Sazuna/UAT_keywords huggingface dataset:
Are Local Group Dwarf Spheroidal Galaxies the First Safe Planet-hosting Environments?. We explore whether Local Group dwarf spheroidal (dSph) galaxies might have hosted Earth-like planets dwelling unexposed for several billions of years to major galactic threats to life, such as supernovae and gamma-ray bursts. To this aim, we developed a novel semiempirical model that exploits the observed chemical abundances and star formation histories of a selected sample of local dSphs, to explore whether their stars may have (i) reached the minimum metallicity to trigger planet formation and (ii) avoided exposure to destructive events long enough to provide time for possible biological development. From our work two scenarios emerge. If planet formation is possible for [Fe/H] ≲ ‑1, then in all dSphs with 5 × 103 L⊙ ≤ LV ≤ 2 × 107 L⊙ a fraction ≈0.1%–10% of stars might have safely hosted terrestrial planets for more than 1 Gyr. In this scenario, ancient ultrafaint dwarf galaxies (UFDs, LV ≤ 105 L⊙) would have been the first to reach this condition in the history of the Local Group. Conversely, if planets form for [Fe/H] ≥ ‑0.6 then they should not exist in UFDs, while only ≈0.001%–0.1% of stars in dSphs with LV ≥ 3 × 105 L⊙ would host planets dwelling in safe conditions for long times. Interestingly, we find a "luminosity sweet spot" at LV ∼ 106 L⊙, where dSphs in our sample safely host terrestrial planets up to 4 Gyr and in any planet formation scenario explored. In conclusion, planet formation at low metallicity is key to understanding which types of galaxies might have formed Earth-like planets that dwelt unexposed to galactic threats over several billions of years, first in the history of the Local Group.

Keywords: Dwarf galaxies, Astrobiology, Galaxy evolution, Planet formation
Identifying a Protocluster Formation at z ∼ 4.5 in the COSMOS Field: An Extension of the Taralay Protocluster, Traced by Lyα Emitters Surrounding a Submillimeter Galaxy. We report the discovery of a large-scale structure containing multiple overdensities at z = 4.54 ± 0.03 in the COSMOS field, with the most prominent one likely infalling toward the recently identified Taralay protocluster. We use combined wideband and narrowband (NB) optical photometry to identify Lyα emitters (LAEs) within a 21 cMpc radius from the submillimeter source J1000+0234, at z = 4.54, to identify typical star-forming galaxies that may trace an underlying structure. Our approach selects line emitters as NB excess objects and we use the COSMOS2020 photometric redshift catalog to eliminate potential low-redshift interlopers whose line emission (e.g., [O III] at z ∼ 0.3) might be responsible for the observed excess in the narrow band. In comparison with the LAE density in the field, our results point to a mean LAE number overdensity of  δ¯=3  spanning a region of 27 × 20 × 36 cMpc3, probably evolving into a moderate-mass cluster ((3–10) × 1014 M⊙) at z ∼ 0. This work supports the idea that submillimeter sources, although offset from the major overdensity peaks, serve as traces of moderately massive, potentially infalling structures.

Keywords: High-redshift galaxy clusters, Large-scale structure of the universe, Lyman-alpha galaxies, Narrow band photometry, High-redshift galaxies
Watching Our Galaxy Grow Up: The Mass and Color Evolution of the Milky Way. Using our rich observations within the Milky Way to better understand galaxy evolution requires understanding what the Milky Way looks like "as a galaxy"—that is, its "true" shape and abundance profiles (unskewed by observational biases), signatures of past mergers and significant accretion events, and even its total stellar mass and integrated spectral energy distribution, which have historically been difficult to constrain. We present a new approach to determining the Milky Way's integrated mass and colors, using recent measurements of the intrinsic density profiles of stellar populations spanning nearly 13 Gyr in time and 1.5 dex in metallicity (representing nearly all of the Galaxy's stars). We trace the evolution of the Milky Way in various diagnostic spaces, explore the impact of specific events on the present-day Milky Way's integrated properties, and use TNG50 simulations to identify "young" Galactic analogs and their eventual fates, compared to the real Milky Way's path. From the simulation comparisons, we find strong evidence for an earlier-than-average stellar mass assembly of the Milky Way, and that present-day Milky Way analogs follow a similar growth history, albeit at slightly later times; we also find that analogs of the early Milky Way are in no way guaranteed to follow the Milky Way's subsequent path. This empirical study offers new constraints on our "Galaxy as a galaxy"—today and across cosmic time—and on its place in the general galactic population.

