adsabs/SciX_UAT_keywords huggingface dataset:
C3: Cluster Clustering Cosmology. II. First Detection of the Baryon Acoustic Oscillations Peak in the Three-point Correlation Function of Galaxy Clusters

Third-order statistics of the cosmic density field provides a powerful cosmological probe containing synergistic information to the more commonly explored second-order statistics. Here, we exploit a spectroscopic catalog of 72,563 clusters of galaxies extracted from the Sloan Digital Sky Survey (SDSS), providing the first detection of the baryon acoustic oscillations (BAO) peak in the three-point correlation function (3PCF) of galaxy clusters. We measure and analyze both the connected and the reduced 3PCF of SDSS clusters from intermediate (r ~ 10 Mpc h-1) up to large (r ~ 140 Mpc h-1) scales, exploring a variety of different configurations. From the analysis of reduced 3PCF at intermediate scales, in combination with the analysis of the two-point correlation function, we constrain both the cluster linear and nonlinear bias parameters, b1 = 2.75 ± 0.03 and b2 = 1.2 ± 0.5. We analyze the measurements of the 3PCF at larger scales, comparing them with theoretical models. The data show clear evidence of the BAO peak in different configurations, which appears more visible in the reduced 3PCF rather than in the connected one. From the comparison between theoretical models that do or do not consider the BAO peak, we obtain a quantitative estimate of this evidence, with a Δχ2 between 2 and 94, depending on the considered configuration. Finally, we set up a generic framework to estimate the expected signal-to-noise ratio of the BAO peak in the 3PCF, exploring different possible definitions that can be used to forecast the most favorable configurations to be explored in future surveys, and applying it to the case of the Euclid mission.

Keywords: observational cosmology; cosmological parameters; redshift surveys; galaxy clusters
Transit Duration Variations in Multiplanet Systems

A planet's orbital orientation relative to an observer's line of sight determines the chord length for a transiting planet, i.e., the projected distance a transiting planet travels across the stellar disk. For a given circular orbit, the chord length determines the transit duration. Changes in the orbital inclination, the longitude of ascending node, or both, can alter this chord length and thus result in transit duration variations (TDVs). Variation of the full orbital inclination vector can even lead to de-transiting or newly transiting planets for a system. We use Laplace-Lagrange secular theory to estimate the fastest nodal eigenfrequencies for over 100 short-period planetary systems. The highest eigenfrequency is an indicator of which systems should show the strongest TDVs. We further explore five cases (TRAPPIST-1, Kepler-11, K2-138, Kepler-445, and Kepler-334) using direct N-body simulations to characterize possible TDVs and to explore whether de-transiting planets might be possible for these systems. A range of initial conditions are explored, in which each realization is consistent with the observed transits. We find that tens of percent of multiplanet systems have fast enough eigenfrequencies to expect large TDVs on decade timescales. For the directly integrated cases, we find that de-transiting planets might occur on decade timescales, and TDVs of 10 minutes per decade are expected to be common.

Keywords: exoplanets; exoplanet evolution; exoplanet dynamics; transit duration variation method
Current-sheet Oscillations Caused by the Kelvin-Helmholtz Instability at the Loop Top of Solar Flares

Current sheets (CSs), long stretching structures of magnetic reconnection above solar flare loops, are usually observed to oscillate; their origins, however, are still puzzled at present. Based on a high-resolution 2.5D MHD simulation of magnetic reconnection, we explore the formation mechanism of CS oscillations. We find that large-amplitude transverse waves are excited by the Kelvin-Helmholtz instability at the highly turbulent cusp-shaped region. The perturbations propagate upward along the CS with a phase speed close to local Alfvén speed thus resulting in the CS oscillations we observe. Though the perturbations damp after propagating for a long distance, the CS oscillations are still detectable. In terms of detected CS oscillations, with a combination of differential emission measure techniques, we propose a new method for measuring the magnetic field strength of the CS and its distribution in height.

