adsabs/SciX_UAT_keywords huggingface dataset:
Deep Spitzer/IRAC Data for z 10 Galaxies Reveal Blue Balmer Break Colors: Young Stellar Populations at 500 Myr of Cosmic Time

We present the deepest constraints yet on the median rest-UV+optical spectral energy distribution (SED) of z ~ 10 galaxies prior to James Webb Space Telescope science operations. We constructed stacks based on four robust J 125 dropouts, previously identified across the GOODS fields. We used archival Hubble Space Telescope/Wide Field Camera 3 data and the full-depth Spitzer/IRAC mosaics from the GREATS program, the deepest coverage at ~3-5 μm to date. The most remarkable feature of the SED is a blue IRAC [3.6]-[4.5] = -0.18 ± 0.25 mag color. We also find a nearly flat H 160 - [3.6] = 0.07 ± 0.22 mag color, corresponding to a UV slope β = -1.92 ± 0.25. This is consistent with previous studies and indicative of minimal dust absorption. The observed blue IRAC color and SED fitting suggest that z ~ 10 galaxies have very young (few × 10 Myr) stellar populations, with 80% of stars being formed in the last ≲160 Myr (2σ). While an exciting result, the uncertainties on the SED are too large to allow us to place strong constraints on the presence of a nebular continuum in z ~ 10 galaxies (as might be suggested by the blue [3.6]-[4.5] < 0 mag color). The resulting sSFR is consistent with the specific accretion rate of dark matter halos, indicative of a star formation efficiency showing quite limited evolution at such early epochs.

Keywords: high-redshift galaxies; lyman-break galaxies; galaxy masses; galaxy ages
The Reflectance of Cold Classical Trans-Neptunian Objects in the Nearest Infrared

Recent photometric surveys of Trans-Neptunian Objects (TNOs) have revealed that the cold classical TNOs have distinct z-band color characteristics and occupy their own distinct surface class. This suggested the presence of an absorption band in the reflectance spectra of cold classicals at λ > 0.8 μm. Here we present reflectance spectra spanning 0.55-1.0 μm for six TNOs occupying dynamically cold orbits at a ∼ 44 au. Five of our spectra show a clear and broadly consistent reduction in spectral gradient above 0.8 μm that diverges from their linear red optical continuum and agrees with their reported photometric color data. Despite predictions, we find no evidence that the spectral flattening is caused by an absorption band centered near 1.0 μm. We predict that the overall consistent shape of these five spectra is related to the presence of similar refractory organics on each of their surfaces, and/or their similar physical surface properties such as porosity or grain size distribution. The observed consistency of the reflectance spectra of these five targets aligns with predictions that the cold classicals share a common history in terms of formation and surface evolution. Our sixth target, which has been ambiguously classified as either a hot or cold classical at various points in the past, has a spectrum that remains nearly linear across the full range observed. This suggests that this TNO is a hot classical interloper in the cold classical dynamical range and supports the idea that other such interlopers may be identifiable by their linear reflectance spectra in the range 0.8-1.0 μm.

Keywords: classical kuiper belt objects; trans-neptunian objects; spectroscopy
Homologous Compact Major Blowout-eruption Solar Flares and their Production of Broad CMEs

We analyze the formation mechanism of three homologous broad coronal mass ejections (CMEs) resulting from a series of solar blowout-eruption flares with successively increasing intensities (M2.0, M2.6, and X1.0). The flares originated from NOAA Active Region 12017 during 2014 March 28-29 within an interval of ≈24 hr. Coronal magnetic field modeling based on nonlinear force-free field extrapolation helps to identify low-lying closed bipolar loops within the flaring region enclosing magnetic flux ropes. We obtain a double flux rope system under closed bipolar fields for all the events. The sequential eruption of the flux ropes led to homologous flares, each followed by a CME. Each of the three CMEs formed from the eruptions gradually attained a large angular width, after expanding from the compact eruption-source site. We find these eruptions and CMEs to be consistent with the "magnetic-arch-blowout" scenario: each compact-flare blowout eruption was seated in one foot of a far-reaching magnetic arch, exploded up the encasing leg of the arch, and blew out the arch to make a broad CME.

