bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Population of H ii Regions in NGC 7020
Authors: Dottori Horacio , Díaz Rubén J. , Grosbøl Preben , Bueno Amanda , Gimeno Germán 
Published: March 2021

Abstract
The galaxy NGC 7020 displays an exotic hexagonal ringlike central structure with conspicuous ansae located at two opposite vertices and a tenuous external ring populated by H ii regions. Inside and around the hexagonal structure, Hα emission is also present at the inner disk. To characterize the population of the H ii regions, as well as their ionizing clusters, we imaged NGC 7020 with narrowband Hα and nearby continuum filters attached to GMOS-S installed on the Gemini South telescope. We found 202 H ii regions or complexes of H ii regions evenly distributed between the outer ring and the central disk The nucleus and ansae also present Hα emission. The equivalent width of the Hα line (W
Hα
) is systematically greater at the regions of the outer ring relative to those of the inner disk. We discuss the influence of the metallicity gradient of the disk and the upper limit of the masses of the initial mass function on W
Hα
, and we conclude that the data are still consistent with the occurrence of a younger burst of H ii region formation in the outer ring. The central regions present more massive clusters, M ≥ 106
M
⊙, than those of the outer ring (M ≤ 106
M
⊙). Three clusters within 5″ of the nucleus present masses higher than 108
M
⊙. The presence of diffuse Hα emission in the inner 5″ suggests gas flows in the nuclear region.
The Intensity and Evolution of the Extreme Solar and Geomagnetic Storms in 1938 January
Authors: Hayakawa Hisashi , Hattori Kentaro , Pevtsov Alexei A. , Ebihara Yusuke , Shea Margaret A. , McCracken Ken G. , Daglis Ioannis A. , Bhaskar Ankush T. , Ribeiro Paulo , Knipp Delores J. 
Published: March 2021

Abstract
Major solar eruptions occasionally direct interplanetary coronal mass ejections (ICMEs) to Earth and cause significant geomagnetic storms and low-latitude aurorae. While individual extreme storms are significant threats to modern civilization, storms occasionally appear in sequence, acting synergistically, and cause “perfect storms” on Earth. The stormy interval in 1938 January was one of such cases. Here, we analyze the contemporary records to reveal its time series on their source active regions, solar eruptions, ICMEs, geomagnetic storms, low-latitude aurorae, and cosmic-ray (CR) variations. Geomagnetic records show that three storms occurred successively on January 17/18 (Dcx ≈ −171 nT), January 21/22 (Dcx ≈ −328 nT), and January 25/26 (Dcx ≈ −336 nT). The amplitudes of the CR variations and storm sudden commencements (SSCs) show the impact of the first ICME as the largest (≈6% decrease in CR and 72 nT in SSC) and the ICMEs associated with the storms that followed as more moderate (≈3% decrease in CR and 63 nT in SSC; ≈2% decrease in CR and 63 nT in SSC). Interestingly, a significant solar proton event occurred on January 16/17 and the Cheltenham ionization chamber showed a possible ground-level enhancement. During the first storm, aurorae were less visible at midlatitudes, whereas, during the second and third storms, the equatorward boundaries of the auroral oval were extended down to 40.3° and 40.0° in invariant latitude. This contrast shows that the initial ICME was probably faster, with a higher total magnitude but a smaller southward component.
Revealing Ionization Conditions of Sz 102 with Spatially Resolved [Ne III] Microjets
Authors: Liu 劉 Chun-Fan 君帆 , Shang 尚 Hsien 賢 , Herczeg 沈 Gregory J. 雷歌 , Walter Frederick M. 
Published: March 2021

