Sazuna/UAT_keywords huggingface dataset:
Has the Palomar 14 Globular Cluster Been Captured by the Milky Way?. We examine a new scenario to model the outer halo globular cluster (GC) Palomar 14 (Pal 14) over its lifetime by performing a comprehensive set of direct N-body calculations. We assume Pal 14 was born in a now detached/disrupted dwarf galaxy with a strong tidal field. Pal 14 evolved there until the slope of the stellar mass function (MF) became close to the measured value, which is observed to be significantly shallower than in most GCs. After about 2–3 Gyr, Pal 14 was then captured by the Milky Way (MW). Although the physical size of such a cluster is indistinguishable from a cluster that has lived its entire life in the MW, other parameters like its mass and the MF slope, strongly depend on the time the cluster is taken from the dwarf galaxy. After being captured by the MW on a new orbit, the cluster expands and eventually reaches the appropriate mass and size of Pal 14 after 11.5 Gyr while reproducing the observed MF. These simulations thus suggest that Pal 14 may have formed in a dwarf galaxy with a post-gas expulsion initial half-mass radius and mass of r h = 7 pc and 8 &lt; M/104 &lt; 10 M ⊙, respectively, with a high degree of primordial mass segregation.

Keywords: Globular star clusters, Stellar mass functions, Dwarf galaxies, N-body simulations
Magnetic Field Alignment Relative to Multiple Tracers in the High-mass Star-forming Region RCW 36. We use polarization data from SOFIA HAWC+ to investigate the interplay between magnetic fields and stellar feedback in altering gas dynamics within the high-mass star-forming region RCW 36, located in Vela C. This region is of particular interest as it has a bipolar H II region powered by a massive star cluster, which may be impacting the surrounding magnetic field. To determine if this is the case, we apply the histogram of relative orientations (HRO) method to quantify the relative alignment between the inferred magnetic field and elongated structures observed in several data sets such as dust emission, column density, temperature, and spectral line intensity maps. The HRO results indicate a bimodal alignment trend, where structures observed with dense gas tracers show a statistically significant preference for perpendicular alignment relative to the magnetic field, while structures probed by the photodissociation region (PDR) tracers tend to align preferentially parallel relative to the magnetic field. Moreover, the dense gas and PDR associated structures are found to be kinematically distinct such that a bimodal alignment trend is also observed as a function of line-of-sight velocity. This suggests that the magnetic field may have been dynamically important and set a preferred direction of gas flow at the time that RCW 36 formed, resulting in a dense ridge developing perpendicular to the magnetic field. However, on filament scales near the PDR region, feedback may be energetically dominating the magnetic field, warping its geometry and the associated flux-frozen gas structures, causing the observed preference for parallel relative alignment.

Keywords: Star forming regions, Molecular clouds, Photodissociation regions, Interstellar magnetic fields, Star formation, Interstellar medium, H II regions
Probing Populations of Dark Stellar Remnants in the Globular Clusters 47 Tuc and Terzan 5 Using Pulsar Timing. We present a new method to combine multimass equilibrium dynamical models and pulsar timing data to constrain the mass distribution and remnant populations of Milky Way globular clusters (GCs). We first apply this method to 47 Tuc, a cluster for which there exists an abundance of stellar kinematic data and which is also host to a large population of millisecond pulsars. We demonstrate that the pulsar timing data allow us to place strong constraints on the overall mass distribution and remnant populations even without fitting on stellar kinematics. Our models favor a small population of stellar-mass black holes (BHs) in this cluster (with a total mass of  446‑72+75M⊙ ), arguing against the need for a large (&gt;2000 M ⊙) central intermediate-mass BH. We then apply the method to Terzan 5, a heavily obscured bulge cluster that hosts the largest population of millisecond pulsars of any Milky Way GC and for which the collection of conventional stellar kinematic data is very limited. We improve existing constraints on the mass distribution and structural parameters of this cluster and place stringent constraints on its black hole content, finding an upper limit on the mass in BHs of ∼4000 M ⊙. This method allows us to probe the central dynamics of GCs even in the absence of stellar kinematic data and can be easily applied to other GCs with pulsar timing data, for which data sets will continue to grow with the next generation of radio telescopes.

