adsabs/SciX_UAT_keywords huggingface dataset:
Constraints on the Intergalactic Magnetic Field from Bow Ties in the Gamma-Ray Sky

Pair creation on the cosmic infrared background and subsequent inverse-Compton scattering on the cosmic microwave background potentially reprocesses the TeV emission of blazars into faint GeV halos with structures sensitive to intergalactic magnetic fields (IGMF). Previous work has shown that these halos are then highly anisotropic and extended. If the coherence length of the IGMF is greater than the inverse-Compton cooling length of the pairs, then the orientation of the gamma-ray halo will be correlated with the direction of the magnetic field which is unknown and expected to change for each source. In order to constructively add each source we then use angular power spectra which are insensitive to the jet orientation. By looking at known GeV blazars detected by Fermi, we exclude the existence of an IGMF with coherence lengths >100 Mpc at greater than 3.9σ with current-day strengths in the range 10-16 to 10-15 G, and at 2σ from 10-17 to 10-14 G. This provides a direct measurement of the nonexistence of gamma-ray halos, providing an important check on previous results.

Keywords: bl lacertae objects; gamma-rays; high energy astrophysics
Effects of Forcing Mechanisms on the Multiscale Properties of Magnetohydrodynamics

We performed numerical simulations to study the response of magnetohydrodynamics (MHD) to large-scale stochastic forcing mechanisms parameterized by one parameter, 0 ≤ a ≤ 1, going from direct injection on the velocity field (a = 1) to stirring acts on the magnetic field only (a = 0). We study the multiscale properties of the energy transfer by splitting the total flux in channels mediated by (i) the kinetic nonlinear advection, (ii) the Lorentz force, (iii) the magnetic advection, and (iv) the magnetic stretching term. We further decompose the fluxes into two subchannels given by heterochiral and homochiral components in order to distinguish forward, inverse, and flux-loop cascades. We show that there exists a quasi-singular role of the magnetic forcing mechanism for a ∼ 1: a small injection on the magnetic field a < 1 can strongly deplete the mean flux of kinetic energy transfer throughout the kinetic nonlinear advection channel. We also show that this negligible mean flux is the result of a flux-loop balance between heterochiral (direct) and homochiral (inverse) transfers. Conversely, both homochiral and heterochiral channels transfer energy forward for the other three channels. Cross-exchange between velocity and the magnetic field is reversed around a = 0.4, and except when a ∼ 1, we always observe that heterochiral mixed velocity-magnetic energy triads tend to move energy from magnetic to velocity fields. Our study is an attempt to further characterize the multiscale nature of MHD dynamics by disentangling different properties of the total energy transfer mechanisms, which can be useful for improving subgrid modeling.

Keywords: magnetohydrodynamics; magnetohydrodynamical simulations; interplanetary turbulence
Efficiency of Turbulent Reacceleration by Solenoidal Turbulence and Its Application to the Origin of Radio Megahalos in Cluster Outskirts

Recent radio observations with the Low Frequency Array (LOFAR) discovered diffuse emission extending beyond the scale of classical radio halos. The presence of such megahalos indicates that the amplification of the magnetic field and acceleration of relativistic particles are working in the cluster outskirts, presumably due to the combination of shocks and turbulence that dissipate energy in these regions. Cosmological magnetohydrodynamical (MHD) simulations of galaxy clusters suggest that solenoidal turbulence has a significant energy budget in the outskirts of galaxy clusters. In this paper, we explore the possibility that this turbulence contributes to the emission observed in megahalos through second-order Fermi acceleration of relativistic particles and magnetic field amplification by the dynamo. We focus on the case of A2255 and find that this scenario can explain the basic properties of the diffuse emission component that is observed under assumptions that are used in previous literature. More specifically, we conduct a numerical follow-up, solving the Fokker-Planck equation by using a snapshot of an MHD simulation and deducing the synchrotron brightness integrated along the lines of sight. We find that a volume-filling emission, ranging between 30% and almost 100% of the projected area, depending on our assumptions on the particle diffusion and transport, can be detected at LOFAR sensitivities. Assuming a magnetic field B ~ 0.2 μG, as derived from a dynamo model applied to the emitting region, we find that the observed brightness can be matched when ~1% of the solenoidal turbulent energy flux is channeled into particle acceleration.