Abstract
Forbidden neon emission lines from small-scale microjets can probe high-energy processes in low-mass young stellar systems. We obtained spatially resolved [Ne iii] spectra in the microjets from the classical T Tauri Star Sz 102 using the Hubble Space Telescope Imaging Spectrograph at a spatial resolution of ∼0.″1. The blueshifted and redshifted [Ne iii] emission both peak in intensity within ∼0.″1 of the star and gradually decay along the flow outward to ∼0.″24. The spatial distribution and extent of the [Ne iii] microjet is consistent with a jet that is ionized close to the base and subsequently recombines on a longer timescale than the flow time. Ca ii H and K lines are also detected from the redshifted microjet with a line full-width at half-maximum of ∼170 km s−1, consistent with those of other forbidden emission lines, atop a 300 km s−1 wide stellar component. The launching radius of the Sz 102 jet, inferred from the observed line centroids and the range of inclination angles and stellar masses from the literature, is on the order of ∼0.03 au. The possible proximity of the launching region to the star allows immediate ionization without distance dilution from the circumstellar ionization sources, most likely keV X-ray flares generated by magnetic reconnection events in the star--disk system, to sustain the observed [Ne iii] flux.
Parametric Simulation Studies on the Wave Propagation of Solar Radio Emission: The Source Size, Duration, and Position
Authors: Zhang PeiJin , Wang ChuanBing , Kontar Eduard P. 
Published: March 2021

Abstract
The observed features of the radio source indicate that the waves of solar radio bursts are convoluted with complex propagation effects. In this work, we perform ray-tracing simulations on radio wave transport in the corona and interplanetary region with anisotropic electron density fluctuations. For the first time, the variation of the apparent source size, burst duration, and source position for the fundamental emission and harmonic emission at the frequency of 35 MHz are simulated as a function of the anisotropic parameter α and the angular scattering rate coefficient η = ϵ
2/h
0, where ϵ
2 = 〈δ
n
2〉/n
2 is the density fluctuation level and h
0 is its correlation length near the wave excitation site. It is found that isotropic fluctuations produce a much larger decay time than a highly anisotropic fluctuation for fundamental emission. By comparing the observed duration and source size with the simulation results in the parameter space, we can estimate the scattering coefficient and the anisotropic parameter η = 8.9 × 10−5 km−1 and α = 0.719 with a point pulse source assumption. Position offsets due to wave scattering and refraction can produce the co-spatial of the fundamental and harmonic waves in the observation of some type III radio bursts. The visual speed due to the wave propagation effect can reach 1.5c for η = 2.4 × 10−4 km−1 and α = 0.2 for the fundamental emission in the sky plane, accompanied with large expansion rate of the source size. The direction of the visual speed is mostly identical to the direction of the offset, thus, for the observation aimed at obtaining the source position, the source centroid at the starting time is closer to the wave excitation site.
Daniel Mögling’s Sunspot Observations in 1626–1629: A Manuscript Reference for the Solar Activity before the Maunder Minimum
Authors: Hayakawa Hisashi , Iju Tomoya , Murata Koji , Besser Bruno P. 
Published: March 2021

Abstract
The sunspots have been observed since 1610, and their group numbers have been used for evaluating the amplitude of solar activity. Daniel Mögling recorded his sunspot observations for more than 100 days in 1626–1629 and formed a significant data set of sunspot records before the Maunder Minimum. Here we have analyzed his original manuscripts in the Universitäts- und Landesbibliothek Darmstadt to review Mögling’s personal profile and observational instruments and derived the number and positions of the recorded sunspot groups. In his manuscript, we have identified 134 days with an exact sunspot group number and 3 days of additional descriptions. Our analyses have completely revised the observational dates and group numbers, added 19 days of hitherto overlooked observations, and removed 8 days of misinterpreted observations. We have also revisited the sunspot observations of Schickard and Hortensius and revised their data. These results have been compared with the contemporary observations. Moreover, we have derived the sunspot positions from his sunspot drawings and located them at 2°–23° in heliographic latitude in both solar hemispheres. Contextualized with contemporary observations, these results indicate their temporal migration to lower heliographic latitudes and emphasize their location in the declining phase of solar cycle −12 in the 1620s. Mögling’s observations were probably conducted using a pinhole and camera obscura, which likely made him underestimate the sunspot group number by ≥33%–52%. This underestimation should be noted upon comparison with modern data sets.
Scalaron Gravity near Sagittarius A*: Investigation of Spin of the Black Hole and Observing Requirements
Authors: Kalita Sanjeev 
Published: March 2021

