adsabs/SciX_UAT_keywords huggingface dataset:
The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa from Asteroseismology with TESS

Most previous efforts to calibrate how rotation and magnetic activity depend on stellar age and mass have relied on observations of clusters, where isochrones from stellar evolution models are used to determine the properties of the ensemble. Asteroseismology employs similar models to measure the properties of an individual star by matching its normal modes of oscillation, yielding the stellar age and mass with high precision. We use 27 days of photometry from the Transiting Exoplanet Survey Satellite to characterize solar-like oscillations in the G8 subgiant of the 94 Aqr triple system. The resulting stellar properties, when combined with a reanalysis of 35 yr of activity measurements from the Mount Wilson HK project, allow us to probe the evolution of rotation and magnetic activity in the system. The asteroseismic age of the subgiant agrees with a stellar isochrone fit, but the rotation period is much shorter than expected from standard models of angular momentum evolution. We conclude that weakened magnetic braking may be needed to reproduce the stellar properties, and that evolved subgiants in the hydrogen shell-burning phase can reinvigorate large-scale dynamo action and briefly sustain magnetic activity cycles before ascending the red giant branch.

Keywords: stellar activity; stellar evolution; stellar oscillations; stellar rotation
The Relative Importance of Thermal Gas, Radiation, and Magnetic Pressures around Star-forming Regions in Normal Galaxies and Dusty Starbursts

In this paper, an investigation on the relative importance of the thermal gas, radiation, and (minimum-energy) magnetic pressures around ≈200 star-forming regions in a sample of nearby normal and luminous infrared galaxies is presented. Given the range of galaxy distances, pressure estimates are made on spatial scales spanning ~0.1-3 kpc. The ratio of thermal gas-to-radiation pressures does not appear to significantly depend on star formation rate surface density (ΣSFR), but exhibits a steady decrease with increasing physical size of the aperture over which the quantities are measured. The ratio of magnetic-to-radiation pressures appears to be relatively flat as a function of ΣSFR and similar in value for both nuclear and extranuclear regions, but, unlike the ratio of thermal gas-to-radiation pressures, exhibits a steady increase with increasing aperture size. Furthermore, it seems that the magnetic pressure is typically weaker than the radiation pressure on subkiloparsec scales, and only starts to play a significant role on few-kiloparsec scales. When the internal pressure terms are summed, their ratio to the (ΣSFR-inferred) kiloparsec-scale dynamical equilibrium pressure estimates is roughly constant. Consequently, it appears that the physical area of the galaxy disk, and not necessarily environment (e.g., nuclear versus extranuclear regions) or star formation activity, may play the dominant role in determining which pressure term is most active around star-forming regions. These results are consistent with a scenario in which a combination of processes acting primarily on different physical scales work collectively to regulate the star formation process in galaxy disks.

Keywords: star formation; star forming regions; radio continuum emission; extragalactic magnetic fields; galaxies; stellar feedback; magnetic fields; luminous infrared galaxies; galaxy evolution; dust continuum emission; disk galaxies
A Proposal for Enhancing Technosignature Search toward the Galactic Center

We discuss the possibility of enhancing intelligent life searches toward the Galactic center. From the clockwork orbital motions of stars around the Sgr A* black hole, we can determine the distance to the Galactic center at an exceptional accuracy, despite its remoteness ∼8.3 kpc. In addition, we can define precise reference epochs by selecting a prominent object such as the bright B-type star S2. These properties have a particular affinity for the coordinated signaling scheme that was hypothesized by Seto for systematically connecting intentional senders to searchers without a prior communication. If S2 is actually being used as a common reference clock, we can compress the search directions around the Galactic center by more than 2 orders of magnitude, with the scanning interval of ∼16 yr.

