bluuebunny/crossref_metadata_2025_split huggingface dataset:
Streaming Instability and Turbulence: Conditions for Planetesimal Formation
Authors: Lim 임 Jeonghoon 정훈 , Simon Jacob B. , Li 李 Rixin 日新 , Armitage Philip J. , Carrera Daniel , Lyra Wladimir , Rea David G. , Yang 楊 Chao-Chin 朝欽 , Youdin Andrew N. 
Published: July 2024

Abstract
The streaming instability (SI) is a leading candidate for planetesimal formation, which can concentrate solids through two-way aerodynamic interactions with the gas. The resulting concentrations can become sufficiently dense to collapse under particle self-gravity, forming planetesimals. Previous studies have carried out large parameter surveys to establish the critical particle to gas surface density ratio (Z), above which SI-induced concentration triggers planetesimal formation. The threshold Z depends on the dimensionless stopping time (τ

s
, a proxy for dust size). However, these studies neglected both particle self-gravity and external turbulence. Here, we perform 3D stratified shearing box simulations with both particle self-gravity and turbulent forcing, which we characterize via a turbulent diffusion parameter, α
D. We find that forced turbulence, at amplitudes plausibly present in some protoplanetary disks, can increase the threshold Z by up to an order of magnitude. For example, for τ

s
= 0.01, planetesimal formation occurs when Z ≳ 0.06, ≳0.1, and ≳0.2 at α
D = 10−4, 10−3.5, and 10−3, respectively. We provide a single fit to the critical Z required for the SI to work as a function of α
D and τ

s
(although limited to the range τ

s
= 0.01–0.1). Our simulations also show that planetesimal formation requires a mid-plane particle-to-gas density ratio that exceeds unity, with the critical value being largely insensitive to α
D. Finally, we provide an estimation of particle scale height that accounts for both particle feedback and external turbulence.
Chandra Study of the Proper Motion of HST-1 in the Jet of M87
Authors: Thimmappa Rameshan , Neilsen Joey , Haggard Daryl , Nowak Mike , Markoff Sera 
Published: July 2024

Abstract
The radio galaxy M87 is well known for its jet, which features a series of bright knots observable from radio to X-ray wavelengths. We analyze the X-ray image and flux variability of the knot HST-1 in the jet. Our analysis includes all 112 available Chandra ACIS-S observations from 2000 to 2021, with a total exposure time of ∼884 ks. We use deconvolved images to study the brightness profile of the X-ray jet and measure the relative separation between the core and HST-1. From 2003 to 2005 (which coincides with a bright flare from HST-1), we find a correlation between the flux of HST-1 and its offset from the core. In subsequent data, we find a steady increase in this offset, which implies a bulk superluminal motion for HST-1 of 6.6 ± 0.9 c (2.0 ± 0.3 pc yr−1), in keeping with prior results. We discuss models for the flux–offset correlation that feature either two or four emission regions separated by tens of parsecs. We attribute these results to moving shocks in the jet, which allow us to measure the internal structure of the jet.
Starspots and Undetected Binary Stars Have Distinct Signatures in Young Stellar Associations
Authors: Sullivan Kendall , Kraus Adam L. 
Published: July 2024

Abstract
Young stars form in associations, meaning that young stellar associations provide an ideal environment to measure the age of a nominally coeval population. Isochrone fitting, which is the typical method for measuring the age of a coeval population, can be impacted by observational biases that obscure the physical properties of a population. One feature in isochrone fits of star-forming regions is an apparent mass-dependent age gradient, where lower-mass stars appear systematically younger than higher-mass stars. Starspots and stellar multiplicity are proposed mechanisms for producing the mass-dependent age gradient, but the relative importance of starspots versus multiplicity remains unclear. We performed a synthetic red optical low-resolution spectroscopic survey of a simulated analog to a 10 Myr stellar association including mass-dependent multiplicity statistics and age-dependent starspot coverage fractions. We found that undetected starspots alone do not produce an apparent mass-dependent age gradient, but instead uniformly reduce the average measured age of the population. We also found that binaries continue to produce an apparent mass-dependent age gradient and introduce more scatter in the age measurement than spots, but are easily removed from the population as long as there are good distance measurements to each target. We conclude that it is crucial to incorporate treatments of both starspots and undetected stellar multiplicity into isochrone fits of young stellar associations to attain reliable ages.
Ly

