Sazuna/UAT_keywords huggingface dataset:
Statistical Analysis of Comet Disconnection Events Using STEREO HI and a Data-assimilative Solar Wind Model. Comets tails can reveal information about the local solar wind conditions. They can exhibit various signatures of interactions with the solar wind including bending, developing kinks, and sometimes undergoing tail disconnections. In this study, we investigate comet tail disconnection events observed in the STEREO HI data during the period of 2007–2023. Using the Heliospheric Upwind eXtrapolation model with a time-dependency (HUXt) solar wind model alongside novel solar wind data assimilation (DA) techniques, each disconnection event was investigated to determine its cause. The resulting statistical analysis led to three main conclusions: (1) for every heliospheric current sheet (HCS) crossing predicted by HUXt that occurs when the comet is within the region of influence of DA, a tail disconnection follows; (2) for HCS crossings that occur outside the region where DA can be applied, 54.5% are followed by a tail disconnection; and (3) there is an approximately linear relationship between the speed of the solar wind at the HCS crossing and the time delay to the onset of a disconnection given by the equation Vrel (km s‑1) = (2.23 ± 0.35)Δt (hr) + (400 ± 10)(km s‑1).

Keywords: Comet tails, Solar wind
Parameter Estimation with Nonstationary Noise in Gravitational-wave Data. The sensitivity of gravitational-wave (GW) detectors is characterized by their noise curves, which determine the detector's reach and ability to measure the parameters of astrophysical sources accurately. The detector noise is typically modeled as stationary and Gaussian for many practical purposes and is characterized by its power spectral density (PSD). However, due to environmental and instrumental factors, physical changes in the state of detectors may introduce nonstationarity into the noise. Misestimation of the noise behavior directly impacts the posterior width of the signal parameters. It becomes an issue for studies that depend on accurate localization volumes, such as (i) probing cosmological parameters (e.g., the Hubble constant) using cross-correlation methods with galaxies and (ii) doing electromagnetic follow-up using localization information from parameter estimation done from premerger data. We study the effects of dynamical noise on the parameter estimation of the GW events. We develop a new method to correct dynamical noise by estimating a locally valid pseudo-PSD normalized along a potential signal's time–frequency track. We do simulations by injecting binary neutron star merger signals in various scenarios where the detector goes through a period of nonstationarity with reference noise curves of third-generation detectors (Cosmic Explorer, the Einstein telescope). As an example, for a source where mismodeling of the noise biases the signal-to-noise estimate by even 10%, one would expect the estimated sky localization to be either under- or overreported by ∼20%; errors like this, especially in low latency, could potentially cause follow-up campaigns to miss the actual source location.

Keywords: Gravitational wave detectors, Compact binary stars, Gravitational waves
Introducing the DREAMS Project: DaRk mattEr and Astrophysics with Machine Learning and Simulations. We introduce the DaRk mattEr and Astrophysics with Machine learning and Simulations (DREAMS) project, an innovative approach to understanding the astrophysical implications of alternative dark matter (DM) models and their effects on galaxy formation and evolution. The DREAMS project will ultimately comprise thousands of cosmological hydrodynamic simulations that simultaneously vary over DM physics, astrophysics, and cosmology in modeling a range of systems—from galaxy clusters to ultra-faint satellites. Such extensive simulation suites can provide adequate training sets for machine-learning-based analyses. This paper introduces two new cosmological hydrodynamical suites of warm dark matter (WDM), each comprising 1024 simulations generated using the AREPO code. One suite consists of uniform-box simulations covering a   volume, while the other consists of Milky Way zoom-ins with sufficient resolution to capture the properties of classical satellites. For each simulation, the WDM particle mass is varied along with the initial density field and several parameters controlling the strength of baryonic feedback within the IllustrisTNG model. We provide two examples, separately utilizing emulators and convolutional neural networks, to demonstrate how such simulation suites can be used to disentangle the effects of DM and baryonic physics on galactic properties. The DREAMS project can be extended further to include different DM models, galaxy formation physics, and astrophysical targets. In this way, it will provide an unparalleled opportunity to characterize uncertainties on predictions for small-scale observables, leading to robust predictions for testing the particle physics nature of DM on these scales.

