adsabs/SciX_UAT_keywords huggingface dataset:
Disruption of Dark Matter Minihalos in the Milky Way Environment: Implications for Axion Miniclusters and Early Matter Domination

Many theories of dark matter beyond the weakly interacting massive particles paradigm feature an enhanced matter power spectrum on subparsec scales, leading to the formation of dense dark matter minihalos. Future local observations are promising to search for and constrain such substructures. The survival probability of these dense minihalos in the Milky Way environment is crucial for interpreting local observations. In this work, we investigate two environmental effects: stellar disruption and (smooth) tidal disruption. These two mechanisms are studied using semianalytic models and idealized N-body simulations. For stellar disruption, we perform a series of N-body simulations of isolated minihalo–star encounters to test and calibrate analytic models of stellar encounters before applying the model to the realistic Milky Way disk environment. For tidal disruption, we perform N-body simulations to confirm the effectiveness of the analytic treatment. Finally, we propose a framework to combine the hierarchical assembly and infall of minihalos to the Milky Way with the late-time disruption mechanisms. We make predictions for the mass functions of minihalos in the Milky Way. The mass survival fraction (at M mh ≥ 10‑12 M ⊙) of dense dark matter minihalos, e.g., for axion miniclusters and minihalos from early matter domination, is ∼60% with the relatively low-mass, compact population surviving. The survival fraction is insensitive to the detailed model parameters. We discuss various implications of the framework and future direct detection prospects.

Keywords: dark matter; cosmology; n-body simulations; solar neighborhood; gravitational disruption
Could Switchbacks Originate in the Lower Solar Atmosphere? II. Propagation of Switchbacks in the Solar Corona

The magnetic switchbacks observed recently by the Parker Solar Probe have raised the question about their nature and origin. One of the competing theories of their origin is the interchange reconnection in the solar corona. In this scenario, switchbacks are generated at the reconnection site between open and closed magnetic fields, and are either advected by an upflow or propagate as waves into the solar wind. In this paper we test the wave hypothesis, numerically modeling the propagation of a switchback, modeled as an embedded Alfvén wave packet of constant magnetic field magnitude, through the gravitationally stratified solar corona with different degrees of background magnetic field expansion. While switchbacks propagating in a uniform medium with no gravity are relatively stable, as reported previously, we find that gravitational stratification together with the expansion of the magnetic field act in multiple ways to deform the switchbacks. These include WKB effects, which depend on the degree of magnetic field expansion, and also finite-amplitude effects, such as the symmetry breaking between nonlinear advection and the Lorentz force. In a straight or radially expanding magnetic field the propagating switchbacks unfold into waves that cause minimal magnetic field deflections, while a super-radially expanding magnetic field aids in maintaining strong deflections. Other important effects are the mass uplift the propagating switchbacks induce and the reconnection and drainage of plasmoids contained within the switchbacks. In the Appendix, we examine a series of setups with different switchback configurations and parameters, which broaden the scope of our study.

Keywords: solar wind; magnetohydrodynamics; alfven waves; solar coronal waves; nonlinear regression
Analysis of Hybrid Gas-Dust Outbursts Observed at 67P/Churyumov-Gerasimenko

Cometary outbursts offer a valuable window into the composition of comet nuclei with their forceful ejection of dust and volatiles in explosive events, revealing the interior components of the comet. Understanding how different types of outbursts influence the dust properties and volatile abundances, to better interpret what signatures can be attributed to primordial composition and what features are the result of processing, is an important task best undertaken with a multi-instrument approach. The European Space Agency Rosetta mission to 67P/Churyumov-Gerasimenko carried a suite of instruments capable of carrying out this task in the near-nucleus coma with unprecedented spatial and spectral resolution. In this work, we discuss two outbursts that occurred 2015 November 7 and were observed by three instruments on board: the Alice ultraviolet spectrograph, the Visual Infrared and Thermal Imaging Spectrometer, and the Optical, Spectroscopic, and Infrared Remote Imaging System. Together, the observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with the first outburst showing indicators of a cliff collapse origin and the second more representative of fresh volatiles being exposed via a deepening fracture. This analysis opens up the possibility of remote spectral classification of cometary outbursts with future work.

