bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Case for a Large-scale Occultation Network
Authors: Rice Malena , Laughlin Gregory 
Published: June 2019

Abstract
We discuss the feasibility of and present initial designs and approximate cost estimates for a large (N ∼ 2000) network of small photometric telescopes that is purpose-built to monitor V ≲ 15 Gaia mission program stars for occultations by minor solar system bodies. The implementation of this network would permit measurement of the solar system’s tidal gravity field to high precision, thereby revealing the existence of distant trans-Neptunian objects such as the proposed “Planet Nine.” As a detailed example of the network capabilities, we investigate how occultations by Jovian Trojans can be monitored to track the accumulation of gravitational perturbations, thereby constraining the presence of undetected massive solar system bodies. We also show that the tidal influence of Planet Nine can be discerned from that of smaller, nearer objects in the Kuiper Belt. Moreover, ephemerides for all small solar system bodies observed in occultation could be significantly improved using this network, thereby improving spacecraft navigation and refining solar system modeling. Finally, occultation monitoring would generate direct measurements of size distributions for asteroid populations, permitting a better understanding of their origins.
From Supernova to Supernova Remnant: The Three-dimensional Imprint of a Thermonuclear Explosion
Authors: Ferrand Gilles , Warren Donald C. , Ono Masaomi , Nagataki Shigehiro , Röpke Friedrich K. , Seitenzahl Ivo R. 
Published: June 2019

Abstract
Recent progress in three-dimensional modeling of supernovae (SNe) has shown the importance of asymmetries in the explosion. This calls for a reconsideration of the modeling of the subsequent phase, the supernova remnant (SNR), which has commonly relied on simplified ejecta models. In this paper, we bridge SN and SNR studies by using the output of an SN simulation as the input of an SNR simulation carried on for 500 yr. We consider the case of a thermonuclear explosion of a carbon–oxygen white dwarf star as a model for an SN Ia; specifically, we use the N100 delayed detonation model of Seitenzahl et al. In order to analyze the morphology of the SNR, we locate the three discontinuities that delineate the shell of shocked matter: the forward shock, the contact discontinuity, and the reverse shock, and we decompose their radial variations as a function of angular scale and time. Assuming a uniform ambient medium, we find that the impact of the SN on the SNR may still be visible after hundreds of years. Previous 3D simulations aiming to reproduce Tycho’s SNR, which started out from spherically symmetric initial conditions, failed to reproduce structures at the largest angular scales observed in X-rays. Our new simulations strongly suggest that the missing ingredient was the initial asymmetries from the SN itself. With this work, we establish a way of assessing the viability of SN models based on the resulting morphology of the SNR.
On the Orbital Decay of Globular Clusters in NGC 1052-DF2: Testing a Baryon-only Mass Model
Authors: Dutta Chowdhury Dhruba , van den Bosch Frank C. , van Dokkum Pieter 
Published: June 2019

Abstract
The dark matter content of the ultra-diffuse galaxy NGC 1052-DF2, as inferred from globular cluster (GC) and stellar kinematics, carries a considerable amount of uncertainty, with current constraints also allowing for the complete absence of dark matter. We test the viability of such a scenario by examining whether in a “baryon-only” mass model the observed GC population experiences rapid orbital decay due to dynamical friction. Using a suite of 50 multi-GC N-body simulations that match observational constraints on both the stellar component of NGC 1052-DF2 and its GC population but differ in the initial line-of-sight positions and the tangential velocities of the GCs, we show that there is a substantial amount of realization-to-realization variance in the evolution of the GCs. Nevertheless, over ∼10 Gyr, some of the GCs experience significant orbital evolution. Others evolve less. A combination of reduced dynamical friction in the galaxy core and GC–GC scattering keeps the GCs afloat, preventing them from sinking all the way to the galaxy center. While the current phase-space coordinates of the GCs are not unlikely for a baryon-only mass model, the GC system does evolve over time. Therefore, if NGC 1052-DF2 has no dark matter, some of its GCs must have formed farther out, and the GC system must have been somewhat more extended in the past. The presence of a low-mass cuspy halo, while allowed by the kinematics, seems improbable, as significantly shorter inspiral timescales in the central region would quickly lead to the formation of a nuclear star cluster.
Unlocking CO Depletion in Protoplanetary Disks. II. Primordial C/H Predictions inside the CO Snowline
Authors: Schwarz Kamber R. , Bergin Edwin A. , Cleeves L. Ilsedore , Zhang Ke , Öberg Karin I. , Blake Geoffrey A. , Anderson Dana E. 
Published: June 2019

