Sazuna/UAT_keywords huggingface dataset:
Identification of Cosmic Voids as Massive Cluster Counterparts. We develop a method to identify cosmic voids from the matter density field by adopting a physically motivated concept that voids are the counterpart of massive clusters. To prove the concept we use a pair of ΛCDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. Galaxy cluster-scale dark matter halos are identified in the Mirror simulation at z = 0 by linking dark matter particles. The void corresponding to each cluster is defined in the Reference simulation as the region occupied by the member particles of the cluster. We study the voids corresponding to the halos more massive than 1013 h-1 M⊙. We find a power-law scaling relation between the void size and the corresponding cluster mass. Voids with a corresponding cluster mass above 1015 h-1 M⊙ occupy ∼1% of the total simulated volume, whereas this fraction increases to ∼54% for voids with a corresponding cluster mass above 1013 h-1 M⊙. It is also found that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter density field without their mirror information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We recover voids corresponding to clusters more massive than 3 × 1014 h-1 M⊙ at a 70%-74% level of completeness and reliability. Our results suggest that we are able to identify voids in a way to associate them with clusters of a particular mass scale.

Keywords: Voids
X-Ray Spectroscopy of the Highly Magnetized Pulsar PSR J1846-0258, Its Wind Nebula, and Hosting Supernova Remnant Kes 75. We present broadband X-ray spectroscopy of the energetic components that make up the supernova remnant (SNR) Kesteven 75 using concurrent 2017 August 17-20 XMM-Newton and NuSTAR observations, during which the pulsar PSR J1846-0258 is found to be in the quiescent state. The young remnant hosts a bright pulsar wind nebula powered by the highly energetic ( $\dot{E}=8.1\times {10}^{36}$ erg s-1) isolated, rotation-powered pulsar, with a spin-down age of only $P/2\dot{P}\sim 728\,\mathrm{yr}$ . Its inferred magnetic field (Bs = 4.9 × 1013 G) is the largest known for these objects, and is likely responsible for intervals of flare and burst activity, suggesting a transition between/to a magnetar state. The pulsed emission from PSR J1846-0258 is well-characterized in the 2-50 keV range by a power-law model with photon index ΓPSR = 1.24 ± 0.09 and a 2-10 keV unabsorbed flux of (2.3 ± 0.4) × 10-12 erg s-1 cm-2. We find no evidence for an additional non-thermal component above 10 keV in the current state, as would be typical for a magnetar. Compared to the Chandra pulsar spectrum, the intrinsic pulsed fraction is 71 ± 16% in 2-10 keV band. A power-law spectrum for the pulsar wind nebulae (PWN) yields ΓPWN = 2.03 ± 0.02 in the 1-55 keV band, with no evidence of curvature in this range, and a 2-10 keV unabsorbed flux (2.13 ± 0.02) × 10-11 erg s-1 cm-2. The NuSTAR data reveal evidence for a hard X-ray component dominating the SNR spectrum above 10 keV that we attribute to a dust-scattered PWN component. We model the dynamical and radiative evolution of the Kes 75 system to estimate the birth properties of the neutron star, the energetics of its progenitor, and properties of the PWN. This suggests that the progenitor of Kes 75 was originally in a binary system which transferred most of its mass to a companion before exploding.

Keywords: Neutron stars, Rotation powered pulsars, Pulsars, Supernova remnants, Magnetars
Magnetic Reconnection between Loops Accelerated By a Nearby Filament Eruption. Magnetic reconnection modulated by nonlocal disturbances in the solar atmosphere has been investigated theoretically, but rarely observed. In this study, employing Hα and extreme ultraviolet (EUV) images and line-of-sight magnetograms, we report the acceleration of reconnection by an adjacent filament eruption. In Hα images, four groups of chromospheric fibrils are observed to form a saddle-like structure. Among them, two groups of fibrils converge and reconnect. Two newly reconnected fibrils then form and retract away from the reconnection region. In EUV images, similar structures and evolution of coronal loops are identified. The current sheet forms repeatedly at the interface of reconnecting loops, with a width and length of 1-2 and 5.3-7.2 Mm and a reconnection rate of 0.18-0.3. It appears in the EUV low-temperature channels, with an average differential emission measure (DEM) weighed temperature and EM of 2 MK and 2.5 × 1027 cm-5. Plasmoids appear in the current sheet and propagate along it, and then further along the reconnection loops. The filament, located to the southeast of the reconnection region, erupts and pushes away the loops covering the reconnection region. Thereafter, the current sheet has a width and length of 2 and 3.5 Mm and a reconnection rate of 0.57. It becomes much brighter and appears in the EUV high-temperature channels, with an average DEM-weighed temperature and EM of 5.5 MK and 1.7 × 1028 cm-5. In the current sheet, more hotter plasmoids form. More thermal and kinetic energy is hence converted. These results suggest that the reconnection is significantly accelerated by the propagating disturbance caused by the nearby filament eruption.

