Action-space clustering of tidal streams to infer the Galactic potential

We present a new method for constraining the Milky Way halo gravitational potential by simultaneously fitting multiple tidal streams. This method requires full three-dimensional positions and velocities for all stars to be fit, but does not require identification of any specific stream or determination of stream membership for any star. We exploit the principle that the action distribution of stream stars is most clustered when the potential used to calculate the actions is closest to the true potential. Clustering is quantified with the Kullback-Leibler Divergence (KLD), which also provides conditional uncertainties for our parameter estimates. We show, for toy Gaia-like data in a spherical isochrone potential, that maximizing the KLD of the action distribution relative to a smoother distribution recovers the true values of the potential parameters. The precision depends on the observational errors and the number of streams in the sample; using KIII giants as tracers, we measure the enclosed mass at the average radius of the sample stars accurate to 3% and precise to 20-40%. Recovery of the scale radius is precise to 25%, and is biased 50% high by the small galactocentric distance range of stars in our mock sample (1-25 kpc, or about three scale radii, with mean 6.5 kpc). About 15 streams, with at least 100 stars per stream, are needed to obtain upper and lower bounds on the enclosed mass and scale radius when observational errors are taken into account; 20-25 streams are required to stabilize the size of the confidence interval. If radial velocities are provided for stars out to 100 kpc (10 scale radii), all parameters can be determined with 10% accuracy and 20% precision (1.3% accuracy in the case of the enclosed mass), underlining the need for ground-based spectroscopic follow-up to complete the radial velocity catalog for faint halo stars observed by Gaia.Comment: Accepted versio

Intending to be ethical: An examination of consumer choice in sweatshop avoidance

While much research in ethical consumption has focused on contexts such as food, this research explores ethical consumer decision-making in the context of intention to avoid sweatshop apparel. This research seeks to deepen the Theory of Planned Behavior with respect to the motivation and volitional stages underlying behavior. The findings of the research, based on 794 consumers, are novel and support an enriched framework which reveals that the role of attitude, subjective norm and perceived behavioral control are mediated by desire, intention and plan. The findings have implications for research seeking to address the ‘intention-behavior’ gap

The dependence on morphology of the gas content in galactic disks

The classification S0 was introduced by Hubble to serve as a description of galaxies whose morphological characteristics seemed to lie between the disk-dominated spirals and the spheroidal elliptical systems. Since then there has been extensive discussion as to whether this classification sequence is also an evolutionary sequence. Many studies have focussed on a particular feature such as the luminosity profile, the bulge-to-disk ratio, or the nature of the interstellar matter, but the question of the evolution remains contentious. Equally contentious is the question of the classification itself. For systems with well-developed disks there usually is no problem. Many spheroidal systems also are unambiguously classified as ellipticals in most catalogs. However, there are a number of early systems which have been reclassified following review using improved optical material. For example, Eder et al. (AJ, 102, 572, 1991) found that many of the S0 galaxies which are rich in neutral hydrogen have faint spiral features. The confusion about classification propagates into the discussion of the properties of early-type systems. Attempts to put the classification system on a quantitative basis have in general been unsuccessful. Recently Sandage (private communication) has reviewed the classification of early systems and has defined a set of sub-classes for these objects. The S0 galaxies are divided into three groups, depending on the prominence of the disk. There are six subdivisions of Sa galaxies, depending upon the relative prominence of knots and other arm-like characteristics. We have explored the total gas content in these objects to see if there is a dependence on the galaxy morphology, as denoted by these new subclasses

A feasibility study for a remote laser water turbidity meter

A technique to remotely determine the attenuation coefficient (alpha) of the water was investigated. The backscatter energy (theta = 180 deg) of a pulse laser (lambda = 440 - 660 nm) was found directly related to the water turbidity. The greatest sensitivity was found to exist at 440 nm. For waters whose turbidity was adjusted using Chesapeake Bay sediment, the sensitivity in determining alpha at 440 nm was found to be approximately 5 - 10%. A correlation was also found to exist between the water depth (time) at which the peak backscatter occurs and alpha

A List of Wisconsin Springtails With New Records and Annotations (Hexapoda: Parainsecta: Collembola)

Twenty Collembola species new to Wisconsin were collected from soil at two agricultural sites in southern Wisconsin, including an undescribed species of Isotomidae. The state faunal list now contains 52 species representing seven families

A maximum-likelihood method to improve faint source flux and color estimates

Flux estimates for faint sources or transients are systematically biased high because there are far more truly faint sources than bright. Corrections which account for this effect are presented as a function of signal-to-noise ratio and the (true) slope of the faint-source number-flux relation. The corrections depend on the source being originally identified in the image in which it is being photometered. If a source has been identified in other data, the corrections are different; a prescription for calculating the corrections is presented. Implications of these corrections for analyses of surveys are discussed; the most important is that sources identified at signal-to-noise ratios of three or less are practically useless

Wide-Field Imaging from Space of Early-Type Galaxies and Their Globular Clusters

Wide-field imaging from space will reveal a wealth of information about the globular cluster systems of any galaxies in the local universe that are observed by such a mission. Individual globular clusters around galaxies in the local universe have compact sizes that are ideal for the excellent spatial resolution afforded by space-based imaging, while systems of these globular clusters have large spatial extent that can only be fully explored by wide-field imaging. One example of the science return from such a study is the determination of the major formation epoch(s) of galaxies from the ages of their globular clusters determined via their optical to near-infrared colors. A second example is determining the sites of metal-poor globular cluster formation from their cosmological bias, which constrains the formation of structures early in the universe.Comment: To appear in the conference proceedings of "Wide Field Imaging from Space" published in New Astronomy Reviews, eds. T. McKay, A. Fruchter, & E. Linde

A self-directed learning intervention for radiographers rating mammographic breast density

Purpose: Subjective methods of mammographic breast density (MBD) assessment are prone to inter-reader variability. This work aims to assess the impact of a short self-directed experiential learning intervention on radiographers’ reproducibility of MBD assessment. Method: The study used two sets of images (test and learning intervention) containing left craniocaudal and left mediolateral oblique views. The test set had MBD ratings from VolparaTM and radiologists using the fourth edition Breast Imaging and Data Systems (BI-RADS®). Seven radiographers rated the MBD of the test set before and after a self-directed learning intervention using the percentage descriptors in the fourth edition BI-RADS® Atlas. The inter-reader agreement, agreement between radiographers and VolparaTM as well as radiologist, was assessed using a Weighted Kappa (Kw). Results: Overall, radiographers’ inter-reader agreement (Kw) was substantial (0.79; 95%CI: 0.70–0.87) before the intervention and almost perfect (0.84; 95%CI: 0.77–0.90) after the intervention. Before the intervention, radiographers demonstrated fair agreement with radiologists (0.24; 95%CI:-0.46–0.61) and VolparaTM (0.24; 95% CI: -0.41–0.59). A fair but slightly improved agreement was also observed between radiographers and radiologists (0.31; 95% CI: -0.33 - 0.64) as well as VolparaTM (0.28; 95% CI: -0.34- 0.61) after the intervention. Conclusion: Findings demonstrate that a short duration self-directed experiential learning intervention reduces inter-reader differences in MBD classification, but has a negligible impact on improving the agreement between inexperienced and expert readers