Sazuna/UAT_keywords huggingface dataset:
Tests of AGN Feedback Kernels in Simulated Galaxy Clusters. In cool-core galaxy clusters with central cooling times much shorter than a Hubble time, condensation of the ambient central gas is regulated by a heating mechanism, probably an active galactic nucleus. Previous analytical work has suggested that certain radial distributions of heat input may result in convergence to a quasi-steady global state that does not substantively change on the timescale for radiative cooling, even if the heating and cooling are not locally in balance. To test this hypothesis, we simulate idealized galaxy cluster halos using the ENZO code with an idealized, spherically symmetric heat input kernel intended to emulate. Thermal energy is distributed with radius according to a range of kernels, in which total heating is updated to match total cooling every 10 Myr. Some heating kernels can maintain quasi-steady global configurations, but no kernel we tested produces a quasi-steady state with central entropy as low as those observed in cool-core clusters. The general behavior of the simulations depends on the proportion of heating in the inner 10 kpc, with low central heating leading to central cooling catastrophes, high central heating creating a central convective zone with an inverted entropy gradient, and intermediate central heating resulting in a flat central entropy profile that exceeds observations. The timescale on which our simulated halos fall into an unsteady multiphase state is proportional to the square of the cooling time of the lowest-entropy gas, allowing more centrally concentrated heating to maintain a longer-lasting steady state.

Keywords: Galaxy clusters, Hydrodynamical simulations, AGN host galaxies, Cooling flows, Active galactic nuclei
Uncovering the Primary X-Ray Emission and Possible Starburst Component in the Polarized NLS1 Mrk 1239. X-ray observations of the unique NLS1 galaxy Mrk 1239 spanning 18 yr are presented. Data from XMM-Newton, Suzaku, Swift, and NuSTAR are combined to obtain a broadband, multi-epoch view of the source. There is spectral variability in the 3-10 keV band over the 18 yr. An analysis of the NuSTAR and Suzaku lightcurves also suggests rapid variability in the 3-10 keV band, which is consistent with the NLS1 definition of the source. However, no variability is seen below 3 keV on any timescale. Two distinct physical models are adopted to describe the data above and below $\sim 3\,\mathrm{keV}$ . The low energies are dominated by a hot, diffuse gas likely associated with a starburst component at large physical scales. The higher-energy spectrum is dominated by emission from the central region. Ionized partial covering and relativistic blurred reflection are considered for the central region emission. In both cases, the underlying power law has a photon index of Γ ∼ 2.3-2.4. A distant reflector, a neutral partial covering component with a covering fraction near ∼1, and contributions from starburst emission are always required. The blurred reflection model requires a reflection-dominated spectrum, which may be at odds with the low emissivity index and radio properties of the source. By contrast, the two absorption components required in the ionized partial covering model may correspond to the two distinct regions of polarization observed in the optical. Regardless of the physical model, spectral changes between epochs are driven by the absorption components—and on short timescales, by intrinsic active galactic nucleus variability.

Keywords: AGN host galaxies, X-ray active galactic nuclei
From Supernova to Remnant: Tracking the Evolution of the Oldest Known X-Ray Supernovae. Core-collapse supernovae (SNe) expand into a medium created by winds from the pre-SN progenitor. The SN explosion and resulting shock wave(s) heat up the surrounding plasma, giving rise to thermal X-ray emission, which depends on the density of the emitting material. Tracking the variation of the X-ray luminosity over long periods of time thus allows for investigation of the kinematics of the SN shock waves, the structure of the surrounding medium, and the nature of the progenitor star. In this paper, X-ray observations of five of the oldest known X-ray SNe—SN 1970G, SN 1968D, SN 1959D, SN 1957D, and SN 1941C—are analyzed, with the aim of reconstructing their light curves over several decades. For those SNe for which we can extract multiepoch data, the X-ray luminosity appears to decline with time, although with large error bars. No increase in the X-ray emission from SN 1970G is found at later epochs, contrary to previous reports. All five SNe show X-ray luminosities that are of comparable magnitude. We compare the late-time X-ray luminosities of these SNe to those of supernova remnants (SNRs) in the Galaxy, which are a few hundred years old, and find that when the tentative decline is taken into account, the luminosity of the old SNe studied herein could fall below the luminosity of some of the younger SNRs within a few hundred years. However, the X-ray luminosity should begin to increase as the SNe expand in the Sedov phase, thus reaching that of the observed SNRs.