Keywords: Solar ultraviolet emission, Solar magnetic reconnection, Plasma physics, Solar corona, Solar magnetic fields
Variations of Peak He/H Ratios in Solar Energetic (E &gt; 4 MeV) Particle Events and Comparisons with Solar Wind He/H Ratios. We determine solar energetic particle (SEP) event He/H peak intensity ratios AHe observed in the four energy channels of the SOHO EPHIN detector covering 4-53 MeV nuc-1. Those SEP AHe values range over two orders of magnitude for 43 large western hemisphere SEP events through the period 1997-2017. AHe of each SEP event are compared with average solar wind (SW) AHe values measured for 8 hr after the SEP event onsets with the solar wind experiment Faraday Cup instrument on Wind. AHe in the 4-8 and 8-21 MeV nuc-1 range are significantly correlated with SW AHe (CC = 0.45 and 0.41), but less so in the 21-41 and 41-53 MeV nuc-1 range, where uncertainties of the AHe values are higher. Median SEP AHe values decline slightly with increasing energy and are ≤0.5 their associated SW values. Both median SEP and SW AHe decline by a factor of ∼2 from the 27 events of cycle 23 to the 16 of cycle 24. Those results suggest a connection between the SW and the seed population of SEP events. An unexpected result is that SEP AHe increases with event peak intensities in our 43 events as He peak intensities increase faster than those of H in larger events.

Keywords: Solar energetic particles, Solar wind
Standard-siren Cosmology Using Gravitational Waves from Binary Black Holes. Gravitational-wave astronomy provides a unique new way to study the expansion history of the universe. In this work, we investigate the impact future gravitational-wave observatories will have on cosmology. Third-generation observatories like the Einstein Telescope and Cosmic Explorer will be sensitive to essentially all of the binary black hole coalescence events in the universe. Recent work by Farr et al. points out that features in the stellar-mass black hole population break the mass-redshift degeneracy, facilitating precise determination of the Hubble parameter without electromagnetic counterparts or host galaxy catalogs. Using a hierarchical Bayesian inference model, we show that with one year of observations by the Einstein Telescope, the Hubble constant will be measured to ≲1%. We also show that this method can be used to perform Bayesian model selection between cosmological models. As an illustrative example, we find that a decisive statement can be made comparing the ΛCDM and RHCT cosmological models using two weeks of data from the Einstein Telescope.

Keywords: Hubble constant, Hierarchical models, Gravitational waves
How to Search for Multiple Messengers—A General Framework Beyond Two Messengers. Quantification of the significance of a candidate multi-messenger detection of cosmic events is an emerging need in the astrophysics and astronomy communities. In this paper we show that a model-independent optimal search does not exist, and we present a general Bayesian method for the optimal model-dependent search, which is scalable to any number and any kind of messengers, and applicable to any model. In the end, we demonstrate it through an example for a joint gravitational wave, high-energy neutrino, short gamma-ray burst event search; which has not been examined heretofore.