α

Halo Properties and Dust in the Circumgalactic Medium of z ∼ 2 Star-forming Galaxies
Authors: Song Zhiyuan , Reddy Naveen A. , Chen Yuguang , Shapley Alice E. , Rezaee Saeed , Weldon Andrew , Fetherolf Tara , Coil Alison L. , Mobasher Bahram , Steidel Charles C. 
Published: July 2024

Abstract
We present Keck Cosmic Web Imager integral-field unit observations around extended Lyα halos of 27 typical star-forming galaxies with redshifts 2.0 < z < 3.2 drawn from the MOSFIRE Deep Evolution Field survey. We examine the average Lyα surface brightness profiles in bins of star formation rate (SFR), stellar mass (M
*), age, stellar continuum reddening, SFR surface density (ΣSFR), and ΣSFR normalized by stellar mass (ΣsSFR). The scale lengths of the halos correlate with stellar mass, age, and stellar continuum reddening and anticorrelate with SFR, ΣSFR, and ΣsSFR. These results are consistent with a scenario in which the down-the-barrel fraction of Lyα emission is modulated by the low-column-density channels in the interstellar medium, and in which the neutral gas covering fraction is related to the physical properties of the galaxies. Specifically, we find that this covering fraction increases with stellar mass, age, and E(B − V) and decreases with SFR, ΣSFR, and ΣsSFR. We also find that the resonantly scattered Lyα emission suffers greater attenuation than the (nonresonant) stellar continuum emission, and that the difference in attenuation increases with stellar mass, age, and stellar continuum reddening, and decreases with ΣsSFR. These results imply that more reddened galaxies have more dust in their circumgalactic medium.
Early Planet Formation in Embedded Disks (eDisk). XV. Influence of Magnetic Field Morphology in Dense Cores on Sizes of Protostellar Disks
Authors: Yen Hsi-Wei , Williams Jonathan P. , Sai Jinshi , Koch Patrick M. , Han Ilseung , Jørgensen Jes K. , Kwon Woojin , Lee Chang Won , Li Zhi-Yun , Looney Leslie W. , Narang Mayank , Ohashi Nagayoshi , Takakuwa Shigehisa , Tobin John J. , de Gregorio-Monsalvo Itziar , Lai Shih-Ping , Lee Jeong-Eun , Tomida Kengo 
Published: July 2024

Abstract
The magnetic field of a molecular cloud core may play a role in the formation of circumstellar disks in the core. We present magnetic field morphologies in protostellar cores of 16 targets in the Atacama Large Millimeter/submillimeter Array large program “Early Planet Formation in Embedded Disks (eDisk),” which resolved their disks with 7 au resolutions. The 0.1 pc scale magnetic field morphologies were inferred from the James Clerk Maxwell Telescope POL-2 observations. The mean orientations and angular dispersions of the magnetic fields in the dense cores are measured and compared with the radii of the 1.3 mm continuum disks and the dynamically determined protostellar masses from the eDisk program. We observe a significant correlation between the disk radii and the stellar masses. We do not find any statistically significant dependence of the disk radii on the projected misalignment angles between the rotational axes of the disks and the magnetic fields in the dense cores, nor on the angular dispersions of the magnetic fields within these cores. However, when considering the projection effect, we cannot rule out a positive correlation between disk radii and misalignment angles in three-dimensional space. Our results suggest that the morphologies of magnetic fields in dense cores do not play a dominant role in the disk formation process. Instead, the sizes of protostellar disks may be more strongly affected by the amount of mass that has been accreted onto star+disk systems, and possibly other parameters, for example, magnetic field strength, core rotation, and magnetic diffusivity.
Time Delay of Fast Radio Burst Population with Respect to the Star Formation History
Authors: Lin Hai-Nan , Li Xin-Yi , Zou Rui 
Published: July 2024

Abstract
In spite of significant progress in the research of fast radio bursts (FRBs) in recent decades, their origin is still under extensive debate. Investigation of the population of FRBs can provide new insight into this interesting problem. In this paper, based on the first Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB catalog, we construct a Bayesian framework to analyze the FRB population, with the selection effect of the CHIME telescope being properly taken into account. The energy function is modeled as the power law with an exponential cutoff. Four redshift distribution models are considered, i.e., the star formation history (SFH) model, and three time-delayed models (Gaussian delay, log-normal delay, and power-law delay). The free parameters are simultaneously constrained using the Bayesian inference method, and the Bayesian information criterion (BIC) is used in model comparison. According to the BIC, the log-normal delay model fits the data best. The power-law delay model and Gaussian delay model can also give reasonable fits, although they are not as good as the log-normal delay model. However, the SFH model is strongly disfavored compared with the three time-delayed models. The energy function is tightly constrained and is almost independent of the redshift models, with the best-fitting power-law index α ≈ 1.8 and cut-off energy