Keywords: X-ray astronomy, Core-collapse supernovae, Type II supernovae, Massive stars, X-ray point sources, X-ray transient sources, Stellar winds, Supernovae
An Alternative Interpretation of Impulsive SEP Events Occurring on 1999 January 9-10. We have examined two impulsive solar energetic particle events that occurred on 1999 January 9-10 (earlier event A and later event B). Both events showed earlier velocity dispersion and later intensity dropout of ions. In particular, in event A, the dropout repeated five times. Through the onset time analysis of solar particles, we find that only at higher energies (&gt;0.2 MeV nucleon-1 for heavy ions and &gt;2.8 keV for electrons) can the analysis provide a consistent path length of ions and electrons. The path length in event A is larger than that in event B. In contrast, at lower energies, the analysis fails to predict the distribution of first arrival of solar particles. The divergence between observation and prediction would increase if the interplanetary scattering of ions were taken into account. We then focus on the lower-energy region, where a negative correlation of ion intensities with plasma β is displayed. We have found that the repeated dropout of ions can be caused by the magnetic reconnection acceleration in the solar wind. In addition, we have discovered an isolated proton dropout event in which a sharply anisotropic pitch-angle distribution of low-energy electrons is also seen. Our observation is consistent with the prediction of Tautz et al. that a minimum power spectral density component parallel to the magnetic field can reduce the magnetic mirroring effect, preventing electron scattering through 90°.

Keywords: Interplanetary turbulence, Solar energetic particles, Solar wind, Solar magnetic fields, Solar particle emission
Multiwavelength Observation of a Failed Eruption from a Helical Kink-unstable Prominence. Multiwavelength observations of a prominence eruption provide an opportunity to uncover the physical mechanism of the triggering and the evolution process of the eruption. In this paper, we investigate a prominence that erupted on 2012 October 14, recorded in Hα, EUV, and X-ray wavelengths. The process of the eruption gives evidence for the existence of a helical magnetic structure showing the twist converting to writhe. The estimated twist is $\sim 6\pi $ (three turns), exceeding the threshold of the kink instability. The rising plasma reached a high speed of 228 km s-1, followed by a sudden rapid acceleration of 2715 m s-2, and was synchronous with a solar flare. Co-spatial cusp-shaped structures were observed in both 131 and 94 Å images from the Atmospheric Imaging Assembly, signifying the location of the magnetic reconnection. The erupted flux rope finally underwent a deceleration with a maximum value of 391 m s-2, which is larger than the freefall acceleration on the Sun (273 m s-2), suggesting that the eruption finally failed, possibly due to an inward magnetic tension force.

Keywords: Solar flares, Solar prominences, Solar magnetic reconnection, Solar filaments, Solar activity
Postmerger Mass Ejection of Low-mass Binary Neutron Stars. We study the postmerger mass ejection of low-mass binary neutron stars (NSs) with the system mass of 2.5 M⊙ and subsequent nucleosynthesis by performing general-relativistic, neutrino-radiation viscous-hydrodynamics simulations in axial symmetry. We find that the merger remnants are long-lived massive NSs surviving more than several seconds, irrespective of the nuclear equations of state (EOSs) adopted. The ejecta masses of our fiducial models are ∼0.06-0.1 M⊙ (depending on the EOS), being ∼30% of the initial disk masses (∼0.15-0.3 M⊙). Postprocessing nucleosynthesis calculations indicate that the ejecta is composed mainly of light r-process nuclei with small amounts of lanthanides (mass fraction ∼0.002-0.004) and heavier species due to the modest average electron fraction (∼0.32-0.34) for a reasonable value of the viscous coefficient. Such abundance distributions are compatible with those in weak r-process stars such as HD 122563 but not with the solar r-process-like abundance patterns found in all measured r-process-enhanced metal-poor stars. Therefore, low-mass binary NS mergers should be rare. If such low-mass NS mergers occur, their electromagnetic counterparts, kilonovae, will be characterized by an early bright blue emission because of the large ejecta mass as well as the small lanthanide fraction. We also show, however, that if the effective turbulent viscosity is very high, the electron fraction of the ejecta could be low enough that the solar r-process-like abundance pattern is reproduced and the lanthanide fraction becomes so high that the kilonova would be characterized by early bright blue and late bright red emissions.