Keywords: Astrostatistics tools, Bayesian statistics, High energy astrophysics, Model selection, Neutrino astronomy, Astrostatistics techniques, Astrostatistics, Gravitational wave astronomy, Gamma-ray astronomy, Astronomical methods, Astrostatistics strategies
Two-dimensional Radiation-hydrodynamic Simulations of Supernova Ejecta with a Central Power Source. We present the results of two-dimensional radiation-hydrodynamic simulations of expanding supernova ejecta with a central energy source. As suggested in previous multidimensional hydrodynamic simulations, a sufficiently powerful central energy source can blow away the expanding supernova ejecta, leading to efficient mixing of stratified layers in the ejecta. We assume that the energy injection is realized in the form of nonthermal radiation from the wind nebula embedded at the center of the ejecta. We found that the multidimensional mixing in the ejecta assists the injected nonthermal radiation escaping from the ejecta. When the nonthermal radiation is absorbed by the ejecta, it is converted into bright thermal radiation or is consumed as the kinetic energy of the supernova ejecta. We found that central energy sources with injection timescale similar to the photon diffusion timescale realize an efficient conversion of the injected energy into thermal radiation. On the other hand, rapid energy injection ends up accelerating the ejecta rather than giving rise to bright thermal emission. This remarkable difference potentially explains the diversity of energetic supernovae including broad-lined Ic and superluminous supernovae.

Keywords: Hydrodynamical simulations, Hydrodynamics, Core-collapse supernovae, Radiative transfer, Supernovae
Grain Alignment and Disruption by Radiative Torques in Dense Molecular Clouds and Implication for Polarization Holes. Dust polarization induced by aligned grains is widely used to study magnetic fields in various astrophysical environments. However, the question of to what optical depth grain alignment still exists in a dense molecular cloud (MC) is unclear. In this paper, we derive analytical formulae for the minimum size of aligned grains (aalign) and rotational disruption (adisr) by RAdiative Torques (RATs) as a function of the local physical parameters within MCs. We first find the analytical approximations for the radiation strength and mean wavelength of the attenuated radiation field in a dense MC with and without embedded stars, and then derive analytical formulae for aalign and adisr as functions of the visual extinction AV and gas density. We find that, within a starless core of density ${n}_{{\rm{H}}}\sim {10}^{5}\,{\mathrm{cm}}^{-3}$ , grains of size $a\lt 0.25\,\mu {\rm{m}}$ can be aligned at AV ∼ 5 by RATs, whereas micron-sized grains can still be aligned at ${A}_{V}\sim 50$ . The increase in aalign with AV can explain the presence of polarization holes observed toward starless cores. For MCs with an embedded protostar, the efficiency of both alignment and rotational disruption increases toward the protostar due to the increasing radiation strength. Such a disruption effect results in the decrease of the polarization degree with AV or emission intensity, reproducing the popular polarization holes observed toward the location of protostars. Finally, we derive the formula for the maximum AV where grain alignment still exists in a starless core, and we discuss its potential for constraining grain growth.

Keywords: Interstellar dust, Interstellar dust extinction, Astrophysical dust processes, Interstellar magnetic fields, Starlight polarization, Dust continuum emission, Interstellar medium
Can Galaxy Evolution Mimic Cosmic Reionization?. Lyα emitting galaxies are powerful tools to probe the late stages of cosmic reionization. The observed sudden drop in Lyα fraction at z &gt; 6 is often interpreted as a sign of reionization, since the intergalactic medium (IGM) is more neutral and opaque to Lyα photons. Crucially, this interpretation of the observations is only valid under the assumption that galaxies themselves experience a minimal evolution at these epochs. By modeling Lyα radiative transfer effects in and around galaxies, we examine whether a change in the galactic properties can reproduce the observed drop in the Lyα fraction. We find that an increase in the galactic neutral hydrogen content or a reduction in the outflow velocity toward higher redshift both lead to a lower Lyα escape fraction, and can thus mimic an increasing neutral fraction of the IGM. We furthermore find that this change in galactic properties leads to systematically different Lyα spectra which can be used to differentiate the two competing effects. Using the CANDELSz7 survey measurements which indicate slightly broader lines at z ∼ 6, we find that the scenario of a mere increase in the galactic column density toward higher z is highly unlikely. We also show that a decrease in outflow velocity is not ruled out by existing data but leads to more prominent blue peaks at z &gt; 6. Our results caution using Lyα observations to estimate the IGM neutral fraction without accounting for the potential change in the galactic properties, e.g., by mapping out the evolution of Lyα spectral characteristics.

