Science with the Virtual Observatory: the AstroGrid VO Desktop

We introduce a general range of science drivers for using the Virtual Observatory (VO) and identify some common aspects to these as well as the advantages of VO data access. We then illustrate the use of existing VO tools to tackle multi wavelength science problems. We demonstrate the ease of multi mission data access using the VOExplorer resource browser, as provided by AstroGrid (http://www.astrogrid.org) and show how to pass the various results into any VO enabled tool such as TopCat for catalogue correlation. VOExplorer offers a powerful data-centric visualisation for browsing and filtering the entire VO registry using an iTunes type interface. This allows the user to bookmark their own personalised lists of resources and to run tasks on the selected resources as desired. We introduce an example of how more advanced querying can be performed to access existing X-ray cluster of galaxies catalogues and then select extended only X-ray sources as candidate clusters of galaxies in the 2XMMi catalogue. Finally we introduce scripted access to VO resources using python with AstroGrid and demonstrate how the user can pass on the results of such a search and correlate with e.g. optical datasets such as Sloan. Hence we illustrate the power of enabling large scale data mining of multi wavelength resources in an easily reproducible way using the VO.Comment: 8 pages; 7 figures; proceedings of invited talk at "Multi wavelength astronomy and the Virtual Observatory" conference, December 2008, EuroVO-AIDA program, European Space Astronomy Centre, Spai

Shocked molecular hydrogen in the Orion "bullets"

The physics of shocked outflows in molecular clouds is one of the fundamental astrophysical processes by which the cycle of star formation in our Galaxy is regulated. I outline the basis of our understanding of the star formation process and the violent outflow always associated with it, the physics of shocks in molecular gas, and the consequent excitation of molecular hydrogen (H₂). It is demonstrated th at molecular hydrogen is the best observational diagnostic of this hot, shocked molecular gas and an introduction is given to the observational techniques of near-infrared spectroscopy required in its measurement. I describe a detailed observational study of the physics of shocked H₂ excitation and dynamics in the nearby massive star forming region of the Orion giant molecular cloud, the brightest source of its type, using the recently upgraded CGS4 near-IR spectrometer at UKIRT.We have demonstrated that integrated [Fell] 1.644/im line profiles in the Orion '‘bullets'’ are consistent with theoretical bow-shock predictions for two different “bullets” . We have identified a uniform, broad background component pervading the region in both Fe+ and H., which is inconsistent with a fluorescent component due to the ionizing radiation of the Trapezium stars alone. A collisionally broadened background component of unidentified origin is measured to be Gaussian in profile with an average FW11M of 26±2.5kms_l in the II2 1-0 S(l) line after deconvolution of the instrumental profile and a peak velocity of 2.5±0.5kms- 1 , close to the local ambient rest velocity. Crucially, the extended H2 “bullet” wakes have allowed us to dissect individual molecular bow shock structures but the broad (intrinsic FWHM<27kms~ ), singly-peaked H2 1-0 S(l) profiles observed in the two most clearly resolved, plane-of-sky oriented wakes challenge our present understanding. It is very difficult to reconcile any steady-state molecular bow shock model with these observations in Orion. To fit a single C shock absorber model to individual II2 profiles implies a magnetic field strength far in excess of observed estimates and is not consistent with the bow-shaped wake morphology.We have demonstrated that integrated [Fell] 1.644/μm line profiles in the Orion '‘bullets'’ are consistent with theoretical bow-shock predictions for two different “bullets” . We have identified a uniform, broad background component pervading the region in both Fe⁺ and H₂ which is inconsistent with a fluorescent component due to the ionizing radiation of the Trapezium stars alone. A collisionally broadened background component of unidentified origin is measured to be Gaussian in profile with an average FW11M of 26±2.5kms⁻¹ in the H₂ 1-0 S(l) line after deconvolution of the instrumental profile and a peak velocity of 2.5±0.5kms⁻¹, close to the local ambient rest velocity. Crucially, the extended H₂ “bullet” wakes have allowed us to dissect individual molecular bow shock structures but the broad (intrinsic FWHM≤27kms⁻¹ ), singly-peaked H₂ I-0 S(l) profiles observed in the two most clearly resolved, plane-of-sky oriented wakes challenge our present understanding. It is very difficult to reconcile any steady-state molecular bow shock model with these observations in Orion. To fit a single C shock absorber model to individual H₂ profiles implies a magnetic field strength far in excess of observed estimates and is not consistent with the bow-shaped wake morphology.Alternatively, we may still not be resolving multiple H₂ shock fronts along the line-of-sight. For example, multiple overlapping bullet wakes could give rise to merged sets of doubly-peaked profiles resulting in approximately Gaussian shaped profiles. However. given the appearance of single bow shaped wakes at many observed positions, the accuracy of single Gaussian line-fits, the velocity resolution of our observations (FWHM =23.1±0.3kms⁻¹) and that we see this phenomenon in two different wakes, this explanation is expected to be excluded.If we cannot fit the profiles in Orion with steady state molecular shocks it may be necessary to model the effects of instabilities and turbulence. This will have important consequences. Not only will line profiles be broadened but level populations of shocked species will be altered and hence the observed column densities over a range of transitions.Observations of a range of H₂ column densities in the K band have confirmed the existence of a near-constant background excitation mechanism pervading the entire Orion “bullet's” region. The background H₂ emission can be modelled by a combination of fluorescent and shock excited mechanisms, in agreement with the broad H₂ line profiles observed. It is thermalized in the v= l levels but higher levels are dominated by fluorescence. Measurement of the H₂ excitation in the “bullet” wakes M42 HH126-053 and M12 H H120-114 shows a near constant emission spectrum, within each wake, that may be modelled by a. combination of shocked and fluorescent excitation, now more strongly dominated by collisional processes but also containing an intrinsic wake-only fluorescent component. The column density ratios clearly show a range of gas temperatures as expected for cooling, post-shock gas. Furthermore, the uniformity of these ratios on small-scales (these observations) and also on large scales, contradicts combinations of fundamentally different types of shock. However, the near constancy of this excitation with position within each individual wake is inconsistent with bow C shock models previously fitted at OMC-1, in which significantly different line ratios occur depending on the shock velocity which varies in the bow