log
(

E

c

/

erg
)
≈
42

. The FRB population shows on average a 3 ∼ 5 billion yr time delay with respect to the SFH. Therefore, the hypothesis that the FRB population traces the SFH is conclusively ruled out.
Candidate Members of the VMP/EMP Disk System of the Galaxy from the SkyMapper and SAGES Surveys
Authors: Hong Jihye , Beers Timothy C. , Lee Young Sun , Huang Yang , Hirai Yutaka , Cabrera Garcia Jonathan , Shank Derek , Xu Shuai , Yuan Haibo , Mardini Mohammad K. , Catapano Thomas , Zhao Gang , Fan Zhou , Zheng Jie , Wang Wei , Tan Kefeng , Zhao Jingkun , Li Chun 
Published: July 2024

Abstract
Photometric stellar surveys now cover a large fraction of the sky, probe to fainter magnitudes than large-scale spectroscopic surveys, and are relatively free from the target selection biases often associated with such studies. Photometric-metallicity estimates that include narrow/medium-band filters can achieve comparable accuracy and precision to existing low-resolution spectroscopic surveys such as Sloan Digital Sky Survey/SEGUE and LAMOST. Here we report on an effort to identify likely members of the Galactic disk system among the very metal-poor (VMP; [Fe/H] ≤ −2) and extremely metal-poor (EMP; [Fe/H] ≤ −3) stars. Our analysis is based on an initial sample of ∼11.5 million stars with full space motions selected from the SkyMapper Southern Survey (SMSS) and Stellar Abundance and Galactic Evolution Survey (SAGES). After applying a number of quality cuts to obtain the best available metallicity and dynamical estimates, we analyze a total of ∼5.86 million stars in the combined SMSS/SAGES sample. We employ two techniques that, depending on the method, identify between 876 and 1476 VMP stars (6.9%−11.7% of all VMP stars) and between 40 and 59 EMP stars (12.4%−18.3% of all EMP stars) that appear to be members of the Galactic disk system on highly prograde orbits (v

ϕ
> 150 km s−1). The total number of candidate VMP/EMP disklike stars is 1496, the majority of which have low orbital eccentricities, ecc ≤ 0.4; many have ecc ≤ 0.2. The large fractions of VMP/EMP stars associated with the Milky Way disk system strongly suggest the presence of an early-forming “primordial” disk.
The Curious Case of Twin Fast Radio Bursts: Evidence for Neutron Star Origin?
Authors: Bera Apurba , James Clancy W. , Deller Adam T. , Bannister Keith W. , Shannon Ryan M. , Scott Danica R. , Gourdji Kelly , Marnoch Lachlan , Glowacki Marcin , Ekers Ronald D. , Ryder Stuart D. , Dial Tyson 
Published: July 2024

Abstract
Fast radio bursts (FRBs) are brilliant short-duration flashes of radio emission originating at cosmological distances. The vast diversity in the properties of currently known FRBs and the fleeting nature of these events make it difficult to understand their progenitors and emission mechanism(s). Here we report high time resolution polarization properties of FRB 20210912A, a highly energetic event detected by the Australian Square Kilometre Array Pathfinder (ASKAP) in the Commensal Real-time ASKAP Fast Transients survey, which show intraburst position angle (PA) variation similar to Galactic pulsars and unusual variation of Faraday rotation measure (RM) across its two sub-bursts. The observed intraburst PA variation and apparent RM variation pattern in FRB 20210912A may be explained by a rapidly spinning neutron star origin, with rest-frame spin periods of ∼1.1 ms. This rotation timescale is comparable to the shortest known rotation period of a pulsar and close to the shortest possible rotation period of a neutron star. Curiously, FRB 20210912A exhibits a remarkable resemblance to the previously reported FRB 20181112A, including similar rest-frame emission timescales and polarization profiles. These observations suggest that these two FRBs may have similar origins.
Global Lunar Crater Density Using Buffered Nonsparseness Correction
Authors: Huang Ya Huei , Riedel Christian , Soderblom Jason M. , Brown Krein Stephanie , Orgel Csilla , Conrad Jack W. , Hirabayashi Masatoshi , Minton David A. 
Published: July 2024