Keywords: comets; ultraviolet astronomy; small solar system bodies; neutral coma gases
Computed Rotational Collision Rate Coefficients for Recently Detected Anionic Cyanopolyynes

We report new results from quantum calculations of energy-transfer processes taking place in interstellar environments and involving two newly observed molecular species: C5N- and C7N- in collision with He atoms and p-H2 molecules. These species are part of the anionic molecular chains labeled as cyanopolyynes, which have been observed over the years in molecule-rich circumstellar envelopes and in molecular clouds. In the present work, we first carry out new ab initio calculations for the C7N- interaction potential with He atoms and then obtain state-to-state rotationally inelastic cross sections and rate coefficients involving the same transitions, which have been observed experimentally by emission in the interstellar medium (ISM) from both of these linear species. For the C5N-/He system, we extend the calculations already published in Biwas et al. to compare more directly the two molecular anions. We extend further the quantum calculations by also computing in this work collision rate coefficients for the hydrogen molecule interacting with C5N-, using our previously computed interaction potential. Additionally, we obtain the same rate coefficients for the C7N-/H2 system by using a scaling procedure that makes use of the new C7N-/He rate coefficients, as discussed in detail in the present paper. Their significance in affecting internal state populations in ISM environments where the anionic cyanopolyynes have been found is analyzed by using the concept of critical density indicators. Finally, similarities and differences between such species and the comparative efficiency of their collision rate coefficients are discussed. These new calculations suggest that, at least for the case of these longer chains, the rotational populations could reach local thermal equilibrium conditions within their observational environments.

Keywords: collisional processes
FluxCT: A Web Tool for Identifying Contaminating Flux in Kepler and TESS Target Pixel Files

We announce FluxCT, a web tool for identifying contaminating flux in Kepler and TESS target pixel files due to secondary visual sources. We demonstrate the usage of this tool and discuss the benefits of this tool over a simple Gaia radius search. FluxCT focuses on clarity and simplicity, where the only input needed from the user is a KIC or TIC ID. By more appropriately accounting for the actual shape of the photometric pixel apertures, FluxCT can produce much more accurate estimates of contaminating flux than simple radial cone searches.

Keywords: stellar astronomy; educational software; astronomy software
The Fate of the Interstellar Medium in Early-type Galaxies. II. Observational Evidence for Morphological Quenching

The mechanism by which galaxies stop forming stars and get rid of their interstellar medium (ISM) remains elusive. Here, we study a sample of more than 2000 elliptical galaxies in which dust emission has been detected. This is the largest sample of such galaxies ever analyzed. We infer the timescale for removal of dust in these galaxies and investigate its dependence on physical and environmental properties. We obtain a dust-removal timescale in elliptical galaxies of τ = 2.26 ± 0.18 Gyr, corresponding to a half-life time of 1.57 ± 0.12 Gyr. This timescale does not depend on environment, stellar mass, or redshift. We observe a departure of dusty elliptical galaxies from the relation between star formation rate and dust mass. This is caused by the star formation rates declining faster than the dust masses and indicates that there exists an internal mechanism that affects star formation but leaves the ISM intact. Morphological quenching together with ionization or outflows caused by older stellar populations (Type Ia supernovae or planetary nebulae) is consistent with these observations. * Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Keywords: early-type galaxies; elliptical galaxies; galaxy ages; galaxy evolution; galaxy quenching; interstellar medium; dust destruction
Dark Sirens to Resolve the Hubble-Lemaître Tension

The planned sensitivity upgrades to the LIGO and Virgo facilities could uniquely identify host galaxies of dark sirens—compact binary coalescences without any electromagnetic counterparts—within a redshift of z = 0.1. This is aided by the higher-order spherical harmonic modes present in the gravitational-wave signal, which also improve distance estimation. In conjunction, sensitivity upgrades and higher modes will facilitate an accurate, independent measurement of the host galaxy's redshift in addition to the luminosity distance from the gravitational-wave observation to infer the Hubble-Lemaître constant H0 to better than a few percent in 5 yr. A possible Voyager upgrade or third-generation facilities would further solidify the role of dark sirens for precision cosmology in the future.