Keywords: solar flares; solar magnetic reconnection; magnetohydrodynamical simulations
Keck Integral-field Spectroscopy of M87 Reveals an Intrinsically Triaxial Galaxy and a Revised Black Hole Mass

The three-dimensional intrinsic shape of a galaxy and the mass of the central supermassive black hole provide key insight into the galaxy's growth history over cosmic time. Standard assumptions of a spherical or axisymmetric shape can be simplistic and can bias the black hole mass inferred from the motions of stars within a galaxy. Here, we present spatially resolved stellar kinematics of M87 over a two-dimensional 250″ × 300″ contiguous field covering a radial range of 50 pc-12 kpc from integral-field spectroscopic observations at the Keck II Telescope. From about 5 kpc and outward, we detect a prominent 25 km s-1 rotational pattern, in which the kinematic axis (connecting the maximal receding and approaching velocities) is 40° misaligned with the photometric major axis of M87. The rotational amplitude and misalignment angle both decrease in the inner 5 kpc. Such misaligned and twisted velocity fields are a hallmark of triaxiality, indicating that M87 is not an axisymmetrically shaped galaxy. Triaxial Schwarzschild orbit modeling with more than 4000 observational constraints enabled us to determine simultaneously the shape and mass parameters. The models incorporate a radially declining profile for the stellar mass-to-light ratio suggested by stellar population studies. We find that M87 is strongly triaxial, with ratios of p = 0.845 for the middle-to-long principal axes and q = 0.722 for the short-to-long principal axes, and determine the black hole mass to be $({5.37}_{-0.25}^{+0.37}\pm 0.22)\times {10}^{9}{M}_{\odot }$ , where the second error indicates the systematic uncertainty associated with the distance to M87.

Keywords: galaxy dynamics; galaxy masses; supermassive black holes; early-type galaxies; galaxy dark matter halos; galaxy evolution; galaxies; galaxy kinematics
Detecting the Figure Rotation of Dark Matter Halos with Tidal Streams

The dark matter halos that surround Milky Way-like galaxies in cosmological simulations are, to first order, triaxial. Nearly 30 yr ago it was predicted that such triaxial dark matter halos should exhibit steady figure rotation or tumbling motions for durations of several gigayears. The angular frequency of figure rotation predicted by cosmological simulations is described by a log-normal distribution of pattern speed Ωp with a median value 0.15 h km s-1 kpc-1 (∼0.15 h rad Gyr-1 ∼ 9° h Gyr-1) and a width of 0.83h km s-1 kpc-1. These pattern speeds are so small that they have generally been considered both unimportant and undetectable. In this work we show that even extremely slow figure rotation can significantly alter the structure of extended stellar streams produced by the tidal disruption of satellites in the Milky Way halo. We simulate the behavior of a Sagittarius-like polar tidal stream in triaxial dark matter halos with different shapes, when the halos are rotated about the three principal axes. For pattern speeds typical of cosmological halos, we demonstrate, for the first time, that a Sagittarius-like tidal stream would be altered to a degree that is detectable even with current observations. This discovery will potentially allow for a future measurement of figure rotation of the Milky Way's dark matter halo, perhaps enabling the first evidence of this relatively unexplored prediction of cold dark matter.

Keywords: dark matter; galaxy dark matter halos; milky way dark matter halo; galaxy dynamics; milky way dynamics; sagittarius dwarf spheroidal galaxy; tidal disruption
Jupiter's Temperature Structure: A Reassessment of the Voyager Radio Occultation Measurements

The thermal structure of planetary atmospheres is an essential input for predicting and retrieving the distribution of gases and aerosols, as well as the bulk chemical abundances. In the case of Jupiter, the temperature at a reference level-generally taken at 1 bar-serves as the anchor in models used to derive the planet's interior structure and composition. Most models assume the temperature measured by the Galileo probe. However, those data correspond to a single location, an unusually clear, dry region, affected by local atmospheric dynamics. On the other hand, the Voyager radio occultation observations cover a wider range of latitudes, longitudes, and times. The Voyager retrievals were based on atmospheric composition and radio refractivity data that require updating and were never properly tabulated; the few existing tabulations are incomplete and ambiguous. Here we present a systematic electronic digitization of all available temperature profiles from Voyager, followed by their reanalysis, employing currently accepted values of the abundances and radio refractivities of atmospheric species. We find the corrected temperature at the 1 bar level to be up to 4 K greater than the previously published values, i.e., 170.3 ± 3.8 K at 12°S (Voyager 1 ingress) and 167.3 ± 3.8 K at 0°N (Voyager 1 egress). This is to be compared with the Galileo probe value of 166.1 ± 0.8 K at the edge of an unusual feature at 6.°57N. Altogether, this suggests that Jupiter's tropospheric temperatures may vary spatially by up to 7 K between 7°N and 12°S.