Keywords: Warm dark matter, Galactic and extragalactic astronomy, Magnetohydrodynamical simulations, Cosmological parameters
Blowing Star Formation Away in AGN Hosts (BAH). II. Investigating the Origin of the H<SUB>2</SUB> Emission Excess in Nearby Galaxies with JWST MIRI. We use James Webb Space Telescope Mid-Infrared Instrument Medium-resolution Spectrometer observations of 3C 293 (UGC 8782), CGCG 012-070 and NGC 3884 to investigate the origin of the H2 emission. These three nearby active galactic nucleus (AGN) hosts are known to present H2 emission excess relative to star-forming galaxies, as traced by the H2 S(3)/PAH11.3 μm line ratio. We define the kinematically disturbed region (KDR) by the AGN and the virially dominated region based on the H2 line widths, using the W80 parameter. From the correlations between W80 and H2 S(3)/PAH11.3 μm, as well as the higher H2 S(5)/H2 S(3) and [Fe II]5.34 μm/PAH11.3 μm ratios and flatter power-law temperature distributions observed in the KDR, we conclude that the H2 emission in the KDR is primarily driven by shock-heated gas. For 3C 293, the KDR is cospatial with the radio core, indicating that the origin of the shocks is the interaction of the radio jet with the interstellar medium, which is also responsible for the observed molecular and ionized gas outflows in this source. The other galaxies are weak radio sources; however, due to the lack of high-resolution radio images, we cannot rule out low-power jets as the origin of the shock-heated H2. Our results indicate that the excess H2 emission excess is associated with shock heating of the gas, generated by outflows or by the interaction of the radio jet with the ambient gas.

Keywords: Active galaxies
Comparison of HMG and Flat Rotation Velocities Inferred from Galaxy–Galaxy Weak Lensing. Despite the success of dark matter models, unresolved issues require exploring alternatives such as modified gravity theories. In this context, we examine the compatibility of the hyperconical modified gravity (HMG) with galaxy rotation curves inferred from weak-lensing data. The research addresses the existing limitations of modified Newtonian dynamics (MOND), which often struggle with universal applicability across different galactic scales. By assuming local validity of general relativity and analyzing recent data on circular velocities from galaxy–galaxy weak lensing, our findings interpret the flat rotation curves as an effect of fictitious acceleration inherited from the cosmic expansion, without invoking dark matter. The results indicate that HMG successfully reproduces flat velocity curves on scales of 1 Mpc slightly better than MOND. Therefore, these observations support HMG as a viable gravitational model, highlighting its potential to account for dynamics on galaxies and other scales. Further research with extensive data sets is required to confirm these preliminary insights.

Keywords: Weak gravitational lensing, Spacetime metric, Galaxy dynamics, Modified Newtonian dynamics
Revisiting the Hubble Constant, Sound Horizon, and Cosmography from Late-time Universe Observations. The Hubble tension has become one of the central problems in cosmology. In this work, we determine the Hubble constant H0 and sound horizon rd by using the combination of baryon acoustic oscillations (BAOs) from DESI surveys, time-delay lensed quasars from H0LiCOW collaborations, and the Pantheon supernova (SN) observations. We consider two cosmological approaches, i.e., Taylor series and Padé polynomials, to avoid cosmological dependence. The reason for using this combination of data is that the absolute distance provided by strong gravitational lensing helps anchor the relative distance of BAOs, and SNe provide a robust history of Universe evolution. Combining the six time-delay distance (6DΔt) plus four angular diameter distance to the deflector (4Dd) measurements of time-delay lensed quasars, the BAOs, and the Type Ia SN data sets, we obtain a model-independent result of   Mpc and   for the Taylor series cosmography and   Mpc and   for the Padé polynomial cosmography. The determination of rd and H0 prefers larger H0 and smaller rd than Planck data under the assumption of a flat Lambda cold dark matter model. However, the values of H0 are consistent with the H0 determination from the SH0ES collaboration.

