bluuebunny/crossref_metadata_2025_split huggingface dataset:
HST Observations of the Globular Cluster NGC 6402 (M14) and Its Peculiar Multiple Populations
Authors: D’Antona Francesca , Milone Antonino P. , Johnson Christian I. , Tailo Marco , Vesperini Enrico , Caloi Vittoria , Ventura Paolo , Marino Anna Fabiola , Dell’Agli Flavia 
Published: February 2022

Abstract
We present Hubble Space Telescope (HST) photometric results for NGC 6402, a highly reddened, very luminous Galactic globular cluster (GC). Recent spectroscopic observations of its red giant stars have shown a quite peculiar behavior in the chemistry of its multiple populations. These results have prompted UV and optical HST observations aimed at obtaining the cluster’s “chromosome map” (ChM), an efficient tool for classifying GCs and characterizing their multiple populations. We find that the discontinuity in the abundance distributions of O, Mg, Al, and Na inferred from spectroscopy is more nuanced in the ChM, which is mostly sensitive to nitrogen. Nevertheless, photometry in optical bands reveals a double main sequence, indicating a discontinuity in the helium content of the populations. The population with the largest chemical anomalies (extreme) peaks at a helium mass fraction Y ∼ 0.31. This helium content is consistent with results from the analysis of the distribution of horizontal branch stars and the spectrophotometry of the red giants. The ChM and the color–magnitude diagrams are compared with those of NGC 2808, a prototype GC with helium abundances up to Y ≳ 0.35, and both confirm that NGC 6402 does not host stellar populations with such extreme helium content. Further, the ChM reveals the presence of a group of stars with higher metallicity, thus indicating that NGC 6402 is a Type II cluster. The modalities of formation of the multiple populations in NGC 6402 are briefly surveyed, with main attention on the asymptotic giant branch and supermassive star models, and on possible cluster merging.
Resurrection of Nonthermal Emissions from Type Ib/c Supernova Remnants
Authors: Yasuda Haruo , Lee Shiu-Hang , Maeda Keiichi 
Published: February 2022

Abstract
Supernova remnants (SNRs) are important objects in investigating the links among supernova (SN) explosion mechanism(s), progenitor stars, and cosmic-ray acceleration. Nonthermal emission from SNRs is an effective and promising tool for probing their surrounding circumstellar media (CSM) and, in turn, the stellar evolution and mass-loss mechanism(s) of massive stars. In this work, we calculate the time evolution of broadband nonthermal emissions from Type Ib/c SNRs, whose CSM structures are derived from the mass-loss history of their progenitors. Our results predict that Type Ib/c SNRs make a transition of brightness in radio and γ-ray bands from an undetectable dark for a certain period to a rebrightening phase. This transition originates from their inhomogeneous CSM structures in which the SNRs are embedded within a low-density wind cavity surrounded by a high-density wind shell and the ambient interstellar medium (ISM). The “resurrection” in nonthermal luminosity happens at an age of ∼1000 yr old for a Wolf-Rayet star progenitor evolved within a typical ISM density. Combining with the results of Type II SNR evolution recently reported by Yasuda et al., this result sheds light on a comprehensive understanding of nonthermal emissions from SNRs with different SN progenitor types and ages, which is made possible for the first time by the incorporation of realistic mass-loss histories of the progenitors.
Direct Far-infrared Metal Abundances (FIRA). I. M101
Authors: Lamarche C. , Smith J. D. , Kreckel K. , Linden S. T. , Rogers N. S. J. , Skillman E. , Berg D. , Murphy E. , Pogge R. , Donnelly G. P. , Kennicutt R. , Bolatto A. , Croxall K. , Groves B. , Ferkinhoff C. 
Published: February 2022

