerical reconstruction, and optimizing the reconstruction distance by finding the extreme value of the function, which identifies the focal plane of the reconstructed image. The structure of the surface topography is then characterized using the characterization model. We perform simulations of the recording, reconstruction, and characterization to verify the effectiveness of the proposed method. To further demonstrate the approach, a simple holographic recording system is constructed to measure a standard resolution target, and the measurement results are compared with a commercial instrument. The simulation and experiment demonstrate, respectively, 31.16% and 34.41% improvement in step-height characterization accuracy.

A Generalist, Automated ALFALFA Baryonic Tully–Fisher Relation

The baryonic Tully–Fisher relation (BTFR) has applications in galaxy evolution as a test bed for the galaxy–halo connection and in observational cosmology as a redshift-independent secondary distance indicator. This analysis leverages the 31,000+ galaxy Arecibo Legacy Fast ALFA (Arecibo L-band Feed Array) Survey (ALFALFA) sample—which provides redshifts, velocity widths, and H i content for a large number of gas-bearing galaxies in the local universe—to fit and test an extensive local universe BTFR. The fiducial relation is fit using a 3000-galaxy subsample of ALFALFA, and is shown to be consistent with the full sample. This BTFR is designed to be as inclusive of ALFALFA and comparable samples as possible. Velocity widths measured via an automated method and M b proxies extracted from survey data can be uniformly and efficiently measured for other samples, giving this analysis broad applicability. We also investigate the role of sample demographics in determining the best-fit relation. We find that the best-fit relations are changed significantly by changes to the sample mass range and to second order by changes to mass sampling, gas fraction, different stellar mass and velocity width measurements. We use a subset of ALFALFA with demographics that reflect the full sample to measure a robust BTFR slope of 3.30 ± 0.06. We apply this relation and estimate source distances, finding general agreement with flow-model distances as well as average distance uncertainties of ∼0.17 dex for the full ALFALFA sample. We demonstrate the utility of these distance estimates by applying them to a sample of sources in the Virgo vicinity, recovering signatures of infall consistent with previous work.

Future prospects on testing extensions to ΛCDM through the weak lensing of gravitational waves

With planned space-based and 3rd generation ground-based gravitational wave detectors (LISA, Einstein Telescope, Cosmic Explorer), and proposed DeciHz detectors (DECIGO, Big Bang Observer), it is timely to explore statistical cosmological tests that can be employed with the forthcoming plethora of data, $10^4-10^6$ mergers a year. We forecast the combination of the standard siren measurement with the weak lensing of gravitational waves from binary mergers. For 10 years of 3rd generation detector runtime, this joint analysis will constrain the dark energy equation of state with marginalised $1\sigma$ uncertainties of $\sigma(w_0)$~0.005 and $\sigma(w_a)$~0.04. This is comparable to or better than forecasts for future galaxy/intensity mapping surveys, and better constraints are possible when combining these and other future probes with gravitational waves. We find that combining mergers with and without an electromagnetic counterpart helps break parameter degeneracies. Using DeciHz detectors in the post-LISA era, we demonstrate for the first time how merging binaries could achieve a precision on the sum of neutrino masses of $\sigma(\Sigma m_{\nu})$~0.05 eV using $3\times10^6$ sources up to $z=3.5$ with a distance uncertainty of $1\%$, and ~percent or sub-percent precision also on curvature, dark energy, and other parameters, independently from other probes. Finally, we demonstrate how the cosmology dependence in the redshift distribution of mergers can be exploited to improve dark energy constraints if the cosmic merger rate is known, instead of relying on measured distributions as is standard in cosmology. In the coming decades gravitational waves will become a formidable probe of both geometry and large scale structure.

Value network and firm performance: the role of knowledge distance and environmental uncertainty

PurposeThis study aims to empirically examine the relationships among perceived environmental uncertainty (EV), the level of knowledge distance (KD) and the impact of value network on firm performance.Design/methodology/approachThe quantitative analysis is based on data from 243 Chinese companies with engineering, procurement and construction (EPC) business in the context of the COVID-19 pandemic.FindingsThe two dimensions of value network [network centrality (NC) and network openness (NO)] have a different impact on firm performance [financial performance (FP) and market performance (MP)]. NC has a positive impact on FP, but not on MP. NO has a positive effect on MP, but not on FP. A reduced KD mediates the relationship between value network and firm performance. Moreover, it fully mediates the relationship between NC and MP, NO and FP. Finally, during the COVID-19 pandemic, only EV has a moderating effect on KD and MP.Research limitations/implicationsThis study is limited in terms of data set because it relies on a limited amount of cross-sectional data from one specific country. Therefore, researchers are encouraged to test the proposed propositions further.Practical implicationsThe present findings suggest that EPC professionals should pay more attention to the EV, which may be impacted by policy, technology and the economy. This research has actionable implications for the reform of EPC in the construction industry, and practical recommendations for EPC firms to improve their corporate performance.Originality/valueThe results measure the complementary effects of both dimensions of value network (NC and NO) on two distinct aspects of firm performance (MP and FP) and assess the moderating effect of EV and KD in the context of the COVID-19 pandemics.