Keywords: galaxy clusters
Dynamical Classifications of Multi-opposition TNOs as of 2023 December

We report the dynamical classifications of 3357 observed outer solar system objects listed as transneptunian objects (TNOs) or Centaurs by the Minor Planet Center. We use the Gladman et al. classification scheme to identify 28 Jupiter-coupled objects (all secure), 168 Centaurs (all secure), 234 scattering TNOs (70 secure/164 insecure), 204 detached TNOs (118 secure/86 insecure), 1650 classical TNOs (1494 secure/156 insecure), and 1073 resonant TNOs (907 secure, 166 insecure). Among the resonant TNOs, the most observationally populated resonance is the close-in 3:2 MMR with 452 objects, followed by the 2:1 with 105 objects, the 7:4 with 103 objects, the 5:3 with 68 objects, and the 5:2 with 56 objects. We discuss a few notable objects here, but all classifications and plots of the 10 Myr integrations are available in a linked GitHub repository.

Keywords: trans-neptunian objects; kuiper belt; classical kuiper belt objects; detached objects; resonant kuiper belt objects
Jet-Accretion System in the Nearby mJy Radio Galaxies

It is generally thought that FRII radio galaxies host thin optically thick disks, while FRIs are powered by advection-dominated accretion flows. Sources with an efficient engine are optically classified as high-excitation radio galaxies (HERGs) and those with an inefficient motor as low-excitation radio galaxies (LERGs). Recently, the study of radio galaxies down to mJy fluxes has cast serious doubts on the LERG-FRI and HERG-FRII correspondence, revealing that many LERGs show FRII radio morphologies. The FR catalogs recently compiled by Capetti et al. and Baldi et al. have allowed us to explore this issue in the local (z ≤ 0.15) mJy universe. Our statistical study shows that the majority of nearby mJy objects are in a late stage of their life. FRII-LERGs appear more similar to the old FRI-LERGs than to the young FRII-HERGs. FRII-LERGs may be aged HERGs that, having exhausted their cold fuel, have changed their accretion regime or are a separate LERG class particularly efficient in launching jets. Exploiting the empirical relations that convert L[O III] and L1.4 GHz into accretion power and jet kinetic power, respectively, we observed that LERGs with similar masses and accretion rates seem to expel jets of different powers. We speculate that intrinsic differences related to the black hole properties (spin and magnetic field at its horizon) can determine the observed spread in jet luminosity. In this view, FRII-LERGs should have the fastest spinning black holes and/or the most intense magnetic fluxes. On the contrary, compact LERGs (i.e., FR0s) should host extremely slow black holes and/or weak magnetic fields.

Keywords: radio active galactic nuclei
Expected Impact of Glints from Space Debris in the LSST

We examine the simple model put forth in a recent note by Loeb regarding the brightness of space debris in the size range of 1–10 cm and their impact on the Rubin Observatory Legacy Survey of Space and Time (LSST) transient object searches. Their main conclusion was that "image contamination by untracked space debris might pose a bigger challenge [than large commercial satellite constellations in Low-Earth orbit]." Following corrections and improvements to this model, we calculate the apparent brightness of tumbling low-Earth orbit (LEO) debris of various sizes, and we briefly discuss the likely impact and potential mitigations of glints from space debris in LSST. We find the majority of the difference in predicted signal-to-noise ratio (S/N), about a factor of 6, arises from the defocus of LEO objects due to the large Simonyi Survey Telescope primary mirror and finite range of the debris. The largest change from the Loeb estimates is that 1–10 cm debris in LEO pose no threat to LSST transient object alert generation because their S/N for detection will be much lower than estimated by Loeb due to defocus. We find that only tumbling LEO debris larger than 10 cm or with significantly greater reflectivity, which give 1 ms glints, might be detected with high confidence (S/N > 5). We estimate that only one in five LSST exposures low on the sky during twilight might be affected. More slowly tumbling objects of larger size can give flares in brightness that are easily detected; however, these will not be cataloged by the LSST Science Pipelines because of the resulting long streak.