Keywords: Observational cosmology, Cosmological parameters
Direct Evidence for Active Galactic Nuclei Feedback from Fast Molecular Outflows in Reionization-era Quasars. Galactic outflows driven by rapidly accreting quasars at high redshift are widely expected to play a key role in the short- and long-term future evolution of their host galaxies. Using new and archival Atacama Large Millimeter/submillimeter Array data, we observed the OH 119 μm doublet lines in order to search for cold molecular outflows in a sample of 11 unobscured, IR-luminous quasars at z &gt; 6. This represents the first survey for molecular winds in reionization-era quasars, and we detect unambiguous outflows in 8/11 (73%) of the quasars. The outflows we find are substantially faster, by ≍300 km s−1 on average, than outflows observed in a roughly coeval sample of nonquasar IR-luminous galaxies, suggesting that the active galactic nuclei (AGN) drive the winds to higher velocities. On the other hand, the implied molecular outflow rates are relatively modest given the high luminosities, suggesting typical mass-loading factors ~0.5 in the cold gas. The outflows are consistent with expectations for momentum-driven winds regardless of the driving source, but the kinetic energy in the outflows suggests that the AGN must be at least partially responsible for driving the winds. Accordingly, we find trends between the outflow properties and the Eddington ratio of the black hole accretion, though this may be linked to the underlying trend with AGN luminosity. We find that the kinetic power carried in the cold outflow phase is typically only ~0.1% of the total AGN luminosity. Our study provides evidence in favor of AGN feedback on the cold molecular gas in z &gt; 6 quasar host galaxies, demonstrating that cold outflows are very common and powerful in the most extreme reionization-era quasars.

Keywords: Galaxy quenching, Ultraluminous infrared galaxies, Quasars
Probing the Galactic Neutrino Flux at Neutrino Energies above 200 TeV with the Baikal Gigaton Volume Detector. Recent observations of the Galactic component of the high-energy neutrino flux, together with the detection of the diffuse Galactic gamma-ray emission up to sub-PeV energies, open new possibilities to study the acceleration and propagation of cosmic rays in the Milky Way. At the same time, both large nonastrophysical backgrounds at TeV energies and the scarcity of neutrino events in the sub-PeV band currently limit these analyses. Here, we use the sample of cascade events with estimated neutrino energies above 200 TeV, detected by the partially deployed Baikal Gigaton Volume Detector (GVD) in 6 yr of operation, to test the continuation of the Galactic neutrino spectrum to sub-PeV energies. We find that the distribution of the arrival directions of Baikal-GVD cascades above 200 TeV in the sky suggests an excess of neutrinos from low Galactic latitudes with the chance probability of 1.4 × 10‑2. We also find the excess above 200 TeV in the most recent IceCube public data sets, both of cascades and tracks. The chance probability of the excess in the combined IceCube and Baikal-GVD analysis is 3.4 × 10‑4. The flux of Galactic neutrinos above 200 TeV challenges often-used templates for neutrino search based on cosmic-ray simulations.

Keywords: Galactic cosmic rays, Neutrino astronomy, High energy astrophysics
ODIN: High Clustering Strength of Protoclusters at Cosmic Noon. The One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey is carrying out a systematic search for protoclusters during Cosmic Noon, using Lyα-emitting galaxies (LAEs) as tracers. Once completed, ODIN aims to identify hundreds of protoclusters at redshifts of 2.4, 3.1, and 4.5 across seven extragalactic fields, covering a total area of up to 91 deg2. In this work, we report the high clustering strength of the ODIN protoclusters, determined via measurements of their cross-correlation with LAEs. Our sample consists of 150 protocluster candidates at z = 2.4 and 3.1, identified in two ODIN fields with a total area of 13.9 deg2. At z = 2.4 and 3.1, the inferred protocluster biases are   and  , corresponding to mean halo masses of   and  , respectively. By the present day, these protoclusters are expected to evolve into virialized galaxy clusters with a mean mass of ∼1014.5 M⊙. By comparing the observed number density of protoclusters to that of halos with the same measured clustering strength, we find that the completeness of our sample is of order unity. Finally, the similar descendant masses derived for our samples at z = 2.4 and 3.1, assuming that the halo number density remains constant, suggest that they represent similar structures observed at different cosmic epochs. As a consequence, any observed differences between the two samples can be understood as redshift evolution. The ODIN protocluster samples will thus provide valuable insights into the cosmic evolution of cluster galaxies.