Keywords: cosmology; hubble constant; hubble-lemaitre law; compact binary stars; gravitational wave astronomy; gravitational wave sources; gravitational wave detectors
NuSTAR Observations of AGNs with Low Observed X-Ray to [O III] Luminosity Ratios: Heavily Obscured AGNs or Turned-off AGNs?

Type 2 active galactic nuclei (AGNs) show signatures of accretion onto a supermassive black hole through strong, high-ionization, narrow emission lines extended on scales of hundreds to thousands of parsecs, but they lack the broad emission lines from close in to the black hole that characterize type 1 AGNs. The lack of broad emission could indicate obscuration of the innermost nuclear regions, or could indicate that the black hole is no longer strongly accreting. Since high-energy X-rays can penetrate thick obscuring columns, they have the power to distinguish these two scenarios. We present high-energy NuSTAR observations of nine Seyfert 2 AGNs from the Infrared Astronomical Satellite 12 μm survey, supplemented with low-energy X-ray observations from Chandra, XMM-Newton, and Swift. The galaxies were selected to have anomalously low observed 2-10 keV luminosities compared to their [O III] optical luminosities, a traditional diagnostic of heavily obscured AGNs, reaching into the Compton-thick regime for the highest hydrogen column densities (N H > 1.5 × 1024 cm-2). Based on updated [O III] luminosities and intrinsic X-ray luminosities based on physical modeling of the hard X-ray spectra, we find that one galaxy was misclassified as type 2 (NGC 5005) and most of the remaining AGNs are obscured, including three confirmed as Compton thick (IC 3639, NGC 1386, and NGC 3982). One galaxy, NGC 3627, appears to have recently deactivated. Compared to the original sample that the nine AGNs were selected from, this is a rate of approximately 1%. We also find a new X-ray changing-look AGN in NGC 6890.

Keywords: seyfert galaxies; x-ray active galactic nuclei; liner galaxies; scaling relations
Culminating the Peak Cusp to Descry the Dark Side of Halos

The ConflUent System of Peak trajectories (CUSP) is a rigorous formalism in the framework of the peak theory that allows one to derive from first principles and no free parameters the typical halo properties from the statistics of peaks in the filtered Gaussian random field of density perturbations. The predicted halo mass function, spherically averaged density, velocity dispersion, velocity anisotropy, ellipticity, prolateness, and potential profiles, as well as the abundance and number density profiles of accreted and stripped subhalos and diffuse dark matter, accurately recover the results of cosmological N-body simulations. CUSP is thus a powerful tool for the calculation, in any desired hierarchical cosmology with Gaussian perturbations, of halo properties beyond the mass, redshift, and radial ranges covered by simulations. More importantly, CUSP unravels the origin of the characteristic features of those properties. In this paper, we culminate its construction. We show that all halo properties but those related to subhalo stripping are independent of the assembly history of those objects, and that the Gaussian is the only smoothing window able to find the finite collapsing patches while properly accounting for the entropy increase produced in major mergers.

Keywords: galaxy dark matter halos; hierarchical cosmology
Search for Eccentric Binary Neutron Star Mergers in the First and Second Observing Runs of Advanced LIGO

We present a search for gravitational waves from merging binary neutron stars (BNSs) which have non-negligible eccentricity as they enter the Laser Interferometer Gravitational Wave Observatory (LIGO) observing band. We use the public Advanced LIGO data which covers the period from 2015 through 2017 and contains ∼164 days of LIGO-Hanford and LIGO-Livingston coincident observing time. The search was conducted using matched-filtering using the PyCBC toolkit. We find no significant BNS candidates beyond GW170817, which has previously been reported by searches for binaries in circular orbits. We place a 90% upper limit of ∼1700 mergers Gpc-3 yr-1 for eccentricities ≲0.43 at a dominant-mode gravitational-wave frequency of 10 Hz. The absence of a detection with these data is consistent with theoretical predictions of eccentric BNS merger rates. Using our measured rate we estimate the sensitive volume of future gravitational-wave detectors and compare this to theoretical rate predictions. We find that, in the absence of a prior detection, the rate limits set by six months of Cosmic Explorer observations would constrain all current plausible models of eccentric BNS formation.