Shocked H2 and Fe+ Dynamics in the Orion Bullets

Observations of H2 velocity profiles in the two most clearly defined Orion bullets are extremely difficult to reconcile with existing steady-state shock models. We have observed [FeII] 1.644um velocity profiles of selected bullets and H2 1-0 S(1) 2.122um velocity profiles for a series of positions along and across the corresponding bow-shaped shock fronts driven into the surrounding molecular cloud. Integrated [FeII] velocity profiles of the brightest bullets are consistent with theoretical bow shock predictions. However, observations of broad, singly-peaked H2 1-0 S(1) profiles at a range of positions within the most clearly resolved bullet wakes are not consistent with molecular shock modelling. A uniform, collisionally broadened background component which pervades the region in both tracers is inconsistent with fluorescence due to the ionizing radiation of the Trapezium stars alone.Comment: 20 pages including 18 figures, published in MNRA

SCIENCE WITH VO TOOLS: THE ASTROGRID VO DESKTOP

ABSTRACT We introduce a general range of science drivers for using the Virtual Observatory (VO) and identify some common aspects to these as well as the advantages of VO data access. We then illustrate the use of existing VO tools to tackle multi wavelength science problems. We demonstrate the ease of multi mission data access using the VOExplorer resource browser, as provided by AstroGrid (http://www.astrogrid.org) and show how to pass the various results into any VO enabled tool such as TopCat for catalogue correlation. VOExplorer offers a powerful data-centric visualisation for browsing and filtering the entire VO registry using an iTunes type interface. This allows the user to bookmark their own personalised lists of resources and to run tasks on the selected resources as desired. We introduce an example of how more advanced querying can be performed to access existing X-ray cluster of galaxies catalogues and then select extended only X-ray sources as candidate clusters of galaxies in the 2XMMi catalogue. Finally we introduce scripted access to VO resources using python with AstroGrid and demonstrate how the user can pass on the results of such a search and correlate with e.g. optical datasets such as Sloan. Hence we illustrate the power of enabling large scale data mining of multi wavelength resources in an easily reproducible way using the VO