Keywords: Globular star clusters, Black holes, Millisecond pulsars, Stellar dynamics, Pulsars, Stellar mass functions, Star clusters
The Molecular Cloud Life Cycle. II. Formation and Destruction of Molecular Clouds Diagnosed via H<SUB>2</SUB> Fluorescent Emission. Molecular hydrogen (H2) formation and dissociation are key processes that drive the gas life cycle in galaxies. Using the SImulating the LifeCycle of Molecular Clouds zoom-in simulation suite, we explore the utility of future observations of H2 dissociation and formation for tracking the life cycle of molecular clouds. The simulations used in this work include nonequilibrium H2 formation, stellar radiation, sink particles, and turbulence. We find that at early times in the cloud evolution H2 formation rapidly outpaces dissociation and molecular clouds build their mass from the atomic reservoir in their environment. Rapid H2 formation is also associated with a higher early star formation rate. For the clouds studied here, H2 is strongly out of chemical equilibrium during the early stages of cloud formation but settles into a bursty chemical steady state about 2 Myr after the first stars form. At the latest stage of cloud evolution, dissociation outweighs formation and the clouds enter a dispersal phase. We discuss how theories of the molecular cloud life cycle and star formation efficiency may be distinguished with observational measurements of H2 fluorescence with a space-based high-resolution far-UV spectrometer, such as the proposed Hyperion and Eos NASA Explorer missions. Such missions would enable measurements of the H2 dissociation and formation rates, which we demonstrate can be connected to different phases in a molecular cloud's star-forming life, including cloud building, rapidly star forming, H2 chemical equilibrium, and cloud destruction.

Keywords: Interstellar line emission, Molecular clouds, Photodissociation regions, Star formation, Interstellar medium, Diffuse molecular clouds
Local Interstellar Spectra and Solar Modulation of Cosmic-Ray Proton and Helium. Galactic cosmic rays suffer from solar modulation when they propagate through the heliosphere. The transfer of the local interstellar spectrum (LIS) to the top-of-atmosphere spectra is influenced by solar wind convection, and diffusion on the heliospheric magnetic field (HMF), among other factors. In this work, we derive the LIS of proton (p) and helium (He) covering energies from a few MeV/n to TeV/n, using a nonparameterization method. The study utilizes monthly AMS-02 data on proton and helium fluxes and their ratio to examine the evolution of solar modulation from 2011 May to 2017 May. To improve the fitting, the force-field approximation is modified by assigning different solar modulation potentials for high (ϕ  h ) and low (ϕ  l ) energy ranges. A sigmoid function is employed to describe the transition between these energy ranges. The analysis reveals that the break in proton and helium fluxes occurs at the same rigidity value, with a mean of approximately 6 GV and this break is more pronounced during the HMF reversal period. The ϕ  l  is close to the result of Advanced Composition Explorer while the ϕ  h  is close to the result of neutron monitor data. Furthermore, the long-term behavior of the proton-to-helium ratio ratio is found to naturally arise from the model when considering different Z/A values and the LISs for proton and helium.

Keywords: Solar activity, Heliosphere, Cosmic rays
3D Hydrodynamic Simulations of Massive Main-sequence Stars. III. The Effect of Radiation Pressure and Diffusion Leading to a 1D Equilibrium Model. We present 3D hydrodynamical simulations of core convection with a stably stratified envelope of a 25 M ⊙ star in the early phase of the main sequence. We use the explicit gas-dynamics code PPMstar, which tracks two fluids and includes radiation pressure and radiative diffusion. Multiple series of simulations with different luminosities and radiative thermal conductivities are presented. The entrainment rate at the convective boundary, internal gravity waves in and above the boundary region, and the approach to dynamical equilibrium shortly after a few convective turnovers are investigated. We perform very long simulations on 8963 grids accelerated by luminosity boost factors of 1000, 3162 and 10,000. In these simulations, the growing penetrative convection reduces the initially unrealistically large entrainment. This reduction is enabled by a spatial separation that develops between the entropy gradient and the composition gradient. The convective boundary moves outward much more slowly at the end of these simulations. Finally, we present a 1D method to predict the extent and character of penetrative convection beyond the Schwarzschild boundary. The 1D model is based on a spherically averaged reduced entropy equation that takes the turbulent dissipation as input from the 3D hydrodynamic simulation and takes buoyancy and all other energy sources and sinks into account. This 1D method is intended to be ultimately deployed in 1D stellar evolution calculations and is based on the properties of penetrative convection in our simulations carried forward through the local thermal timescale.