Keywords: elliptical orbits; gravitational waves; compact objects; neutron stars
Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar

Our recent studies of axial-symmetry breaking in the nearby (d < 3 kpc) star counts are sensitive to the distortions of stellar orbits perpendicular and parallel to the orientation of the bar just within and beyond the outer Lindblad resonance (OLR) radius. Using the location of the sign flip in the left-right asymmetry in stars counts about the anticenter line to determine the OLR radius ROLR, and treating the bar as if it were a weakly nonaxisymmetric effect, we use ROLR and recent measurements of the Galactic rotation curve and the Sun-Galactic-center distance R0 to determine the pattern speed Ωp of the Galactic bar, as well as the Galactic corotation radius RCR. After removing the effect of the Large and Small Magellanic Clouds from our asymmetry measurement, we find that ROLR = (0.96 ± 0.03)R0 = 7.85 ± 0.25 kpc, Ωp = 49.3 ± 2.2 km s-1 kpc-1, RCR = (0.58 ± 0.04)R0 = 4.76 ± 0.27 kpc, revealing, as we shall show, that the Milky Way's bar is likely both weak and fast, though we also note possible evidence for non-steady-state effects in the bar region.

Keywords: galactic bulge; galactic center; milky way dynamics; milky way rotation
Analysis of the 3.2–3.3 μm Interstellar Absorption Feature on Three Milky Way Sightlines

We report new analyses of spectra of the 3.2–3.3 μm absorption feature observed in the diffuse interstellar medium toward three Milky Way sources: 2MASS J17470898 ‑ 2829561 (2M1747) and the Quintuplet Cluster, both located in the Galactic center, and Cygnus OB2-12. The 3.2–3.3 μm interval coincides with the CH-stretching region for compact polycyclic aromatic hydrocarbons (PAHs). We focus on the 2M1747 spectrum. Its published optical depth spectrum contains residual telluric transmission features, which arise from the 0.06 difference in mean airmasses between the observations of the source and its telluric standard star. We corrected the published spectrum by adding the airmass residual optical depth spectrum. The corrected spectrum is well fit by a superposition of four Gaussians. The absorption spectra of the other two sources were also fit by four Gaussians, with similar central wavelengths, widths, and relative peak opacities. We associate the three longer wavelength Gaussians covering the 3.23–3.31 μm interval with compact PAHs in positive, neutral, and negative charge states. We identify the shortest-wavelength Gaussian, near 3.21 μm, with irregularly shaped PAHs. Constraints imposed by spectral smoothness on the corrected 2M1747 spectrum, augmented by a PAH cluster formation model for post-asymptotic giant branch stars, suggests that >99% of the PAHs in the diffuse interstellar medium reside in small clusters. This study supports the PAH hypothesis, and it suggests that a family of primarily compact PAHs with a C66H20 (circumvalene) parent is consistent with the observed mid-infrared and ultraviolet interstellar absorption spectrum.

Keywords: interstellar dust; interstellar dust extinction; interstellar dust processes; carbonaceous grains; polycyclic aromatic hydrocarbons; infrared astronomy; molecular spectroscopy; astrochemistry; ultraviolet astronomy; post-asymptotic giant branch stars
Image Synthesis for Solar Flare Prediction

Solar flare prediction is a topic of interest to many researchers owing to the potential of solar flares to affect various technological systems, both terrestrial and in orbit. In recent years, the forecasting task has become progressively more reliant on data-driven computations and machine-learning algorithms. Although these efforts have improved solar flare predictions, they still falter in doing so for large solar flares, in particular under operational conditions, since large-flare data are very scarce and labeled data are heavily imbalanced. In this work, we seek to address this fundamental issue and present a scheme for generating synthetic magnetograms to reduce the imbalance in the data. Our method consists of (1) synthetic oversampling of line-of-sight magnetograms using Gaussian mixture model representation, followed by (2) a global optimization technique to ensure consistency of both physical features and flare precursors, and (3) the mapping of the generated representations to realistic magnetogram images using deep generative models. We show that these synthetically generated data indeed improve the capacity of solar flare prediction models and that, when tested on such a state-of-the-art model, it significantly enhances its forecasting performance, achieving an F1-score as high as 0.43 ± 0.08 and a true skill statistic of 0.64 ± 0.10 for X-class flares in the 24 hr operational solar flare data split.