Abstract
Accurately determining gas-phase metal abundances within galaxies is critical as metals strongly affect the physics of the interstellar medium. To date, the vast majority of widely used gas-phase abundance indicators rely on emission from bright optical lines, whose emissivities are highly sensitive to the electron temperature. Alternatively, direct-abundance methods exist that measure the temperature of the emitting gas directly, though these methods usually require challenging observations of highly excited auroral lines. Low-lying far-infrared (FIR) fine structure lines are largely insensitive to electron temperature and thus provide an attractive alternative to optically derived abundances. Here, we introduce the far-infrared abundance (FIRA) project, which employs these FIR transitions, together with both radio free–free emission and hydrogen recombination lines, to derive direct, absolute gas-phase oxygen abundances. Our first target is M101, a nearby spiral galaxy with a relatively steep abundance gradient. Our results are consistent with the O++ electron temperatures and absolute oxygen abundances derived using optical direct-abundance methods by the CHemical Abundance Of Spirals (CHAOS) program, with a small difference (∼1.5σ) in the radial abundance gradients derived by the FIR/free–free-normalized versus CHAOS/direct-abundance techniques. This initial result demonstrates the validity of the FIRA methodology—with the promise of determining absolute metal abundances within dusty star-forming galaxies, both locally and at high redshift.
Gravity versus Magnetic Fields in Forming Molecular Clouds
Authors: Ibáñez-Mejía Juan C. , Mac Low Mordecai-Mark , Klessen Ralf S. 
Published: February 2022

Abstract
Magnetic fields are dynamically important in the diffuse interstellar medium. Understanding how gravitationally bound, star-forming clouds form requires modeling of the fields in a self-consistent, supernova-driven, turbulent, magnetized, stratified disk. We employ the FLASH magnetohydrodynamics code to follow the formation and early evolution of clouds with final masses of 3–8 × 103
M
⊙ within such a simulation. We use the code’s adaptive mesh refinement capabilities to concentrate numerical resolution in zoom-in regions covering single clouds, allowing us to investigate the detailed dynamics and field structure of individual self-gravitating clouds in a consistent background medium. Our goal is to test the hypothesis that dense clouds are dynamically evolving objects far from magnetohydrostatic equilibrium. We find that the cloud envelopes are magnetically supported with field lines parallel to density gradients and flow velocity, as indicated by the histogram of relative orientations and other statistical measures. In contrast, the dense cores of the clouds are gravitationally dominated, with gravitational energy exceeding internal, kinetic, or magnetic energy and accelerations due to gravity exceeding those due to magnetic or thermal pressure gradients. In these regions, field directions vary strongly, with a slight preference toward being perpendicular to density gradients, as shown by three-dimensional histograms of relative orientation.
The Extended Field-aligned Suprathermal Proton Beam and Long-lasting Trapped Energetic Particle Population Observed Upstream of a Transient Interplanetary Shock
Authors: Lario D. , Richardson I. G. , Wilson III L. B. , Berger L. , Jian L. K. , Trotta D. 
Published: February 2022

Abstract
The properties of the suprathermal particle distributions observed upstream of interplanetary shocks depend not only on the properties of the shocks but also on the transport conditions encountered by the particles as they propagate away from the shocks. The confinement of particles in close proximity to the shocks, as well as particle scattering processes during propagation to the spacecraft, lead to the common observation of upstream diffuse particle distributions. We present observations of a rare extended anisotropic low-energy (≲30 keV) proton beam together with a trapped ≳500 keV proton population observed in association with the arrival of an oblique interplanetary shock at the Advanced Composition Explorer, the Interplanetary Monitoring Platform-8, and the Wind spacecraft on 2001 January 31. Continuous injection of particles by the traveling shock into a smooth radial magnetic field region formed in the tail of a modest high-speed solar wind stream produced an extended foreshock region of energetic particles. The absence of enhanced magnetic field fluctuations upstream of the shock results in the observation of a prolonged anisotropic field-aligned beam of ≲30 keV protons as well as a population of higher-energy (≳500 keV) protons with small pitch-angle cosine (μ ∼ 0) extending far from the shock.
A Simple Model for Mixing and Cooling in Cloud–Wind Interactions
Authors: Abruzzo Matthew W. , Bryan Greg L. , Fielding Drummond B. 
Published: February 2022