Keywords: radio occultation; atmospheric refraction; jupiter; atmospheric composition; solar system formation
The Correlation of Outflow Kinematics with Star Formation Rate. VI. Gas Outflows in AGNs

We investigate the connection between ionized gas outflows and star formation activity using a large sample of type 1 and 2 active galactic nuclei (AGNs) with far-infrared detections or star formation rate (SFR) estimates. The strength of ionized gas outflows, measured by the velocity dispersion and velocity shift of the [O III] emission line, clearly shows a correlation with SFR. The connection between specific star formation rate (sSFR) and [O III] gas velocity dispersion indicates that AGNs with stronger outflows are hosted by galaxies with higher SFR. Compared with star-forming galaxies in the main sequence, both type 1 and type 2 AGNs show sSFRs similar to that of non-AGN galaxies, indicating no instantaneous AGN feedback, while sSFR is higher (lower) for AGNs with stronger (weaker) outflows than that of main-sequence galaxies. These results are consistent with a delayed AGN feedback scenario. However, it is also possible that a decease/increase of gas fraction may cause the correlation without AGN feedback.

Keywords: agn host galaxies; galaxy formation; supermassive black holes; star formation
The First Y Dwarf Data from JWST Show that Dynamic and Diabatic Processes Regulate Cold Brown Dwarf Atmospheres

The James Webb Space Telescope (JWST) is now observing Y dwarfs, the coldest known brown dwarfs, with effective temperatures T eff ≲ 475 K. The first published observations provide important information: not only is the atmospheric chemistry out of equilibrium, as previously known, but the pressure-temperature profile is not in the standard adiabatic form. The rapid rotation of these Jupiter-size, isolated, brown dwarfs dominates the atmospheric dynamics, and thermal and compositional changes disrupt convection. These processes produce a colder lower atmosphere, and a warmer upper atmosphere, compared to a standard adiabatic profile. Leggett et al. presented empirical models where the pressure-temperature profile was adjusted so that synthetic spectra reproduced the 1 ≲ λ (μm) ≲ 20 spectral energy distributions of brown dwarfs with 260 ≤ T eff (K) ≤ 540. We show that spectra generated by these models fit the first JWST Y dwarf spectrum better than standard-adiabat models. Unexpectedly, there is no 4.3 μm PH3 feature in the JWST spectrum and atmospheres without phosphorus better reproduce the 4 μm flux peak. Our analysis of new JWST photometry indicates that the recently discovered faint secondary of the WISE J033605.05-014350AB system has T eff ≈ 295 K, making it the first dwarf in the significant luminosity gap between the 260 K WISE J085510.83-071442.5, and all other known Y dwarfs. The adiabat-adjusted disequilibrium-chemistry models are recommended for analyses of all brown dwarfs cooler than 600 K, and a grid is publicly available. Photometric color transformations are provided in an appendix.

Keywords: y dwarfs; brown dwarfs; atmospheric structure; infrared astronomy; atmospheric dynamics; atmospheric composition
Model-independent Test for the Cosmic Distance-Duality Relation with Pantheon and eBOSS DR16 Quasar Sample

In this Paper, we carry out a new model-independent cosmological test for the cosmic distance-duality relation (CDDR) by combining the latest five baryon acoustic oscillation (BAO) measurements and the Pantheon type Ia supernova (SNIa) sample. Particularly, the BAO measurement from the extended Baryon Oscillation Spectroscopic Survey data release 16 quasar sample at effective redshift z = 1.48 is used, and two methods, i.e., a compressed form of the Pantheon sample and the artificial neural network combined with the binning SNIa method, are applied to overcome the redshift-matching problem. Our results suggest that the CDDR is compatible with the observations, and the high-redshift BAO and SNIa data can effectively strengthen the constraints on the violation parameters of CDDR with the confidence interval decreasing by more than 20%. In addition, we find that the compressed form of observational data can provide a more rigorous constraint on the CDDR, and thus can be generalized to the applications of other actual observational data with limited sample size in the test for CDDR.

