Flux-ratio anomalies from discs and other baryonic structures in the Illustris simulation

The flux ratios in the multiple images of gravitationally lensed quasars can provide evidence for dark matter substructure in the halo of the lensing galaxy if the flux ratios differ from those predicted by a smooth model of the lensing galaxy mass distribution. However, it is also possible that baryonic structures in the lensing galaxy, such as edge-on discs, can produce flux-ratio anomalies. In this work, we present the first statistical analysis of flux-ratio anomalies due to baryons from a numerical simulation perspective. We select galaxies with various morphological types in the Illustris simulation and ray-trace through the simulated halos, which include baryons in the main lensing galaxies but exclude any substructures, in order to explore the pure baryonic effects. Our ray-tracing results show that the baryonic components can be a major contribution to the flux-ratio anomalies in lensed quasars and that edge-on disc lenses induce the strongest anomalies. We find that the baryonic components increase the probability of finding high flux-ratio anomalies in the early-type lenses by about 8% and by about 10 - 20% in the disc lenses. The baryonic effects also induce astrometric anomalies in 13% of the mock lenses. Our results indicate that the morphology of the lens galaxy becomes important in the analysis of flux-ratio anomalies when considering the effect of baryons, and that the presence of baryons may also partially explain the discrepancy between the observed (high) anomaly frequency and what is expected due to the presence of subhalos as predicted by the CDM simulations.Comment: 16 pages, 11 figures, accepted by MNRA

Managing scheduled routing with a high-level communications language

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 152-156).by Christopher D. Metcalf.Ph.D

Collisional Control of Ground State Polar Molecules and Universal Dipolar Scattering

We explore the impact of the short range interaction on the scattering of ground state polar molecules, and study the transition from a weak to strong dipolar scattering over an experimentally reasonable range of energies and electric field values. In the strong dipolar limit, the scattering scales with respect to a dimensionless quantity defined by mass, induced dipole moment, and collision energy. The scaling has implications for all quantum mechanical dipolar scattering, and therefore this universal dipolar scaling provides estimates of scattering cross sections for any dipolar system.Comment: 4 pages, 2 figure

Identifying strong lenses with unsupervised machine learning using convolutional autoencoder

In this paper, we develop a new unsupervised machine learning technique comprised of a feature extractor, a convolutional autoencoder, and a clustering algorithm consisting of a Bayesian Gaussian mixture model. We apply this technique to visual band space-based simulated imaging data from the Euclid Space Telescope using data from the strong gravitational lenses finding challenge. Our technique promisingly captures a variety of lensing features such as Einstein rings with different radii, distorted arc structures, etc., without using predefined labels. After the clustering process, we obtain several classification clusters separated by different visual features which are seen in the images. Our method successfully picks up 3c63 per cent of lensing images from all lenses in the training set. With the assumed probability proposed in this study, this technique reaches an accuracy of 77.25 \ub1 0.48 per cent in binary classification using the training set. Additionally, our unsupervised clustering process can be used as the preliminary classification for future surveys of lenses to efficiently select targets and to speed up the labelling process. As the starting point of the astronomical application using this technique, we not only explore the application to gravitationally lensed systems, but also discuss the limitations and potential future uses of this technique

Brown Dwarfs in Young Moving Groups from Pan-STARRS1. I. AB Doradus

Substellar members of young ($\lesssim$150 Myr) moving groups are valuable benchmarks to empirically define brown dwarf evolution with age and to study the low-mass end of the initial mass function. We have combined Pan-STARRS1 (PS1) proper motions with optical$-$IR photometry from PS1, 2MASS and $\textit{WISE}$ to search for substellar members of the AB Dor Moving Group within $\approx$50 pc and with spectral types of late-M to early-L, corresponding to masses down to $\approx$30 M$_{Jup}$ at the age of the group ($\approx$125 Myr). Including both photometry and proper motions allows us to better select candidates by excluding field dwarfs whose colors are similar to young AB~Dor Moving Group members. Our near-IR spectroscopy has identified six ultracool dwarfs (M6$-$L4; $\approx$30$-$100 M$_{Jup}$) with intermediate surface gravities (INT-G) as candidate members of the AB Dor Moving Group. We find another two candidate members with spectra showing hints of youth but consistent with field gravities. We also find four field brown dwarfs unassociated with the AB Dor Moving Group, three of which have INT-G gravity classification. While signatures of youth are present in the spectra of our $\approx$125 Myr objects, neither their $J-K$ nor $W1-W2$ colors are significantly redder than field dwarfs with the same spectral types, unlike younger ultracool dwarfs. We also determined PS1 parallaxes for eight of our candidates and one previously identified AB Dor Moving Group candidate. Although radial velocities (and parallaxes, for some) are still needed to fully assess membership, these new objects provide valuable insight into the spectral characteristics and evolution of young brown dwarfs.Comment: ApJ, accepte

The Transverse Peculiar Velocity of the Q2237+0305 Lens Galaxy and the Mean Mass of Its Stars