Keywords: Galaxy evolution, Radiative transfer, Intergalactic medium, Lyman-alpha galaxies, Reionization
Multiple Populations in Low-mass Globular Clusters: Palomar 13. Since the discovery of chemically peculiar stars in globular clusters in the last century, the study of multiple populations has become increasingly important, given that chemical inhomogeneity is found in almost all globular clusters. Despite various proposed theories attempting to explain this phenomenon, fitting all the observational evidence in globular clusters with one single theory remains notoriously difficult and currently unsuccessful. In order to improve existing models and motivate new ones, we are observing globular clusters at critical conditions, e.g., metal-rich end, metal-poor end, and low mass end. In this paper, we present our first attempt to investigate multiple populations in low mass globular clusters. We obtained low-resolution spectra around 4000 Šof 30 members of the globular cluster Palomar 13 using OSIRIS/Multi-object spectrograph mounted at the Gran Telescopio Canarias. The membership of red giant branch stars is confirmed by the latest proper motions from Gaia DR2 and literature velocities. After comparing the measured CN and CH spectral indices with those of the stellar models, we found a clear sign of nitrogen variation among the red giant branch stars. Palomar 13 may be the lowest mass globular cluster showing multiple populations.

Keywords: Globular star clusters, Stellar abundances, Stellar kinematics, Stellar evolution
Unraveling the Complex Structure of AGN-driven Outflows. V. Integral-field Spectroscopy of 40 Moderate-luminosity Type-2 AGNs. There is an ongoing debate on whether feedback from active galactic nuclei (AGNs) can effectively regulate the star formation activities in their host galaxies. To investigate the feedback effect of AGN-driven outflows, we perform integral-field spectroscopic observations of 40 moderate-luminosity ( ${10}^{41.5}\lt {L}_{[O}\,{\rm\small{III}}];\mathrm{cor}\lt {10}^{43.1}$ erg s-1 ) Type-2 AGNs at z &lt; 0.1, which present strong outflow signatures in the integrated [O iii] kinematics. Based on the radial profile of the normalized [O iii] velocity dispersion by stellar velocity dispersion, we measure the kinematic outflow size and extend the kinematic outflow size-luminosity relation reported in Kang &amp; Woo into a wider luminosity range (over four orders of magnitude in [O iii] luminosity). The shallow slope of the kinematic outflow size-luminosity relation indicates that while ionizing photons can reach out further, kinetic energy transfer is much less efficient due to various effects, demonstrating the importance of kinematical analysis in quantifying the outflow size and energetics. By comparing the outflow kinematics with the host galaxy properties, we find that AGNs with strong outflows have higher star formation rate and higher H i gas fraction than those AGNs with weak outflows. These results suggest that the current feedback from AGN-driven outflows do not instantaneously suppress or quench the star formation in the host galaxies while its effect is delayed.

Keywords: AGN host galaxies, Galaxy formation, Active galactic nuclei, Star formation
Candidate z ∼ 2.5 Lyman Continuum Sources in the GOODS Fields. We use the wealth of deep archival optical spectroscopy on the GOODS-South field from Keck, the VLT, and other facilities to select candidate high-redshift Lyman continuum (LyC) leakers in the Hubble Deep UV Legacy Survey (HDUV) data set. We select sources at $2.35\lt z\lt 3.05$ , where the HST/WFC3 F275W filter probes only the redshifted LyC. We find five moderately F275W-bright sources (four detected at $\gtrsim 3\sigma $ significance) in this redshift range. However, two of these show evidence in their optical spectra of contamination by foreground galaxies along the line of sight. We then perform an F275W error-weighted sum of the fluxes of all 129 galaxies at $2.35\lt z\lt 3.05$ in both the GOODS-N and GOODS-S HDUV areas to estimate the total ionizing flux. The result is dominated by just five candidate F275W-bright LyC sources. Lastly, we examine the contributions to the metagalactic ionizing background, finding that, at the sensitivity of the HDUV F275W data and allowing for the effects of LyC transmission in the intergalactic medium (IGM), star-forming galaxies can match the UV flux required to maintain an ionized IGM at $z\sim 2.5$ .