Abstract
We introduce a simple entropy-based formalism to characterize the role of mixing in pressure-balanced multiphase clouds and demonstrate example applications using enzo-e (magneto)hydrodynamic simulations. Under this formalism, the high-dimensional description of the system’s state at a given time is simplified to the joint distribution of mass over pressure (P) and entropy (K = P
ρ
−γ
). As a result, this approach provides a way to (empirically and analytically) quantify the impact of different initial conditions and sets of physics on the system evolution. We find that mixing predominantly alters the distribution along the K direction and illustrate how the formalism can be used to model mixing and cooling for fluid elements originating in the cloud. We further confirm and generalize a previously suggested criterion for cloud growth in the presence of radiative cooling and demonstrate that the shape of the cooling curve, particularly at the low-temperature end, can play an important role in controlling condensation. Moreover, we discuss the capacity of our approach to generalize such a criterion to apply to additional sets of physics and to build intuition for the impact of subtle higher-order effects not directly addressed by the criterion.
Quasi-matter Bounce Cosmology in Light of Planck
Authors: Arab Mohammad , Khorasani Mohsen 
Published: February 2022

Abstract
We study quasi-matter bounce cosmology in light of Planck cosmic microwave background angular anisotropy measurements along with the BICEP2/Keck Array data. We propose a new primordial scalar power spectrum by considering a linear approximation of the equation of state w ≅ w
0 + κ(η − η
0) for quasi-matter field in the contracting phase of the universe. Using this new primordial scalar power spectrum, we constrain the zeroth-order approximation of the equation of state w
0 = −0.00340 ± 0.00044 and first-order correction

10

4

ζ
=
−

1.67

−
0.83

+
1.50

at the 1σ confidence level by Planck temperature and polarization in combination with the BICEP2/Keck Array data in which ζ = 12κ/k
* with pivot scale k
*. The spectral index of scalar perturbations is determined to be n
Bs = 0.9623 ± 0.0055, which lies 7σ away from the scale-invariant primordial spectrum. We find scale dependency for n

s
at the 1σ confidence level and a tighter constraint on the running of the spectral index compared to ΛCDM+α

s
cosmology. The running of the spectral index in quasi-matter bounce cosmology is α
Bs = π
ζ/2c

s
= −0.0021 ± 0.0016, which is nonzero at the 1.3σ level, whereas in ΛCDM+α

s
it is nonzero at the 0.8σ level for Planck temperature and polarization data. The sound speed of density fluctuations of the quasi-matter field at the crossing time is

c

s

=

0.097

−
0.023

+
0.037

, which is not a very small value in the contracting phase.
Burton’s Curse: The Impact of Bulk Flows on the Galactic Longitude–Velocity Diagram and the Illusion of a Continuous Perseus Arm
Authors: Peek J. E. G. , Tchernyshyov Kirill , Miville-Deschenes Marc-Antoine 
Published: February 2022

Abstract
In this work, we demonstrate that the Perseus Arm is not a continuous structure of molecular gas in the second quadrant. We first show that the observed, distanced-resolved velocity structure of the Galaxy in the outer disk is capable of creating illusory spiral arms, as was first proposed by Burton. Second, we measure the distances to a collection of CO clouds at velocities consistent with the Perseus arm with 135° < l < 160°. We find these distances using 3D dust maps from Green et al. We determine that these molecular clouds do not preferentially lie at the distance of a purported Perseus arm but rather extend over 3 kpc in distance, with some evidence for a closer, high pitch angle structure between 1 and 1.5 kpc away. Finally, we demonstrate that velocity perturbations of the amplitude found near the Perseus arm can wreak havoc on our interpretation of the longitude–velocity diagram for more than half of the Milky Way disk.
Buildup of the Magnetic Flux Ropes in Homologous Solar Eruptions
Authors: Wang Rui , Liu Ying D. , Yang Shangbin , Hu Huidong 
Published: February 2022

