adsabs/SciX_UAT_keywords huggingface dataset:
Cyanopolyyne Chemistry in the L1544 Prestellar Core: New Insights from GBT Observations

We report a comprehensive study of the cyanopolyyne chemistry in the prototypical prestellar core L1544. Using the 100 m Robert C. Byrd Green Bank Telescope, we observe three emission lines of HC3N, nine lines of HC5N, five lines of HC7N, and nine lines of HC9N. HC9N is detected for the first time toward the source. The high spectral resolution (~0.05 km s-1) reveals double-peak spectral line profiles with the redshifted peak a factor 3-5 brighter. Resolved maps of the core in other molecular tracers indicate that the southern region is redshifted. Therefore, the bulk of the cyanopolyyne emission is likely associated with the southern region of the core, where free carbon atoms are available to form long chains, thanks to the more efficient illumination of the interstellar field radiation. We perform a simultaneous modeling of the HC5N, HC7N, and HC9N lines to investigate the origin of the emission. To enable this analysis, we performed new calculation of the collisional coefficients. The simultaneous fitting indicates a gas kinetic temperature of 5-12 K, a source size of 80″, and a gas density larger than 100 cm-3. The HC5N:HC7N:HC9N abundance ratios measured in L1544 are about 1:6:4. We compare our observations with those toward the well-studied starless core TMC-1 and with the available measurements in different star-forming regions. The comparison suggests that a complex carbon chain chemistry is active in other sources and is related to the presence of free gaseous carbon. Finally, we discuss the possible formation and destruction routes in light of the new observations.

Keywords: astrochemistry; star formation; interstellar medium; interstellar molecules; chemical abundances
Turbulent Heating of Solar Wind Plasma Downstream of Magnetohydrodynamic Shocks

Interplanetary (IP) shocks are believed to play a significant role in both amplifying the background level of turbulent fluctuations and in heating the bulk solar wind (SW). This study investigates the thermodynamic properties downstream of IP shocks. We examine the temperature, density, and specific entropy changes in the shocked plasma, taking into consideration the geometric aspects of IP shock propagation within the expanding SW. Specifically, in our analysis, we account for the fact that any particular temporal range of one-point measurement may correspond to vastly different physically relevant temporal and/or spatial dimensions, such as the age of the shocked plasma and/or radial distance to the place where the plasma encountered the shock. Thus, our approach resolves the contradictions in previously reported temperature and specific entropy profiles in downstream regions and suggests that downstream regions exhibit greater turbulent heating compared to the pristine SW. This may contribute to the overall heating of the SW plasma. The paper presents a phenomenological parameter to predict specific entropy profiles and demonstrates the consistency of the proposed model with observations. We discuss the implications of these results for the thermodynamics of the SW beyond 1 au.

Keywords: interplanetary shocks; interplanetary turbulence; solar wind
No Evidence that the Majority of Black Holes in Binaries Have Zero Spin

The spin properties of merging black holes observed with gravitational waves can offer novel information about the origin of these systems. The magnitudes and orientations of black hole spins offer a record of binaries' evolutionary history, encoding information about massive stellar evolution and the astrophysical environments in which binary black holes are assembled. Recent analyses of the binary black hole population have yielded conflicting portraits of the black hole spin distribution. Some works suggest that black hole spins are small but nonzero and exhibit a wide range of misalignment angles relative to binaries' orbital angular momenta. Other works conclude that the majority of black holes are nonspinning while the remainder are rapidly rotating and primarily aligned with their orbits. We revisit these conflicting conclusions, employing a variety of complementary methods to measure the distribution of spin magnitudes and orientations among binary black hole mergers. We find that the existence of a subpopulation of black holes with vanishing spins is not required by current data. Should such a subpopulation exist, we conclude that it must contain ≲60% of binaries. Additionally, we find evidence for significant spin-orbit misalignment among the binary black hole population, with some systems exhibiting misalignment angles greater than 90°, and see no evidence for an approximately spin-aligned subpopulation.

Keywords: gravitational wave astronomy; ligo; astronomy data analysis; stellar mass black holes; compact binary stars
Can Planet Nine Be Detected Gravitationally by a Subrelativistic Spacecraft?