Abstract
The density of craters on a planetary surface directly relates to the age of the surface. As the surface ages, however, craters can be erased by subsequent large impacts via direct overprinting, known as geometric crater obliteration. Such counts become increasingly limited as surfaces become more heavily cratered. Techniques to infer the statistics of the regions obliterated by craters were developed in the past decade. Such techniques, however, have only been used for regional studies. Herein, we present a study of the global density of lunar impact craters ≥20 km in diameter using both traditional crater-counting and buffered nonsparseness correction (BNSC) crater-counting techniques. By comparing the measurements, we quantify the influence of geometric crater obliteration on the visible lunar crater record. Our results reveal that geometric crater obliteration erased up to three-fifths of craters ≥20 km in diameter that formed on the most ancient lunar terrains, whereas younger surfaces, like the Procellarum KREEP Terrane, show little to no evidence of such crater obliteration. The differences in derived crater densities highlight ancient surfaces in which the effects of geometric crater obliteration must be considered to characterize their cratering histories. Furthermore, our results identify the most heavily cratered area on the Moon, a region of the lunar highlands between Smythii basin and the South Pole–Aitken (SPA) basin (Smythii–SPA–Highlands); the number of impacts revealed by the BNSC technique for this region is consistent with estimates derived from the abundance of highly siderophile elements and from modeling crustal porosity.
La creatio ex nihilo . Une réception chrétienne en comparaison avec des lectures juives de la période du Second Temple
Authors: Bauks Michaela 
Published: July 2024

Examine l’idée d’une creatio ex nihilo dans la pensée du judaïsme ancien à travers quelques textes de la Bible (Gn 1,2 ; Es 45,7 ; Pr 8,27) , de la mer Morte, des targoums et 2 M 7,28. L’hypothèse défendue est que ce concept n’est pas directement issu de ces textes. Selon eux, l’évocation d’une matière précédant la création divine ne contredit pas la conviction que le Dieu d’Israël est le créateur de l’ordre universel .
Conférences familiales et principes sous-jacents
Authors: Ban Paul 
Published: July 2024

Les travaux sur les conférences familiales ont jusqu’à présent porté principalement sur l’expérimentation et les résultats. La compréhension des mécanismes sous-jacents est laissée quelque peu de côté. Trois approches permettent d’avancer dans cette démarche : le développement communautaire, la médiation transformative et le fonctionnement des organisations. Le développement du concept de feedback présente un apport intéressant. Le feedback de renforcement produit une amplification dans la direction initiale ; le feedback d’équilibrage génère des comportements surprenants et problématiques en vue de maintenir le statu quo. Les feedbacks de renforcement et feedback d’équilibrage sont couramment activés par les familles ; leur prise en compte est un outil de compréhension précieux pour les facilitateurs indépendants qui organisent les conférences familiales. La démonstration passe ensuite par le concept d’alignement qui permet à un collectif, équipe ou famille, d’entrer dans une dynamique d’harmonie interne, laquelle ouvre l’accès au dialogue. Le dialogue, se distingue de la simple discussion, en ce qu’il favorise l’écoute réciproque approfondie avec en corollaire, la suspension momentanée des vues personnelles. La mise en œuvre de ces techniques favorise l’accès à l’empowerment des familles lors du temps familial privé, étape cruciale dans la prise de décision par la famille lors de la conférence familiale.
Wahi Kōrero outil de lancement d’une conférence familiale
Authors: Alföldi Francis 
Published: July 2024

Une lecture fluide de ce texte nécessite en premier lieu de distinguer entre deux termes paraissant à priori fort semblables : whaikōrero et wahi kōrero. La présente communication porte principalement sur le wahi kōrero , un prototype original destiné aux coordinateurs de conférence familiale. Le procédé permet d’assister le lancement de la conférence familiale, à l’instant de la prise de parole par le coordinateur, au cours de la première étape appelée : partage d’information. Le prototype tire ses sources de la tradition māorie, notamment évoquée au travers de deux concepts clef : le tikanga et la géomentalité. Cet outil encore expérimental est largement inspiré du rituel māori intitulé le whaikōrero. Sont également discutés, les motifs qui contre-indiquent le transfert direct du whaikōrero au sein d’une culture autre que māorie, des motifs qui ont conduit au repérage et à l’adoption d’un autre terme : le wahi kōrero . Le prototype instrumental intègre ainsi dans sa structure, plusieurs techniques inspirées de la tradition māorie : le whakaaraara , le pepeha , le mihi , le kaupapa , le kōrero whakararata , le waiata . Chacun de ces procédés fait l’objet d’une présentation en lien avec son rôle spécifique dans le lancement de la conférence familiale. Cette communication évoque aussi les premières expérimentations du prototype sur le terrain. L’article et les concepts originaux qui en assurent le fondement sont issus des travaux d’auteurs et de chercheurs māoris ayant publié en langue anglaise ; toutes ces notions font l’objet de citations dûment référencées. Sans le savoir,
Conférences familiales, comment ouvrir le champ des possibles en protection de l’enfance ?
Authors: Lombardot Esther 
Published: July 2024

