The COINS Sample - VLBA Identifications of Compact Symmetric Objects

We present results of multifrequency polarimetric VLBA observations of 34 compact radio sources. The observations are part of a large survey undertaken to identify CSOs Observed in the Northern Sky (COINS). Compact Symmetric Objects (CSOs) are of particular interest in the study of the physics and evolution of active galaxies. Based on VLBI continuum surveys of ~2000 compact radio sources, we have defined a sample of 52 CSOs and CSO candidates. In this paper, we identify 18 previously known CSOs, and introduce 33 new CSO candidates. We present continuum images at several frequencies and, where possible, images of the polarized flux density and spectral index distributions for the 33 new candidates and one previously known but unconfirmed source. We find evidence to support the inclusion of 10 of these condidates into the class of CSOs. Thirteen candidates, including the previously unconfirmed source, have been ruled out. Eleven sources require further investigation. The addition of the 10 new confirmed CSOs increases the size of this class of objects by 50%.Comment: 24 pages, incl 8 figures. Accepted for publication in ApJ. Figure quality degraded in the interests of space, full gzipped PS version also available at http://www.ee.nmt.edu/~apeck/papers

Playing Beowulf: Bridging computational thinking, arts and literature through game-making

Preparing younger generations to engage meaningfully with digital technology is often seen as one of the goals of 21st century education. JeanetteWing’s seminal work on Computational Thinking (CT) is an important landmark for this goal: CT represents a way of thinking, a set of problem-solving skills which can be valuable when interacting with digital technologies, and with different fields of knowledge, such as Arts and Humanities. Even if this cross-areas relevance has been celebrated and acknowledged in theoretical research, there has been a lack of practical projects exploring these links between CT and non-STEM fields. This research develops these links. We present a specific case – a game produced by two 14 years-old boys – within Playing Beowulf, a collaboration with the British library’s Young Researchers programme, in which students aged 13–14 from an inner-London (UK) school have developed games based on their own readings of the Anglo-Saxon poem Beowulf during an after-school club. The game was produced using MissionMaker, a software (currently under development at UCL Knowledge Lab) that allows users to create and code their own first-person 3D games in a simple way, using pre-made 3D assets, such as rooms, props, characters and weapons and a simplified programming language manipulated through drop-down lists. We argue that MissionMaker, by simplifying the development process (low floor), can be a means to foster the building of knowledge in both STEM (CT) and Arts and Humanities, building bridges between these two areas inside and outside traditional schooling

Pebbles versus planetesimals

In the core accretion scenario, a massive core forms first and then accretes an envelope. When discussing how this core forms some divergences appear. First scenarios of planet formation predict the accretion of km-sized bodies, called planetesimals, while more recent works suggest growth by accretion of pebbles, which are cm-sized objects. These two accretion models are often discussed separately and we aim here at comparing the outcomes of the two models with identical initial conditions. We use two distinct codes: one computing planetesimal accretion, the other pebble accretion. Using a population synthesis approach, we compare planet simulations and study the impact of the two solid accretion models, focussing on the formation of single planets. We find that the planetesimal model predicts the formation of more giant planets, while the pebble accretion model forms more super-Earth mass planets. This is due to the pebble isolation mass concept, which prevents planets formed by pebble accretion to accrete gas efficiently before reaching Miso. This translates into a population of planets that are not heavy enough to accrete a consequent envelope but that are in a mass range where type I migration is very efficient. We also find higher gas mass fractions for a given core mass for the pebble model compared to the planetesimal one caused by luminosity differences. This also implies planets with lower densities which could be confirmed observationally. Focusing on giant planets, we conclude that the sensitivity of their formation differs: for the pebble accretion model, the time at which the embryos are formed, as well as the period over which solids are accreted strongly impact the results, while for the planetesimal model it depends on the planetesimal size and on the splitting in the amount of solids available to form planetesimals

Probing the Magnetized Interstellar Medium Surrounding the Planetary Nebula Sh 2-216