Keywords: Neutron stars, High energy astrophysics, Nucleosynthesis, R-process, Gravitational wave sources
Using Machine Learning to Find Ghostly Damped Lyα Systems in the SDSS DR14. We report the discovery of 59 new ghostly absorbers from the Sloan Digital Sky Survey Data Release 14. These absorbers, with zabs ∼ zQSO, reveal no Lyα absorption, and they are mainly identified through the detection of strong metal absorption lines in the spectra. The number of such previously known systems is 30. The new systems are found with the aid of machine-learning algorithms. The spectra of 41 (out of total of 89) absorbers also cover the Lyβ spectral region. By fitting the damping wings of the Lyβ absorption in the stacked spectrum of 21 (out of 41) absorbers with relatively stronger Lyβ absorption, we measured an H I column density of log N(H I) = 21.50. This column density is 0.5 dex higher than that of the previous work. We also found that the metal absorption lines in the stacked spectrum of the 21 ghostly absorbers with stronger Lyβ absorption have similar properties as those in the stacked spectrum of the remaining systems. This circumstantial evidence strongly suggests that the majority of our ghostly absorbers are indeed DLAs.

Keywords: Quasar absorption line spectroscopy, Quasars, Interstellar line absorption, Circumgalactic medium, Interstellar absorption, Active galactic nuclei, Intergalactic medium
A Study of Equatorial Coronal Holes during the Maximum Phase of Four Solar Cycles. The 11 yr solar cycle (SC) is characterized by periodic changes in solar activity indicators such as the number of sunspots, coronal holes, and active regions (ARs), as well as the occurrence rate of solar energetic events such as filament eruptions, flares, and coronal mass ejections. In this work we performed a statistical study of the equatorial coronal holes (ECHs) and ARs during the maximum phase of the last four SCs: SC 21 (1979-1982), SC 22 (1989-1992), SC 23 (1999-2002), and SC 24 (2012-2015). We compared the number of ECHs and ARs, separations between their centroids, solar wind speed, pressure, and the number of intense geomagnetic storm (IGS) data over these four cycles. We note a strong anticorrelation between the number of ARs and ECHs. We found that the number of close ARs and ECHs, solar wind speed, and the number of IGS increases with average sunspot maximum number for even cycles and decreases with average sunspot maximum for odd cycles. Also, we find strong odd-even trends in the relation between the wind properties and the numbers of close AR and ECH. These results obtained from the annual average data suggest a possible link between ECH and AR proximity and the solar wind phenomena, though odd-even trends point to the importance of other effects (e.g., Sun-Earth magnetic alignment) as well.

Keywords: Solar cycle, Solar wind, Solar active regions, Solar coronal holes, Solar activity, Solar storm, Solar evolution
Detecting Kozai-Lidov Imprints on the Gravitational Waves of Intermediate-mass Black Holes in Galactic Nuclei. A third object in the vicinity of a binary system causes variations in the eccentricity and the inclination of the binary through the Kozai-Lidov (KL) effect. We examine if such variations leave a detectable imprint on the gravitational waves of a binary consisting of intermediate-mass black holes and stellar-mass objects. As a proof of concept, we present an example where LISA may detect the KL-modulated gravitational wave signals of such sources from at least a distance of 1 Mpc if the perturbation is caused by a supermassive black hole tertiary. Although the quick pericenter precession induced by general relativity significantly reduces the appropriate parameter space for this effect by quenching the KL oscillations, we still find reasonable parameters where the KL effect may be detected with high signal-to-noise ratios.