Keywords: search for extraterrestrial intelligence; astrobiology; galactic center
Large Impacts onto the Early Earth: Planetary Sterilization and Iron Delivery

Late accretion onto the Hadean Earth included large impacts that could have influenced early habitability, either by sterilizing the planet or alternatively catalyzing the origin of life by delivering iron required to create a reducing environment/atmosphere. We present 3D numerical simulations of 1500-3400 km diameter impacts on the early Earth in order to quantify their effects on planetary habitability. We find sterilizing impact events require larger projectiles than previously assumed, with a 2000-2700 km diameter impactor required to completely melt Earth's surface and an extrapolated >700 km diameter impactor required for ocean vaporization. We also find that reducing environments are less likely to arise following large impacts than previously suggested, because >70% of the projectile iron is deposited in the crust and upper mantle where it is not immediately available to reduce surface water and contribute to forming a reducing atmosphere. Although the largest expected late-accretion impacts (~1 lunar mass) delivered sufficient iron to the atmosphere to have reduced an entire ocean mass of water, such impacts would also have melted the entire surface, potentially sequestering condensing iron that is not oxidized quickly. The hypothesis that life emerged in the aftermath of large impacts requires an efficient mechanism of harnessing the reducing power of iron sequestered in the crust/mantle, or an origin-of-life pathway that operates in more weakly reducing post-impact environments that require smaller quantities of impact-delivered iron.

Keywords: planetary science; earth (planet); impact phenomena; habitable planets; astrobiology
Class Symbolic Regression: Gotta Fit 'Em All

We introduce "Class Symbolic Regression" (Class SR), the first framework for automatically finding a single analytical functional form that accurately fits multiple data sets—each realization being governed by its own (possibly) unique set of fitting parameters. This hierarchical framework leverages the common constraint that all the members of a single class of physical phenomena follow a common governing law. Our approach extends the capabilities of our earlier Physical Symbolic Optimization (Φ-SO) framework for symbolic regression, which integrates dimensional analysis constraints and deep reinforcement learning for unsupervised symbolic analytical function discovery from data. Additionally, we introduce the first Class SR benchmark, comprising a series of synthetic physical challenges specifically designed to evaluate such algorithms. We demonstrate the efficacy of our novel approach by applying it to these benchmark challenges and showcase its practical utility for astrophysics by successfully extracting an analytic galaxy potential from a set of simulated orbits approximating stellar streams.

Keywords: neural networks; astronomy data analysis; astronomy software; open source software; analytical mathematics
Advanced Composition Explorer Observations of Turbulence from 1998 through 2002: Data Intervals

We have published several papers describing solar wind turbulence at 1 au using data from the Advanced Composition Explorer spacecraft. In an oversight that we regret, we never published the list of data intervals that constitute the database of observations. As we have recently returned to this database of observations in comparisons of turbulent observations by the Voyager spacecraft against established results from 1 au, we wish to now correct our oversight and publish the list of intervals that constitute the 1 au observations. Along with this, we show the distribution of some common solar wind parameters as contained within the database.

Keywords: solar wind; heliosphere; magnetohydrodynamics
The Fate of the Interstellar Medium in Early-type Galaxies. III. The Mechanism of Interstellar Medium Removal and the Quenching of Star Formation

Understanding how galaxies quench their star formation is crucial for studies of galaxy evolution. Quenching is related to a decrease of cold gas. In the first paper we showed that the dust removal timescale in early-type galaxies (ETGs) is about 2.5 Gyr. Here we present carbon monoxide and 21 cm hydrogen line observations of these galaxies and measure the timescale of removal of the cold interstellar medium (ISM). We find that all the cold ISM components (dust and molecular and atomic gas) decline at similar rates. This allows us to rule out a wide range of potential ISM-removal mechanisms (including starburst-driven outflows, astration, or a decline in the number of asymptotic giant branch stars), and artificial effects like the stellar mass–age correlation, environmental influence, mergers, and selection bias, leaving ionization by evolved low-mass stars and ionization/outflows by Type Ia supernovae or active galactic nuclei as viable mechanisms. We also provide evidence for an internal origin of the detected ISMs. Moreover, we find that the quenching of star formation in these galaxies cannot be explained by a reduction in the gas amount alone, because the star formation rates (SFRs) decrease faster (on a timescale of about 1.8 Gyr) than the amount of cold gas. Furthermore, the star formation efficiency (SFE) of the ETGs ( ${\rm{SFE}}\equiv {\rm{SFR}}/{M}_{{{\rm{H}}}_{2}}$ ) is lower than that of star-forming galaxies, whereas their gas mass fractions ( ${f}_{{{\rm{H}}}_{2}}\equiv {M}_{{{\rm{H}}}_{2}}/{M}_{* }$ ) are normal. This may be explained by the stabilization of gas against fragmentation, for example due to morphological quenching, turbulence, or magnetic fields.