Keywords: transient sources; light pollution; sky surveys; ground-based astronomy; artificial satellites
The SN 2023ixf Progenitor in M101. II. Properties

We follow our first paper with an analysis of the ensemble of the extensive preexplosion ground- and space-based infrared observations of the red supergiant (RSG) progenitor candidate for the nearby core-collapse supernova SN 2023ixf in Messier 101, together with optical data prior to the explosion obtained with the Hubble Space Telescope (HST). We have confirmed the association of the progenitor candidate with the supernova (SN), as well as constrained the metallicity at the SN site, based on SN observations with instruments at Gemini-North. The internal host extinction to the SN has also been confirmed from a high-resolution Keck spectrum. We fit the observed spectral energy distribution (SED) for the star, accounting for its intrinsic variability, with dust radiative-transfer modeling, which assumes a silicate-rich dust shell ahead of the underlying stellar photosphere. The star is heavily dust obscured, likely the dustiest progenitor candidate yet encountered. We found median estimates of the star's effective temperature and luminosity of 2770 K and 9.0 × 104 L ⊙, with 68% credible intervals of 2340–3150 K and (7.5–10.9) × 104 L ⊙, respectively. The candidate may have a Galactic RSG analog, IRC ‑10414, with a strikingly similar SED and luminosity. Via comparison with single-star evolutionary models we have constrained the initial mass of the progenitor candidate from 12 M ⊙ to as high as 14 M ⊙. We have had available to us an extraordinary view of the SN 2023ixf progenitor candidate, which should be further followed up in future years with HST and the James Webb Space Telescope.

Keywords: type ii supernovae; massive stars; late-type stars; m supergiant stars; stellar evolution
The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). I. Sample Selection

We present the first active galactic nuclei (AGN) catalog of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) observed between 2017 January and 2020 June. HETDEX is an ongoing spectroscopic survey (3500-5500 Å) with no target preselection based on magnitudes, colors or morphologies, enabling us to select AGN based solely on their spectral features. Both luminous quasars and low-luminosity Seyferts are found in our catalog. AGN candidates are selected with at least two significant AGN emission lines, such as the Lyα and C IV λ1549 line pair, or with a single broad emission line with FWHM > 1000 km s-1. Each source is further confirmed by visual inspections. This catalog contains 5322 AGN, covering an effective sky coverage of 30.61 deg2. A total of 3733 of these AGN have secure redshifts, and we provide redshift estimates for the remaining 1589 single broad-line AGN with no crossmatched spectral redshifts from the Sloan Digital Sky Survey Data Release 14 of QSOs. The redshift range of the AGN catalog is 0.25 < z < 4.32, with a median of z = 2.1. The bolometric luminosity range is 109-1014 L ⊙ with a median of 1012 L ⊙. The median r-band magnitude of our AGN catalog is 21.6 mag, with 34% having r > 22.5, and 2.6% reaching the detection limit at r ~ 26 mag of the deepest imaging surveys we searched. We also provide a composite spectrum of the AGN sample covering 700-4400 Å.

Keywords: active galactic nuclei
The Impact of Kinetic Neutrals on the Heliotail

The shape of the heliosphere is thought to resemble a long, comet tail, however, recently it has been suggested that the heliosphere is tailless with a two-lobe structure. The latter study was done with a three-dimensional (3D) magnetohydrodynamic code, which treats the ionized and neutral hydrogen atoms as fluids. Previous studies that described the neutrals kinetically claim that this removes the two-lobe structure of the heliosphere. In this work, we use the newly developed Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics (SHIELD) model. SHIELD is a self-consistent kinetic-MHD model of the outer heliosphere that couples the MHD solution for a single plasma fluid from the BATS-R-US MHD code to the kinetic solution for neutral hydrogen atoms solved by the Adaptive Mesh Particle Simulator, a 3D, direct simulation Monte Carlo model that solves the Boltzmann equation. We use the same boundary conditions as our previous simulations using multi-fluid neutrals to test whether the two-lobe structure of the heliotail is removed with a kinetic treatment of the neutrals. Our results show that despite the large difference in the neutral hydrogen solutions, the two-lobe structure remains. These results are contrary to previous kinetic-MHD models. One such model maintains a perfectly ideal heliopause and does not allow for communication between the solar wind and interstellar medium. This indicates that magnetic reconnection or instabilities downtail play a role for the formation of the two-lobe structure.