Abstract
CO is thought to be the main reservoir of volatile carbon in protoplanetary disks, and thus the primary initial source of carbon in the atmospheres of forming giant planets. However, recent observations of protoplanetary disks point toward low volatile carbon abundances in many systems, including at radii interior to the CO snowline. One potential explanation is that gas phase carbon is chemically reprocessed into less volatile species, which are frozen on dust grain surfaces as ice. This mechanism has the potential to change the primordial C/H ratio in the gas. However, current observations primarily probe the upper layers of the disk. It is not clear if the low volatile carbon abundances extend to the midplane, where planets form. We have run a grid of 198 chemical models, exploring how the chemical reprocessing of CO depends on disk mass, dust grain size distribution, temperature, cosmic-ray and X-ray ionization rate, and initial water abundance. Building on our previous work focusing on the warm molecular layer, here we analyze the results for our grid of models in the disk midplane at 12 au. We find that either an ISM level cosmic-ray ionization rate or the presence of UV photons due to a low dust surface density are needed to chemically reduce the midplane CO gas abundance by at least an order of magnitude within 1 Myr. In the majority of our models CO does not undergo substantial reprocessing by in situ chemistry and there is little change in the gas phase C/H and C/O ratios over the lifetime of the typical disk. However, in the small subset of disks where the disk midplane is subject to a source of ionization or photolysis, the gas phase C/O ratio increases by up to nearly 9 orders of magnitude due to conversion of CO into volatile hydrocarbons.
The Magnetic Properties of Heating Events on High-temperature Active-region Loops
Authors: Ugarte-Urra Ignacio , Crump Nicholas A. , Warren Harry P. , Wiegelmann Thomas 
Published: June 2019

Abstract
Understanding the relationship between the magnetic field and coronal heating is one of the central problems of solar physics. However, studies of the magnetic properties of impulsively heated loops have been rare. We present results from a study of 34 evolving coronal loops observed in the Fe xviii line component of 94 Å filter images obtained by the Atmospheric Imaging Assembly (AIA)/Solar Dynamics Observatory (SDO) from three active regions with different magnetic conditions. We show that the peak intensity per unit cross section of the loops depends on their individual magnetic and geometric properties. The intensity scales proportionally to the average field strength along the loop (B
avg) and inversely with the loop length (L) for a combined dependence of

. These loop properties are inferred from magnetic extrapolations of the photospheric Helioseismic and Magnetic Imager (HMI)/SDO line-of-sight and vector magnetic field in three approximations: potential and two nonlinear force-free (NLFF) methods. Through hydrodynamic modeling (enthalpy-based thermal evolution loop (EBTEL) model) we show that this behavior is compatible with impulsively heated loops with a volumetric heating rate that scales as

.
Radiative Torques of Irregular Grains: Describing the Alignment of a Grain Ensemble
Authors: Herranen Joonas , Lazarian A. , Hoang Thiem 
Published: June 2019

Abstract
The radiative torque (RAT) mechanism is the most promising way of explaining observed polarization arising from aligned grains. We explore the efficiency of the grain alignment by an anisotropic radiation flow for an extensive ensemble of grain shapes, grain sizes (a), and wavelength (λ). We calculate the distribution of the ratios of the amplitudes of the two major components of the RATs, which is an essential parameter that is used in the theory of RAT alignment in Lazarian & Hoang. While this distribution is different for the different classes of grain shapes that we considered, the most probable values of the parameter are centered in the range of q
max ∼ 0.5–1.5. The functional form from the calculated RATs is in good agreement with the analytical model. We find that the RAT efficiency scales as (λ/a)−2.6 for λ ≳ 1.8a, which has a slightly shallower slope than previously found in LH07. This increases the power of predictions obtained with the RAT theory. We also confirm that superparamagnetic inclusions are necessary for achieving high degrees of alignment, and constrain the parameter space describing the requirements for achieving these alignment degrees.
Differences in Faraday Rotation between Adjacent Extragalactic Radio Sources as a Probe of Cosmic Magnetic Fields
Authors: Vernstrom T. , Gaensler B. M. , Rudnick L. , Andernach H. 
Published: June 2019

Abstract
Faraday rotation measures (RMs) of extragalactic radio sources provide information on line-of-sight magnetic fields, including contributions from our Galaxy, source environments, and the intergalactic medium (IGM). Looking at differences in RMs, ΔRM, between adjacent sources on the sky can help isolate these different components. In this work, we classify adjacent polarized sources in the NRAO VLA Sky Survey (NVSS) as random or physical pairs. We recompute and correct the uncertainties in the NVSS RM catalog, since these were significantly overestimated. Our sample contains 317 physical and 5111 random pairs, all with Galactic latitudes