Keywords: Galaxy evolution, Milky Way evolution, Milky Way Galaxy, Galactic archaeology
COSMOS-Web: The Overabundance and Physical Nature of "Little Red Dots"—Implications for Early Galaxy and SMBH Assembly. JWST has revealed a population of compact and extremely red galaxies at z ≳ 4, which likely host active galactic nuclei (AGNs). We present a sample of 434 "little red dots" (LRDs), selected from the 0.54 deg2 COSMOS-Web survey. We fit galaxy and AGN spectral energy distribution models to derive redshifts and physical properties; the sample spans z ∼ 5─9 after removing brown dwarf contaminants. As a thought experiment, we consider two extreme physical scenarios: either LRDs are all AGNs, and their continuum emission is dominated by the accretion disk, or they are all compact star-forming galaxies, and their continuum is dominated by stars. If LRDs are AGN-dominated, our sample exhibits bolometric luminosities ∼1045−47 erg s−1, spanning the gap between JWST AGNs in the literature and bright, rare quasars. We derive a bolometric luminosity function (LF) ∼ 100 times the (UV-selected) quasar LF, implying a nonevolving black hole accretion density of ∼10−4M⊙ yr−1 Mpc−3 from z ∼ 2─9. By contrast, if LRDs are dominated by star formation, we derive stellar masses ∼108.5−10 M⊙. MIRI/F770W is key to deriving accurate stellar masses; without it, we derive a mass function inconsistent with Λ cold dark matter. The median stellar mass profile is broadly consistent with the maximal surface densities seen in the nearby Universe, though the most massive objects exceed this limit, requiring substantial AGN contribution to the continuum. Nevertheless, stacking all available X-ray, mid-IR, far-IR/submillimeter, and radio data yields nondetections. Whether dominated by dusty AGNs or compact star-formation, the high masses/luminosities and remarkable abundance of LRDs implies a dominant mode of early galaxy/SMBH growth.

Keywords: Active galactic nuclei, High-redshift galaxies, Galaxies, Quasars
Searching for Pulsars in Globular Clusters with the Fast-folding Algorithm and a New Pulsar Discovered in M13. We employed the fast-folding algorithm on L-band globular cluster (GC) observations taken with the Five-hundred-meter Aperture Spherical radio Telescope to search for new pulsars, especially those with a long rotational period. We conducted a search across 16 GCs that collectively host 93 known pulsars, as well as 14 GCs that do not contain any known pulsars. The majority of these known pulsars were successfully redetected in our survey. The few nondetections could be attributed to the high accelerations of these pulsars. Additionally, we have discovered a new binary millisecond pulsar, namely M13I (or PSR J1641+3627I) in GC M13 (or NGC 6205), and obtained its phase-coherent timing solution using observations spanning 6 yr. M13I has a spin period of 6.37 ms and an orbital period of 18.23 days. The eccentricity of the binary orbit is 0.064, with a companion mass range of approximately 0.45 to 1.37 M⊙. The orbital properties of M13I are remarkably different from those of the other known pulsars in M13, indicating that this pulsar has undergone a different evolutionary path compared to the rest.