Planet Nine was proposed as an explanation for the clustering of orbits for some trans-Neptunian objects. Recently, the use of a subrelativistic spacecraft was proposed to indirectly probe Planet Nine's gravitational influence. Here we study the effects of the drag and electromagnetic forces exerted on a subrelativistic spacecraft by the interstellar medium (ISM) and compare these forces with the gravitational force induced by Planet Nine. We find that the resulting noise due to density and magnetic fluctuations would dominate over Planet Nine's gravitational signal at subrelativistic speeds, V ≳ 0.001 c. We then identify the parameter space required to overcome the drag and magnetic noise from the ISM turbulence and enable the detection of Planet Nine's gravity. Finally, we discuss practical strategies to mitigate the effect of the drag and electromagnetic forces.

Keywords: solar system planets; small solar system bodies; interstellar medium; interplanetary medium
Exploring the Evolution of Massive Clumps in Simulations That Reproduce the Observed Milky Way α-element Abundance Bimodality

The Milky Way (MW) stellar disk has both a thin and a thick component. The thin disk is composed mostly of younger stars (≲8 Gyr) with a lower abundance of α-elements, while the thick disk contains predominantly older stars (≳8-12 Gyr) with a higher α abundance, giving rise to an α-bimodality most prominent at intermediate metallicities. A proposed explanation for the bimodality is an episode of clumpy star formation, where high-α stars form in massive clumps that appear in the first few billion years of the MW's evolution, while low-α stars form throughout the disk and over a longer time span. To better understand the evolution of clumps, we track them and their constituent stars in two clumpy MW simulations that reproduce the α-abundance bimodality, one with 10% and the other with 20% supernova feedback efficiency. We investigate the paths that these clumps take in the chemical space ([O/Fe]-[Fe/H]) as well as their mass, star formation rate (SFR), formation location, lifetime, and merger history. The clumps in the simulation with lower feedback last longer on average, with several lasting hundreds of millions of years. Some of the clumps do not reach high-α, but the ones that do on average have a higher SFR, longer lifetime, greater mass, and form closer to the Galactic center than the ones that do not. Most clumps that reach high-α merge with others and eventually spiral into the Galactic center, but shed stars along the way to form most of the thick-disk component.

Keywords: galaxy abundances; galaxy disks; galaxy evolution; galaxy formation; galaxy structure; hydrodynamical simulations
Estimating the Ages of FGK Dwarf Stars through the Use of GALEX FUV Magnitudes

Stellar age cannot be directly measured, yet age determinations are fundamental to understanding the evolution of stars, planets, and galaxies. The work presented here builds upon the idea of a stellar-activity age. We utilized far-ultraviolet (FUV) photometry acquired by the Galaxy Evolution Explorer (GALEX) space telescope as an indicator of chromospheric activity to infer ages of late-F, G, and K type dwarf stars. We derived a purely empirical correlation between FUV magnitudes and stellar age in conjunction with (B - V) color. Our attention is restricted to Sun-like stars with color range $0.55\leqslant (B-V)\leqslant 0.71$ and absolute magnitude range 4.3 ≤ MV ≤ 5.3. The correlation is defined in terms of a FUV-excess parameter $Q(\mathrm{FUV}-B,B-V)$ . We related stellar age, τ, to Q through the relation ${\mathrm{log}}_{e}(\tau )={\mathrm{log}}_{e}(a)+{bQ}$ , where a and b are fit parameters and functions of (B - V). This correlation is functional up to 6 Gyr for FGK dwarfs. With such a correlation, one only needs Johnson (B - V) and FUV measurements to estimate the stellar age for Population I dwarf stars of solar-like temperature and metallicity. Such a calibration has utility in population studies of FGK dwarfs for further understanding of the chemical evolution of the Milky Way. As an illustration of one such application, we have constructed activity and FUV-age distributions for a sample of thin and thick disk stars, as distinguished by their chemical abundances. Considerable overlap is found between the activity distribution and age range of the two populations. We discuss the possibility that some high-[α/Fe] thick disk stars were formed as a result of the accretion of dwarf galaxies as recently as 4 Gyr ago.

