adsabs/SciX_UAT_keywords huggingface dataset:
Toward Interpreting the IBEX Ribbon with Mirror Diffusion in Interstellar Turbulent Magnetic Fields

We investigate the role of the magnetohydrodynamic (MHD) turbulence measured by Voyager in the very local interstellar medium (VLISM) in modeling the Interstellar Boundary Explorer ribbon. We demonstrate that the mirroring by compressible modes of MHD turbulence dominates over that by the mean magnetic field. Based on the new mirror diffusion mechanism identified by Lazarian & Xu for particles with large pitch angles in MHD turbulence, we find that the mirror diffusion can both confine pickup ions and preserve their initial pitch angles, and thus it accounts for the enhanced intensity of energetic neutral atoms that return to the heliosphere. The ribbon width is determined by both the range of pitch angles for effective turbulent mirroring and the field line wandering induced by Alfvénic modes. It in turn provides a constraint on the amplitude of magnetic fluctuations of fast modes. The field line wandering also affects the coherence of the ribbon structure across the sky. By extrapolating the magnetic energy spectrum measured by Voyager, we find that the injection scale of the turbulence in the VLISM must be less than ~500 au for the ribbon structure to be coherent.

Keywords: pickup ions; magnetohydrodynamics; heliosheath
The Hubble Space Telescope's Near-UV and Optical Transmission Spectrum of Earth as an Exoplanet

We observed the 2019 January total lunar eclipse with the Hubble Space Telescope's STIS spectrograph to obtain the first near-UV (1700-3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O3) are appropriately captured in mission concept studies. O3 is photochemically produced from O2, a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth's transmission spectrum at optical and near-IR wavelengths, but the strongest O3 signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O3 and Rayleigh scattering in the 3000-5500 Šregion in Earth's transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth's atmosphere due to extremely strong O3 absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O3 layer rather than above it.

Keywords: lunar eclipses; exoplanet atmospheres; earth (planet); the moon; earth atmosphere
Hadronic High-energy Emission from Magnetically Arrested Disks in Radio Galaxies

We propose a novel interpretation that gamma rays from nearby radio galaxies are hadronic emission from magnetically arrested disks (MADs) around central black holes (BHs). The magnetic energy in MADs is higher than the thermal energy of the accreting plasma, where the magnetic reconnection or turbulence may efficiently accelerate nonthermal protons. They emit gamma rays via hadronic processes, which can account for the observed gamma rays for M87 and NGC 315. Nonthermal electrons are also accelerated with protons and produce MeV gamma rays, which is useful to test our model by proposed MeV satellites. The hadronic emission from the MADs may significantly contribute to the GeV gamma-ray background and produce the multi-PeV neutrino background detectable by IceCube-Gen2. In addition, gamma rays from MADs provide electron-positron pairs through two-photon pair production at the BH magnetosphere. These pairs can screen the vacuum gap, which affects high-energy emission and jet-launching mechanisms in radio galaxies.

Keywords: radio active galactic nuclei; low-luminosity active galactic nuclei; gamma-rays; accretion; non-thermal radiation sources; cosmic background radiation
First Results from the JWST Early Release Science Program Q3D: Powerful Quasar-driven Galactic Scale Outflow at z = 3