Abstract
In this paper the author applies the scalaron gravity field and corresponding Yukawa coupling (derived by Kalita from the consideration of quantum vacuum fluctuations with UV and IR scales) to examine the scales of stellar orbits near the Galactic Center black hole, which can be probed by upcoming astrometric facilities for constraining modified gravity. Through the assumption that the pericenter shift of stellar orbits becomes of the order of spin and quadrupole moment effects of the black hole, it is found that for semimajor axes bounded below by time scales of gravitational wave emission and stellar age and above by S-2 like orbits (a = 990 au) the black hole spin with 0.1 ≤ χ ≤ 0.980 is eligible to probe scalaron masses within (10−22–10−18) eV and also the scalaron coupling, α = 2.73 × 10−4 derived earlier from quantum vacuum fluctuations. The orbital eccentricities are considered as e = 0.1, 0.5, and 0.9. Astrometric categories with σ = 10, 50, and 100 μas are used to probe the time scales and number of observing campaigns required for simultaneously constraining scalaron mass and black hole spin. It is found that extraction of black hole spin is possible within a = (74–433) au through 10 μas facilities. The present analysis is realized to be an independent opportunity to simultaneously constrain scalaron coupling, black hole spin, and tidal charge and hence to reveal the true nature of the spacetime structure of our nearest supermassive black hole.
Black Hole and Galaxy Coevolution in Moderately Luminous Active Galactic Nuclei at z ∼ 1.4 in SXDF
Authors: Setoguchi Kenta , Ueda Yoshihiro , Toba Yoshiki , Akiyama Masayuki 
Published: March 2021

Abstract
We investigate the relation of black hole mass versus host stellar mass and that of mass accretion rate versus star formation rate (SFR) in moderately luminous (

), X-ray selected broad-line active galactic nuclei (AGNs) at z = 1.18–1.68 in the Subaru/XMM-Newton Deep Field. The far-infrared to far-ultraviolet spectral energy distributions of 85 AGNs are reproduced with the latest version of Code Investigating GALaxy Emission (CIGALE), where the AGN clumpy torus model SKIRTOR is implemented. Most of their hosts are confirmed to be main-sequence star-forming galaxies. We find that the mean ratio of the black hole mass (M
BH) to the total stellar mass (M
stellar) is

, which is similar to the local black hole–to–bulge mass ratio. This suggests that if the host galaxies of these moderately luminous AGNs at z ∼ 1.4 are dominated by bulges, they already established the local black hole mass–bulge mass relation; if they are disk dominant, their black holes are overmassive relative to the bulges. The AGN bolometric luminosities and SFR show a good correlation with ratios higher than that expected from the local black hole-to-bulge mass relation, suggesting that these AGNs are in a SMBH-growth dominant phase.
Hierarchical Inference with Bayesian Neural Networks: An Application to Strong Gravitational Lensing
Authors: Wagner-Carena Sebastian , Park Ji Won , Birrer Simon , Marshall Philip J. , Roodman Aaron , Wechsler Risa H. ,   (LSST Dark Energy Science Collaboration)
Published: March 2021

Abstract
In the past few years, approximate Bayesian Neural Networks (BNNs) have demonstrated the ability to produce statistically consistent posteriors on a wide range of inference problems at unprecedented speed and scale. However, any disconnect between training sets and the distribution of real-world objects can introduce bias when BNNs are applied to data. This is a common challenge in astrophysics and cosmology, where the unknown distribution of objects in our universe is often the science goal. In this work, we incorporate BNNs with flexible posterior parameterizations into a hierarchical inference framework that allows for the reconstruction of population hyperparameters and removes the bias introduced by the training distribution. We focus on the challenge of producing posterior PDFs for strong gravitational lens mass model parameters given Hubble Space Telescope–quality single-filter, lens-subtracted, synthetic imaging data. We show that the posterior PDFs are sufficiently accurate (statistically consistent with the truth) across a wide variety of power-law elliptical lens mass distributions. We then apply our approach to test data sets whose lens parameters are drawn from distributions that are drastically different from the training set. We show that our hierarchical inference framework mitigates the bias introduced by an unrepresentative training set’s interim prior. Simultaneously, we can precisely reconstruct the population hyperparameters governing our test distributions. Our full pipeline, from training to hierarchical inference on thousands of lenses, can be run in a day. The framework presented here will allow us to efficiently exploit the full constraining power of future ground- and space-based surveys (https://github.com/swagnercarena/ovejero).
A Broadband X-Ray View of the Precessing Accretion Disk and Pre-eclipse Dip in the Pulsar Her X-1 with NuSTAR and XMM-Newton
Authors: Brumback McKinley C. , Hickox Ryan C. , Fürst Felix S. , Pottschmidt Katja , Tomsick John A. , Wilms Jörn , Staubert Rüdiger , Vrtilek Saeqa 
Published: March 2021