Keywords: stellar evolution; stellar activity; ultraviolet photometry; milky way evolution; milky way disk
TESS Discovery of Twin Planets near 2:1 Resonance around Early M Dwarf TOI 4342

With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase improvements to the MIT Quick Look Pipeline (QLP) through the discovery and validation of a multiplanet system around M dwarf TOI 4342 (T mag = 11.032, M ⋆ = 0.63 M ⊙, R ⋆ = 0.60 R ⊙, T eff = 3900 K, d = 61.54 pc). With updates to QLP, including a new multiplanet search, as well as faster cadence data from TESS's First Extended Mission, we discovered two sub-Neptunes ( ${R}_{b}={2.266}_{-0.038}^{+0.038}$ R ⊕ and ${R}_{c}={2.415}_{-0.040}^{+0.043}$ R ⊕; P b = 5.538 days and P c = 10.689 days) and validated them with ground-based photometry, spectra, and speckle imaging. Both planets notably have high transmission spectroscopy metrics of 36 and 32, making TOI 4342 one of the best systems for comparative atmospheric studies. This system demonstrates how improvements to QLP, along with faster cadence full-frame images, can lead to the discovery of new multiplanet systems.

Keywords: exoplanet astronomy; transit photometry; m dwarf stars
The Second Data Release of the Survey of the MAgellanic Stellar History (SMASH)

The Large and Small Magellanic Clouds (LMC and SMC) are the largest satellite galaxies of the Milky Way and close enough to allow for a detailed exploration of their structure and formation history. The Survey of the MAgellanic Stellar History (SMASH) is a community Dark Energy Camera (DECam) survey of the Magellanic Clouds using ∼50 nights to sample over ∼2400 deg2 centered on the Clouds at ∼20% filling factor (but with contiguous coverage in the central regions) and to depths of ∼24th mag in ugriz. The primary goals of SMASH are to map out the extended stellar peripheries of the Clouds and uncover their complicated interaction and accretion history as well as to derive spatially resolved star formation histories of the central regions and create a "movie" of their past star formation. Here we announce the second SMASH public data release (DR2), which contains all 197 fully calibrated DECam fields including the main body fields in the central regions. The DR2 data are available through the Astro Data Lab hosted by the NSF's National Optical-Infrared Astronomy Research Laboratory. We highlight three science cases that make use of the SMASH DR2 data and will be published in the future: (1) preliminary star formation histories of the LMC, (2) the search for Magellanic star clusters using citizen scientists, and, (3) photometric metallicities of Magellanic Cloud stars using the DECam u-band.

Keywords: magellanic clouds; local group; milky way galaxy; dwarf galaxies; dwarf irregular galaxies; surveys; large magellanic cloud; small magellanic cloud; photometry; ccd photometry
The Southern H II Region Discovery Survey. II. The Full Catalog

The Southern H II Region Discovery Survey (SHRDS) is a 900 hr Australia Telescope Compact Array 4-10 GHz radio continuum and radio recombination line (RRL) survey of Galactic H II regions and infrared-identified H II region candidates in the southern sky. For this data release, we reprocess all previously published SHRDS data and include an additional ∼450 hr of observations. The search for new H II regions is now complete over the range 259° < ℓ < 346°, ∣b∣ < 4° for H II region candidates with predicted 6 GHz continuum peak brightnesses ≳30 mJy beam-1. We detect radio continuum emission toward 730 targets altogether including previously known nebulae and H II region candidates. By averaging ∼18 RRL transitions, we detect RRL emission toward 206 previously known H II regions and 436 H II region candidates. Including the northern sky surveys, over the last decade the H II Region Discovery Surveys have more than doubled the number of known Galactic H II regions. The census of H II regions in the Wide-field Infrared Survey Explorer (WISE) Catalog of Galactic H II Regions is now complete for nebulae with 9 GHz continuum flux densities ≳250 mJy. We compare the RRL properties of the newly discovered SHRDS nebulae with those of all previously known H II regions. The median RRL FWHM line width of the entire WISE Catalog H II region population is 23.9 km s-1 and is consistent between Galactic quadrants. The observed Galactic longitude-velocity asymmetry in the population of H II regions probably reflects underlying spiral structure in the Milky Way.