Keywords: Lyman-alpha galaxies, Protoclusters, High-redshift galaxy clusters
Dynamical Friction by Coupled Dark Energy. In this paper, we examine dynamical friction at galactic scales within the framework of coupled dark energy (CDE). This model posits dark energy as coupled quintessence, which maintains a minimal coupling to gravity but interacts nonminimally with both dark matter and baryonic matter. Since our focus is primarily on the Newtonian regime within galaxies, we begin by deriving the Newtonian limit of the model. Subsequently, we calculate the dynamical friction force using three different approaches. We demonstrate that, in the absence of interaction between dark energy and matter, standard quintessence does not generate any dynamical friction at the galactic scale. However, the presence of interaction does cause dynamical friction. By applying the resulting analytic expressions to a real self-gravitating system, namely the Fornax galaxy, and by implementing the constraints on the free parameter of the model obtained from galactic observations, we demonstrate that the CDE model leads to significant deviations from the standard cold dark matter model at galactic scales. On the other hand, if the cosmological constraints are assumed for the free parameter, the effects of the model are expected to be negligible at the galactic level, at least in dynamical friction.

Keywords: Fornax dwarf spheroidal galaxy, Dynamical friction, Dark matter, Dark energy
Turbulent Suppression of Alfvénic Wave Resonances in Coronal Loops. Alfvénic wave turbulence is a leading mechanism for explaining the heating of the solar corona and the acceleration of the solar wind. Alfvénic waves are observed to be prevalent throughout the inner corona. An intriguing aspect of the observed waves is that active-region loops show decayless standing Alfvénic oscillations, while quiet-Sun loops show only propagating Alfvénic waves. Given the weaker rates of resonant damping found in the quiet Sun (compared to those estimated from decaying oscillations of active-region loops), the reason for the lack of observed standing oscillations is unclear. We suggest that this may be due to the presence of efficient (or strong) Alfvénic wave turbulence in the quiet Sun, which limits the ability of waves to form resonant oscillations in the coronal cavity. To test this idea, we model the coronal velocity fluctuations using a previously developed 3D reduced magnetohydrodynamic model. In this model, we implement a semi-realistic profile for atmospheric plasma conditions along the magnetic field and a homogeneous plasma perpendicular to the magnetic field. Results are presented for different models of the background atmosphere that effectively have different levels of coronal turbulence. For the Alfvénic waves in the simulation, we see that resonant modes are present when the coronal turbulence is in a weak regime. However, decreasing the nonlinear timescale leads to a faster development of turbulence. This can suppress the presence of standing modes when the nonlinear timescale is comparable to or shorter than the Alfvén travel time.

Keywords: Magnetohydrodynamics, The Sun, Solar coronal heating, Solar physics, Solar coronal waves, Quiet solar corona, Active solar corona
The Multiwavelength Extinction Law and Its Variation in the Coalsack Molecular Cloud Based on the Gaia, APASS, SMSS, 2MASS, GLIMPSE, and WISE Surveys. Accurate interpretation of observations relies on the interstellar dust extinction law, which also serves as a powerful diagnostic for probing dust properties. In this study, we investigate the multiwavelength extinction law of the quiescent, starless molecular cloud Coalsack and explore its potential variation across different interstellar environments: the surrounding region, the nearby high Galactic latitude region, the inner dense region, and the inner diffuse region. Using a sample of 368,524 dwarf stars selected from Gaia DR3 as tracers, we establish the effective temperature Teff–intrinsic color relations to derive the intrinsic color indices and optical‑mid-infrared (MIR) color excess (CE) for 20 bands. Linear fits to the CE–CE diagrams provide CE ratios, which are subsequently converted into relative extinction. The resulting extinction curves for different environments exhibit steep slopes in the near-infrared (NIR) and flat profiles in the MIR. In the optical–NIR range, the Coalsack extinction law is consistent with the RV = 3.1 of S. Wang &amp; X. Chen and B. S. Hensley &amp; B. T. Draine, while in the MIR, it follows the RV = 5.5 of J. C. Weingartner &amp; B. T. Draine, similar to the results of active star-forming clouds. At an angular resolution of  , our extinction map reveals fine cloud structures. No correlation is found between RV and EB,V for EB,V &gt; 0.3 mag, implying a uniform optical extinction law in the Coalsack cloud. The derived average RV value is 3.24 ± 0.32.