Keywords: solar flares; solar coronal mass ejections
Dark X-Ray Galaxies in the A1367 Galaxy Cluster

We have characterized a sample of extended X-ray sources in the A1367 galaxy cluster that lack optical counterparts. The sources are galaxy size and have an average total mass of 1.3 × 1011 solar masses. The average hot gas mass is 3.0 × 109 solar masses and the average X-ray luminosity is 4.3 × 1041 erg cm-2 s-1. Analysis of a composite source spectrum indicates the X-ray emission is thermal, with temperature of 1.25-1.45 keV and has low metallicity, 0.026-0.067 solar. The average hot gas radius (12.7 kpc) is well matched to nominal stripping radius. We argue that this optically dark, X-ray bright galaxy population forms by a sequence of stripping followed by heating and mixing with the intracluster medium.

Keywords: galaxy evolution
Inferred Properties of Planets in Mean-motion Resonances are Biased by Measurement Noise

Planetary systems with mean-motion resonances hold special value in terms of their dynamical complexity and their capacity to constrain planet formation and migration histories. The key toward making these connections, however, is to have a reliable characterization of the resonant dynamics, especially the so-called "libration amplitude," which qualitatively measures how deep the system is into the resonance. In this work, we identify an important complication with the interpretation of libration amplitude estimates from observational data of resonant systems. Specifically, we show that measurement noise causes inferences of the libration amplitude to be systematically biased to larger values, with noisier data yielding a larger bias. We demonstrated this through multiple approaches, including using dynamical fits of synthetic radial velocity data to explore how the libration amplitude distribution inferred from the posterior parameter distribution varies with the degree of measurement noise. We find that even modest levels of noise still result in a slight bias. The origin of the bias stems from the topology of the resonant phase space and the fact that the available phase-space volume increases nonuniformly with increasing libration amplitude. We highlight strategies for mitigating the bias through the usage of particular priors. Our results imply that many known resonant systems are likely deeper in resonance than previously appreciated.

Keywords: exoplanets; orbital resonances; celestial mechanics
Search for High-energy Neutrino Emission from Galactic X-Ray Binaries with IceCube

We present the first comprehensive search for high-energy neutrino emission from high- and low-mass X-ray binaries conducted by IceCube. Galactic X-ray binaries are long-standing candidates for the source of Galactic hadronic cosmic rays and neutrinos. The compact object in these systems can be the site of cosmic-ray acceleration, and neutrinos can be produced by interactions of cosmic rays with radiation or gas, in the jet of a microquasar, in the stellar wind, or in the atmosphere of the companion star. We study X-ray binaries using 7.5 yr of IceCube data with three separate analyses. In the first, we search for periodic neutrino emission from 55 binaries in the Northern Sky with known orbital periods. In the second, the X-ray light curves of 102 binaries across the entire sky are used as templates to search for time-dependent neutrino emission. Finally, we search for time-integrated emission of neutrinos for a list of 4 notable binaries identified as microquasars. In the absence of a significant excess, we place upper limits on the neutrino flux for each hypothesis and compare our results with theoretical predictions for several binaries. In addition, we evaluate the sensitivity of the next generation neutrino telescope at the South Pole, IceCube-Gen2, and demonstrate its power to identify potential neutrino emission from these binary sources in the Galaxy.

Keywords: neutrino astronomy; neutrino telescopes; x-ray binary stars; galactic cosmic rays
Motion Planning for the Robotic Fiber Positioners of the Large Sky Area Multiobject Fiber Spectrocopy Telescope

The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) is one of the most effective multiobject spectroscopic instruments. Its survey efficiency is guaranteed by simultaneously positioning multiple fibers via 4000 robotic fiber positioners (RFPs). With the further updates to LAMOST, the new-generation RFPs will be smaller, and the number of RFPs will increase to 5000. The RFPs are densely packed with shared working space. Thus, they may collide with each other, leading to them damaged and reducing the survey speed. In this study, we propose a new motion planning algorithm that prevents the collision of RFPs. To simplify the collision avoidance problem, we transform the motion planning process from a dynamic one into a static one by selecting one of the RFPs in each collision pair as the waiting robot. Accordingly, we design a method for choosing the waiting robot, and use a rapidly exploring random tree to plan a collision-free path for the waiting robot. However, there may be blocks between the waiting robots and their neighbors. Therefore, we also design methods to resolve these blocks. Simulations suggest that the proposed algorithm can prevent 98.4% of the collisions. About 99.9% of the positioners can reach their targets without collisions. Although developed for LAMOST, we believe that our algorithm can also be used for other instruments with equal-arm theta-phi positioners, such as the Dark Energy Spectroscopic Instrument.

