Observations of wind speed profiles over Greater London, UK, using a Doppler lidar

To calculate the potential wind loading on a tall building in an urban area, an accurate representation of the wind speed profile is required. However, due to a lack of observations, wind engineers typically estimate the characteristics of the urban boundary layer by translating the measurements from a nearby reference rural site. This study presents wind speed profile data obtained from a Doppler lidar in central London, UK, during an 8 month observation period. Used in conjunction with wind speed data measured at a nearby airport, the data have been used to assess the accuracy of the predictions made by the wind engineering tools currently available. When applied to multiple changes in surface roughness identified from morphological parameters, the non-equilibrium wind speed profile model developed by Deaves (1981) provides a good representation of the urban wind speed profile. For heights below 500 m, the predicted wind speed remains within the 95% confidence interval of the measured data. However, when the surface roughness is estimated using land use as a proxy, the model tends to overestimate the wind speed, particularly for very high wind speed periods. These results highlight the importance of a detailed assessment of the nature of the surface when estimating the wind speed above an urban surface

Resonance line-profile calculations based on hydrodynamical models of cataclysmic variable winds

We present synthetic line profiles as predicted by the models of 2-D line- driven disk winds due to Proga, Stone & Drew. We compare the model line profiles with HST observations of the cataclysmic variable IX Vel. The model wind consists of a slow outflow that is bounded on the polar side by a fast stream. We find that these two components of the wind produce distinct spectral features. The fast stream produces profiles which show features consistent with observations. These include the appearance of the P-Cygni shape for a range of inclinations, the location of the maximum depth of the absorption component at velocities less than the terminal velocity, and the transition from absorption to emission with increasing inclination. However the model profiles have too little absorption or emission equivalent width. This quantitative difference between our models and observations is not a surprise because the line-driven wind models predict a mass loss rate that is lower than the rate required by the observations. We note that the model profiles exhibit a double-humped structure near the line center which is not echoed in observations. We identify this structure with a non-negligible redshifted absorption which is formed in the slow component of the wind where the rotational velocity dominates over expansion velocity. We conclude that the next generation of disk wind models, developed for application to CVs, needs to yield stronger wind driving out to larger disk radii than do the present models.Comment: LaTeX, 19 pages, to appear in Ap

Should there be a female age limit on public funding for Assisted Reproductive Technology? Differing conceptions of justice in resource allocation

Should there be a female age limit on public funding for assisted reproductive technology (ART)? The question bears significant economic and sociopolitical implications and has been contentious in many countries. We conceptualise the question as one of justice in resource allocation, using three much-debated substantive principles of justice—the capacity to benefit, personal responsibility, and need—to structure and then explore a complex of arguments. Capacity-to-benefit arguments are not decisive: There are no clear cost-effectiveness grounds to restrict funding to those older women who still bear some capacity to benefit from ART. Personal responsibility arguments are challenged by structural determinants of delayed motherhood. Nor are need arguments decisive: They can speak either for or against a female age limit, depending on the conception of need used. We demonstrate how these principles can differ not only in content but also in the relative importance they are accorded by governments. Wide variation in ART public funding policy might be better understood in this light. We conclude with some inter-country comparison. New Zealand and Swedish policies are uncommonly transparent and thus demonstrate particularly well how the arguments we explore have been put into practice

Cygnus OB2 DANCe: A high-precision proper motion study of the Cygnus OB2 association

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.We present a high-precision proper motion study of 873 X-ray and spectroscopically selected stars in the massive OB association Cygnus OB2 as part of the DANCe project. These were calculated from images spanning a 15 yr baseline and have typical precisions <1 mas yr−1. We calculate the velocity dispersion in the two axes to be σα(c) = 13.0+0.8 −0.7 and σδ (c) = 9.1+0.5 −0.5 km s−1, using a two-component, two-dimensional model that takes into account the uncertainties on the measurements. This gives a three-dimensional velocity dispersion of σ3D = 17.8 ± 0.6 km s−1 implying a virial mass significantly larger than the observed stellar mass, confirming that the association is gravitationally unbound. The association appears to be dynamically unevolved, as evidenced by considerable kinematic substructure, non-isotropic velocity dispersions and a lack of energy equipartition. The proper motions show no evidence for a global expansion pattern, with approximately the same amount of kinetic energy in expansion as there is in contraction, which argues against the association being an expanded star cluster disrupted by process such as residual gas expulsion or tidal heating. The kinematic substructures, which appear to be close to virial equilibrium and have typical masses of 40– 400 M, also do not appear to have been affected by the expulsion of the residual gas. We conclude that Cyg OB2 was most likely born highly substructured and globally unbound, with the individual subgroups born in (or close to) virial equilibrium, and that the OB association has not experienced significant dynamical evolution since then.Peer reviewe

Population-based identification of H a-excess sources in the Gaia DR2 and IPHAS catalogues

We present a catalogue of point-like H a-excess sources in the Northern Galactic Plane. Our catalogue is created using a new technique that leverages astrometric and photomeric information from Gaia to select H a-bright outliers in the INT Photometric H a Survey of the Northern Galactic Plane (IPHAS), across the colour-absolute magnitude diagram. To mitigate the selection biases due to stellar population mixing and to extinction, the investigated objects are first partitioned with respect to their positions in the Gaia colour-absolute magnitude space, and Galactic coordinates space, respectively. The selection is then performed on both partition types independently.MM acknowledges the support by the Spanish Ministry of Science, Innovation and University (MICIU/FEDER, UE) through grant RTI2018-095076-B-C21, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ‘Mar ́ıa de Maeztu’) through grant CEX2019- 000918-MPostprint (published version

IGAPS: the merged IPHAS and UVEX optical surveys of the northern Galactic plane

The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i, r, narrow-band Ha, g, and URGO. The IGAPS footprint fills the Galactic coordinate range, |b| 5s confidence).Peer ReviewedPostprint (published version

Classification of Chandra X-Ray Sources in Cygnus OB2

© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We have devised a predominantly Naive Bayes−based method to classify X-ray sources detected by Chandra in the Cygnus OB2 association into members, foreground objects, and background objects. We employ a variety of X-ray, optical, and infrared characteristics to construct likelihoods using training sets defined by well-measured sources. Combinations of optical photometry from the Sloan Digital Sky Survey (riz) and Isaac Newton Telescope Photometric Hα Survey (r I i I Hα), infrared magnitudes from United Kingdom Infrared Telescope Deep Sky Survey and Two-Micron All Sky Survey (JHK), X-ray quantiles and hardness ratios, and estimates of extinction A v are used to compute the relative probabilities that a given source belongs to one of the classes. Principal component analysis is used to isolate the best axes for separating the classes for the photometric data, and Gaussian component separation is used for X-ray hardness and extinction. Errors in the measurements are accounted for by modeling as Gaussians and integrating over likelihoods approximated as quartic polynomials. We evaluate the accuracy of the classification by inspection and reclassify a number of sources based on infrared magnitudes, the presence of disks, and spectral hardness induced by flaring. We also consider systematic errors due to extinction. Of the 7924 X-ray detections, 5501 have a total of 5597 optical/infrared matches, including 78 with multiple counterparts. We find that ≈6100 objects are likely association members, ≈1400 are background objects, and ≈500 are foreground objects, with an accuracy of 96%, 93%, and 80%, respectively, with an overall classification accuracy of approximately 95%.Peer reviewe