Keywords: heliosphere; heliopause; heliosheath; termination shock; stellar wind bubbles; solar wind termination; magnetohydrodynamical simulations; magnetohydrodynamics
The SAMI Galaxy Survey: Detection of Environmental Dependence of Galaxy Spin in Observations and Simulations Using Marked Correlation Functions

The existence of a kinematic morphology-density relation remains uncertain, and instead stellar mass appears the more dominant driver of galaxy kinematics. We investigate the dependence of the stellar spin parameter proxy ${\lambda }_{{R}_{e}}$ on environment using a marked cross-correlation method with data from the Sydney Australian Astronomical Observatory Multi-object Integral-field Spectrograph (SAMI) Galaxy Survey. Our sample contains 710 galaxies with spatially resolved stellar velocity and velocity dispersion measurements. By utilizing the highly complete spectroscopic data from the Galaxy and Mass Assembly Survey, we calculate marked cross-correlation functions for SAMI galaxies using a pair count estimator and marks based on stellar mass and ${\lambda }_{{R}_{e}}$ . We detect an anticorrelation of stellar kinematics with environment at the 3.2σ level, such that galaxies with low ${\lambda }_{{R}_{e}}$ values are preferably located in denser galaxy environments. However, a significant correlation between stellar mass and environment is also found (correlation at 2.4σ), as found in previous works. We compare these results to mock observations from the cosmological Evolution and Assembly of Galaxies and their Environments (EAGLE) simulations, where we find a similar significant ${\lambda }_{{R}_{{\rm{e}}}}$ anticorrelation with environment, and a mass and environment correlation. We demonstrate that the environmental correlation of ${\lambda }_{{R}_{{\rm{e}}}}$ is not caused by the mass-environment relation. The significant relationship between ${\lambda }_{{R}_{{\rm{e}}}}$ and environment remains when we exclude slow rotators. The signals in SAMI and EAGLE are strongest on small scales (10-100 kpc) as expected from galaxy interactions and mergers. Our work demonstrates that the technique of marked correlation functions is an effective tool for detecting the relationship between ${\lambda }_{{R}_{{\rm{e}}}}$ and environment.

Keywords: two-point correlation function; redshift surveys; galaxy kinematics; galaxy environments; galaxy clusters
The Observed O VI Is Just the Tip of the Iceberg: Estimating the Hidden Material in Circumgalactic and Intergalactic Clouds

This paper proposes a new method for estimating the total quantity of material in moving circumgalactic and intergalactic clouds from O VI measurements. We simulate high-velocity clouds (HVCs) with the FLASH hydrodynamic code and track the ionization and recombination of all ionization levels of oxygen as a function of time. We calculate the O VI/oxygen ratio (f O VI ) in our dynamic nonequilibrium ionization clouds, finding that it differs significantly from that in static gas. We find that O VI exists in cool, medium, and hot gas in the clouds. As such, it traces all of the hydrogen rather than merely the ionized hydrogen. The total quantity of hydrogen along a typical observed line of sight through a cloud can be estimated from the observed O VI column density, metallicity, and our f O VI . We provide the simulations' f O VI values, a prescription for finding f O VI for observed dynamic clouds, and a methodology for calculating the total hydrogen column density from f O VI and an observed O VI column density. As examples, we use our f O VI values to estimate the total hydrogen column densities along various observed sight lines through two HVCs, Complex C and the Magellanic Stream, finding that these clouds contain more material than previous lower limits. We also extend this analysis to low-redshift intergalactic O VI clouds, finding that they contain several times more baryonic material than previously thought and therefore may account for a significant fraction of the Universe's baryons.

Keywords: high-velocity clouds; magellanic stream; interstellar clouds; intergalactic clouds; hydrodynamical simulations; hot ionized medium
Spinning Bar and a Star-formation Inefficient Repertoire: Turbulence in Hickson Compact Group NGC 7674