Keywords: early-type galaxies; elliptical galaxies; quenched galaxies; galaxy quenching; interstellar medium; post-starburst galaxies; stellar feedback; galaxy ages; co line emission; h i line emission; cold neutral medium; molecular gas
Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

In the Martian induced magnetosphere, the motion of planetary ions is significantly controlled by the ambient electric fields, which can be decomposed into three components: the motional, Hall, and ambipolar electric fields. Each of them is dominant in different regions and provides the ion acceleration with a particular effectiveness. Therefore, it is necessary to characterize the global distribution of these electric field components. In this study, a global multifluid Hall-MHD model is applied, which considers the motional, Hall, and ambipolar electric fields in ion transport and magnetic induction equations to self-consistently investigate the morphology of the electric fields in the Martian space environment. Numerical results suggest that the motional electric field is dominant in the upstream of the bow shock and in the magnetosheath along the Z MSE direction, leading to the formation of the ion plume escape channel. At the bow shock, the ambipolar electric field points outward, to decelerate and deflect the solar wind plasma flow. In the magnetosheath region, the ambipolar and motional electric fields with inward direction tend to reaccelerate the solar wind ions. However, along the magnetic pileup boundary, the Hall electric field pointing outward prevents the solar wind ions from penetrating the Martian induced magnetosphere, which also prevails in the Martian magnetotail region, to accelerate the ions' tailward escape. This is the first systematic investigation of the global distribution of electric fields, which is helpful to understand the processes of ion acceleration/deceleration and escape within the Mars-solar wind interaction.

Keywords: mars; solar-planetary interactions; magnetohydrodynamics
Broadband Multiwavelength Study of LHAASO-detected Active Galactic Nuclei

Recently, the Large High Altitude Air Shower Observatory (LHAASO) collaboration presented the first catalog of γ-ray sources using 508 days of LHAASO data, from 2021 March to 2022 September. This catalog contains four blazars and a possible LINER-type active galactic nucleus (AGN) counterpart. In this work, we establish averaged multiwavelength spectral energy distributions (SEDs) by combining data from the Fermi-Large Area Telescope, Swift, Zwicky Transient Facility, and Wide-field Infrared Survey Explorer (WISE) covering the same period as the LHAASO detection. In general, these five AGNs are found in low states at all wavelengths. To study the multiwavelength properties of these AGNs, several jet emission models, including the one-zone leptonic model, the one-zone leptonic and hadronuclear (pp) model, the one-zone proton-synchrotron model, and the spine-layer model, are applied to reproduce their averaged SEDs. We find that the one-zone leptonic model can reproduce most of the SEDs, except for the high-energy tail of the LHAASO spectra of Mrk 421 and Mrk 501. To improve the fitting, emission from pp interactions is favored in the framework of a one-zone model. The spine-layer model, which can be treated as a multizone scenario, can also provide good spectral fits. The influence of different extragalactic background light models on fitting a LHAASO energy spectrum is also discussed.