Quasar-driven galactic outflows are a major driver of the evolution of massive galaxies. We report observations of a powerful galactic-scale outflow in a z = 3 extremely red and intrinsically luminous (L bol ≃ 5 × 1047erg s-1) quasar SDSSJ1652 + 1728 with the Near-infrared Spectrograph on board JWST. We analyze the kinematics of rest-frame optical emission lines and identify the quasar-driven outflow extending out to ~10 kpc from the quasar with a velocity offset of (v r = ± 500 km s-1) and high velocity dispersion (FWHM = 700-2400 km s-1). Due to JWST's unprecedented surface brightness sensitivity in the near-infrared, we unambiguously show that the powerful high velocity outflow in an extremely red quasar encompasses a large swath of the host galaxy's interstellar medium. Using the kinematics and dynamics of optical emission lines, we estimate the mass outflow rate-in the warm ionized phase alone-to be at least 2300 ± 1400 M ⊙ yr-1. We measure a momentum flux ratio between the outflow and the quasar accretion disk of ~1 on a kpc scale, indicating that the outflow was likely driven in a relatively high (>1023cm-2) column density environment through radiation pressure on dust grains. We find a coupling efficiency between the bolometric luminosity of the quasar and the outflow of 0.1%, matching the theoretical prediction of the minimum coupling efficiency necessary for negative quasar feedback. The outflow has sufficient energetics to drive the observed turbulence seen in shocked regions of the quasar host galaxy, which are likely directly responsible for prolonging the time that it takes for gas to cool efficiently.

Keywords: quasars; galaxy evolution; agn host galaxies
A Study of the Observational Properties of Coronal Mass Ejection Flux Ropes near the Sun

We present the observational properties of coronal mass ejection (CME) flux ropes (FRs) near the Sun based on a set of 35 events from solar cycle 24 (2010-2017). We derived the CME FR properties using the Flux Rope from Eruption Data technique. According to this technique, the geometrical properties are obtained from a flux-rope fit to CMEs and the magnetic properties from the reconnected flux in the source region. In addition, we use the magnetic flux in the dimming region at the eruption site. Geometric properties like radius of the FR and the aspect ratio are derived from the FR fitting. The reconnected flux exhibits a positive correlation with flare fluence in soft X-rays (SXRs), peak flare intensity in SXRs, CME speed, and kinetic energy, with correlation coefficients (cc) 0.78, 0.6, 0.48, and 0.55, respectively. We found a moderate positive correlation between magnetic flux in the core dimming regions and the toroidal flux obtained from the Lundquist solution for a force-free FR (cc = 0.43). Furthermore, we correlate the core dimming flux and CME mass (cc = 0.34). The area of the core dimming region shows a moderate correlation with the radius of the FR (cc = 0.4). Thus, we infer that greater magnetic content (poloidal and toroidal fluxes) indicates a more energetic eruption in terms of flare size, CME speed, kinetic energy, mass, and radius of the FR, suggesting important implications for space weather predictions.

Keywords: solar coronal mass ejections; solar magnetic reconnection; solar x-ray flares
Polarized Synchrotron Foreground Assessment for CMB Experiments

Polarized Galactic synchrotron emission is an undesirable foreground for cosmic microwave background experiments observing at frequencies <150 GHz. We perform a combined analysis of observational data at 1.4, 2.3, 23, 30, and 33 GHz to quantify the spatial variation of the polarized synchrotron spectral index, β pol, on ~3.°5 scales. We compare results from different data combinations to address limitations and inconsistencies present in these public data, and form a composite map of β pol. Data quality masking leaves 44% sky coverage (73% for ∣b∣ > 45°). Generally -3.2 < β pol ≲ -3 in the inner Galactic plane and spurs, but the Fan Region in the outer galaxy has a flatter index. We find a clear spectral index steepening with increasing latitude south of the Galactic plane with Δβ pol = 0.4, and a smaller steepening of 0.25 in the north. Near the south Galactic pole the polarized synchrotron spectral index is β pol ≈ -3.4. Longitudinal spectral index variations of Δβ pol ~ 0.1 about the latitudinal mean are also detected. Within the BICEP2/Keck survey footprint, we find consistency with a constant value, β pol = -3.25 ± 0.04 (statistical) ±0.02 (systematic). We compute a map of the frequency at which synchrotron and thermal dust emission contribute equally to the total polarized foreground. The limitations and inconsistencies among data sets encountered in this work make clear the value of additional independent surveys at multiple frequencies, especially between 10 and 20 GHz, provided these surveys have sufficient sensitivity and control of instrumental systematic errors.