Keywords: Globular star clusters, Millisecond pulsars
Size Distributions of Arcsecond-scale Properties of Solar Flare Ribbons. Solar flare ribbons are believed to map the footpoints of newly reconnected magnetic flux tubes; therefore, shedding light on the reconnecting current sheet, which is rarely observed by direct imaging or spectroscopy. Here we study the detailed evolution of flare ribbons down to the arcsecond scale for 10 flares characterized by the classic double ribbons. Identifying the flaring pixels by combining the intensity variances of the UV filter ratio and an intensity threshold, we found that the waiting time distributions of the flaring pixels are well described by power laws, distinct from those in the preflare or quiet-Sun regions, and that the power-law slopes are generally consistent with those predicted by nonstationary Poisson processes in the nonlinear regime or by the 2D/3D self-organized criticality (SOC) model. The size distributions for flaring duration also follow power laws but the slopes are more scattered. In contrast, the size distributions for other parameters, including peak intensity, energy, and radial magnetic field strength of the flaring pixels, deviate from power laws, and the estimated slopes significantly differ from the SOC predictions. These results suggest that a nonstationary Poisson process or an avalanche-like process might be ongoing temporally in the reconnecting current sheet, but in other aspects, e.g., space- and energy-wise, the avalanche is likely modulated by other physical processes or the fine structures of the reconnecting current sheet.

Keywords: Solar active regions, Solar chromosphere, Solar flares
Magnetohydrodynamic Study of Mars's Response to Short-term Solar Wind Dynamic Pressure Enhancements. As a weakly magnetized planet, Mars interacts directly with the highly variable solar wind, where small-scale and short-duration structures are ubiquitous. Among solar wind parameters, dynamic pressure, as the dominant external pressure, plays a key role in shaping the pressure level and structures in the downstream induced magnetosphere. In this study, a multispecies global magnetohydrodynamic model is used to investigate Mars's response to a series of idealized solar wind dynamic pressure enhancements with varying durations and magnitudes, aiming to capture responses in different plasma regions and isolate the effects of dynamic pressure. For the subsolar region, the simulations reveal a sequence of response phases, each exhibiting distinct temporal characteristics. Beyond the subsolar region, the terminator ionosphere and global ion escape show prolonged disturbances. These results highlight the importance of short-term upstream variability in shaping both local and global features of the Martian plasma environment and provide context for interpreting spacecraft observations that sample only limited regions of the system.

Keywords: Space plasmas, Mars, Solar-planetary interactions, Magnetohydrodynamical simulations
Asymmetric Tangential Velocity inside Switchbacks: Implication for Switchback Origin. Switchbacks are structures in the solar wind marked by large rotations in the magnetic field direction without significant changes in its magnitude, typically accompanied by enhanced bulk speed. Parker Solar Probe (PSP) measurements have established the switchback as a prominent feature of the near-Sun solar wind. Detailed observations have shed light on switchback properties, leading to various proposed mechanisms for their generation. However, one key aspect that remains unexplored is the distribution of the tangential bulk velocity within switchbacks. A particular challenge has been accurately determining the tangential component of the plasma flow in the near-Sun plasma. With the most recent Solar Probe Cup measurements, it has been possible to gather sufficient statistics of proton tangential speed data in near-Sun solar wind switchbacks. This is important because some switchback models, particularly those involving solar wind interactions, predict that the tangential velocity should exhibit a strong one-sided polarity inside switchbacks. In this study, we examine the tangential component of the bulk velocity inside switchbacks during PSP encounters. Our findings reveal that switchbacks preferentially exhibit a positive tangential bulk velocity, strongly supporting the hypothesis that the majority of switchbacks are generated by the interaction of slow and fast wind across a superspiral outside the Alfvén critical point.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar coronal heating, Solar wind, Alfven waves
On the Origin of Super-global Spin-up Trends of X-Ray Pulsars in HMXB Systems. Most X-ray pulsars in high-mass X-ray binary (HMXB) systems exhibit both global and local trends of spin acceleration (spin-up) and deceleration (spin-down). Moreover, decades-long monitored objects display even more general spin-up trends in their spin evolution and simultaneously demonstrate a decrease in the orbital period, so-called orbital decay. Although obvious, this general behavior leaves open the question of the energy source and the mechanism of angular momentum transfer that ensures the neutron star's (NS's) spin acceleration. We hypothesize that the observed spin acceleration of X-ray pulsars in HMXB (Roche lobe overflow and sgXRB) systems results from orbital angular momentum transfer via tidal interactions with their massive companions. To study these phenomena, we sample five well-studied objects with the longest observational history of their spin periods from the population of known Galactic persistent X-ray pulsars in HMXB systems. We obtain the spin frequency change from the observational data and estimate energy loses for orbital decay and pulsars' spin acceleration. We propose a new term of super-global spin-up trends, and show that their observable values do not exceed theoretical upper limits predicted within the scenario of orbital decay due to the tidal interaction between the NS and its massive companion.