Keywords: Intermediate-mass black holes, Gravitational wave sources
Distinguishing between Wet and Dry Atmospheres of TRAPPIST-1 e and f. The nearby TRAPPIST-1 planetary system is an exciting target for characterizing the atmospheres of terrestrial planets. The planets e, f, and g lie in the circumstellar habitable zone and could sustain liquid water on their surfaces. During the extended pre-main-sequence phase of TRAPPIST-1, however, the planets may have experienced extreme water loss, leading to a desiccated mantle. The presence or absence of an ocean is challenging to determine with current and next-generation telescopes. Therefore, we investigate whether indirect evidence of an ocean and/or a biosphere can be inferred from observations of the planetary atmosphere. We introduce a newly developed photochemical model for planetary atmospheres, coupled to a radiative-convective model, and validate it against modern Earth, Venus, and Mars. The coupled model is applied to the TRAPPIST-1 planets e and f, assuming different surface conditions and varying amounts of CO2 in the atmosphere. As input for the model we use a constructed spectrum of TRAPPIST-1, based on near-simultaneous data from X-ray to optical wavelengths. We compute cloud-free transmission spectra of the planetary atmospheres and determine the detectability of molecular features using the Extremely Large Telescope (ELT) and the James Webb Space Telescope (JWST). We find that under certain conditions the existence or nonexistence of a biosphere and/or an ocean can be inferred by combining 30 transit observations with ELT and JWST within the K band. A nondetection of CO could suggest the existence of an ocean, whereas significant CH4 hints at the presence of a biosphere.

Keywords: Exoplanet atmospheric composition , Planetary atmospheres, Exoplanet atmospheres
Thermonuclear Reaction Rates and Primordial Nucleosynthesis. Assuming the best numerical value for the cosmic baryonic density and the existence of three neutrino flavors, standard Big Bang nucleosynthesis is a parameter-free model. It is important to assess if the observed primordial abundances can be reproduced by simulations. Numerous studies have shown that the simulations overpredict the primordial 7Li abundance by a factor of $\approx 3$ compared to the observations. The discrepancy may be caused by unknown systematics in 7Li observations, poorly understood depletion of lithium in stars, errors in thermonuclear rates that take part in the lithium and beryllium synthesis, or physics beyond the standard model. Here, we focus on the likelihood of a nuclear physics solution. The status of the key nuclear reaction rates is summarized. Big Bang nucleosynthesis simulations are performed with the most recent reaction rates, and the uncertainties of the predicted abundances are established using a Monte Carlo technique. Correlations between abundances and reaction rates are investigated based on the metric of mutual information. The rates of four reactions impact the primordial 7Li abundance: 3He(α,γ)7Be, d(p,γ)3He, 7Be(d,p)2α, and 7Be(n,p)7Li. We employ a genetic algorithm to search for simultaneous rate changes in these four reactions that may account for all observed primordial abundances. When the search is performed for reaction rate ranges that are much wider than recently reported uncertainties, no acceptable solutions are found. Based on the currently available evidence, we conclude that it is highly unlikely for the cosmological lithium problem to have a nuclear physics solution.