We present 1420 MHz polarization images of a 2.5 X 2.5 degree region around the planetary nebula (PN) Sh 2-216. The images are taken from the Canadian Galactic Plane Survey (CGPS). An arc of low polarized intensity appears prominently in the north-east portion of the visible disk of Sh 2-216, coincident with the optically identified interaction region between the PN and the interstellar medium (ISM). The arc contains structural variations down to the ~1 arcminute resolution limit in both polarized intensity and polarization angle. Several polarization-angle "knots" appear along the arc. By comparison of the polarization angles at the centers of the knots and the mean polarization angle outside Sh 2-216, we estimate the rotation measure (RM) through the knots to be -43 +/- 10 rad/m^2. Using this estimate for the RM and an estimate of the electron density in the shell of Sh 2-216, we derive a line-of-sight magnetic field in the interaction region of 5.0 +/- 2.0 microG. We believe it more likely the observed magnetic field is interstellar than stellar, though we cannot completely dismiss the latter possibility. We interpret our observations via a simple model which describes the ISM magnetic field around Sh 2-216, and comment on the potential use of old PNe as probes of the magnetized ISM.Comment: 25 pages, 4 figures. Accepted for publication in the Astrophysical Journa

Police referrals for domestic abuse before and during the first COVID-19 lockdown: An analysis of routine data from one specialist service in South Wales

Background COVID-19 lockdown measures may have led to more, and increasingly severe, domestic abuse. This study examines police referrals to a specialist domestic abuse service in Wales, UK before and during the first lockdown. Methods Routine data relating to 2292 police referrals for female adult victim-survivors from December 2019 until July 2020 were analysed and presented in the form of descriptive statistics to monitor changes in referral rates and the profile of those referrals. Results There was little increase in the overall volume of police referrals during lockdown, but the proportion assessed as high risk increased, and children became the primary source of third-party referrals, with a higher proportion of reports made by other third parties as restrictions eased. Police reports for cases of Child/Adolescent to Parent Violence (C/APV) occurred almost exclusively during lockdown. Conclusions The increase in risk level despite less clear increase in volume may suggest unmet need, with victims less likely to seek help during lockdown other than for more severe instances. Increased reports by children suggest increased exposure of children to domestic abuse during school closure. Unmet need for women and children may have been made visible to services, and acquaintances, as measures began to ease

Coral recovery in the central Maldives archipelago since the last major mass-bleaching, in 1998

Increasing frequency and severity of disturbances is causing global degradation of coral reef ecosystems. This study examined temporal changes in live coral cover and coral composition in the central Maldives from 1997 to 2016, encompassing two bleaching events, a tsunami, and an outbreak of Acanthaster planci. We also examined the contemporary size structure for five dominant coral taxa (tabular Acropora, Acropora muricata, Acropora humilis, Pocillopora spp, and massive Porites). Total coral cover increased throughout the study period, with marked increases following the 1998 mass-bleaching. The relative abundance of key genera has changed through time, where Acropora and Pocillopora (which are highly susceptible to bleaching) were under-represented following 1998 mass-bleaching but increased until outbreaks of A. planci in 2015. The contemporary size-structure for all coral taxa was dominated by larger colonies with peaked distributions suggesting that recent disturbances had a disproportionate impact on smaller colonies, or that recruitment is currently limited. This may suggest that coral resilience has been compromised by recent disturbances, and further bleaching (expected in 2016) could lead to highly protracted recovery times. We showed that Maldivian reefs recovered following the 1998 mass-bleaching event, but it took up to a decade, and ongoing disturbances may be eroding reef resilience

Three-dimensional structure of magnetic skyrmions

Magnetic skyrmions (skyrmions hereafter) are magnetization configurations, whose topological robustness and nanoscale size have led to speculation that they could find use as a next-generation information carrier. Skyrmions have been observed in magnetic multilayer materials that are thin compared to the radius of a skyrmion, and chiral cubic single crystals that can be far larger than any characteristic skyrmion scale. In these single crystals, one would expect that skyrmions could exhibit interesting three-dimensional (3D) characteristics. Here, the symmetry of the micromagnetic free energy is investigated. This symmetry permits a complex 3D modulation of a skyrmion string, which we show to be a requirement of a skyrmion coexisting with the conical state. We discuss the implications of this modulation with respect to Thiele\u27s equation and interskyrmion interactions. Further to this internal modulation, we study theoretically and show experimentally that the strings themselves must contort towards the surfaces of their confining crystals