Abstract
We present a broadband X-ray timing study of the variations in pulse behavior with the superorbital cycle in the low-mass X-ray binary Her X-1. This source shows a 35 day superorbital modulation in X-ray flux that is likely caused by occultation by a warped, precessing accretion disk. Our data set consists of four joint XMM-Newton and NuSTAR observations of Her X-1 which sample a complete superorbital cycle. We focus our analysis on the first and fourth observations, which occur during the bright “main-on” phase, because these observations have strongly detected pulsations. We added an archival XMM-Newton observation during the “short-on” phase of the superorbital cycle because our observations at that phase are lower in signal to noise. We find that the energy-resolved pulse profiles show the same shape at similar superorbital phases, and the profiles are consistent with expectations from a precessing disk. We demonstrate that a simple precessing accretion disk model is sufficient to reproduce the observed pulse profiles. The results of this model suggest that the similarities in the observed pulse profiles are due to reprocessing by a precessing disk that has returned to its original precession phase. We determine that the broadband spectrum is well fit by an absorbed power law with a soft blackbody component and show that the spectral continuum also exhibits a dependence on the superorbital cycle. We also present a brief analysis of the energy-resolved light curves of a pre-eclipse dip, which shows soft X-ray absorption and hard X-ray variability during the dip.
Ultra-steep-spectrum Radio “Jellyfish” Uncovered in A2877
Authors: Hodgson Torrance , Bartalucci Iacopo , Johnston-Hollitt Melanie , McKinley Benjamin , Vazza Franco , Wittor Denis 
Published: March 2021

Abstract
We report on the discovery of a mysterious ultra-steep-spectrum (USS) synchrotron source in the galaxy cluster A2877. We have observed the source with the Murchison Widefield Array at five frequencies across 72–231 MHz and found the source to exhibit strong spectral curvature over this range, as well as the steepest known spectra of a synchrotron cluster source, with a spectral index across the central three frequency bands of

. Higher-frequency radio observations, including a deep observation with the Australia Telescope Compact Array, fail to detect any of the extended diffuse emission. The source is approximately 370 kpc wide and bears an uncanny resemblance to a jellyfish with two peaks of emission and long tentacles descending south toward the cluster center. While the “USS Jellyfish” defies easy classification, we here propose that the phenomenon is caused by the reacceleration and compression of multiple aged electron populations from historic active galactic nucleus (AGN) activity, a so-called “radio phoenix,” by an as yet undetected weak cluster-scale mechanism. The USS Jellyfish adds to a growing number of radio phoenix in cool-core clusters with unknown reacceleration mechanisms; as the first example of a polyphoenix, however, this implies that the mechanism is on the scale of the cluster itself. Indeed, we show that in simulations, emission akin to the USS Jellyfish can be produced as a short-lived transient phase in the evolution of multiple interacting AGN remnants when subject to weak external shocks.
Polarization Predictions in the GRB Prompt Phase with the Internal Shock Model
Authors: Lan Mi-Xiang , Wang Hao-Bing , Xu Siyao , Liu Siming , Wu Xue-Feng 
Published: March 2021

Abstract
As the standard gamma-ray burst (GRB) prompt-emission model, the internal shock (IS) model can reproduce the fast-rise and slow-decay features of the pulses in the GRB light curve. The time- and energy-dependent polarization can deliver important physical information on the emission region and can be used to test models. Polarization predictions for the GRB prompt phase with the magnetized IS model should be investigated carefully. The magnetic field of the magnetized IS model is very likely to be mixed and decays with radius. The synchrotron emission in the presence of such a decaying magnetic field can recover the Band-like spectrum of the GRB prompt phase. We investigate the dependence of the polarization of GRB prompt emission on both time and energy in the framework of the magnetized IS model. Due to the large range of parameters, it is hard to distinguish the magnetized IS model and the magnetic-reconnection model through polarization degree (PD) curves. The energy-dependent PD could increase toward the high-energy band for the magnetized IS model, while it decreases to zero above the megaelectronvolt band for the dissipative photosphere model. Therefore, we conclude that the energy dependence of PD can be used to distinguish these two models for the GRB prompt emission. Finally, we find that, independent of the observational energy band, the profiles of the ξ