Keywords: Cosmic abundances, Nuclear reaction cross sections, Reaction rates, Nuclear astrophysics, Big Bang nucleosynthesis
On the Mass Distribution of the Intracluster Light in Galaxy Groups and Clusters. We take advantage of a semianalytic model with a state-of-art implementation of the formation of the intracluster light (ICL) to study the mass distribution of the ICL in galaxy groups and clusters, at different redshifts. We assume the ICL to follow a Navarro-Frenk-White (NFW) profile with a different concentration, linked to that of the dark matter by the relation cICL = γ cDM, where the parameter γ is set to reproduce the observed relation between the stellar mass in the brightest cluster galaxy (BCG) and ICL in the innermost 100 kpc and the halo mass (M*100 - M500) at z = 0. The model is then tested against several theoretical and observational results, from the present time to z ∼ 1.5. Our analysis shows that the fraction of stellar mass in the BCG and ICL within the innermost 100 kpc is an increasing function of redshift, parameter γ, and a decreasing function of the halo mass. The value of γ required to match the observed M*100 - M500 is γ = 3 at z = 0, but there are indications that it might be a function of redshift and halo mass. This result indicates that the distribution of the ICL is more concentrated than the dark matter one, but less concentrated than previously found by other studies. We suggest that a modified version of the NFW is a good description of the distribution of the diffuse light in groups and clusters, which makes the ICL a reliable tracer of the dark matter, in good agreement with recent observational findings.

Keywords: Galaxy formation, Galaxy evolution
Model-independent Constraints on Cosmic Curvature: Implication from Updated Hubble Diagram of High-redshift Standard Candles. The cosmic curvature (Ωk) is a fundamental parameter for cosmology. In this paper, we propose an improved model-independent method to constrain the cosmic curvature, which is geometrically related to the Hubble parameter H(z) and luminosity distance DL(z). Using the currently largest H(z) sample from the well-known cosmic chronometers, as well as the luminosity distance DL(z) from the relation between the UV and X-ray luminosities of 1598 quasars and the newly compiled Pantheon sample including 1048 SNe Ia, 31 independent measurements of the cosmic curvature Ωk(z) can be expected covering the redshift range of 0.07 &lt; z &lt; 2. Our estimation of Ωk(z) is fully compatible with flat universe at the current level of observational precision. Meanwhile, we find that, for the Hubble diagram of 1598 quasars as a new type of standard candle, the spatial curvature is constrained to be Ωk = 0.08 ± 0.31. For the latest Pantheon sample of SNe Ia observations, we obtain Ωk = - 0.02 ± 0.14. Compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves constraints with competitive precision. More interestingly, it is suggested that the reconstructed curvature Ωk is negative in the high-redshift region, which is also consistent with the results from the model-dependent constraints in the literature. Such findings are confirmed by our reconstructed evolution of Ωk(z), in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form.

Keywords: Cosmological parameters, Hubble diagram, Quasars
Combinations of Standard Pings and Standard Candles: An Effective and Hubble Constant-free Probe of Dark Energy Evolution. On the basis of the theoretical predication that a small fraction of fast radio bursts (FRBs) might be associated with gravitational waves (GWs), Wei et al. proposed FRB/GW association systems, i.e., the joint measurement of dispersion measures (DM) of FRBs and luminosity distances DL of GWs (the combination DM · DL), as an effective complementary cosmic probe, which has the advantage of being independent of the Hubble constant H0. However, it is still unclear what the progenitor of FRBs is and whether a GW signal should be associated with them. In this paper, we propose that, with the fundamental assumption that luminosity distance is a monotonously increasing function of redshift, this DM · DL method could be further extended to the combination of DM measurements of localized FRBs and independent DL measurements of type Ia supernovae (SNe Ia) at similar redshifts. In practice, this extended combination, i.e., DM · DL as a function of redshift from independent DM and DL measurements, may be more applicable. In addition, we investigated the constraining power of this extended combination on dark energy evolution. It was obtained that, in the frame of the Chevalier-Polarski-Linder parameterization, the power of constraints on the dark energy equation of state from only ∼500 DM · DL combinations is even stronger than the one from the currently available 1048 Pantheon SNe Ia. More interestingly, we also found that, compared with the popular luminosity distance-redshift relation alone, the combination DM · DL, as a function of redshift, is more effective in constraining the parameter characterizing the evolution of dark energy. This benefit, along with rapid progress in the upcoming FRB observations, can be of great importance for studying the nature of dark energy.

Keywords: Radio bursts, Type Ia supernovae, Cosmological parameters