An adaptive Gaussian process based manifold transfer learning to expensive dynamic multi-objective optimization

Expensive dynamic multi-objective optimization problems (EDMOPs) is one kind of DMOPs where the objectives change over time and the function evaluations commonly involve computationally intensive simulations or costly physical experiments. Hence, the key to solve EDMOPs is to quickly and accurately track the time-varying Pareto optimal fronts under the limit of small number of function evaluations, in which how to augment enough training data to build informative surrogate models and manage the models during the search process. To overcome the issue, we propose a transfer learning based surrogate assisted evolutionary algorithm (TrSA-DMOEA) to efficiently solve EDMOPs. Specifically, when a change occurs, we propose a knee point-based manifold transfer learning method based on geodesic flow kernel, which exploits the knowledge from previous high-quality knee solutions to augment the training data for building Gaussian process models, thereby improving the computational complexity and the quality of solutions. Moreover, to efficiently find the optima with limited budget of function evaluations, a novel surrogate-assisted mechanism based on an adaptive acquisition function is introduced, which achieves a balance between convergence and diversity by adaptively adjusting the weights of the angle-penalized distance and average uncertainty at different search stages. By comparing with state-of-the-art algorithms on widely used test problems, the experimental results demonstrate that the proposed method outperforms others and is able to efficiently solve EDMOPs.

Empirical Distance Metrics Relationships and Uncertainties in Seismic Hazard Assessment

ABSTRACTThe seismic hazard of an area is determined based on the ground motion observed at that site. The intensity of the ground motion can be predicted using ground -motion models (GMMs). GMMs typically use distance metrics such as the Joyner–Boore distance (RJB) and the rupture distance (RRUP). However, apart from RJB and RRUP, probabilistic seismic hazard analysis (PSHA) also utilizes point-source-based distances like the epicentral distance (REPI) and the hypocentral distance (RHYP). These distance metrics are used for point sources when the fault geometry is unknown or is ignored. To obtain an accurate seismic hazard of an area, we need to determine the relationship between the distance metrics. In this study, we develop empirical relationships between RJB and various other distance metrics. This method avoids conducting computationally intensive tasks such as computing finite-fault-based distances for different fault geometry of a virtual rupture plane for each point source. The empirical equations provide the relation between RJB and target distance metric (Rtarget) based on the magnitude of the earthquake and the dip angle of the fault. In addition, we also require the depth to the top of the rupture to calculate RHYP. We discuss the steps to include the variability due to the conversion of the distance metrics in the PSHA. We have compared the results of this study with other published studies for distance conversion. A simple PSHA study of a circular area of 100 km using Pezeshk et al. (2011) as the GMM determined an increase in hazard using the proposed empirical equations and their uncertainties. The equations developed in this study can be directly applied in PSHA and are independent of the GMMs used for seismic hazard calculations. The equations can also be used for different fault geometries with a range of dip angles varying from 10° to 90°, for magnitudes 5.0–8.0, and distances up to 200 km. We have focused on the central and eastern United States.

Observational constraints of an anisotropic boost due to the projection effects using redMaPPer clusters

ABSTRACT Optical clusters identified from red-sequence galaxies suffer from projection effects, where interloper galaxies along the line of sight to a cluster are mistaken as genuine members of the cluster. In the previous study, we found that the projection effects cause the boost on the amplitudes of clustering and lensing on large scale compared to the expected amplitudes in the absence of any projection effects. These boosts are caused by preferential selections of filamentary structure aligned to the line of sight due to distance uncertainties in photometric surveys. We model the projection effects with two simple assumptions and develop a novel method to quantify the size of the boost using cluster-galaxy cross-correlation functions. We validate our method using mock cluster catalogues built from cosmological N-body simulations and find that we can obtain unbiased constraints on the boost parameter with our model. We then apply our analysis on the SDSS redMaPPer clusters and find that the size of the boost is roughly 20 per cent for all the richness bins except the cluster sample with the richness bin λ ∈ [30, 40]. This is the first study to constrain the boost parameter independent from cluster cosmology studies and provides a self-consistency test for the projection effects.