Keywords: observational cosmology; diffuse radiation
Mid-infrared Studies of Dusty Sources in the Galactic Center

Mid-infrared (MIR) images of the Galactic center show extended gas and dust features along with bright infrared sources (IRS). Some of these dust features are a part of ionized clumpy streamers orbiting Sgr A*, known as the mini-spiral. We present their proper motions over a 12 yr time period and report their flux densities in N-band filters and derive their spectral indices. The observations were carried out by VISIR at the ESO's Very Large Telescope. High-pass filtering led to the detection of several resolved filaments and clumps along the mini-spiral. Each source was fit by a 2D Gaussian profile to determine the offsets and aperture sizes. We perform aperture photometry to extract fluxes in two different bands. We present the proper motions of the largest consistent set of resolved and reliably determined sources. In addition to stellar orbital motions, we identify a stream-like motion of extended clumps along the mini-spiral. We also detect MIR counterparts of the radio tail components of the IRS 7 source. They show a clear kinematical deviation with respect to the star. They likely represent Kelvin-Helmholtz instabilities formed downstream in the shocked stellar wind. We also analyze the shape and orientation of the extended late-type IRS 3 star that is consistent with the Atacama Large Millimeter/submillimeter Array submillimeter detection of the source. Its puffed-up envelope with a radius of ~2 × 106 R ⊙ could be the result of the red-giant collision with a nuclear jet, which was followed by tidal prolongation along the orbit.

Keywords: galactic center; infrared photometry; galaxy kinematics
Dynamical Tidal Locking Theory: A New Source of the Spin of Dark Matter Halos

We revisit the question of what mechanism is responsible for the spins of halos of dark matter. The answer to this question is of high importance for modeling galaxy intrinsic alignment, which can potentially contaminate current and future lensing data. In particular, we show that when the dark matter halos pass nearly each other in dense environments—namely halo assemblies—they swing and spin each other via exerting mutual tidal torques. We show that this has a significant contribution to the spin of dark matter halos comparable to that calculated by the so-called tidal torque theory. We use the results of the state-of-the-art simulation of Illutris to check the prediction of this theory against the simulation data.

Keywords: cosmology; large-scale structure of the universe
Multimessenger Characterization of Markarian 501 during Historically Low X-Ray and γ-Ray Activity

We study the broadband emission of Mrk 501 using multiwavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi's Large Area Telescope (LAT), NuSTAR, Swift, GASP-WEBT, and the Owens Valley Radio Observatory. Mrk 501 showed an extremely low broadband activity, which may help to unravel its baseline emission. Nonetheless, significant flux variations are detected at all wave bands, with the highest occurring at X-rays and very-high-energy (VHE) γ-rays. A significant correlation (>3σ) between X-rays and VHE γ-rays is measured, supporting leptonic scenarios to explain the variable parts of the emission, also during low activity. This is further supported when we extend our data from 2008 to 2020, and identify, for the first time, significant correlations between the Swift X-Ray Telescope and Fermi-LAT. We additionally find correlations between high-energy γ-rays and radio, with the radio lagging by more than 100 days, placing the γ-ray emission zone upstream of the radio-bright regions in the jet. Furthermore, Mrk 501 showed a historically low activity in X-rays and VHE γ-rays from mid-2017 to mid-2019 with a stable VHE flux (>0.2 TeV) of 5% the emission of the Crab Nebula. The broadband spectral energy distribution (SED) of this 2 yr long low state, the potential baseline emission of Mrk 501, can be characterized with one-zone leptonic models, and with (lepto)-hadronic models fulfilling neutrino flux constraints from IceCube. We explore the time evolution of the SED toward the low state, revealing that the stable baseline emission may be ascribed to a standing shock, and the variable emission to an additional expanding or traveling shock.