Keywords: distance measure; cosmological parameters; observational cosmology
Long-term Periodicities in Kepler Photometry of Open Cluster NGC 6811

Long-term photometric variability can sometimes be related to the emergence of starspots in the photosphere following a quasi-periodic magnetic activity cycle. In order to investigate the existence and properties of magnetic cycles in a narrow range of fundamental parameters, we focused on solar-type stars in the intermediate-age open cluster NGC 6811 (1 Gyr). The cluster membership was analyzed both in terms of stellar kinematics and Gaia photometry. Rotation periods and photometric variability were analyzed for 138 stars from Kepler light curves and we discuss the existing trends and relationships. We also searched a sample of 11 solar-type stars for cycle-like periodicities and in each case classified the variability as either cyclic, multicyclic, flat, or acyclic. The results suggest a significant scatter, possibly due to sensitive nonlinearities in the dynamo process. This raises theoretical questions on whether these periodicities can be associated to activity cycles and what determines the stellar cycle presence or its period. Also, the lack of solar-twin flat activity stars in NGC 6811 combined with other recent results, suggests that the presence of magnetic grand minima in the Sun is a relatively recent phenomenon.

Keywords: open star clusters; stellar activity; solar analogs; light curves
The Physical Nature of Starburst-driven Galactic Outflows

We present the fourth simulation of the Cholla Galactic OutfLow Simulations suite. Using a physically motivated prescription for clustered supernova feedback, we successfully drive a multiphase outflow from a disk galaxy. The high resolution (<5 pc) across a relatively large domain (20 kpc) allows us to capture the hydrodynamic mixing and dynamical interactions between the hot and cool (T ∼ 104 K) phases in the outflow, which in turn leads to direct evidence of a qualitatively new mechanism for cool gas acceleration in galactic winds. We show that mixing of momentum from the hot phase to the cool phase accelerates the cool gas to 800 km s-1 on kiloparsec scales, with properties inconsistent with the physical models of ram pressure acceleration or bulk cooling from the hot phase. The mixing process also affects the hot phase, modifying its radial profiles of temperature, density, and velocity from the expectations of radial supersonic flow. This mechanism provides a physical explanation for the high-velocity, blueshifted, low-ionization absorption lines often observed in the spectra of starburst and high-redshift galaxies.

Keywords: active galaxies; starburst galaxies; hydrodynamical simulations; stellar feedback; circumgalactic medium; galaxy evolution
Chemical Analysis of the Brightest Star of the Cetus II Ultrafaint Dwarf Galaxy Candidate

We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, abundances or upper limits of 18 elements from carbon to europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the α-elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, and Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova originating from a star with a mass of ~11.2 M ⊙. In addition, the star has a potassium abundance of [K/Fe] = 0.81, which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature that is also present in a number of UFD galaxies. A comparison including globular clusters and stellar stream stars suggests that high K is a specific characteristic of some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: chemical abundances; stellar abundances
Determining Which Binary Component Hosts the TESS Transiting Planet

The NASA TESS mission has discovered many transiting planets orbiting bright nearby stars, and high-resolution imaging studies have revealed that a number of these exoplanet hosts reside in binary or multiple star systems. In such systems, transit observations alone cannot determine which star in the binary system actually hosts the orbiting planet. The knowledge of which star the planet orbits is necessary for determining accurate physical properties for the planet, especially its true radius and mean bulk density. We derived the mean stellar densities for the components of 23 binary systems using the light curve transit shape and the binary flux ratio from speckle imaging, then tested the consistency with stellar models to determine which component is the host star. We found that 70% of the TESS transiting planets in our sample orbit the primary star.