Keywords: h ii regions; surveys; radio spectroscopy; radio continuum emission; galaxy structure; milky way dynamics; milky way galaxy; interstellar medium
Sensitivity Study of r-process Abundances to Nuclear Masses

The impact of nuclear mass uncertainties on the r-process abundances has been systematically studied with the classical r-process model by varying the mass of every individual nucleus in the range of ±0.1 to ±3.0 MeV based on six different mass models. A new quantitative relation between the uncertainties of r-process abundances and those of the nuclear masses is extracted, i.e., a mass uncertainty of ±0.5 MeV would lead to an abundance uncertainty of a factor around 2.5. It is found that this conclusion holds true for various mass models.

Keywords: nucleosynthesis; r-process; solar abundances
Kinematical Signs of Dust Trapping and Feedback in a Local Pressure Bump in the Protoplanetary Disk around HD 142527 Revealed with ALMA

We analyzed the archival data of the continuum emission at six wavelengths from 3 to 0.4 mm and 13CO and C18O (1-0, 2-1, and 3-2) lines in the protoplanetary disk around HD 142527 obtained with the Atacama Large Millimeter/submillimeter Array. We performed fitting to the spectral energy distributions obtained at the six wavelengths with the graybody slab models to estimate the distributions of the dust surface density and spectral index of dust absorption coefficient β. We also estimated the distribution of the gas column density by fitting the C18O spectra and measured the disk rotation by fitting the Keplerian disk models to the C18O data. We found super- and sub-Keplerian rotation inside and outside the dust ring in the northwest in the HD 142527 disk, suggestive of the presence of a local pressure bump. In comparison with our estimated dust and gas distributions, the location of the pressure bump is coincident with the region showing a three times higher dust density and a three times lower gas-to-dust mass ratio than the mean values in the disk, suggesting dust trapping in the pressure bump. Nevertheless, there is no correlation between our derived β distribution and the location of the pressure bump. In addition, we found that the width of the dust ring is comparable to or larger than the width of the pressure bump, which could suggest that dust feedback is significant in the pressure bump.

Keywords: protoplanetary disks; planet formation; dust continuum emission; co line emission; gas-to-dust ratio
UV Slopes at All Redshifts Are Consistent with H = 1 Stochastic Star Formation Histories

Multiple investigations support describing galaxy growth as a stochastic process with correlations over a range of timescales governed by a parameter, H, empirically and theoretically constrained to be near unity. Here, we show that the distribution of UV-slopes, β, derived from an ensemble of theoretical H = 1 star formation histories is consistent with data at all redshifts z ≤ 16. At z = 0, the median value <β H=1> = - 2.27 agrees well with the canonical β 0 = -2.23 for local starbursts. At 4 ≲ z ≲ 16, JWST data span the model distribution's 2nd to 98th percentiles. Values of -2.8 ≤ β ≤ -2.5 should be common in early galaxies without reference to exotic stellar populations-arising solely from a null hypothesis of H = 1 for the underlying diversity of galaxy growth histories. Future data should be interpreted with this fact in mind.

Keywords: high-redshift galaxies; galaxy formation
The Origin of Kinematically Persistent Planes of Satellites as Driven by the Early Evolution of the Cosmic Web in ΛCDM

Kinematically persistent planes (KPPs) of satellites are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of "skeletons," ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local cosmic web (CW), characterized via the so-called Lagrangian volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of Milky Way–mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LV deformations in terms of the reduced tensor of inertia (TOI), we find an outstanding alignment between the LV principal directions and the KPP satellites' orbital poles. The most compressive local mass flows (along the ${\hat{e}}_{3}$ eigenvector) are strong at early times, feeding the so-called ${\hat{e}}_{3}$ -structure, while the smallest TOI axis rapidly decreases. The ${\hat{e}}_{3}$ -structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is ≲4 Gyr old. KPP protosatellites aligned with ${\hat{e}}_{3}$ are those whose orbital poles are either aligned from early times or have been successfully bent at ${\hat{e}}_{3}$ -structure collapse. KPP satellites associated with ${\hat{e}}_{1}$ tend to have early trajectories already parallel to ${\hat{e}}_{3}$ . We show that KPPs can arise as a result of the ΛCDM-predicted large-scale dynamics acting on particular sets of protosatellites, the same dynamics that shape the local CW environment.