Keywords: Hydrodynamical simulations, Stellar interiors, Stellar convective zones, Stellar structures, Hydrodynamics, Massive stars, Stellar oscillations, Astrophysical fluid dynamics
Detection of the Extended γ-Ray Emission from the New Supernova Remnant G321.3–3.9 with Fermi-LAT. With the 15 yr of Pass 8 data recorded by the Fermi Large Area Telescope, we report the detection of an extended gigaelectronvolt emission component with a 68% containment radius of 0.°85, which is spatially associated with the newly identified supernova remnant (SNR) G321.3–3.9. The γ-ray spectrum is best described by a log-parabola model in the energy range of 100 MeV–1 TeV, which shows a significant spectral curvature at ∼1 GeV. Either a leptonic or a hadronic model could explain the multiwavelength data of G321.3–3.9, while the leptonic model predicts a too-low strength of magnetic field. Also considering the flat radio spectrum of G321.3–3.9 and the γ-ray upper limit in the low energy band, the hadronic model is favored. The spatial coincidence between the γ-ray morphology and the diffuse thermal X-ray emission of G321.3–3.9 and the curved gigaelectronvolt γ-ray spectrum make G321.3–3.9 similar to the typical middle-aged SNRs interacting with molecular clouds (MCs). Such characteristics provide further evidence of the potential hadronic origin for its γ-ray emission. However, there is no MC detected around G321.3–3.9, which challenges the hadronic model.

Keywords: Supernova remnants, Gamma-ray astronomy, Gamma-ray sources, Cosmic rays
Inspect the Time Lag in Galactic Cosmic-Ray Solar Modulation. It is well known that there is a time lag between the solar activity and the galactic cosmic-ray flux. How to accurately describe this delay is the key problem in making precise predictions of cosmic-ray flux. In this work, a response function in convolution is first used to describe the relative contribution of the solar wind blowout at earlier times to the current flux (the origin of time lag), and its explicit profile is obtained by our 3D time-dependent numerical model. It is found that our response function is superior to other functions in accounting for the time lag effect, and its rigidity and physical process dependence are studied thoroughly. At last, this description is partly demonstrated by a simplified derivation based on the underling physical processes.

Keywords: Galactic cosmic rays, Heliosphere
Cosmic-Ray Flux Correlation between MCMU and JBGO Neutron Monitors. Neutron monitors (NMs) are large ground-based detectors of atmospheric secondary particles, mostly neutrons, from primary cosmic rays. Their sky direction and rigidity imply a well-defined incoming (asymptotic) direction in space. From 2015 December 16 to 2017 January 8, 6 of the 18 NM counters had been transferred from McMurdo to Jang Bogo, both in Antarctica, so data from similar detectors were recorded simultaneously at these two nearby NM stations. Autocorrelations of these NM count rates are well fit as the sum of three components: an exponential function and a cosine with a period of 1 day, both centered at zero lag, plus a constant. Fitting the cross correlation of the two count rates, the functions are no longer centered at zero lag. The best-fit cosine phase is at time lag ‑160.22 ± 0.12 minutes. Calculating cosmic-ray trajectories in Earth's magnetic field throughout the time interval, the mean difference in response-weighted asymptotic longitudes corresponds to time lag ‑169.41 ± 0.31 minutes, in close agreement with the observed lag. Thus, the cosine term is consistent with and provides a technique to cleanly measure the cosmic-ray anisotropy. In contrast, the peak term shows a time lag of –14.55 minutes, much closer to the –9.60 minutes lag in rotation due to the difference in geographic longitude. We find a similar behavior in the correlations between other pairs of stations. We propose that rapid fluctuations in the counting rate may be primarily due to cosmic-ray particles of very high energy.