B
− PD curve for the time-integrated and time-resolved PDs are very similar, where ξ

B
is the magnetic field strength ratio of the ordered component to the random component.
On the Relation between Kappa Distribution Functions and the Plasma Beta Parameter in the Earth’s Magnetosphere: THEMIS Observations
Authors: Eyelade Adetayo V. , Stepanova Marina , Espinoza Cristóbal M. , Moya Pablo S. 
Published: March 2021

Abstract
The Earth’s magnetosphere represents a natural plasma laboratory that allows us to study the behavior of particle distribution functions in the absence of Coulomb collisions, typically described by the kappa distributions. We have investigated the properties of these functions for ions and electrons in different magnetospheric regions, thereby making it possible to reveal the κ-parameters for a wide range of plasma beta (β) values (from 10−3 to 102). This was done using simultaneous ion and electron measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft spanning the years 2008–2018. It was found that for a fixed plasma β, the κ-index and core energy (E

c
) of the distribution can be modeled by the power law

for both species, and the relation between β, κ, and E

c
is much more complex than earlier reported: both A and γ exhibit systematic dependencies with β. Our results indicate that β ∼ 0.1–0.3 is a range where the plasma is more dynamic, since it is influenced by both the magnetic field and temperature fluctuations, which suggests that the transition between magnetically and kinetically dominated plasmas occurs at these values of β. For β > 1, both A and γ take nearly constant values, a feature that is especially notable for the electrons and might be related to their demagnetization. The relation between β, κ, and E

c
that we present is an important result that can be used by theoretical models in the future.
Distribution of testate amoebae in bryophyte communities in São Miguel Island (Azores Archipelago)
Authors: Souto Martin , Gonçalves Vítor , Pontevedra-Pombal Xabier , Raposeiro Pedro 
Published: March 2021

Testate amoebae are a polyphyletic group of protists living preferentially in soils, freshwaters and wetlands. These Protozoa have a worldwide distribution, but their presence and diversity in the Azores (a remote oceanic archipelago) is poorly known, with only twelve taxa recorded so far. The published information reflects occasional collections from sporadic field visits from naturalists to São Miguel Island, mainly in the nineteenth century. To overcome this limitation, a standardised survey was carried out on the Island, sampling different types of habitats from several localities to provide the distribution and information on species ecology of testate amoebae.
In this study, 43 species of testate amoebae were recorded (within a total of 499 occurrences), belonging to two orders of Protista (26 Arcellinida and 17 Euglyphida). The most frequently occurring testate amoebae were Euglypha strigosa, Trinema lineare, Euglypha rotunda, Assulina muscorum and Cyclopyxis eurystoma. The most diverse genus was Euglypha (six species). A total of 38 species are new records for the Azores Archipelago. These data help to improve knowledge of the geographical distribution of testate amoebae in the northern hemisphere and their diversity in the Azores Archipelago.
Usages gouvernementaux de la participation citoyenne au Chili : mobiliser, contrôler, légitimer (1964-2010)
Authors: Pinet Nicolas 
Published: March 2021

Cet article analyse les représentations qu’ont les gouvernants démocrates chiliens de la participation citoyenne et l’usage qu’ils en font, tant au niveau discursif qu’au niveau des politiques publiques. Leurs rapports ambivalents vis-à-vis de la participation des citoyens qui, tout à la fois, légitime leur pouvoir et peut le remettre en cause sont-ils à attribuer au contexte et au personnel politique, ou, au contraire, à la structuration même de l’institutionnalité démocratique ? Pour répondre, l’analyse porte successivement sur le gouvernement d’Eduardo Frei Montalva (1964-1970), sur celui de Salvador Allende (1970-1973) et sur les gouvernements successifs de la Concertation (1990-2010). On conclut que, malgré des contextes opposés, les gouvernants entretiennent un rapport instrumental similaire à la participation citoyenne, dont ils ont besoin, soit pour mener à bien leur projet politique – dans les deux premiers cas –, soit pour réassurer leur propre légitimité et celle des institutions démocratiques – troisième cas.