International retailer performance: Disentangling the interplay between rule of law and culture

Understanding the complexity of institutional factors in host countries and adapting strategies accordingly is crucial for international retailers, given the high failure rate of global operations. This paper investigates the impact of formal institutions (i.e., legal environments) and informal institutions (i.e., cultural values) on the performance of international retailers. We analyzed the data on 144 international retailers and 565 subsidiaries owned by these retailers, using three measures of retailer performance: sales per square meter, return on equity, and Tobin's Q. Our findings show that retailer performance is influenced by the interactions of the host country's rule of law and three cultural dimensions. Specifically, strong rule of law enhances the performance of international retailers in host countries, especially with high power distance or high uncertainty avoidance. In highly collectivistic countries, retailers can also build strong relationships to govern transactions. Results provide key insights that explain international retailers’ performance in different countries and deliver guidelines for retailer strategies.

A Three-dimensional Map of the Milky Way Using 66,000 Mira Variable Stars

We study the three-dimensional structure of the Milky Way using 65,981 Mira variable stars discovered by the Optical Gravitational Lensing Experiment survey. The spatial distribution of the Mira stars is analyzed with a model containing three barred components that include the X-shaped boxy component in the Galactic center (GC) and an axisymmetric disk. We take into account the distance uncertainties by implementing the Bayesian hierarchical inference method. The distance to the GC is R 0 = 7.66 ± 0.01(stat.) ± 0.39(sys.) kpc, while the inclination of the major axis of the bulge to the Sun–GC line of sight is θ = 20.°2 ± 0.°6(stat.) ± 0.°7(sys.). We present, for the first time, a detailed three-dimensional map of the Milky Way composed of young and intermediate-age stellar populations. Our analysis provides independent evidence for both the X-shaped bulge component and the flaring disk (being plausibly warped). We provide the complete data set of properties of Miras that were used for calculations in this work. The table includes mean brightness and amplitudes in nine photometric bands (covering a range of wavelengths from 0.5 to 12 μm), photometric chemical type, estimated extinction, and calculated distance with its uncertainty for each Mira variable. The median distance accuracy to a Mira star is at the level of 6.6%.

Mapping of Destructive Tectonic Earthquakes in the West Nusa Tenggara (NTB) Region Based on the Zhao Attenuation Function

NTB is a group of small islands located between the earthquake zone, namely in the south there is a subduction zone of the Eurasian and Indo-Australian plates and in the north, there is a back-arc fault or Flores Thrust. Earthquakes in this area are very active in the form of shallow tectonic earthquakes of large magnitude, so the risk of disaster is very high. Based on this, our research aims to map the distribution of destructive earthquakes using the attenuation function Zhao, released in 2006. The Zhao attenuation function has been applied to earthquake sources in subduction zones which are inputs for seismic hazards in various parts of the world, because the distance uncertainty factor used has better accuracy. The distribution of earthquake epicenter points in the West Nusa Tenggara region is clustered in four places, namely the Eurasian and Indo-Australian plate subduction zones in the sea south of the West Nusa Tenggara islands, the non-volcanic zone to the south of the West Nusa Tenggara islands, the volcanic zone to the east, and the Back Arc Thrust zone in the waters north of the NTB islands. Meanwhile, the hypocenter distribution is spread majorly on the Eurasian plate. Most of the islands of West Nusa Tenggara are characterized on the MMI VII-VIII intensity scale, and only a small part is characterized on the V-VI MMI intensity scale. The implications of the results of this research are useful in disaster mitigation, so it is hoped that there will be a reduction in disaster risk.

