The Star Formation History of the Solar Neighbourhood from the White Dwarf Luminosity Function

The termination in the white dwarf luminosity function is a standard diagnostic tool for measuring the total age of nearby stellar populations. In this paper, an algorithm is presented for inverting the full white dwarf luminosity function to obtain a maximum likelihood estimate of the time varying star formation rate of the host stellar population. Tests with synthetic data demonstrate that the algorithm converges over a wide class of underlying star formation rate forms. The algorithm successfully estimates the moving average star formation rate as a function of lookback time in the presence of realistic measurement noise, though suffers from degeneracies around discontinuities in the underlying star formation rate. The inversion results are most sensitive to the choice of white dwarf cooling models, with the models produced by different groups giving quite different results. The results are relatively insensitive to the progenitor metallicity, initial mass function, initial-final mass relation and ratio of H/He atmosphere white dwarfs. Application to two independent determinations of the Solar neighbourhood white dwarf luminosity function gives similar results. The star formation rate has a bimodal form, with broad peaks at 2-3 Gyr and 7-9 Gyr in the past, separated by a significant lull of magnitude 30-90% depending on choice of cooling models. The onset of star formation occurs around 8-10 Gyr ago. The total integrated star formation rate is ~0.014 stars/pc3 in the Solar neighbourhood, for stars more massive than 0.6M_{solar}.Comment: 18 pages, 17 figures. Accepted to MNRA

Church-State Ties, Roman Catholic Episcopacies, and Human Rights in Latin America

From the 1960s through the 1980s, Latin America\u27s Catholic bishops\u27 conferences diverged in their responses to state sanctioned human rights abuse. At the national level, some bishops\u27 conferences played leadership roles in nascent human rights movements, others delayed public criticism while pursuing private human rights advocacy, and still others responded with silence or public support for repressive governments. Why? To answer this question, this study presents comparative case studies of the Catholic Church in Argentina, Chile, and Brazil with secondary comparative case studies of Colombia, El Salvador, and Guatemala. Drawing on the theoretical perspective of path dependence, I argue that varied patterns of Church-state interaction arose, in large measure, due to varied configurations in the institutional ties linking Church and state. Where ties are dense, the Church derives its interest in conjunction with the state, relies on the state to pursue those interests, and works to ensure a close and generally collaborative relationship with successive governments via generally non-contentious political behavior. Where ties are sparse, the Church derives its interest from other sources (the political ideology of bishops, the Vatican, the experience of clergy and/or adherents, etc.) and must rely on sources other than the state to pursue those interests. The result is the evolution of a Church that faces fewer obstacles discouraging confrontation when faced with state practices or policies that it opposes. Where ties are of intermediate density, the Church derives its interest from non-state sources (such as the Vatican), but often relies on state assistance or state approval to organize and pursue those interests. As a result, engaging in contentious interaction with the state can be discouraged by the state\u27s leverage over some Church programs. In this situation, pursuing confrontation with the state necessitates difficult cost-benefit analysis for an episcopal conference. The resolution of intra-episcopal conflict prompts delays in decisive responses

The kinematics of Galactic disc white dwarfs in Gaia DR2

We present an analysis of the kinematics of Galactic disc white dwarf stars in the Solar neighbourhood using data from Gaia Data Release 2. Selection of white dwarfs based on parallax provides the first large, kinematically unbiased sample of Solar neighbourhood white dwarfs to date. Various classical properties of the Solar neighbourhood kinematics have been detected for the first time in the WD population. The disc white dwarf population exhibits a correlation between absolute magnitude and mean age, which we exploit to obtain an independent estimate of the Solar motion with respect to the Local Standard of Rest. This is found to be $(U,V,W)_{\odot} = (9.5\pm1.2, 7.5\pm1.2, 8.2\pm1.2)$ kms$^{-1}$. The $UW$ components agree with studies based on main sequence stars, however the $V$ component differs and may be affected by systematics arising from metallicity gradients in the disc. The velocity ellipsoid is shown to vary strongly with magnitude, and exhibits a significant vertex deviation in the $UV$ plane of around 15 degrees, due to the non-axisymmetric Galactic potential. The results of this study provide an important input to proper motion surveys for white dwarfs, which require knowledge of the velocity distribution in order to correct for missing low velocity stars that are culled from the sample to reduce subdwarf contamination.Comment: Accepted for publication in MNRA

PKS2005-489 at VHE: four years of monitoring with HESS and simultaneous multi-wavelength observations