Keywords: Neutron stars, Accretion, High energy astrophysics, High mass x-ray binary stars, Pulsars
X-Ray Studies of PSR J1838–0655 and its Wind Nebula Associated with HESS J1837–069 and 1LHAASO J1837–0654u. We analyzed X-ray data from Chandra, XMM-Newton, NICER, and NuSTAR to characterize the properties of the pulsar PSR J1838‑0655 and its pulsar wind nebula (PWN) associated with HESS J1837‑069. Based on 5.5 yr of NICER monitoring, we detected a glitch around MJD 59300, characterized by a fractional frequency jump of approximately 2 × 10‑6. We constructed semi-phase-coherent timing solutions for pre- and postglitch epochs, allowing for phase alignment of multi-instrument data and a subsequent measurement of the pulsed spectrum of the pulsar. This analysis confirmed previously reported spectral curvature and revealed a peak energy of  73‑26+85  keV in the pulsar's spectral energy distribution (SED), based on a logpar model fit of the pulsed spectrum. We discuss these findings within the framework of pulsar magnetospheric emission scenarios. The PWN's X-ray spectrum is well described by a power law with a photon index of 2.1 ± 0.3, softer than previously reported measurements. We also characterized the X-ray emission from another extended X-ray source AX J1837.3‑0652 within the extent of HESS J1837‑069. Based on the spatial and spectral properties of these X-ray sources, we propose a leptonic emission scenario for HESS J1837‑069 and demonstrate its feasibility through SED modeling. Finally, we discuss the implications of our model results and alternative scenarios for the gamma-ray emission.

Keywords: High energy astrophysics, Rotation powered pulsars, Gamma-ray sources, Pulsars, Radiative processes, Spectral energy distribution, X-ray sources, Pulsar wind nebulae
Millisecond Pulsars in M2: New Discoveries and a Detailed Timing Analysis. Globular clusters (GCs) offer a unique environment for discovering and studying millisecond pulsars. In this paper, we present a multiepoch search and detailed timing analysis of millisecond pulsars in the GC M2, using the Five-hundred-meter Aperture Spherical radio Telescope. We have discovered two new binary millisecond pulsars in M2, designated M2F and M2G. We provide measurements of the emission properties of all known pulsars in M2, including their polarization profiles, rotation measures (RMs), flux densities, scintillation characteristics, and so forth. In particular, we report the first RM at the distance and direction of this cluster. Additionally, we report the first phase-coherent timing solutions for the M2 pulsars. From our Bayesian timing analysis, we have measured their spin and orbital parameters with high precision, including the advance of periastron for M2A and M2E indicating total system masses of 1.75(13) and 1.80(5) solar masses, respectively. Using archival data from the Hubble Space Telescope, we have identified an optical counterpart of M2C, which is likely the white dwarf companion of the pulsar. By combining results from optical and radio observations, we have reconstructed the binary evolution track of this system and estimated the cooling age of the companion to be approximately 10 Myr, making it the youngest white dwarf in any known GC binary pulsars. Furthermore, using the spin period derivatives of M2 pulsars, we have investigated the gravitational potential of the cluster and found that our results strongly support the latest central stellar velocity dispersion measurement in M2.