Persistent identification and citation of software

This work has been funded by Jisc in the Research@Risk scheme.Software underpins the academic research process across disciplines. To be able to understand, use/reuse and preserve data, the software code that generated, analysed or presented the data will need to be retained and executed. An important part of this process is being able to persistently identify the software concerned. This paper discusses the reasons for doing so and introduces a model of software entities to enable better identification of what is being identified. The DataCite metadata schema provides a persistent identification scheme and we consider how this scheme can be applied to software. We then explore examples of persistent identification and reuse. The examples show the differences and similarities of software used in academic research, which has been written and reused at different scales. The key concepts of being able to identify what precisely is being used and provide a mechanism for appropriate credit are important to both of them.Publisher PDFPeer reviewe

Covering All the Basics: Reforms for a More Just Society

On July 3, 2018, the Government of British Columbia announced the creation of an expert committee to “test the feasibility of a basic income in BC and help find ways to make life better for British Columbians.” This is the report of that committee, the Expert Panel on Basic Income. Through this report, we endeavour to present comprehensive, consistent, and evidence-based advice to the B.C. government in response to the tasks set out in the terms of reference. We do this in six parts, which: introduce our task and provide a summary of the report; present a justice-based framework within which we can analyze the alternatives; provide background information used throughout the report ; describe and analyze potential basic income programs; present our vision for the future and a set of recommendations that will move B.C. on the path toward that vision

Cross-Linking Between Journal Publications and Data Repositories: A Selection of Examples

This article provides a selection of examples of the many ways that a link can be made between a journal article (whether in a data journal or otherwise) and a dataset held in a data repository. In some cases the method of linking is well established, while in others, they have yet to be rolled out uniformly across the journal landscape. We explore ways in which these examples might be implemented in a data journal, such as Geoscience Data Journal, as explored by the PREPARDE project

Basic Income Simulations for the Province of British Columbia

An important component of the work to be completed by the British Columbia’s Expert Panel on Basic Income is to design simulations to look at how various basic income (BI) models could work in B.C. (B.C. Poverty Reduction, 2018). The intent of these simulations is to identify the potential impacts and financial implications for B.C. residents of different variants of a BI. Given the poverty reduction targets passed by the B.C. government, detailed in Petit and Tedds (2020d), the potential impacts include those on the incidence and the depths of poverty in the province (B.C. Poverty Reduction, n.d.). The panel ran over 16,000 different BI scenarios to consider in B.C., which were modelled using Statistics Canada’s Social Policy Simulation Database and Model (SPSD/M) program. We evaluate different BI scenarios in terms of their implications for a variety of measures, including cost, number of recipients, rates of poverty, depths of poverty, distributional affects, and inequality impacts. This paper provides details regarding these simulations. Our goal in this paper is simply to consider different versions of a basic income in terms of both their cost implications and their implications for poverty reduction. We believe that identifying the most effective variants of a basic income in terms of these two criteria will help sharpen the conversation about the applicability of a basic income as a policy option for B.C

The XMM-Newton wide angle survey (XWAS): the X-ray spectrum of type-1 AGN

Aims. We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2−10 keV (rest-frame) luminosities from ∼1042−1045 erg s−1 and are detected up to redshift ∼4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift.We discuss the implications for models of AGN emission. Methods. We fitted the observed 0.2−12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results. We constrained the mean spectral index of the broad band X-ray continuum to (Γ) = 1.96 ± 0.02 with intrinsic dispersion σ(Γ) = 0.27+0.01 −0.02. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2−10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in >∼3% of our objects, with rest-frame column densities ∼a few ×1022 cm−2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is ∼36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT ∼ 100 eV and σkT ∼ 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.We acknowledge Chris Done, Bozena Czerny, Gordon Stewart, Pilar Esquej and Ken Pounds for useful comments. We acknowledge the anonymous referee for a careful reading of the manuscript and for comments that improved the paper. S.M., M.W. and J.A.T. acknowledge support from the UK STFC research council. F.J.C. acknowledges financial support for this work from the Spanish Ministerio de Educación y Ciencia under project ESP2006-13608-C02-01. A.C. acknowledges financial support from the Spanish Ministerio de Educación y Ciencia fellowship and also from the MIUR and The Italian Space Agency (ASI) grants PRIN-MUR 2006-02-5203 and No. I/088/06/0. M.K. acknowledges support from the NASA grant NNX08AX50G and NNX07AG02G