VHE observations of PKS 2005-489 were made with HESS from 2004 through 2007, together with three simultaneous multi-wavelength campaigns performed with XMM-Newton and RXTE in 2004 and 2005. A strong VHE signal, ~17sigma total, is detected during the four years of HESS observations (90.3 hrs live time). The integral flux above the average analysis threshold of 400 GeV is ~3% of the Crab and varies weakly on time-scales from days to years. At X-ray energies the flux is observed to vary by more than an order of magnitude between 2004 and 2005. Strong changes in the X-ray spectrum (DeltaGamma~0.7) are also observed, which appear to be mirrored in the VHE band. The SED of PKS 2005-489, constructed for the first time with contemporaneous data on both humps, shows significant evolution. The large flux variations in the X-ray band, coupled with weak or no variations in the VHE band and a similar spectral behavior, suggest the emergence of a new, separate, harder emission component in September 2005.F. Acero, B. Nicholas, G. Rowell,...and et al, and H.E.S.S. Collaboration

Search for a dark matter annihilation signal from the galactic center halo with H.E.S.S.

A search for a very-high-energy (VHE;≥ 100 GeV) γ-ray signal from self-annihilating particle dark matter (DM) is performed towards a region of projected distance r∼45–150 pc from the Galactic center. The background-subtracted -ray spectrum measured with the High Energy Stereoscopic System (H.E.S.S.) γ-ray instrument in the energy range between 300 GeVand 30 TeV shows no hint of a residual γ-ray flux. Assuming conventional Navarro-Frenk-White and Einasto density profiles, limits are derived on the velocity-weighted annihilation cross section (σv)as a function of the DM particle mass. These are among the best reported so far for this energy range and in particular differ only little between the chosen density profile parametrizations. In particular, for the DM particle mass of 1 TeV, values for h (σv) above 3x10⁻²⁵ cm³ s⁻1 are excluded for the Einasto density profile.A. Abramowski... N. Maxted... B. Nicholas... G. Rowell... et al. (H.E.S.S. Collaboration

A 7mm line survey of the shocked and disrupted molecular gas towards the W28 field TeV gamma-ray sources

We present 7mm Mopra observations of the dense molecular gas towards the W28 supernova remnant (SNR) field, following a previous 12mm line survey of this region. These observations take advantage of the 7mm beam size to probe the dense and disrupted gas in the region at ~1 arcmin scales. Our observations are focused towards the north-eastern (NE) HESS J1801-233 and southern HESS J1800-240B TeV gamma-ray sources, with slightly less observations towards HESS J1800-240A & C. Using the CS (1-0) transition we reveal multiple regions of dense gas, nH2 ~10^5 cm^-3. We report the discovery of dense gas towards HESS J1800-240C, at the site of a 1720MHz OH maser. The NE molecular cloud is known to be disrupted, many 1720MHz OH masers and broad CO line emission are detected at the rim of W28. Here we reveal this shock interaction region contains generally extended clumpy CS, as well as clumpy SiO and CH3OH emission with broad line profiles. The FWHM of the molecular lines extend up to 18 km/s on the W28 side of the NE cloud. The detection of SiO towards maser clumps OH C, D, E & F provide further evidence of the shocked conditions in the NE cloud. Several other lines associated with star formation are also detected towards the southern source, notably the energetic HII complex G5.89-0.39. The spatial match of dense gas with the TeV emission further supports the CR origin for the gamma-rays. We estimate the mass of several extended dense clouds within the field and predict the TeV flux from the dense cloud components. The predicted fluxes are on the order of 10^{-14} - 10^{-13} ph/cm^2/s, which should be detectable and possibly resolved by a future TeV instrument, such as the Cherenkov Telescope Array.Comment: 18 pages + 2 pages appendix accepted for publication in MNRA

Diagnosis and Management of Esophageal Injuries: A Western Trauma Association Critical Decisions Algorithm

ABSTRACT: This is a recommended management algorithm from the Western Trauma Association addressing the diagnostic evaluation and management of esophageal injuries in adult patients. Because there is a paucity of published prospective randomized clinical trials that have generated Class I data, the recommendations herein are based primarily on published observational studies and expert opinion of Western Trauma Association members. The algorithms and accompanying comments represent a safe and sensible approach that can be followed at most trauma centers. We recognize that there will be patient, personnel, institutional, and situational factors that may warrant or require deviation from the recommended algorithm. We encourage institutions to use this guideline to formulate their own local protocols. The algorithm contains letters at decision points; the corresponding paragraphs in the text elaborate on the thought process and cite pertinent literature. The annotated algorithm is intended to (a) serve as a quick bedside reference for clinicians; (b) foster more detailed patient care protocols that will allow for prospective data collection and analysis to identify best practices; and (c) generate research projects to answer specific questions concerning decision making in the management of adults with esophageal injuries