Keywords: Galaxy formation, Galaxy distances, Observational cosmology, Active galaxies, Galaxy evolution, High-redshift galaxies
Predictions of Astrometric Jitter for Sun-like Stars. I. The Model and Its Application to the Sun as Seen from the Ecliptic. The advent of Gaia, capable of measuring stellar wobbles caused by orbiting planets, raised interest in the astrometric detection of exoplanets. Another source of such wobbles (often also called jitter) is stellar magnetic activity. A quantitative assessment of the stellar astrometric jitter is important for a more reliable astrometric detection and characterization of exoplanets. We calculate the displacement of the solar photocenter due to the magnetic activity for an almost 16 yr period (1999 February 2-2014 August 1). We also investigate how the displacement depends on the spectral passband chosen for observations, including the wavelength range to be covered by the upcoming Small-JASMINE mission of JAXA. This is done by extending the SATIRE-S model for solar irradiance variability to calculating the displacement of the solar photocenter caused by the magnetic features on the surface of the Sun. We found that the peak-to-peak amplitude of the solar photocenter displacement would reach 0.5 μas if the Sun were located 10 pc away from the observer and observed in the Gaia G filter. This is by far too small to be detected by the Gaia mission. However, the Sun is a relatively inactive star so one can expect significantly larger signals for younger, and, consequently, more active stars. The model developed in this study can be combined with the simulations of emergence and surface transport of magnetic flux which have recently become available to model the astrometric jitter over the broad range of magnetic activities.

Keywords: Solar activity, Astrometric exoplanet detection, Stellar atmospheres, Stellar activity
Mass Segregation as a New Indicator of Binary, IMBH, and Stellar-mass Black Hole Systems in Globular Clusters. This study presents the mass segregation of 35 Galactic globular clusters (GCs) through the radial profile of the mean mass of main-sequence stars. Most of them are found to be mass segregated due to two-body relaxation effects. The GCs with a larger core to half-mass-radius ratio tend to be less mass segregated. Recent simulations show that energy sources can quench mass segregation in relaxed GCs. Combining mass segregation and core binary fractions (fc), we find a moderate anticorrelation between them when fc is below 0.15. Four GCs that have a small amount of mass segregation are selected as possible intermediate-mass black hole holders. However, none of them are strong candidates considering their half-mass relaxation times.

Keywords: Globular star clusters, Intermediate-mass black holes, Binary stars, Stellar kinematics, Stellar mass black holes, Star clusters
Very-high-energy Emission and Cascade Radiation of Gamma-Ray Burst Afterglows: Homogeneous versus Wind External Media. Recent detection of sub-TeV emission from gamma-ray bursts (GRBs) represents a breakthrough in the GRB study. The multiwavelength data of the afterglows of GRB 190114C support the synchrotron self-Compton (SSC) origin for its sub-TeV emission. We present a comparative analysis on the SSC emission of GRB afterglows in the homogeneous and wind environments in the framework of the forward shock model. The γγ absorption of very-high-energy photons due to pair production within the source and the Klein-Nishina effect on the inverse Compton scattering are considered. Generally a higher SSC flux is expected for a larger circum-burst density due to a larger Compton parameter, but meanwhile the internal γγ absorption is more severe for sub-TeV emission. The flux ratio between the SSC component and the synchrotron component decreases more quickly with time in the wind medium case than in the homogeneous density medium case. The light curves of the SSC emission are also different for the two types of media. We also calculate the cascade emission resulting from the absorbed high-energy photons. In the ISM environment with n ≳ 1 cm-3, the cascade synchrotron emission could be comparable to the synchrotron emission of the primary electrons in the optical band, which may flatten the optical afterglow light curve at an early time (t &lt; 1 hr). In the wind medium with A* ≳ 0.1, the cascade emission in the eV-GeV band is comparable or even larger than the emission of the primary electrons at the early time.

Keywords: Gamma-ray bursts, Gamma-rays