Keywords: astronomical instrumentation
Non-universality of the Turbulent Spectra at Sub-ion Scales in the Solar Wind: Dispersive Effects versus the Doppler Shift

Large surveys of the power spectral density of the magnetic fluctuations in the solar wind have reported different slope distributions at MHD, sub-ion and sub-electron scales: the smaller the scale, the broader the distribution. Here, we review briefly some of the most relevant explanations of the broadening of the slopes at sub-ion scales. Then, we present a new one that has been overlooked in the literature, which is based on the relative importance of the dispersive effects with respect to the Doppler shift due to the mean flow speed. We build a toy model based on a dispersion relation of a linear mode that matches at high frequency (ω ≳ ω ci) the Alfvén (respectively whistler) mode at high oblique (respectively quasi-parallel) propagation angles θ kB . Starting with a double power-law spectrum of turbulence ${{k}_{\perp }}^{-1.66}$ in the inertial range and ${{k}_{\perp }}^{-2.8}$ at the sub-ion scales, the transformed spectrum (in frequency f) as it would be measured in the spacecraft reference frame shows a broad range of slopes at the sub-ion scales that depend both on the angle θ kB and the flow speed V. Varying θ kB in the range 4°-106° and V in the range 400-800 km s-1 the resulting distribution of slopes at the sub-ion scales reproduces quite well the observed one in the solar wind. Fluctuations in the solar wind speed and the wavevector anisotropy of the turbulence may explain (or at least contribute to) the variability of the spectral slopes reported from spacecraft observations in the solar wind.

Keywords: interplanetary turbulence; solar wind
HCN Snow Lines in Protoplanetary Disks: Constraints from Ice Desorption Experiments

HCN is among the most commonly detected molecules in star- and planet-forming regions. It is of broad interest as a tracer of star formation physics, a probe of nitrogen astrochemistry, and an ingredient in prebiotic chemical schemes. Despite this, one of the most fundamental astrochemical properties of HCN remains poorly characterized: its thermal desorption behavior. Here, we present a series of experiments to characterize the thermal desorption of HCN in astrophysically relevant conditions, with a focus on predicting the HCN sublimation fronts in protoplanetary disks. We derive HCN-HCN and HCN-H2O binding energies of 3207 ± 197 and 4192 ± 68 K, which translate to disk midplane sublimation temperatures around 85 and 103 K. For a typical midplane temperature profile, HCN should only begin to sublimate ~1-2 au exterior to the H2O snow line. Additionally, in H2O-dominated mixtures (20:1 H2O:HCN), we find that the majority of HCN remains trapped in the ice until H2O crystallizes. Thus, HCN may be retained in disk ices at almost all radii where H2O-rich planetesimals form. This implies that icy body impacts to planetary surfaces should commonly deliver this potential prebiotic ingredient. A remaining unknown is the extent to which HCN is pure or mixed with H2O in astrophysical ices, which impacts the HCN desorption behavior as well as the outcomes of ice-phase chemistry. Pure HCN and HCN:H2O mixtures exhibit distinct IR bands, raising the possibility that the James Webb Space Telescope will elucidate the mixing environment of HCN in star- and planet-forming regions and address these open questions.