СИСТЕМНІ АСПЕКТИ НАВЧАННЯ В УМОВАХ НЕВИЗНАЧЕНОСТІ

The article reveals the systemic aspects of educational, scientific and applied activities on the example of the discipline Highway construction during the training of specialists for the transport and road complex in the direction of "Airports, airfield structures and facilities" and "System analysis in transport infrastructure" and the practice of applying distance learning in the conditions uncertainty caused by the introduction of martial law. The presented author's model is based on the principles of establishing a mechanism for the systematic implementation of the competence approach and the application of innovative technologies of remote asynchronous learning, which was obtained in the process of analyzing domestic and foreign experience under the conditions of uncertainty of the state of war. The object of the research is educational-scientific-applied activity in studying the discipline Construction of highways and airfields from cement concrete, in the conditions of distance learning and uncertainty in the conditions of war. The purpose of the work is to establish a mechanism for the systematic implementation of the competence approach and the application of innovative technologies for the "teacher-student-employer" relationship, which ultimately allows to determine the most effective ways and means of achieving the ultimate goals of educational, scientific and applied activities in the conditions of uncertainty of the introduction of martial law and provision of highly qualified personnel to the transport and road complex of the country. Research methods are systemic, conceptual-methodological and programmatic approaches. Establishing a mechanism for the application of innovative technologies for the model "learning methods - learning results - evaluation" according to the competence algorithm "knowledge of theory - the ability to apply it - the ability to master technologies" to strengthen the relationship "teacher - student - employer" will make it possible to bring the results of the educational process to requirements of employers and provide the transport and road complex with highly qualified personnel. Further development of the object of research is the introduction of educational, scientific and applied activities of teachers to provide highly qualified personnel for the transport and road complex in the conditions of distance learning and the uncertainty of martial law.

How National Culture Influences the Speed of COVID-19 Spread: Three Cross-Cultural Studies.

The COVID-19 pandemic has affected 222 countries and territories around the globe. Notably, the speed of COVID-19 spread varies significantly across countries. This cross-cultural research proposes and empirically examines how national culture influences the speed of COVID-19 spread in three studies. Study 1 examines the effects of Hofstede's national cultural dimensions on the speed of COVID-19 spread in 60 countries. Drawing on the GLOBE study (House et al., 2004), Study 2 investigates how GLOBE cultural dimensions relate to the speed of the pandemic's spread in 55 countries. Study 3 examines the effect of cultural tightness in 31 countries. We find that five national cultural dimensions - power distance, uncertainty avoidance, humane orientation, in-group collectivism, and cultural tightness - are significantly related to the speed of COVID-19 spread in the initial stages, but not in the later stages, of the pandemic. Study 1 shows that the coronavirus spreads faster in countries with small power distance and strong uncertainty avoidance. Study 2 supports these findings and further reveals that countries with low humane orientation and high in-group collectivism report a faster spread of the disease. Lastly, Study 3 shows that COVID-19 spreads slower in countries with high cultural tightness.

Premerger localization of intermediate mass binary black holes with LISA and prospects of joint observations with Athena and LSST

The planned Laser Interferometric Space Antenna (LISA) will be able to detect gravitational waves (GWs) from intermediate mass binary black holes (IMBBHs) in the mass range $\sim 10^{2} \mbox{-} 10^{4}\,M_{\odot}$ up to a redshift $z\sim20$. Modulation effects due to orbital motion of LISA around the Sun facilitate precise premerger localization of the sources, which in turn would help in electromagnetic (EM) followups. In this work, we calculate the uncertainties in sky position, luminosity distance, and time of coalescence as a function of time to coalescence. For representative masses of the IMBBHs, we synthesize a population of binaries uniformly located and oriented on a sphere of radius 3 Gpc and compute the projected parameter measurement uncertainties using the Fisher information matrix. We find that for systems with a total mass of $10^3\,M_{\odot}$, the errors in the sky position and luminosity distance are $\sim 0.4\,\text{deg}^2$ and $\sim 6\%$, respectively, one day prior to coalescence. The coalescence time can be predicted with an uncertainty $\lesssim 10$ sec, one day before coalescence. We also find that for $10^3\,M_{\odot}$, around $40\%$ ($100\%$) of the population has a source localization that is smaller than the field of view of Athena (LSST) one day before the merger. These extremely precise measurements can be used to alert ground-based GW detectors and EM telescopes about the time and location of these mergers. We also discuss mechanisms that may produce EM emission from IMBBH mergers and study its detectability using the planned Legacy Survey of Space and Time (LSST) in the optical and Athena in the x-ray bands. Detection of an EM transient may provide us vital clues about the environments where these mergers occur and the distance estimation can pave the way for cosmography.

Generation Z's expectations of their leaders: A cross-cultural, multi-dimensional investigation of leadership styles.