Keywords: cosmic web; large-scale structure of the universe; dwarf galaxies; galaxy planes; galaxy kinematics
Implications for Chondrule Formation Regions and Solar Nebula Magnetism from Statistical Reanalysis of Chondrule Paleomagnetism

Converging lines of evidence show that protoplanetary disks are complex environments hosting spatial and temporal variability at multiple scales. Here we reanalyze paleomagnetic estimates of solar nebula magnetic field strengths using a Bayesian framework that tests for recording bias due to chondrule motion and explicitly accounts for time-varying ambient fields. We find that LL and CO group chondrule paleointensities likely rotated during cooling (p = 0.79-0.99), validating assumptions in previous paleomagnetic studies. Chondrule rotation also suggests low gas density formation environments beyond 2 and 4 au for LL and CO chondrules, respectively. Our recomputed paleointensities for LL and CO chondrules imply either: (1) temporally constant magnetic fields of ${34}_{-14}^{+36}$ μT and ${106}_{-18}^{+88}$ μT, respectively; or (2) time-varying magnetic fields with peak amplitudes between ${49}_{-21}^{+97}$ μT and ${128}_{-11}^{+307}$ μT. Considering the known mechanisms for sustaining magnetic field gradients and high-amplitude temporal magnetic fluctuations in the solar nebula, we find that magnetic field flux concentrations in disk gaps or time-varying magnetic fields, for example due to the Hall shear instability, are most compatible with the existing data. Using this statistical framework, future paleointensity studies of chondrules can be used to directly test for the variability of magnetic fields in the solar system protoplanetary disk and to distinguish between these scenarios.

Keywords: protoplanetary disks; planetary system formation; asteroid dynamics; chondrites; chondrules; magnetic fields
The Formation of Electron Outflow Jets with Power-law Energy Distribution in Guide-field Magnetic Reconnection

Observationally, electron beams with power-law energy spectra are commonly associated with solar flares. Previous studies have found that during magnetic reconnection with a guide field Bg larger than 0.1 times the asymptotic field B0, electron beams are unable to develop due to the strong deflection caused by the guide field. Using particle-in-cell simulations we show that in force-free reconnection, the development of an electron Kelvin-Helmholz instability can suppress the Hall effect and produce a flute-like outflow exhaust, in which both electrons and ions are nearly frozen-in with the magnetic field. The coupling of a continuously growing electron velocity shear and E × B drift drive the electrons out of magnetic vortices and results in collimated jets with a power-law energy spectrum in the elongated exhaust. The spatial density of electron jets is comparable to the background and is highly inhomogeneous, signifying on asymmetric density structure in guide field reconnection.

Keywords: solar magnetic reconnection; solar energetic particles
Pair Plasma Cascade in Rotating Black Hole Magnetospheres with a Split Monopole Flux Model

An electron-positron cascade in the magnetospheres of Kerr black holes (BHs) is a fundamental ingredient to fueling the relativistic γ-ray jets seen at the polar regions of galactic supermassive BHs (SMBHs). This leptonic cascade occurs in the spark gap region of a BH magnetosphere where the unscreened electric field parallel to the magnetic field is present; hence, it is affected by the magnetic field structure. A previous study explored the case of a thin accretion disk, representative of active galactic nuclei. Here we explore the case of a quasi-spherical gas distribution, as is expected to be present around the SMBH Sgr A* in the center of our Milky Way galaxy, for example. The properties and efficiency of the leptonic cascade are studied. The findings of our study and the implications for SMBH systems in various spectral and accretion states are discussed. The relationships and scalings derived from varying the mass of the BH and background photon spectra are further used to analyze the leptonic cascade process to power jets seen in astronomical observations. In particular, one finds the efficiency of the cascade in a quasi-spherical gas distribution peaks at the jet axis. Observationally, this should lead to a more prominent jet core, in contrast to the thin disk accretion case, where it peaks around the jet-disk interface. One also finds the spectrum of the background photons plays a key role. The cascade efficiency is maximum for a spectral index of 2, while harder and softer spectra lead to a less efficient cascade.

Keywords: plasma astrophysics; jets; black hole physics; gamma-rays