, polarization fractions ≥2%, and angular separations between 1.′5 and 20′. We find an rms ΔRM of 14.9 ± 0.4 and 4.6 ± 1.1 rad m−2 for the random and physical pairs, respectively. This means that polarized extragalactic sources that are close on the sky but at different redshifts have larger differences in RM than two components of one source. This difference of ∼10 rad m−2 is significant at 5σ and persists in different data subsamples. While there have been other statistical studies of ΔRM between adjacent polarized sources, this is the first unambiguous demonstration that some of this RM difference must be extragalactic, thereby providing a firm upper limit on the RM contribution of the IGM. If the ΔRMs originate local to the sources, then the local magnetic field difference between random sources is a factor of 2 larger than that between components of one source. Alternatively, attributing the difference in ΔRMs to the intervening IGM yields an upper limit on the IGM magnetic field strength of 40 nG.
The Lyman Continuum Escape Survey: Ionizing Radiation from [O iii]-strong Sources at a Redshift of 3.1
Authors: Fletcher Thomas J. , Tang Mengtao , Robertson Brant E. , Nakajima Kimihiko , Ellis Richard S. , Stark Daniel P. , Inoue Akio 
Published: June 2019

Abstract
We present results from the LymAn Continuum Escape Survey (LACES), a Hubble Space Telescope (HST) program designed to characterize the ionizing radiation emerging from a sample of Lyα-emitting galaxies at redshift z ≃ 3.1. As many show intense [O iii] emission characteristic of z > 6.5 star-forming galaxies, they may represent valuable low-redshift analogs of galaxies in the reionization era. Using HST Wide Field Camera 3/UVIS F336W to image Lyman continuum emission, we investigate the escape fraction of ionizing photons in this sample. For 61 sources, of which 77% are spectroscopically confirmed and 53 have measures of [O iii] emission, we detect Lyman continuum leakage in 20%, a rate significantly higher than is seen in individual continuum-selected Lyman break galaxies. We estimate that there is a 98% probability that ≤2 of our detections could be affected by foreground contamination. Fitting multiband spectral energy distributions (SEDs) to take account of the varying stellar populations, dust extinctions and metallicities, we derive individual Lyman continuum escape fractions corrected for foreground intergalactic absorption. We find escape fractions of 15%–60% for individual objects and infer an average 20% escape fraction by fitting composite SEDs for our detected samples. Surprisingly, however, even a deep stack of those sources with no individual F336W detections provides a stringent upper limit on the average escape fraction of less than 0.5%. We examine various correlations with source properties and discuss the implications in the context of the popular picture that cosmic reionization is driven by such compact, low-metallicity star-forming galaxies.
Orbital Migration of Interacting Stellar Mass Black Holes in Disks around Supermassive Black Holes
Authors: Secunda Amy , Bellovary Jillian , Low Mordecai-Mark Mac , Ford K. E. Saavik , McKernan Barry , Leigh Nathan W. C. , Lyra Wladimir , Sándor Zsolt 
Published: June 2019

Abstract
The merger rate of stellar-mass black hole binaries (sBHBs) inferred by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) suggests the need for an efficient source of sBHB formation. Active galactic nucleus (AGN) disks are a promising location for the formation of these sBHBs, as well as binaries of other compact objects, because of powerful torques exerted by the gas disk. These gas torques cause orbiting compact objects to migrate toward regions in the disk where inward and outward torques cancel, known as migration traps. We simulate the migration of stellar mass black holes in an example of a model AGN disk, using an augmented N-body code that includes analytic approximations to migration torques, stochastic gravitational forces exerted by turbulent density fluctuations in the disk, and inclination and eccentricity dampening produced by passages through the gas disk, in addition to the standard gravitational forces between objects. We find that sBHBs form rapidly in our model disk as stellar-mass black holes migrate toward the migration trap. These sBHBs are likely to subsequently merge on short timescales. The process continues, leading to the build-up of a population of over-massive stellar-mass black holes. The formation of sBHBs in AGN disks could contribute significantly to the sBHB merger rate inferred by LIGO.
High molecular diversity in the Carabus variolosus/nodulosus complex
Authors: Mossakowski Dietrich , Hejda Radek , Müller-Kroehling Stefan , Paill Wolfgang , Prunar Florin , Rapuzzi Ivan 
Published: June 2019