Keywords: Interstellar dust, Molecular clouds, Interstellar dust extinction, Reddening law, Extinction, Interstellar extinction
Ca II K Polar Network Index of the Sun: A Proxy for Historical Polar Magnetic Field. The Sun's polar magnetic field is pivotal in understanding solar dynamo processes and forecasting future solar cycles. However, direct measurements of the polar field have only been available since the 1970s. The chromospheric Ca II K polar network index (PNI; the fractional area of the chromospheric network regions above a certain latitude) has recently emerged as a reliable proxy for polar magnetic fields. In this study, we derive PNI estimates from newly calibrated, rotation-corrected Ca II K observations from the Kodaikanal Solar Observatory (1904–2007) and modern data from the Rome Precision Solar Photometric Telescope (2000–2022). We use both of those Ca II K archives to identify polar network regions with an automatic adaptive threshold segmentation technique and calculate the PNI. The PNI obtained from both the archives shows a significant correlation with the measured polar field from the Wilcox Solar Observatory (Pearson correlation coefficient r &gt; 0.93) and the derived polar field based on an Advective Flux Transport Model (r &gt; 0.91). The PNI series also shows a significant correlation with faculae counts derived from Mount Wilson Observatory observations (r &gt; 0.87) for both Kodaikanal Solar Observatory and Rome Precision Solar Photometric Telescope data. Finally, we use the PNI series from both archives to reconstruct the polar magnetic field over a 119 yr long period, which includes the last 11 solar cycles (Cycles 14–24). We also obtain a relationship between the amplitude of solar cycles (in 13 month smoothed sunspot number) and the strength of the reconstructed polar field at the preceding solar cycle minimum to validate the prediction of the ongoing solar cycle, Cycle 25.

Keywords: Solar cycle, Solar chromosphere, Magnetic fields
New Cold Subdwarf Discoveries from Backyard Worlds and a Metallicity Classification System for T Subdwarfs. We report the results of a spectroscopic survey of candidate T subdwarfs identified by the Backyard Worlds: Planet 9 program. Near-infrared spectra of 31 sources with red J − W2 colors and large J-band reduced proper motions show varying signatures of subsolar metallicity, including strong collision-induced H2 absorption, obscured methane and water features, and weak K I absorption. These metallicity signatures are supported by spectral model fits and 3D velocities, indicating thick disk and halo population membership for several sources. We identify three new metal-poor T subdwarfs ([M/H] ≲ ─0.5), CWISE J062316.19+071505.6, WISEA J152443.14−262001.8, and CWISE J211250.11-052925.2; and 19 new "mild" subdwarfs with modest metal deficiency ([M/H] ≲ −0.25). We also identify three metal-rich brown dwarfs with thick disk kinematics. We provide kinematic evidence that the extreme L subdwarf 2MASS J053253.46+824646.5 and the mild T subdwarf CWISE J113010.07+313944.7 may be part of the Thamnos population, while the T subdwarf CWISE J155349.96+693355.2 may be part of the Helmi stream. We define a metallicity classification system for T dwarfs that adds mild subdwarfs (d/sdT), subdwarfs (sdT), and extreme subdwarfs (esdT) to the existing dwarf sequence. We also define a metallicity spectral index that correlates with metallicities inferred from spectral model fits and iron abundances from stellar primaries of benchmark T dwarf companions. This expansion of the T dwarf classification system supports investigations of ancient, metal-poor brown dwarfs now being uncovered in deep imaging and spectroscopic surveys.

Keywords: Brown dwarfs, L dwarfs, Stellar classification, L subdwarfs, T subdwarfs, T dwarfs