Keywords: gamma-ray sources; high energy astrophysics; relativistic jets
On the Detectability of Ultracompact Binary Pulsar Systems

Using neural networks, we integrate the ability to account for Doppler smearing due to a pulsar's orbital motion with the pulsar population synthesis package PSRPOPPY to develop accurate modeling of the observed binary pulsar population. As a first application, we show that binary neutron star systems where the two components have highly unequal mass are, on average, easier to detect than systems that are symmetric in mass. We then investigate the population of ultracompact (1.5 minutes ≤ Pb ≤ 15 minutes) neutron star-white dwarf (NS-WD) and double neutron star (DNS) systems, which are promising sources for the Laser Interferometer Space Antenna gravitational-wave detector. Given the nondetection of these systems in radio surveys thus far, we estimate a 95% confidence upper limit of ∼1450 and ∼1100 ultracompact NS-WD and DNS systems in the Milky Way that are beaming toward the Earth, respectively. We also show that using survey integration times in the range 20 s-200 s with time-domain resampling will maximize the signal-to-noise ratio as well as the probability of detection of these ultracompact binary systems. Among all the large-scale radio pulsar surveys, those that are currently being carried out using archival data collected with the Arecibo radio telescope have a ∼50%-80% chance of detecting at least one of these systems using current integration integration times and ∼80%-95% using optimal integration times in the next several years.

Keywords: binary pulsars; pulsars; radio pulsars; gravitational waves
Discovery of a Supercluster Candidate at z ∼ 1.1

We report a promising candidate for a distant supercluster at z ∼ 1.1 in the Dark Energy Survey Science Verification data. We examine smoothed semi-3D galaxy density maps in various photo-z slices. Among several overdense regions, in this work we report the most significant one as having a 3σ overdensity at a redshift of ∼1.1, over a ∼160 Mpc scale, much larger than the regular cluster scale (several Mpc). The shape of the supercluster is not circular in the sky projection. Therefore, we regard the point of maximum overdensity as the center for quantitative measurements. Two different estimates suggest the mass of the supercluster to be ${1.37}_{-0.79}^{+1.31}\times {10}^{17}\,{M}_{\odot }$ , more than one order more massive than regular galaxy clusters. Except for protosuperclusters found with emission-line galaxies, this could be the most distant supercluster to date defined by regular galaxies. A spectroscopic confirmation would make this a very interesting object for cosmology. We discuss the possible implications of such a massive structure for ΛCDM cosmology.

Keywords: galaxies
The Effects of Magnetic Boundary on the Uniform Distribution of Energetic Particle Intensities Observed by Multiple Spacecraft

In the decay phase of solar energetic particle (SEP) events, particle intensities observed by widely separated spacecraft usually present comparable intensities (within a factor of 2-3) that evolve similarly in time. The phenomenon of SEP events is called a reservoir, which could be observed frequently in intensive gradual SEP events. In this work, we find the effects of the magnetic boundary could help to form the reservoir phenomenon in energetic proton and electron events. In the 1978 January 1 and the 2000 November 8 SEP events, we find the effects of the magnetic boundary associated with the reservoir phenomenon were observed simultaneously in the sheath of magnetic cloud/interplanetary coronal mass ejection. Based on the observations, we suggest that the effects of the magnetic boundary could be due to the magnetic mirrors and/or the small diffusion coefficients in the sheath region and they could help to form the reservoir phenomenon in both the energetic proton and electron events in some large SEP events.

Keywords: solar activity; solar flares; interplanetary shocks; shocks
ALMA Observations of Massive Clouds in the Central Molecular Zone: Jeans Fragmentation and Cluster Formation

We report Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 continuum observations of 2000 au resolution toward four massive molecular clouds in the Central Molecular Zone of the Galaxy. To study gas fragmentation, we use the dendrogram method to identify cores as traced by the dust continuum emission. The four clouds exhibit different fragmentation states at the observed resolution despite having similar masses at the cloud scale (∼1-5 pc). Assuming a constant dust temperature of 20 K, we construct core mass functions of the clouds and find a slightly top-heavy shape as compared to the canonical initial mass function, but we note several significant uncertainties that may affect this result. The characteristic spatial separation between the cores as identified by the minimum spanning tree method, ∼104 au, and the characteristic core mass, 1-7 ${M}_{\odot }$, are consistent with predictions of thermal Jeans fragmentation. The three clouds showing fragmentation may be forming OB associations (stellar mass ∼103 ${M}_{\odot }$). None of the four clouds under investigation seem to be currently able to form massive star clusters like the Arches and the Quintuplet (≳104 ${M}_{\odot }$), but they may form such clusters by further gas accretion onto the cores.