Gen Z representatives from one Western and one Eastern European country were the subjects of an empirical study investigating leadership style preferences and effects of motivation and performance on leader preferences. Data from 131 Ukrainian and 157 Austrian Gen Z representatives were analyzed. Different dimensions of leadership were examined, including transactional/transformational leadership and production/employee/change orientation of leaders. The results show significant differences in expectations between cultures, and within different leadership styles. Generation Z representatives from collectivist cultures with high power distance, long-term orientation, and high uncertainty avoidance have higher expectations of their future leaders than those from individualistic countries with lower power distance, less long-term orientation, and low uncertainty avoidance. A higher level of work motivation leads to a higher relevance of transformational, transactional pecuniary, and transactional non-pecuniary leadership styles in a collectivist, uncertainty-avoiding country with high power distance (Ukraine), while there is no effect in an individualistic country with low uncertainty avoidance and low power distance (Austria). Also, higher levels of work motivation lead to more appreciation of employee / production / change orientation in Ukraine, but only to higher levels of employee orientation in Austria. High performers in Austria tend to accept transactional sanction-based leadership, while this is not the case in Ukraine. In general, generations that may be described as universally similar have different perceptions depending on the culture they grew up in. For business leaders, the study provides insights into Gen Z employees and their leadership expectations. Managers from different business sectors working with employees from different cultural backgrounds should be aware of their employees’ different expectations. Recruiters will eventually have a better understanding of which arguments regarding leadership their future employees prefer and can adjust their recruitment messages accordingly.

Restricted shares and CSR: Evidence from foreign strategic investors in China

Using hand-collected ownership data from a large sample of Chinese listed firms, we examine the link between foreign strategic ownership and firms' corporate social responsibility (CSR). We find that foreign strategic ownership is significantly associated with greater CSR performance. The restrictions of shares are the main motivation behind foreign strategic investors (FSIs) increasing firms' CSR engagement. The influence of foreign ownership on CSR is driven by strategic investors with non-tradable shares, but not by Qualified Foreign Institutional Investors (QFIIs) with tradable shares. FSIs with longer restriction horizons and in firms with stronger political connections are found to have more pronounced effects on CSR. We also find FSIs' home country characteristics, including the legal system, cultural background, geographic distance, trade relationship, and economic policy uncertainty, are significant factors in explaining their incentives to increase firm CSR in China. From the perspective of corporate governance, we find that the impacts of FSIs on firms' CSR performance is more pronounced when shareholder power is stronger and executive power is weaker in the firm. Difference-in-differences tests and tests based on instrumental variables provide confirming evidence. Overall, our findings suggest that restricted ownership, political connections, and foreign investors' home country characteristics provide incentives for FSIs to pay more attention to firms' long-term reputation and thus enhance CSR engagement.

Revisiting the measurement of absolute foil-separation for RDDS measurements and introduction of an optical measurement method

Uncertainties in absolute plunger distances are an often overlooked component in measurements with the Recoil Distance Doppler-shift (RDDS) method when the Differential Decay Curve (DDC) method cannot be used for the analysis. It is shown how these uncertainties arise when the capacitance method is used to determine absolute distances and how they influence the obtained lifetime values of a plunger experiment. Furthermore, a new approach to obtain absolute foil separations for plunger measurements using a high precision optical distance probe is introduced, which can reduce these uncertainties by a large margin. The performance of this method is demonstrated by comparisons to the capacitance method as well as to a precise measurement of absolute distances using known lifetimes in 181Ta.

Modeling distance uncertainties in two-dimensional space

Distances are functions of spatial positions, therefore distance uncertainties should be resulted from transmission of spatial position uncertainties via the functional relationships accordingly. How to model the transmission precisely, a challenging problem in GIScience, has increasingly drawn attentions during the past several decades. Aiming at the limitations of presently available solutions to the problem, this article derived probability distribution functions and corresponding density functions of distance uncertainties in two-dimensional space related to one or two uncertain endpoints respectively, under the premise that real positions, corresponding with the observed position of an uncertain point, follow the kernel function within its error circle. The density functions were employed to explore the diffusing law of uncertainty information from point positions to distances, which opened up a new way for thoroughly solving problems of measuring distance uncertainties. It turns out that the proposed methods in this article are more efficient, robust than the corresponding Monte Carlo ones, which verifies their effectiveness and advantages.

Searching the SETI Ellipsoid with Gaia

The search for extraterrestrial intelligence (SETI) Ellipsoid is a geometric method for prioritizing technosignature observations based on the strategy of receiving signals synchronized to conspicuous astronomical events. Precise distances to nearby stars from Gaia makes constraining Ellipsoid crossing times possible. Here we explore the utility of using the Gaia Catalog of Nearby Stars to select targets on the SN 1987A SETI Ellipsoid, as well as the Ellipsoids defined by 278 classical novae. Less than 8% of stars within the 100 pc sample are inside the SN 1987A SETI Ellipsoid, meaning the vast majority of nearby stars are still viable targets for monitoring over time. We find an average of 734 stars per year within the 100 pc volume will intersect the Ellipsoid from SN 1987A, with ∼10% of those having distance uncertainties from Gaia better than 0.1 lyr.