Keywords: exoplanets; high angular resolution; speckle interferometry
The Origin of Persistently Nonthermal Solar Wind Electrons: the Steady Electron Runaway Model's Demonstration of Dreicer Bifurcation using Measured {{E}}_{allel } and Ion-Electron Coulomb Drag

The Steady Electron Runaway Model (SERM) develops the hypothesis that the solar wind's observed ubiquitous nonthermal electron velocity distribution functions (eVDFs) are caused by Dreicer's velocity space bifurcation in the strong dimensionless ${{\mathbb{E}}}_{\parallel }$ required by quasi-neutrality. SERM's predicted partitions for the pressure and density are contrasted with appropriately adapted eVDF properties from the Wind 3DP experiment (1995-1998), based on in situ observations of ${{\mathbb{E}}}_{\parallel }$ . The observed number fraction of electrons in runaway, δ 3DP, follows a thousandfold decline of Dreicer's predicted fraction, δ, across the observed tenfold reduction of ${{\mathbb{E}}}_{\parallel }$ , satisfying δ 3DP ≃ δ 0.89. SERM's predictions are shown to reproduce the observed variations with ${{\mathbb{E}}}_{\parallel }$ of the electron partial pressure and excess kurtosis, ${{ \mathcal K }}_{e}$ . ${{ \mathcal K }}_{e}$ and ${{\mathbb{E}}}_{\parallel }$ are positively correlated across 4 yr, as expected by the SERM-Dreicer origin of the suprathermals. SERM quantitatively explains the observed 50 yr anticorrelation between δ 3DP and the partition slope temperature ratios. This documentation quantitatively establishes Coulomb runaway physics as the missing determinant of the ubiquitous nonthermal solar wind eVDF. Astrophysical plasmas, like stellar winds, are unavoidably inhomogeneous, requiring ${{\mathbb{E}}}_{\parallel }$ to enforce quasi-neutrality. Between the stars ${{\mathbb{E}}}_{\parallel }$ is expected to be sufficiently large that measurable runaway density fractions (0.1%-30%) will occur, producing widespread leptokurtic eVDFs. Using inhomogeneous two-fluid information, SERM predicts spatially dependent leptokurtic eVDF profiles consonant with Coulomb collisions and the fluid's E ∥(r). SERM can also comment on its eVDFs' consistency with Maxwellians presumed in the Spitzer-Härm closure. The solar wind profile shows the implied strong radial gradient of the plasma eVDF's transformation from near thermal to strongly leptokurtic across 1.5-6 R ⊙.

Keywords: solar wind; space plasmas; collisional processes
Very-high-energy Gamma-Ray Afterglows of GRB 201015A and GRB 201216C

Gamma-ray bursts (GRBs) 201015A and 201216C are valuable cases where very-high-energy (VHE) gamma-ray afterglows have been detected. By analyzing their prompt emission data, we find that GRB 201216C is an extremely energetic, long GRB with a hard gamma-ray spectrum, while GRB 201015A is a relative subenergetic, soft-spectrum GRB. Attributing their radio-optical-X-ray afterglows to the synchrotron radiation of the relativistic electrons accelerated in their jets, we fit their afterglow lightcurves with the standard external shock model and infer their VHE afterglows from the synchrotron self-Compton scattering process of the electrons. It is found that the jet of GRB 201015A is midrelativistic (Γ0 = 44), surrounded by a very dense medium (n = 1202 cm-3), and the jet of GRB 201216C is ultrarelativistic (Γ0 = 331), surrounded by a moderate dense medium (n = 5 cm-3). The inferred peak luminosity of the VHE gamma-ray afterglows of GRB 201216C is approximately 10-9 erg cm-2 s-1 at 57-600 s after the GRB trigger, making it detectable with the MAGIC telescopes at a high confidence level, even though the GRB is at a redshift of 1.1. Comparing their intrinsic VHE gamma-ray lightcurves and spectral energy distributions with GRBs 180720B, 190114C, and 190829A, we show that their intrinsic peak luminosity of VHE gamma-ray afterglows at 104 s after the GRB trigger is variable from 1045 to 5 × 1048 erg s-1, and their kinetic energy, initial Lorentz factor, and medium density are diverse among bursts.

Keywords: gamma-ray bursts