Keywords: active galaxies; bl lacertae objects; markarian galaxies; active galactic nuclei; blazars
Long-term Evolution of the Sun's Magnetic Field during Cycles 15-19 Based on Their Proxies from Kodaikanal Solar Observatory

The regular observation of the solar magnetic field is available only for about the last five cycles. Thus, to understand the origin of the variation of the solar magnetic field, it is essential to reconstruct the magnetic field for the past cycles, utilizing other data sets. Long-term uniform observations for the past 100 yr as recorded at the Kodaikanal Solar Observatory (KoSO) provide such an opportunity. We develop a method for the reconstruction of the solar magnetic field using the synoptic observations of the Sun's emission in the Ca II K and Hα lines from KoSO for the first time. The reconstruction method is based on the fact that the Ca II K intensity correlates well with the unsigned magnetic flux, while the sign of the flux is derived from the corresponding Hα map that provides the information of the dominant polarities. Based on this reconstructed magnetic map, we study the evolution of the magnetic field in Cycles 15-19. We also study bipolar magnetic regions (BMRs) and their remnant flux surges in their causal relation. Time-latitude analysis of the reconstructed magnetic flux provides an overall view of magnetic field evolution: emergent magnetic flux, its further transformations with the formation of unipolar magnetic regions (UMRs), and remnant flux surges. We identify the reversals of the polar field and critical surges of following and leading polarities. We found that the poleward transport of opposite polarities led to multiple changes of the dominant magnetic polarities in poles. Furthermore, the remnant flux surges that occur between adjacent 11 yr cycles reveal physical connections between them.

Keywords: solar magnetic fields; sunspot cycle; solar chromosphere; h alpha photometry
On the Energization of Pickup Ions Downstream of the Heliospheric Termination Shock by Comparing 0.52-55 keV Observed Energetic Neutral Atom Spectra to Ones Inferred from Proton Hybrid Simulations

We present an unprecedented comparison of ~0.52-55 keV energetic neutral atom (ENA) heliosheath measurements, remotely sensed by the Interstellar Boundary Explorer (IBEX) mission and the Ion and Neutral Camera (INCA) on the Cassini mission, with modeled ENAs inferred from interstellar pickup protons that have been accelerated at the termination shock, using hybrid simulations, to assess the pickup ion energetics within the heliosheath. This is the first study to use hybrid simulations that are able to accurately model the acceleration of ions to tens of keV energies, which is essential in order to model ENA fluxes in the heliosheath, covering the full energy range observed by IBEX and CASSINI/INCA. The observed ENA intensities are an average value over the time period from 2009 to the end of 2012, along the Voyager 2 (V2) trajectory. The hybrid simulations upstream of the termination shock, where V2 crossed, are constrained by observations. We report an energy-dependent discrepancy between observed and simulated ENA fluxes, with the observed ENA fluxes being persistently higher than the simulated ones. Our analysis reveals that the termination shock may not accelerate pickup ions to sufficient energies to account for the observed ENA fluxes. We, thus, suggest that the further acceleration of these pickup ions is most likely occurring within the heliosheath, via additional physical processes like turbulence or magnetic reconnection. However, the redistribution of energy inside the heliosheath remains an open question.

Keywords: heliosheath; heliosphere; termination shock; solar wind; pickup ions; interstellar medium
Improvements to Pan-STARRS1 Astrometry. II. Corrections for Differential Chromatic Refraction

In a previous paper, we applied the Gaia DR2 catalog to improve the astrometric accuracy of about 1.7 billion objects in Pan-STARRS1 Data Release 2 (PS1 DR2). We report here on further improvements made by utilizing Gaia EDR3 and correcting for the effects of differential chromatic refraction (DCR) in decl. We extend the correction algorithm in Paper I by iteratively subtracting color- and decl.-dependent PS1/Gaia EDR3 decl. residuals. We determine the astrometric improvement for ~440 million reference objects that are point-like and cross-match to Gaia EDR3. For this set of objects, Gaia EDR3 provides a ~3% improvement in PS1 astrometry over Gaia DR2, and DCR corrections provide an additional ~5% improvement. DCR corrections increase substantially for objects observed away from the zenith. DCR corrections lead to an astrometric improvement of ~30% for blue objects (0 < g - i < 1) that are 50° away from the zenith. The amplitude of systematic astrometric errors from these effects is substantially reduced to less than 1 mas for objects with PS1 colors in the range 0 < g - i < 4.5, which makes this a useful astrometric reference catalog in fields where there are few Gaia stars. The improved astrometric data will be available through the Mikulski Archive for Space Telescopes PS1 catalog interfaces.