Éducatrice spécialisée depuis une vingtaine d’années, c’est le constat des limites du système de protection de l’enfance qui m’a conduite à faire la formation de coordinateur de conférence familiale avec Francis Alfoldi. Référente au sein d’un service d’Aide Sociale à l’Enfance, je constate l’isolement que le placement induit en déracinant l’enfant de son environnement familial. Si les parents n’ont pas la capacité de répondre aux besoins de leur enfant, qu’en est-il de leur environnement, de leur famille ? Comment permettre à ces enfants de maintenir des liens avec leur environnement en s’appuyant sur les personnes-ressources qui les entourent ? Les conférences familiales impliquent de faire vivre les ressources familiales, de mobiliser l’entourage de l’enfant afin de construire des réponses concrètes face aux difficultés rencontrées. Cet article met en avant la mise en œuvre des conférences familiales au sein de deux services d’Aide Sociale à l’Enfance et revient sur ces 18 premiers mois d’expérimentation. C’est au travers d’expérience de terrain que la richesse du procédé se dévoile. La famille n’est plus écartée du système de protection, elle s’organise pour la garantir. Ma position de coordinatrice m’a amené à être le témoin d’un processus qui met l’entourage de l’enfant en mouvement. Je reste stupéfaite des solutions que les familles arrivent à construire pour faire face à leurs difficultés. La conférence familiale est un procédé concret qui permet aux familles de retrouver leur pouvoir d’agir. S’appuyer sur les ressources familiales en première intention tombe sous les sens, alors pourquoi les professionnels sont-ils parfois perplexes devant une telle proposition ? Si la conférence familiale est un processus qui nécessite un changement de posture pour le travailleur social, elle ouvre également le champ des possibles.
« Souveraineté numérique européenne »
Authors: Pogurschi Alina 
Published: July 2024

Cet article vise à étudier les contours de la notion de « souveraineté numérique européenne » sous l’angle du concept « classique » de la souveraineté que l’on retrouve chez Jean Bodin et Thomas Hobbes. L’objectif est d’apprécier l’adéquation de ce concept avec les problématiques imposées par le numérique et la mondialisation d’un côté, et la manière dont l’Union européenne pourrait répondre à ces problématiques d’un autre côté. La solution proposée est de redéfinir ce concept grâce à la notion de « souveraineté numérique européenne », ce qui permettrait l’exercice conjoint par l’Union européenne et les États membres de la souveraineté en matière de numérique. Les manifestations concrètes d’une « souveraineté numérique européenne » sont enfin mises en évidence et analysées à travers la mise en œuvre de la politique européenne du numérique.
Reconciling the Interconnectedness and Autonomy of European Union Democracies
Authors: Lord Christopher 
Published: July 2024

Comment les démocraties contemporaines peuvent-elles être « ordonnées au niveau international » de manière à combiner leur interdépendance avec une forme d’autonomie interne où leurs citoyens sont libres, égaux et efficaces dans l’utilisation de leurs démocraties pour s’accorder mutuellement des droits et des obligations, et contrôler leurs propres lois ? J’utilise deux justifications de l’autorité politique pour examiner cette question. L’une, associée à David Hume, suggère une justification instrumentale de l’autorité politique comme moyen de fournir des biens collectifs essentiels. L’autre, associée à Emmanuel Kant, considère que l’autorité politique est justifiée par des droits et des devoirs. J’utilise les deux pour suggérer comment l’Union peut être au service des démocraties membres en conciliant leur interdépendance avec leur autonomie.
Quelle souveraineté ? Rôle et fonction de la philosophie politique dans les études européennes
Authors: Spector Céline 
Published: July 2024

Cette contribution se propose de revenir sur l’apport de la philosophie politique aux études européennes. L’Union européenne pose à la philosophie moderne de redoutables difficultés, qui tiennent d’abord à l’identification de sa forme politique. Mais à cette dimension explicative s’adjoint une dimension normative : il s’agit de dégager quelle serait pour l’Union la forme adéquate de souveraineté et de gouvernement qui pourrait lui convenir. Dans cette mesure, la philosophie politique peut espérer énoncer les principes qui doivent l’organiser de manière légitime – principes qui orientent l’amélioration de ses institutions en visant la démocratie, la liberté et la justice.