Keywords: Globular star clusters, Millisecond pulsars, Radio telescopes, Binary pulsars, Radio pulsars
Molecular Jets from an Evolved Protostar: Insights from JWST-ALMA Synergy. The combination of the Atacama Large Millimeter/submillimeter Array (ALMA) and JWST/MIRI mid-infrared observations offers a transformative view of protostellar jets and outflows by probing cold and warm gas components across diverse physical conditions. We present a detailed comparison of gas distribution in these regimes for the jet/outflow system associated with G205.46−14.56S3 (HOPS 315), focusing on the inner ∼800 au along the jet. ALMA CO and SiO trace both lobes of the bipolar jet, revealing high-velocity collimated jets and wider outflow components. JWST/MIRI detects mainly the blueshifted lobe; the redshifted side is likely obscured by strong mid-infrared extinction. Shorter-wavelength MIRI H2 rotational lines (S(7)─S(4)) trace compact jet structures resembling SiO emission, while longer-wavelength lines (S(3)─S(1)) reveal more extended emission akin to low-velocity CO. From H2 rotational emission, we identify two molecular gas temperature components: warm (∼773 ± 44 K) and hot (∼2499 ± 721 K). Using the ortho-to-para ratio, we estimate visual extinction AV ≍ 23.3 ± 2.5 mag. JWST/MIRI emission implies a jet mass-loss rate of  ṀJ,blue,jwst≍(0.27±0.1)×10−6M⊙yr−1 . The combination of ALMA and JWST reveals stratified layers within the outflow and jet, as well as shock structures, providing a comprehensive view of their physical conditions. This multiwavelength study demonstrates that combining submillimeter observations from ALMA with infrared data from JWST is crucial for uncovering the full physical and chemical structure of protostellar jets and outflows.

Keywords: Submillimeter astronomy, Stellar jets, Infrared astronomy, Stellar winds, Protostars, Planet formation
Calculation of a Dynamical Substitute for the Real Earth–Moon System Based on Hamiltonian Analysis. The Earth–Moon libration points no longer exhibit the dynamical characteristics of "equilibrium points" due to perturbation effects when applying the ephemeris model. By decoupling the forced motions within the ephemeris model and computing the dynamical substitute trajectories, we can reconstruct a dynamical system that recovers the "equilibrium points" feature. Diverging from the conventional analytical approach rooted in the framework of Newtonian mechanics, this paper presents a novel method for calculating dynamical substitute based on the Hamiltonian mechanics framework. First, the Hamiltonian equations for the ephemeris model are formulated. Subsequently, the problem of decoupling forced motions is reformulated as solving a nonautonomous differential equation through canonical transformations. Then, an iterative method based on frequency analysis is employed for the computation. Eventually, approximate analytical solutions for five libration points over a 360 yr period are provided. Simulation results demonstrate that the computed approximate analytical solutions are in excellent agreement with the numerical integration results derived from the ephemeris model, thereby validating the efficacy of the proposed method. The Hamiltonian dynamical system derived herein enables the analysis of nonlinear central manifold motions via canonical transformations, facilitating the construction of higher-order analytical solutions for libration point orbits. This framework also provides a robust foundation for exploring characterization parameters of libration point orbits within the real Earth–Moon system.

Keywords: Earth-moon system
Subparsec Jet Morphologies of M87 at 43 GHz: Effects of Asymmetric Plasmoids within the Jet. Radio observations of the M87 jet reveal limb-brightened features that exhibit temporal variations, with the brighter limb side not remaining consistently fixed at the subparsec scales. Utilizing a force-free jet model that considers exclusively the relativistic plasma dynamics along large-scale magnetic fields attached onto the central black hole, we examine the effects of asymmetric plasmoid injections within the subparsec jet. At subparsec scales, the jet velocity is predominantly influenced by poloidal velocity, leading to distinctive characteristics in both the morphology and trajectories of the plasmoids injected within the jet. We explore the potential modifications to the limb-brightened subparsec jet images resulting from the injection of asymmetric, shearing plasma, which is traditionally considered solely under conditions of stationary and symmetric mass loading. By comparing the model jet properties with the 43 GHz observations of the M87 jet, it is suggested that the asymmetric injection of plasmoids within the jet offers a satisfactory explanation for the observed velocity variations and morphological dynamics of the M87 jet.

Keywords: Black hole physics, Relativistic jets