Keywords: sky surveys; astrometry
Magnetic Field Strength from Turbulence Theory. I. Using Differential Measure Approach

The mean plane-of-sky magnetic field strength is traditionally obtained from the combination of polarization and spectroscopic data using the Davis-Chandrasekhar-Fermi (DCF) technique. However, we identify the major problem of the DCF technique to be its disregard of the anisotropic character of MHD turbulence. On the basis of the modern MHD turbulence theory we introduce a new way of obtaining magnetic field strength from observations. Unlike the DCF technique, the new technique uses not the dispersion of the polarization angle and line-of-sight velocities, but increments of these quantities given by the structure functions. To address the variety of astrophysical conditions for which our technique can be applied, we consider turbulence in both media with magnetic pressure higher than the gas pressure, corresponding, e.g., to molecular clouds, and media with gas pressure higher than the magnetic pressure, corresponding to the warm neutral medium. We provide general expressions for arbitrary admixtures of Alfvén, slow, and fast modes in these media and consider in detail particular cases relevant to diffuse media and molecular clouds. We successfully test our results using synthetic observations obtained from MHD turbulence simulations. We demonstrate that our differential measure approach, unlike the DCF technique, can be used to measure the distribution of magnetic field strengths, can provide magnetic field measurements with limited data, and is much more stable in the presence of induced large-scale variations of nonturbulent nature. Furthermore, our study uncovers the deficiencies of earlier DCF research.

Keywords: interstellar medium; interstellar magnetic fields; interstellar dynamics
Transmission Spectroscopy of the Lowest-density Gas Giant: Metals and a Potential Extended Outflow in HAT-P-67b

Extremely low-density exoplanets are tantalizing targets for atmospheric characterization because of their promisingly large signals in transmission spectroscopy. We present the first analysis of the atmosphere of the lowest-density gas giant currently known, HAT-P-67b. This inflated Saturn-mass exoplanet sits at the boundary between hot and ultrahot gas giants, where thermal dissociation of molecules begins to dominate atmospheric composition. We observed a transit of HAT-P-67b at high spectral resolution with CARMENES and searched for atomic and molecular species using cross-correlation and likelihood mapping. Furthermore, we explored potential atmospheric escape by targeting Hα and the metastable helium line. We detect Ca II and Na I with significances of 13.2σ and 4.6σ, respectively. Unlike in several ultrahot Jupiters, we do not measure a day-to-night wind. The large line depths of Ca II suggest that the upper atmosphere may be more ionized than models predict. We detect strong variability in Hα and the helium triplet during the observations. These signals suggest the possible presence of an extended planetary outflow that causes an early ingress and late egress. In the averaged transmission spectrum, we measure redshifted absorption at the ~3.8% and ~4.5% level in the Hα and He I triplet lines, respectively. From an isothermal Parker wind model, we derive a mass-loss rate of $\dot{M}\sim {10}^{13}\,{\rm{g}}\,{{\rm{s}}}^{-1}$ and an outflow temperature of T ~ 9900 K. However, due to the lack of a longer out-of-transit baseline in our data, additional observations are needed to rule out stellar variability as the source of the Hα and He signals.

Keywords: exoplanet atmospheric composition; exoplanet atmospheric dynamics; exoplanet atmospheric evolution; hot jupiters; high resolution spectroscopy