Keywords: Galactic cosmic rays, Cosmic anisotropy, Cosmic ray detectors, Forbush effect
Alleviating H <SUB>0</SUB> and S <SUB>8</SUB> Tensions Simultaneously in K-essence Cosmology. The present work begins by examining the early-Universe inflationary epoch of a special K-essence model, which incorporates a linear coupling term between the scalar field potential and the canonical Lagrangian. For the power-law potential, we both numerically and analytically prove that the inflationary parameters such as the spectral index and tensor-to-scalar ratio are compatible with the recent BICEP/Keck observations. Continuing this work, our analysis based on comparing early-Universe observations with late-Universe measurements indicates that the tension on the Hubble parameter H 0 and the growth of structure parameter S 8 can be alleviated simultaneously. More precisely, compared to the standard ΛCDM model, our model can reduce H 0 tension to roughly 2.2σ, and the S 8 discrepancy diminishes to 0.82σ.

Keywords: Early universe, Cosmic microwave background radiation, Observational cosmology, Quantum cosmology, Cosmic inflation, Supernovae
Time Variation of the Solar Tachocline. We have used solar oscillation frequencies and frequency splittings obtained over solar cycles 23 and 24 and the rising phase of solar cycle 25 to investigate whether the tachocline properties (the change in the rotation rate across the tachocline. i.e., the jump, the width, and the position) show any time variation. We confirm that the change in rotation rate across the tachocline changes substantially; however, the change does not show a simple correlation with solar cycle unlike, for instance, changes in mode frequencies. The change during the ascending phase of solar cycle 25 is almost a mirror image of the change during the descending part of solar cycle 24, tempting us to speculate that the tachocline has a much longer period than either the sunspot or the magnetic cycle. We also find that the position of the tachocline, defined as the midpoint of the change in rotation rate, showed significant changes during solar cycle 24. The width of the tachocline, on the other hand, has shown significant changes during solar cycle 23 but not later. The change in the tachocline becomes more visible if we look at the upper and lower extents of the tachocline, defined as (position ± width). We find that for epochs around solar maxima and minima, the extent decreases before increasing again—a few more years of data should clarify this trend. Our results reinforce the need to continue helioseismic monitoring of the Sun to understand solar activity and its evolution.

Keywords: Solar cycle, Solar rotation, Helioseismology, The Sun, Solar oscillations
Synchrotron Polarization of a Hybrid Distribution of Relativistic Thermal and Nonthermal Electrons in Gamma-Ray Burst Prompt Emission. Synchrotron polarization of relativistic nonthermal electrons in gamma-ray bursts (GRBs) has been widely studied. However, recent numerical simulations of relativistic shocks and magnetic reconnection have found that a more realistic electron distribution consists of a power-law component plus a thermal component, which requires observational validation. In this paper, we investigate synchrotron polarization using a hybrid energy distribution of relativistic thermal and nonthermal electrons within a globally toroidal magnetic field in GRB prompt emission. Our results show that compared to the case of solely nonthermal electrons, the synchrotron polarization degrees (PDs) in these hybrid electrons can vary widely, depending on different parameters, and that the PD decreases progressively with frequency in the gamma-ray, X-ray, and optical bands. The time-averaged PD spectrum displays a significant bump in the gamma-ray and X-ray bands, with the PDs higher than ∼60% if the thermal peak energy of the electrons is much smaller than the conjunctive energy of the electrons between the thermal and nonthermal distributions. The high-synchrotron PDs (≳60%) in the gamma-ray and X-ray bands, which generally cannot be produced by solely nonthermal electrons with typical power-law slopes, can be achieved by hybrid electrons and primarily originates from the exponential decay part of the thermal component. Moreover, this model can roughly explain the PDs and spectral properties of some GRBs, where GRB 110301A with a high PD ( 70‑22+22% ) may be potential evidence for the existence of relativistic thermal electrons.