Keywords: astrochemistry; solid matter physics; interstellar molecules; protoplanetary disks
A Light-curve Analysis of the X-Ray Flash First Observed in Classical Novae

An X-ray flash, expected in a very early phase of a nova outburst, was at last detected with the SRG/eROSITA in the classical nova YZ Reticuli 2020. The observed flash timescale, luminosity, and blackbody temperature substantially constrain the nova model. We present light-curve models of the X-ray flash for various white dwarf (WD) masses and mass-accretion rates. We have found the WD mass in YZ Ret to be as massive as M WD ~ 1.3 M ☉ with mass-accretion rates of ${\dot{M}}_{\mathrm{acc}}\sim 5\times {10}^{-10}\mbox{--}5\times {10}^{-9}\,{M}_{\odot }$ yr-1, including the case where the mass-accretion rate is changing between them, consistent with the SRG/eROSITA observation. The X-ray observation confirms the luminosity to be close to the Eddington limit at the X-ray flash. The occurrence of optically thick winds, with the photospheric radius exceeding ~0.1 R ☉, terminated the X-ray flash of YZ Ret by strong absorption. This sets a constrain on the starting time of wind mass loss. A slight contamination of the hydrogen-rich envelope by the core material seems to be preferred to explain the very short duration of the X-ray flash.

Keywords: classical novae; high energy astrophysics; cataclysmic variable stars; x-ray astronomy; white dwarf stars
A Uniform Analysis of Debris Disks with the Gemini Planet Imager. I. An Empirical Search for Perturbations from Planetary Companions in Polarized Light Images

The Gemini Planet Imager (GPI) has excelled in imaging debris disks in the near-infrared. The GPI Exoplanet Survey imaged 24 debris disks in polarized H-band light, while other programs observed half of these disks in polarized J and/or K1 bands. Using these data, we present a uniform analysis of the morphology of each disk to find asymmetries suggestive of perturbations, particularly those due to planet–disk interactions. The multiwavelength surface brightness, disk color, and geometry permit the identification of any asymmetries such as warps or disk offsets from the central star. We find that 19 of the disks in this sample exhibit asymmetries in surface brightness, disk color, disk geometry, or a combination of the three, suggesting that for this sample, perturbations, as seen in scattered light, are common. The relationship between these perturbations and potential planets in the system is discussed. We also explore correlations among stellar temperatures, ages, disk properties, and observed perturbations. We find significant trends between the vertical aspect ratio and the stellar temperature, disk radial extent, and the dust grain size distribution power law, q. We also confirm a trend between the disk color and stellar effective temperature, where the disk becomes increasingly red/neutral with increasing temperature. Such results have important implications for the evolution of debris disk systems around stars of various spectral types.

Keywords: debris disks; circumstellar disks; exoplanets; planetary-disk interactions; near infrared astronomy
Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection

Characterizing habitable exoplanets and/or their moons is of paramount importance. Here we show the results of our magnetic field topological modeling, which demonstrate that terrestrial exoplanet-exomoon coupled magnetospheres work together to protect the early atmospheres of both the exoplanet and the exomoon. When exomoon magnetospheres are within the exoplanet's magnetospheric cavity, the exomoon magnetosphere acts like a protective magnetic bubble providing an additional magnetopause confronting the stellar winds when the moon is on the dayside. In addition, magnetic reconnection would create a critical pathway for the atmosphere exchange between the early exoplanet and exomoon. When the exomoon's magnetosphere is outside of the exoplanet's magnetosphere it then becomes the first line of defense against strong stellar winds, reducing the exoplanet's atmospheric loss to space. A brief discussion is given on how this type of exomoon would modify radio emissions from magnetized exoplanets.

Keywords: exoplanet astronomy
A Candidate Kiloparsec-scale Quasar Pair at z = 5.66

We report the discovery of a close quasar pair candidate at z = 5.66, J2037-4537. J2037-4537 is resolved into two quasar images at the same redshift in ground-based observations. Follow-up spectroscopy shows significant differences in both the continuum slopes and emission line properties of the two images. The two quasar images have a projected separation of 1"24 (7.3 kpc at z = 5.66) and a redshift difference of Δz ≲ 0.01. High-resolution images taken by the Hubble Space Telescope do not detect the foreground lensing galaxy. The observational features of J2037-4537 strongly disfavor the lensing hypothesis. If J2037-4537 is a physical quasar pair, it indicates a quasar clustering signal of ~105 at a separation of ~10 proper kpc (pkpc), and gives the first observational constraint on the pair fraction of z > 5 quasars, fpair(r < 30 pkpc) > 0.3%. The properties of J2037-4537 are consistent with those of merger-triggered quasar pairs in hydrodynamical simulations of galaxy mergers.