Keywords: galactic center; star formation; molecular clouds
Rapid Premerger Localization of Binary Neutron Stars in Third-generation Gravitational-wave Detectors

Premerger localization of binary neutron stars (BNSs) is one of the most important scientific goals for the third-generation (3G) gravitational-wave detectors. It will enable the electromagnetic observation of the whole process of BNS coalescence, especially for the premerger and merger phases, which have not been observed yet, opening a window for deeper understandings of compact objects. To reach this goal, we describe a novel combination of multiband matched filtering and semianalytical localization algorithms to achieve early-warning localization of long BNS signals in 3G detectors. Using our method we are able to efficiently simulate one month of observations with a three-detector 3G network, and show that it is possible to provide accurate sky localizations more than 30 minutes before the merger. Our simulation shows that there could be ~10 (~100) BNS events localized within 100 deg2, 20 (6) minutes before merger, per month of observation.

Keywords: gravitational waves; gravitational wave astronomy; compact binary stars
An Empirical Proxy for the Second Integral of Motion in Rotating Barred or Tri-axial Potentials

We identify an effective proxy for the analytically unknown second integral of motion (I2) for rotating barred or tri-axial potentials. Planar orbits of a given energy follow a tight sequence in the space of the time-averaged angular momentum and its amplitude of fluctuation. The sequence monotonically traces the main orbital families in the Poincaré map, even in the presence of resonant and chaotic orbits. This behavior allows us to define the calibrated angular momentum, the average angular momentum ( $\overline{{L}_{z}}$ ) normalized by the amplitude of its fluctuation ( ${\sigma }_{{L}_{z}}$ ), as a numerical proxy for I2. It also implies that the amplitude of fluctuation in Lz, previously underappreciated, contains valuable information. This new proxy allows one to classify orbital families easily and accurately, even for real orbits in N-body simulations of barred galaxies. It is a good diagnostic tool of dynamical systems, and may facilitate the construction of equilibrium models.

Keywords: galaxy dynamics; orbits; barred spiral galaxies
Rotation Curves in z ∼ 1-2 Star-forming Disks: Evidence for Cored Dark Matter Distributions

We report high-quality, Hα or CO rotation curves (RCs) to several Re for 41 large, massive, star-forming disk galaxies (SFGs) across the peak of cosmic galaxy evolution (z ∼ 0.67-2.45), taken with the ESO-VLT, the LBT and IRAM-NOEMA. Most RC41 SFGs have reflection-symmetric RCs plausibly described by equilibrium dynamics. We fit the major axis position-velocity cuts using beam-convolved forward modeling generated in three dimensions, with models that include a bulge and turbulent disk component embedded in a dark matter (DM) halo. We include priors for stellar and molecular gas masses, optical light effective radii and inclinations, and DM masses from abundance-matching scaling relations. Two-thirds or more of the z ≥ 1.2 SFGs are baryon dominated within a few Re of typically 5.5 kpc and have DM fractions less than maximal disks (median $\langle {f}_{\mathrm{DM}}({R}_{e})\rangle =0.12$ ). At lower redshift (z < 1.2), that fraction is less than one-third. DM fractions correlate inversely with the baryonic angular momentum parameter, baryonic surface density, and bulge mass. Inferred low DM fractions cannot apply to the entire disk and halo but more plausibly reflect a flattened, or cored, inner DM density distribution. The typical central "DM deficit" in these cores relative to Navarro-Frenk-White (NFW) distributions is ∼30% of the bulge mass. The observations are consistent with rapid radial transport of baryons in the first-generation massive gas-rich halos forming globally gravitationally unstable disks and leading to efficient build-up of massive bulges and central black holes. A combination of heating due to dynamical friction and AGN feedback may drive DM out of the initial cusps.

Keywords: high-redshift galaxies; galaxy kinematics; galaxy dynamics; galaxy structure