Starting point of this study was the problem considering the status of Carabus variolous and C. nodulosus: French and some German authors classified them as species, most German authors as subspecies and Casale as semispecies.
We performed analyses of mitochondrial genes (COI-5', COI-3', ND5) as well as nuclear ones (ITS2, wingless) and analysed the DNA sequences using Seqotron, CLUSTALX (editing and alignment), MEGA, DNAML, SplitsTree (phylogeny and network), 4SALE (compensatory base changes), and BEAST (coalescence).
We could study specimens from all regions except the western most part of the distribution area (Massif Central and French Jura, France).
The mitochondrial DNA data resulted in a geographic pattern of high diversity within both taxa indicating a series of glacial refuges. In addition, a considerably large area was found were introgressive hybridisation took place in the past - at least two times by nodulosus of different regions into variolosus.
The nuclear DNA data show a clear and constant difference between both taxa.
In consequence, this complex of forms may be characterised as semispecies from an evolutionary viewpoint but taxonomically as one species because of hybridisation and the lack of compensatory bases changes.
An artisan approach to biodiversity software development
Authors: Noé Nico 
Published: June 2019

In a discipline where interoperability is crucial, funding is limited and reinventing the wheel is frowned upon (and rightfully so), the development of data management tools and biodiversity data portals is generally approached in an industrial way: the same application - whose specifications are often written by a committee - is developed as a complex “one size fits all” tool to be used by various groups in different contexts.
While this approach generally makes sense, for the last 15 years the Belgian Biodiversity Platform has sometimes tried a complementary approach where an artisan-minded software developer is assigned to a specific “customer” and is given a direct communication channel and tons of freedom to develop a simple, made-to-measure application. This empirical experience has shown some unexpected advantages but also, as always, some new challenges. It takes inspiration in things as diverse as the Agile software manifesto and the apprenticeship model of medieval Europe.
This talk will present this unusual approach and reflect on this ongoing experience, hopefully extracting pieces of wisdom that is useful to the broader community. For example, the following questions will be discussed:

How does this method help mobilize biodiversity data? Can it “convert” scientists to Open Data?

Has it some effects on the team stability and developer retention?

Aren’t you writing the same code again and again, resulting in an unmaintainable mess?

Isn’t this an example of living in isolation? What about sharing data with global initiatives such as GBIF?

How does this method help mobilize biodiversity data? Can it “convert” scientists to Open Data?
Has it some effects on the team stability and developer retention?
Aren’t you writing the same code again and again, resulting in an unmaintainable mess?
Isn’t this an example of living in isolation? What about sharing data with global initiatives such as GBIF?
Semantic Interoperability Solutions for the Essential Variables: Focus on biodiversity
Authors: Buttigieg Pier Luigi , Walls Ramona , Thessen Anne 
Published: June 2019

The Earth system is enduring multiple, interacting stressors causing immense and irreversible change to its biosphere. The unprecedented magnitude of human influence on the planet is a cause for much concern, but also an opportunity to mitigate undesirable impact by instituting socio-ecological management strategies and monitoring their effectiveness. To do so, local and global policy developers and decision makers must have access to clear and globally consistent information streams that serve as planetary diagnostics. This need is being addressed by several international, multi-agency networks which have developed sets of "Essential Variables" (EVs) to improve consistency in the observation of key phenomena within their domains of operation. For example, the implementation of the Essential Climate Variables (ECVs) led by the Global Climate Observing System (GCOS) has set an example being followed in the marine and biodiversity domains by, respectively, the Global Ocean Observing System's (GOOS) Essential Ocean Variables (EOVs) and the Group on Earth Observation Biodiversity Observation Network (GEO BON)'s Essential Biodiversity Variables (EBVs). Each of these EV collections has a subset dedicated to biological and ecological phenomena. This is greatly encouraging for biodiversity science at large, but also runs the risk of parallel and conflicting developments occuring in the EV communities addressing thecross-cutting theme of biodiversity. As a consequence, there is an urgent need for these systems, and the communities behind them, to pursue tight conceptual and technical interoperability in aid of a coherent treatment of biodiversity in planetary-scale monitoring.
In this contribution, we will describe our current research and implementation of a semantic interoperability layer for the EVs, with a focus on biology and ecology. Applying the best practices and core infrastructure of the Open Biological and Biomedical Ontology (OBO) Foundry and Library, we have leveraged both mature and emerging reference ontologies targeting the domains of ecosystems and environment, population and communities, and high-level ecological phenomena. This interoperable collection of ontologies constitutes a foundation for highly expressive EV knowledge representation and management through robust, FAIR-compliant technologies. Further, we are coordinating these efforts with semantic technology adopted by UN agencies, representing global directives and indicators of the UN Sustainable Development Agenda for 2030. With open editorial models behind each of these ontologies, we aim to offer a scalable and inclusive system to bridge data and information products across the EVs through machine-accessible knowledge representation.