Keywords: quasars; double quasars
Quantifying the Impact of the Large Magellanic Cloud on the Structure of the Milky Way's Dark Matter Halo Using Basis Function Expansions

Indications of disequilibrium throughout the Milky Way (MW) highlight the need for compact, flexible, non-parametric descriptions of phase-space distributions of galaxies. We present a new representation of the current dark matter (DM) distribution and potential derived from N-body simulations of the MW and Large Magellanic Cloud (LMC) system using basis function expansions (BFEs). We incorporate methods to maximize the physical signal in the representation. As a result, the simulations of 108 DM particles representing the distorted MW(MW+LMC) system can be described by ~236(2067) coefficients. We find that the LMC induces asymmetric perturbations (odd l, m) to the MW's halo, which are inconsistent with oblate, prolate, or triaxial halos. Furthermore, the energy in high order even modes (l, m > 2) is similar to average triaxial halos found in cosmological simulations. As such, the response of the MW's halo to the LMC must be accounted for in order to recover the imprints of its assembly history. The LMC causes the outer halo (>30 kpc) to shift from the disk center of mass (COM) by ~15-25 kpc at present day, manifesting as a dipole in the BFE and in the radial velocities of halo stars. The shift depends on the LMC's infall mass, the distortion of the LMC's halo and the MW halo response.Within 30 kpc, halo tracers are expected to orbit the COM of the MW's disk, regardless of LMC infall mass. The LMC's halo is also distorted by MW tides; we discuss the implications for its mass loss and the subsequent effects on current Magellanic satellites.

Keywords: milky way dynamics; large magellanic cloud; milky way dark matter halo
Ring Gap Structure around Class I Protostar WL 17

WL 17 is a Class I object and was considered to have a ring–hole structure. We analyzed the structure around WL 17 to investigate the detailed properties of this object. We used Atacama Large Millimeter/submillimeter Array archival data, which have a higher angular resolution than previous observations. We investigated the WL 17 system with the 1.3 mm dust continuum and 12CO and C18O (J = 2–1) line emissions. The dust continuum emission showed a clear ring structure with inner and outer edges of ∼11 and ∼21 au, respectively. In addition, we detected an inner disk of <5 au radius enclosing the central star within the ring, the first observation of this structure. Thus, WL 17 has a ring–gap structure, not a ring–hole structure. We did not detect any marked emission in either the gap or inner disk, indicating that there is no sign of a planet, circumplanetary disk, or binary companion. We identified the source of both blueshifted and redshifted outflows based on the 12CO emission, which is clearly associated with the disk around WL 17. The outflow mass ejection rate is ∼3.6 × 10‑7 M ⊙ yr‑1 and the dynamical timescale is as short as ∼104 yr. The C18O emission showed that an inhomogeneous infalling envelope, which can induce episodic mass accretion, is distributed in the region within ∼1000 au from the central protostar. With these new findings, we can constrain the scenarios of planet formation and dust growth in the accretion phase of star formation.

Keywords: protoplanetary disks; circumstellar disks; star formation; young stellar objects
HD 166620: Portrait of a Star Entering a Grand Magnetic Minimum

HD 166620 was recently identified as a Maunder minimum candidate based on nearly 50 years of Ca II H and K activity data from Mount Wilson and Keck HIRES. These data showed clear cyclic behavior on a 17 yr timescale during the Mount Wilson survey that became flat when picked up later with Keck HIRES planet-search observations. Unfortunately, the transition between these two data sets-and therefore the transition into the candidate Maunder minimum phase-contained little to no data. Here, we present additional Mount Wilson data not present in Baum et al., along with photometry over a nearly 30 yr baseline that definitively traces the transition from cyclic activity to a prolonged phase of flat activity. We present this as conclusive evidence of the star entering a grand magnetic minimum and therefore the first true Maunder minimum analog. We further show that neither the overall brightness nor the chromospheric activity level (as measured by S HK) is significantly lower during the grand magnetic minimum than its activity cycle minimum, implying that an anomalously low mean or instantaneous activity levels are not a good diagnostic or criterion for identifying additional Maunder minimum candidates. Intraseasonal variability in S HK, however, is lower in the star's grand minimum; this may prove a useful symptom of the phenomenon.

Keywords: stellar activity; maunder minimum; solar cycle