The physics regulating star formation (SF) in Hickson Compact Groups (HCG) has thus far been difficult to describe, due to their unique kinematic properties. In this study, we expand upon previous works to devise a more physically meaningful SF relation able to better encompass the physics of these unique systems. We combine CO(1-0) data from the Combined Array from Research in Millimeter Astronomy to trace the column density of molecular gas ${{\rm{\Sigma }}}_{\mathrm{gas}}$ and deep Hα imaging taken on the Southern Astrophysical Research Telescope tracing ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ to investigate SF efficiency across face-on HCG, NGC 7674. We find a lack of universality in SF, with two distinct sequences present in the ${{\rm{\Sigma }}}_{\mathrm{gas}}$ - ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ plane; one for inside and one for outside the nucleus. We devise an SF relation based on the multi-freefall nature of gas and the critical density, which itself is dependent on the virial parameter ${\alpha }_{\mathrm{vir}}$ , the ratio of turbulent to gravitational energy. We find that our modified SF relation fits the data and describes the physics of this system well with the introduction of a virial parameter of about 5-10 across the galaxy. This ${\alpha }_{\mathrm{vir}}$ leads to an order-of-magnitude reduction in SFR compared to ${\alpha }_{\mathrm{vir}}\approx 1$ systems.

Keywords: star formation; star forming regions; agn host galaxies; galaxies; hickson compact group
Intensive Swift and LCO Monitoring of PG 1302–102: Active Galactic Nucleus Disk Reverberation Mapping of a Supermassive Black Hole Binary Candidate

We present an intensive multiwavelength monitoring campaign of the quasar PG 1302‑102 with Swift and the Las Cumbres Observatory network telescopes. At z ∼ 0.3, it tests the limits of the reverberation mapping (RM) technique in probing the accretion disk around a supermassive black hole (SMBH) and extends the parameter space to high masses and high accretion rates. This is also the first time the RM technique has been applied to test disk structures predicted in the SMBH binary model that has been suggested for this source. PG 1302‑102 was observed at a ∼daily cadence for ∼9 months in 14 bands spanning from X-ray to UV and optical wavelengths, and it shows moderate to significant levels of variability correlated between wavelengths. We measure the interband time lags, which are consistent with a τ ∝ λ 4/3 relation as expected from standard disk reprocessing, albeit with large uncertainties. The disk size implied by the lag spectrum is consistent with the expected disk size for its black hole mass within uncertainties. While the source resembles other reverberation-mapped active galactic nuclei in many respects, and we do not find evidence supporting the prevalent hypothesis that it hosts an SMBH binary, we demonstrate the feasibility of studying SMBH binaries from this novel angle and suggest possibilities for the LSST Deep Drilling Fields.

Keywords: active galactic nuclei; supermassive black holes; reverberation mapping
The Origin of Jupiter's Obliquity

The origin of the 3.°12 obliquity of Jupiter's spin axis to its orbit normal is unknown. Improved estimates of Jupiter's moment of inertia rule out a previously proposed explanation involving a resonance with the precession of the inclined orbit of Uranus. We find that a nonadiabatic crossing of the resonance between Jupiter's spin precession and the -f 5 + f 6 + g 6 mode could have tilted Jupiter to its present-day obliquity starting from a 0° primordial obliquity. This places constraints on the migration rates of the satellites Ganymede and Callisto.

Keywords: jupiter; spin-orbit resonances
Taurid Stream #628: A Reservoir of Large Cometary Impactors

The Desert Fireball Network observed a significant outburst of fireballs belonging to the Southern Taurid Complex of meteor showers between 2015 October 27 and November 17. At the same time, the Cameras for Allsky Meteor Surveillance project detected a distinct population of smaller meteors belonging to the irregular IAU shower #628, the s-Taurids. While this returning outburst was predicted and observed in previous work, the reason for this stream is not yet understood. 2015 was the first year that the stream was precisely observed, providing an opportunity to better understand its nature. We analyze the orbital elements of stream members and establish a size-frequency distribution from millimeter to meter size range. The stream is highly stratified with a large change of entry speed along Earth's orbit. We confirm that the meteoroids have orbital periods near the 7:2 mean motion resonance with Jupiter. The mass distribution of this population is dominated by larger meteoroids, unlike that for the regular Southern Taurid shower. The distribution index is consistent with a gentle collisional fragmentation of weak material. A population of meter-sized objects is identified from satellite observations at a rate consistent with a continuation of the size-frequency distribution established at centimeter size. The observed change of longitude of perihelion among the s-Taurids points to recent (a few centuries ago) activity from fragmentation involving surviving asteroid 2015 TX24. This supports a model for the Taurid Complex showers that involves an ongoing fragmentation cascade of comet 2P/Encke siblings following a breakup some 20,000 yr ago.

Keywords: meteor streams; fireballs; short period comets