Abstract
Homologous coronal mass ejections (CMEs) are an interesting phenomenon, and it is possible to investigate the formation of CMEs by comparing multi-CMEs under a homologous physical condition. AR 11283 had been present on the solar surface for several days when a bipole emerged on 2011 September 4. Its positive polarity collided with the preexisting negative polarity belonging to a different bipole, producing recurrent solar activities along the polarity inversion line (PIL) between the colliding polarities, namely the so-called collisional PIL (cPIL). Our results show that a large amount of energy and helicity were built up in the form of magnetic flux ropes (MFRs), with recurrent release and accumulation processes. These MFRs were built up along the cPIL. A flux deficit method is adopted and shows that magnetic cancellation happens along the cPIL due to the collisional shearing scenario proposed by Chintzoglou et al. The total amount of canceled flux was ∼0.7 × 1021 Mx with an uncertainty of ∼13.2% within the confidence region of the 30° Sun-center distance. The canceled flux amounts to 24% of the total unsigned flux of the bipolar magnetic region. The results show that the magnetic fields beside the cPIL are very sheared, and the average shear angle is above 70° after the collision. The fast expansion of the twist kernels of the MFRs and the continuous eruptive activities are both driven by the collisional shearing process. These results are important for better understanding the buildup process of the MFRs associated with homologous solar eruptions.
The High Fraction of Thin Disk Galaxies Continues to Challenge ΛCDM Cosmology
Authors: Haslbauer Moritz , Banik Indranil , Kroupa Pavel , Wittenburg Nils , Javanmardi Behnam 
Published: February 2022

Abstract
Any viable cosmological framework has to match the observed proportion of early- and late-type galaxies. In this contribution, we focus on the distribution of galaxy morphological types in the standard model of cosmology (Lambda cold dark matter, ΛCDM). Using the latest state-of-the-art cosmological ΛCDM simulations known as Illustris, IllustrisTNG, and EAGLE, we calculate the intrinsic and sky-projected aspect ratio distribution of the stars in subhalos with stellar mass M
* > 1010
M
⊙ at redshift z = 0. There is a significant deficit of intrinsically thin disk galaxies, which however comprise most of the locally observed galaxy population. Consequently, the sky-projected aspect ratio distribution produced by these ΛCDM simulations disagrees with the Galaxy And Mass Assembly (GAMA) survey and Sloan Digital Sky Survey at ≥12.52σ (TNG50-1) and ≥14.82σ (EAGLE50) confidence. The deficit of intrinsically thin galaxies could be due to a much less hierarchical merger-driven build-up of observed galaxies than is given by the ΛCDM framework. It might also arise from the implemented sub-grid models, or from the limited resolution of the above-mentioned hydrodynamical simulations. We estimate that an 85 times better mass resolution realization than TNG50-1 would reduce the tension with GAMA to the 5.58σ level. Finally, we show that galaxies with fewer major mergers have a somewhat thinner aspect ratio distribution. Given also the high expected frequency of minor mergers in ΛCDM, the problem may be due to minor mergers. In this case, the angular momentum problem could be alleviated in Milgromian dynamics because of a reduced merger frequency arising from the absence of dynamical friction between extended dark matter halos.
Montrer des causes et des effets : visages et photographies
Authors: Wiesing Lambert 
Published: February 2022

Montrer des émotions sur un visage ou montrer quelque chose par une photographie, est-ce identique ? Que signifie montrer ( das Zeigen ) ou faire voir ( sehen lassen ) ? La question engage une réflexion sur la nature de l’image photographique : en refusant de faire du cliché photographique (comme du visage) la trace ou l’index d’un quelque chose, l’auteur affirme importance du langage et de l’usage pour tout artefact, où l’équivalence linguistique du dissemblable devient un aspect nécessaire de la praxis qui vise à montrer du doigt.
La radicale « caméra-réalité » de Siegfried Kracauer
Authors: Maigné Carole 
Published: February 2022

La « camera-réalité », néologisme qualifiant la nature du médium photographique, est un « objet théorique » qui interroge l’irruption de l’image photographique en philosophie. Siegfried Kracauer définit dans Théorie du film le réalisme propre à l’image photographique, en revisitant le concept d’affinité, dans une discussion serrée avec l’héritage kantien qu’il connaît parfaitement : il y va d’une redéfinition de l’expérience esthétique par l’enregistrement, entre déliaison et rédemption, le trait d’union entre caméra et réalité signant un effort conceptuel à notre avis remarquable.
Points de vue sur la jeunesse – Volume 1
Authors: Nico Magda 
Published: February 2022