Using 11-years of OGLE V-band photometry of Q2237+0305, we measure the transverse velocity of the lens galaxy and the mean mass of its stars. We can do so because, for the first time, we fully include the random motions of the stars in the lens galaxy in the analysis of the light curves. In doing so, we are also able to correctly account for the Earth's parallax motion and the rotation of the lens galaxy, further reducing systematic errors. We measure a lower limit on the transverse speed of the lens galaxy, v_t > 338 km/s (68% confidence) and find a preferred direction to the East. The mean stellar mass estimate including a well-defined velocity prior is 0.12 <= 1.94 at 68% confidence, with a median of 0.52 Msun. We also show for the first time that analyzing subsets of a microlensing light curve, in this case the first and second halves of the OGLE V-band light curve, give mutually consistent physical results.Comment: 11 pages, 9 figures, 1 table; animated magnification pattern video can be found at http://www.astronomy.ohio-state.edu/~sdp/animation.avi; accepted for publication in Ap

Exploring Ecosystems from the Inside: How Immersive Multi-user Virtual Environments Can Support Development of Epistemologically Grounded Modeling Practices in Ecosystem Science Instruction

Recent reform efforts and the next generation science standards emphasize the importance of incorporating authentic scientific practices into science instruction. Modeling can be a particularly challenging practice to address because modeling occurs within a socially structured system of representation that is specific to a domain. Further, in the process of modeling, experts interact deeply with domain-specific content knowledge and integrate modeling with other scientific practices in service of a larger investigation. It can be difficult to create learning experiences enabling students to engage in modeling practices that both honor the position of the novice along a spectrum toward more expert understanding and align well with the practices and reasoning used by experts in the domain. In this paper, we outline the challenges in teaching modeling practices specific to the domain of ecosystem science, and we present a description of a curriculum built around an immersive virtual environment that offers unique affordances for supporting student engagement in modeling practices. Illustrative examples derived from pilot studies suggest that the tools and context provided within the immersive virtual environment helped support student engagement in modeling practices that are epistemologically grounded in the field of ecosystem science

EcoMOBILE – Designing for contextualized STEM learning using mobile technologies and augmented reality

The ubiquity of mobile technologies can unlock new opportunities for “anytime, anywhere” learning, and some argue that portable mobile platforms will inherently lead to more contextualized learning experiences. However, the meaning of contextualization and how to achieve it in mobile designs bears further examination, as the greater the level of contextualization, the more difficult it may be to scale mobile designs. Context is a product of the interaction among learners, the personal, social and physical resources at hand, and mobile technologies. We examine how, through the affordances of mobile technologies, designers might emphasize different aspects of social and physical context in order to support learning. In particular, augmented reality enables students to interact—via mobile wireless devices—with virtual information, visualizations, and simulations superimposed on real-world physical landscapes. The EcoMOBILE activity considered here involved student participation in an outdoor field trip near their school using mobile broadband devices running augmented reality software. We present a case study highlighting two designs focused on a similar middle- grades science learning goal of exploring the local watershed – a place-dependent, collaborative design (“Take a Tour”) and a place-independent, individual design (“Follow the Flow”). We implemented these designs with two different teachers each with four classes of students. We present detailed comparison of the design logic and features of each experience, and a summary of feedback from interviews and student focus groups with attention to feelings of contextualization, engagement and support for learning. Our results showed little difference in student comments related to the contextualization of the experience, which suggests that carefully constructed, yet minimalist designs may support a perception of contextualization that comes from the perspective of the user rather than from the device. A place-independent mobile learning experience may, with minimal modification, be used in a location other than the one in which it was designed, and may still have positive effects on feelings of contextualization, engagement and support for learning among participants

Teacher Perceptions of the Practicality and Effectiveness of Immersive Ecological Simulations as Classroom Curricula

Recent research with Multi-User Virtual Environments (MUVEs) in education has shown that these platforms can be effective and engaging for students; however, educators and administrators have practical concerns about the adoption of MUVE-based curricula. This study looks at implementations of EcoMUVE, a MUVE-based curriculum designed to support middle school learning of ecosystem concepts and processes. Research questions looked at teacher perceptions of the curriculum’s implementation feasibility, alignment with curricular objectives and standards, and perceived value. Results showed that EcoMUVE was very well-received, and technical issues were manageable. Teachers felt the curriculum was effective, aligned well with standards, and compared favorably with a non-MUVE alternative. Particular technological and curriculum features that contributed to EcoMUVE’s perceived value included student-directed learning, an inquiry, role-based pedagogy, immersion in the virtual environment, and the ease of collecting and comparing data with graphs

Atom tracker: Designing a mobile augmented reality experience to support instruction about cycles and conservation of matter in outdoor learning environments

We describe a mobile augmented reality (AR) experience called Atom Tracker designed to help middle school students better understand the cycling of matter in ecosystems with a focus on the concept of conservation of matter and the processes of photosynthesis and respiration. Location-based AR allows students to locate virtual "hotspots," where they interact with multiple representations including vision-based AR animations of virtual atoms during ecological processes such as photosynthesis and physical LEGO® -based representations of molecules. This design case describes the design rationale, the iterative design process, the context for implementation, and reflections on the success and limitations of the Atom Tracker AR experience. An augmented reality interface was chosen due to theoretical support for its utility in supporting interaction with multiple representations (both physical and virtual) of atoms and molecules, the ability to condense and expand temporal and spatial scales associated with ecological processes, and its ability to explicitly situate these representations in real-world contexts that could support learning. Two significant design challenges that we recognized were (a) appropriately leveraging narrative, student engagement and agency when designing around the topic of atoms and molecules, which are inanimate and invisible; and (b) designing for engagement with both virtual and physical resources available during the experience