Keywords: space weather; solar active regions; neural networks; gaussian mixture model; solar flares
Discovery of the Remarkably Red L/T Transition Object VHS J183135.58-551355.9

We present the discovery of VHS J183135.58‑551355.9 (hereafter VHS J1831‑5513), an L/T transition dwarf identified as a result of its unusually red near-infrared colors (J ‑ K S = 3.633 ± 0.277 mag; J ‑ W2 = 6.249 ± 0.245 mag) from the VISTA Hemisphere Survey and CatWISE2020 surveys. We obtain low-resolution near-infrared spectroscopy of VHS J1831‑5513 using the Magellan Folded port InfraRed Echellette spectrograph to confirm its extremely red nature and assess features sensitive to surface gravity (i.e., youth). Its near-infrared spectrum shows multiple CH4 absorption features, indicating an exceptionally low effective temperature for its spectral type. Based on proper-motion measurements from CatWISE2020 and a photometric distance derived from its K s -band magnitude, we find that VHS J1831‑5513 is a likely (∼85% probability) kinematic member of the β Pictoris moving group. Future radial velocity and trigonometric parallax measurements will clarify such membership. Follow-up mid-infrared or higher-resolution near-infrared spectroscopy of this object will allow for further investigation as to the cause(s) of its redness, such as youth, clouds, and viewing geometry.

Keywords: brown dwarfs; l dwarfs; t dwarfs; stellar associations; moving clusters
Assessing the Influence of Urban Lights on Night Sky Brightness with a Smartphone

The darkness of the sky is a critical parameter for assessing the suitability of an astronomical site. Among various sources of light pollution, urban lights pose the most significant threat to ground-based optical astronomical and planetary observations. Quantitatively assessing the impact of urban lights with varying scales and fluxes is indispensable for selecting an ideal optical observation site. In order to quantitatively assess the changes in Night Sky Brightness (NSB) relative to the distance from urban areas and to establish a foundation for safeguarding the light environment at the newly developed Lenghu astronomical site on the Tibetan Plateau, we employed both a Sky Quality Meter and a pre-calibrated smartphone. These instruments were used to measure the NSB in the vicinity of two cities, Da Qaidam and Delingha, which vary in size and radiant flux, on the Tibetan Plateau. The findings indicate that the NSB around both cities decreases significantly as the distance from the city center increases, although the rate of decrease varies between the two locations. This decline can be effectively modeled using an exponential decay function. Notably, the influence of city lights on NSB becomes negligible at distances exceeding 30 km from Da Qaidam, while for Delingha, this distance extends to 50 km due to its larger city size and higher total radiant flux. The methodologies and results presented in this paper offer valuable insights for the selection of astronomical observation sites and the development of light pollution management policies.

Keywords: astronomical site protection; atmospheric effects; telescopes; night sky brightness
An Eccentric Planet Orbiting the Polar V808 Aurigae

We analyze 15 yr of eclipse timings of the polar V808 Aur. The rapid ingress/egress of the white dwarf and bright accretion region provide timings as precise as a few tenths of a second for rapid cadence photometric data. We find that between 2015 and 2018, the eclipse timings deviated from a linear ephemeris by more than 30 s. The rapid timing change is consistent with the periastron passage of a planet in an eccentric orbit about the polar. The best-fit orbital period is 11 ± 1 yr and we estimate a projected mass of $M\sin (i)=6.8\pm 0.7$ Jupiter masses. We also show that the eclipse timings are correlated with the brightness of the polar with a slope of 1.1 s mag‑1. This is likely due to the change in the geometry of the accretion curtains as a function of the mass transfer rate in the polar. While an eccentric planet offers an excellent explanation to the available eclipse data for V808 Aur, proposed planetary systems in other eclipsing polars have often struggled to accurately predict future eclipse timings.

Keywords: cataclysmic variable stars; am herculis stars; exoplanet detection methods; eclipsing binary minima timing method; stellar magnetic fields