La situation exceptionnelle à laquelle la plupart des pays européens doivent faire face conduit légitimement les chercheurs en sciences sociales à se référer à d’autres épisodes historiques extraordinaires dans leur quête pour mieux comprendre le présent et l’avenir du phénomène social et de la population qui est la plus touchée par ce phénomène. Dans cet article, l’auteur soutient que la crise économique qui touche l’Europe, et plus particulièrement certains pays européens et les jeunes, est un moment extraordinairement opportun pour que les chercheurs dans le domaine de la jeunesse utilisent, adaptent et étudient la notion de « génération » et analysent et réexaminent les processus de changement social et leurs conséquences politiques et sociales pour les jeunes. En s’appuyant sur la spécificité d’un pays d’Europe du Sud – le Portugal – et sur son régime moins protecteur de transition des jeunes (Walther, 2006), sur les conséquences en termes d’emploi et de migration du contexte économique actuel, et sur certains des récents événements et déclarations politiques et politisés, le trio constitué par les tendances qui ressortent des études sur la jeunesse, les politiques de la jeunesse et la réalité sociale sera examiné. En ce sens, en prenant l’exemple d’une approche nationale (le Portugal, l’un des pays où la crise est la plus ressentie et où les effets sur les jeunes sont les plus importants et les plus préoccupants), cet article articule les tendances actuelles et les événements liés à la spécificité de cette réalité nationale avec, d’une part, des implications théoriques (y compris la réévaluation de notions telles que le changement générationnel, les différences de mentalité et les conflits entre générations), et, d’autre part, des implications politiques. Pour ce faire, l’auteur cite une littérature importante dans le domaine des études sur la jeunesse et de la sociologie de la jeunesse, des sources secondaires concernant les indicateurs actuels des flux d’émigration et des taux de chômage, ainsi que des études détaillées dans le domaine des transitions vers l’âge adulte. L’article propose une réflexion, plus qu’il n’apporte de réponses, sur ce qui est toujours un processus en cours.
Points de vue sur la jeunesse – Volume 1
Authors: Cuzzocrea Valentina 
Published: February 2022

Cet article passe en revue la catégorie des NEET (ni étudiant, ni employé, ni en formation) en tant qu’instrument pour de futures analyses de transition des jeunes et la pleine intégration des jeunes dans la société. Dans un premier temps, cet article examine l’historique de la catégorie et son utilisation dans la politique européenne et les débats universitaires. Cette catégorie n’a pas seulement catalysé le travail des responsables politiques, elle constitue également un point de référence nécessaire pour réaliser des études dans le domaine de la jeunesse. Pourtant, jusqu’à présent, les experts ont peu contribué à l’analyse et à l’examen des problèmes conceptuels et des incohérences résultant de l’utilisation de cette catégorie. Cet article vise à combler les lacunes identifiées. Dans un deuxième temps, il soutient la nécessité de trouver une catégorie autour de laquelle pourraient naître des débats sur l’intégration des jeunes à travers l’Europe. Cependant, pour être retenue, cette catégorie doit présenter de l’intérêt, quel que soit le système de protection sociale dont dépendent les jeunes. A l’heure actuelle, on peut douter de l’utilité de la catégorie des NEET, au moins lorsque, par exemple, on compare la situation des jeunes qui vivent dans des pays où les citoyens bénéficient d’une aide de l’Etat, quel que soit leur statut relatif à l’emploi, et leur situation dans les pays dans lesquels cet élément est pris en considération ; leur situation n’est pas identique non plus dans les pays où les systèmes de formation facilitent une transition vers le monde du travail et ceux où ces systèmes sont inefficaces, pas plus que dans les pays où les marqueurs de l’âge adulte revêtent des significations culturelles très différentes. En ne tenant pas compte de ces différences, on pourrait mettre hâtivement « les gens dans des cases », risquer de brosser un tableau comparatif non représentatif des véritables besoins des jeunes et par conséquent élaborer des mesures inefficaces. Enfin, après avoir examiné ces aspects transversaux, la dernière partie de l’article s’attarde sur le cas de l’Italie, où les caractéristiques problématiques de la catégorie des NEET s’appliquent tout particulièrement, et envisage de futurs scénarios si ces préoccupations ne sont pas prises en considération dans les débats.