Keywords: Starlight polarization, Gamma-ray bursts, Interstellar synchrotron emission
Resonant Friction on Disks in Galactic Nuclei. We argue that resonant friction has a dramatic effect on a disk whose rotation direction is misaligned with that of its host nuclear star cluster. The disk's gravity causes gravitational perturbation of the cluster that in turn exerts a strong torque back onto the disk. We argue that this torque may be responsible for the observed disruption of the clockwise disk of young stars in the Galactic center, and show in numerical experiments that it produces the observed features in the distribution of the stars' angular momenta. More generally, we speculate that the rotation of nuclear star clusters has a stabilizing effect on the orientation of transient massive accretion disks around the supermassive black holes residing in their centers, and thus on the directions and magnitudes of the black hole spins.

Keywords: Dynamical friction, Galaxy accretion disks, Active galactic nuclei, Black holes
An Independent Measure of the Kinematic Dipole from SDSS. We utilize the Sloan Digital Sky Survey (SDSS) extended Baryon Oscillation Spectroscopic Survey and Baryon Oscillation Spectroscopic Survey catalogs with precise spectroscopic redshifts to estimate the kinematic redshift dipole caused by the proper motion of the solar system. We find that the velocity extracted from the kinematic dipole is consistent with cosmic microwave background (CMB) inferred values. Although the small sky coverage and limited number density of the SDSS sources constrain us from obtaining precise and robust measurements, we leverage the redshift dipole method to estimate the kinematic dipole. The velocity measurements in this study are insensitive to intrinsic clustering, associated with the source count dipole. The kinematic dipole measured in this work and its consistency with CMB values do not guarantee isotropy at large scales. The anisotropy (excess dipole) measured with the NRAO VLA Sky Survey and the Wide-field Infrared Survey Explorer Catalog could be due to the intrinsic distribution of galaxies. The results in this work focus solely on the kinematic dipole term.

Keywords: Cosmology, Large-scale structure of the universe, Observational cosmology, Cosmological principle, Redshift surveys
Thread Displacement and Intensity Oscillations in a Quiescent Prominence. In this paper, we investigate the thread displacement and intensity oscillations in a quiescent prominence observed by New Vacuum Solar Telescope at the Hα line center on 2019 October 31. Each individual thread is traced by the local maximum intensity among its width at various times. In total, 35 threads are detected at six heights parallel to the solar surface. We find 29/35 threads exhibiting the displacement oscillation. A sinusoidal function is used to fit them, and a mean period of 26 minutes is identified. By slicing the same thread at different positions, we find that the oscillation of the thread is very likely a standing wave, but it could also be a long-wavelength propagating wave. After integrating the intensity along the thread width, we also find 8/35 threads presenting their intensity oscillation with a mean period of 7.7 minutes. In total, 7/35 threads exhibit both the displacement and the intensity oscillations.

Keywords: Solar oscillations, Quiescent solar prominence, Magnetohydrodynamics, Quiet solar corona
Identifying Jittering Jet-shaped Ejecta in the Cygnus Loop Supernova Remnant. Analyzing images of the Cygnus Loop, a core-collapse supernova (CCSN) remnant, in different emission bands, we identify a point-symmetrical morphology composed of three symmetry axes that we attribute to shaping by three pairs of jets. The main jet axis has an elongated S shape, appearing as a faint narrow zone in visible and UV. We term it the S-shaped hose, and the structure of three symmetry lines the point-symmetric wind rose. The two other lines connect a protrusion (an ear or a bulge) with a hole on the opposite side of the center (a nozzle or a cavity), structures that we identify in the X-ray, UV, visible, IR, and/or radio images. There is a well-known blowout at the southern end of the S-shaped hose, and we identify a possible opposite blowout at the northern end of the S-shaped hose. The point-symmetrical morphology of the Cygnus Loop is according to the expectation of the jittering jets explosion mechanism (JJEM) of CCSNe, where several to few tens of pairs of jets with stochastically varying directions explode the star. The three pairs of jets that shaped the wind-rose structure of the Cygnus Loop are the last energetic pairs of this series of jets. Our study further supports the JJEM as the main explosion mechanism of CCSNe.

Keywords: Supernova remnants, Stellar jets, Core-collapse supernovae