The Integrated Polarization of Spiral Galaxy Disks

We present integrated polarization properties of nearby spiral galaxies at 4.8 GHz, and models for the integrated polarization of spiral galaxy disks as a function of inclination. Spiral galaxies in our sample have observed integrated fractional polarization in the range < 1% to 17.6%. At inclinations less than 50 degrees, the fractional polarization depends mostly on the ratio of random to regular magnetic field strength. At higher inclinations, Faraday depolarization associated with the regular magnetic field becomes more important. The observed degree of polarization is lower (<4%) for more luminous galaxies, in particular those with L_{4.8} > 2 x 10^{21} W/Hz. The polarization angle of the integrated emission is aligned with the apparent minor axis of the disk for galaxies without a bar. In our axially symmetric models, the polarization angle of the integrated emission is independent of wavelength. Simulated distributions of fractional polarization for randomly oriented spiral galaxies at 4.8 GHz and 1.4 GHz are presented. We conclude that polarization measurements, e.g. with the SKA, of unresolved spiral galaxies allow statistical studies of the magnetic field in disk galaxies using large samples in the local universe and at high redshift. As these galaxies behave as idealized background sources without internal Faraday rotation, they can be used to detect large-scale magnetic fields in the intergalactic medium.Comment: 13 pages, 6 figures; Accepted for publication in The Astrophysical Journa

Utility of the new Movement Disorder Society clinical diagnostic criteria for Parkinson's disease applied retrospectively in a large cohort study of recent onset cases

Objective: To examine the utility of the new Movement Disorder Society (MDS) diagnostic criteria in a large cohort of Parkinson's disease (PD) patients. Methods: Recently diagnosed (&lt;3.5 years) PD cases fulfilling United Kingdom (UK) brain bank criteria in Tracking Parkinson's, a UK multicenter prospective natural history study were assessed by retrospective application of the MDS criteria. Results: In 2000 cases, 1835 (91.7%) met MDS criteria for PD, either clinically established (n = 1261, 63.1%) or clinically probable (n = 574, 28.7%), leaving 165 (8.3%) not fulfilling criteria. Clinically established cases were significantly more likely to have limb rest tremor (89.3%), a good l-dopa response (79.5%), and olfactory loss (71.1%), than clinically probable cases (60.6%, 44.4%, and 34.5% respectively), but differences between probable PD and ‘not PD’ cases were less evident. In cases not fulfilling criteria, the mean MDS UPDRS3 score (25.1, SD 13.2) was significantly higher than in probable PD (22.3, SD 12.7, p = 0.016) but not established PD (22.9, SD 12.0, p = 0.066). The l-dopa equivalent daily dose of 341 mg (SD 261) in non-PD cases was significantly higher than in probable PD (250 mg, SD 214, p &lt; 0.001) and established PD (308 mg, SD 199, p = 0.025). After 30 months' follow-up, 89.5% of clinically established cases at baseline remained as PD (established/probable), and 86.9% of those categorized as clinically probable at baseline remained as PD (established/probable). Cases not fulfilling PD criteria had more severe parkinsonism, in particular relating to postural instability, gait problems, and cognitive impairment. Conclusion: Over 90% of cases clinically diagnosed as early PD fulfilled the MDS criteria for PD. Those not fulfilling criteria may have an atypical parkinsonian disorder or secondary parkinsonism that is not correctly identified by the UK Brain Bank criteria, but possibly by the new criteria

A Faraday Rotation Search for Magnetic Fields in Large Scale Structure

Faraday rotation of radio source polarization provides a measure of the integrated magnetic field along the observational lines of sight. We compare a new, large sample of Faraday rotation measures (RMs) of polarized extragalactic sources with galaxy counts in Hercules and Perseus-Pisces, two nearby superclusters. We find that the average of RMs in these two supercluster areas are larger than in control areas in the same galactic latitude range. This is the first RM detection of magnetic fields that pervade a supercluster volume, in which case the fields are at least partially coherent over several megaparsecs. Even the most conservative interpretation of our observations, according to which Milky Way RM variations mimic the background supercluster galaxy overdensities, puts constraints on the IGM magneto-ionic ``strength'' in these two superclusters. We obtain an approximate typical upper limit on the field strength of about 0.3 microGauss l/(500 kpc), when we combine our RM data with fiducial estimates of electron density from the environments of giant radio galaxies, and of the warm-hot intergalactic medium (WHIM).Comment: 8 pages, 3 figures, 1 table, to appear in the Astrophysical Journa