adsabs/SciX_UAT_keywords huggingface dataset:
The Kiloparsec-scale Neutral Atomic Carbon Outflow in the Nearby Type 2 Seyfert Galaxy NGC 1068: Evidence for Negative AGN Feedback

Active galactic nucleus (AGN) feedback is postulated as a key mechanism for regulating star formation within galaxies. Studying the physical properties of the outflowing gas from AGNs is thus crucial for understanding the coevolution of galaxies and supermassive black holes. Here we report 55 pc resolution ALMA neutral atomic carbon [C I] 3 P 1-3 P 0 observations toward the central 1 kpc of the nearby Type 2 Seyfert galaxy NGC 1068, supplemented by 55 pc resolution CO(J = 1-0) observations. We find that [C I] emission within the central kiloparsec is strongly enhanced by a factor of >5 compared to the typical [C I]/CO intensity ratio of ~0.2 for nearby starburst galaxies (in units of brightness temperature). The most [C I]-enhanced gas (ratio > 1) exhibits a kiloparsec-scale elongated structure centered at the AGN that matches the known biconical ionized gas outflow entraining molecular gas in the disk. A truncated, decelerating bicone model explains well the kinematics of the elongated structure, indicating that the [C I] enhancement is predominantly driven by the interaction between the ISM in the disk and the highly inclined ionized gas outflow (which is likely driven by the radio jet). Our results strongly favor the "CO dissociation scenario" rather than the "in situ C formation" one, which prefers a perfect bicone geometry. We suggest that the high-[C I]/CO intensity ratio gas in NGC 1068 directly traces ISM in the disk that is currently dissociated and entrained by the jet and the outflow, i.e., the "negative" effect of the AGN feedback.

Keywords: active galactic nuclei; galaxy nuclei; galaxy winds; interstellar atomic gas; interstellar phases; molecular gas; seyfert galaxies
The Multiplanet System TOI-421

We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echellé Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Échelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements—and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of Pb = 5.19672 ± 0.00049 days, a mass of Mb = 7.17 ± 0.66 M⊕, and a radius of Rb = ${2.68}_{-0.18}^{+0.19}$ R⊕, whereas the outer warm Neptune, TOI-421 c, has a period of Pc = 16.06819 ± 0.00035 days, a mass of Mc = ${16.42}_{-1.04}^{+1.06}$ M⊕, a radius of Rc = ${5.09}_{-0.15}^{+0.16}$ R⊕, and a density of ρc = ${0.685}_{-0.072}^{+0.080}$ g cm-3. With its characteristics, the outer planet (ρc = ${0.685}_{-0.072}^{+0.080}$ g cm-3) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed. * Based on observations made with ESO Telescopes at the La Silla Observatory under programs ID 1102.C-0923, 0103.C-0874, 0103.C-0759, 0103.C-0442, and 60.A-970. Based on observations obtained with the Nordic Optical Telescope (NOT), operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos (ORM) of the Instituto de Astrofísica de Canarias (IAC). This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This work makes use of observations from the LCOGT network.

Keywords: exoplanet astronomy; exoplanet systems; exoplanets; mini neptunes; hot neptunes; fundamental parameters of stars; high resolution spectroscopy; transit photometry; radial velocity
Active Disturbance Rejection-based Double-loop Control Design for Large Antenna's Servo System

Radio astronomical observations put stringent requirements on the tracking and pointing accuracy of radio telescope antennas. High inertia, low stiffness, underdamped, and multi-resonant frequencies of a large aperture radio telescope's antenna make the high-accuracy control difficult. It is not easy to satisfy control performance using only conventional PID controllers. A low-order Active Disturbance Rejection-based double-loop controller for large antenna is designed in this paper and tested on the Green Bank Telescope model. First, the first-order Linear Active Disturbance Rejecting Controller (LADRC) cascading a first-order low-pass filter and a notch filter is designed for the antenna's velocity loop to achieve the dual-objective optimal velocity tracking. Second, the position loop controller is designed to realize the antenna's position-tracking control by combining the PD controller and a low-pass filter. Further optimization of the position-loop controller helps improve the dynamic performance of the system. The simulation results indicate that the response curves of the proposed PD-LADRC control are smother than those of the Quantitative Feedback Theory (QFT) based controller; the settling time of the PD-LADRC system is 10.1 s and reduces by about 8.2 s than that of the QFT. While using a better position controller reduces settling time to 5 s. The PD-LADRC system also has better wind-disturbance rejection; the worst disturbance response reduces at the gearbox by 68.3% and 60% at the dish, and the recovery time reduces by more than 15 s than the QFT-based controller. In addition, besides easier parameter tuning, the proposed PD-LADRC has better robustness to systematic parameter perturbations and minor tracking error rms in position tracking.

Keywords: radio telescopes; single-dish antennas; pointing accuracy
Quasars with Periodic Variability: Capabilities and Limitations of Bayesian Searches for Supermassive Black Hole Binaries in Time-domain Surveys

Supermassive black hole binaries (SMBHBs) are an inevitable consequence of galaxy mergers. At sub-parsec separations, they are practically impossible to resolve, and the most promising technique is to search for quasars with periodic variability. However, searches for quasar periodicity in time-domain data are challenging due to the stochastic variability of quasars. In this paper, we used Bayesian methods to disentangle periodic SMBHB signals from intrinsic damped random walk (DRW) variability in active galactic nuclei light curves. We simulated a wide variety of realistic DRW and DRW+sine light curves. Their observed properties are modeled after the Catalina Real-time Transient Survey (CRTS) and expected properties of the upcoming Legacy Survey of Space and Time (LSST) from the Vera C. Rubin Observatory. Through a careful analysis of parameter estimation and Bayesian model selection, we investigated the range of parameter space for which binary systems can be detected. We also examined which DRW signals can mimic periodicity and be falsely classified as binary candidates. We found that periodic signals are more easily detectable if the period is short or the amplitude of the signal is large compared to the contribution of the DRW noise. We saw similar detection rates both in the CRTS and LSST-like simulations, while the false-detection rate depends on the quality of the data and is minimal in LSST. Our idealized simulations provide an excellent way to uncover the intrinsic limitations in quasar periodicity searches and set the stage for future searches for SMBHBs.

Keywords: active galactic nuclei; supermassive black holes
Near to Mid-infrared Spectroscopy of (65803) Didymos as Observed by JWST: Characterization Observations Supporting the Double Asteroid Redirection Test

The Didymos binary asteroid was the target of the Double Asteroid Redirection Test (DART) mission, which intentionally impacted Dimorphos, the smaller member of the binary system. We used the Near-Infrared Spectrograph and Mid-Infrared Instrument instruments on JWST to measure the 0.6-5 and 5-20 μm spectra of Didymos approximately two months after the DART impact. These observations confirm that Didymos belongs to the S asteroid class and is most consistent with LL chondrite composition, as was previously determined from its 0.6-2.5 μm reflectance spectrum. Measurements at wavelengths >2.5 μm show Didymos to have thermal properties typical for an S-complex asteroid of its size and to be lacking absorptions deeper than ~2% due to OH or H2O. Didymos' mid-infrared emissivity spectrum is within the range of what has been measured on S-complex asteroids observed with the Spitzer Space Telescope and is most consistent with emission from small (<25 μm) surface particles. We conclude that the observed reflectance and physical properties make the Didymos system a good proxy for the type of ordinary chondrite asteroids that cross near-Earth space, and a good representative of likely future impactors.

Keywords: asteroid satellites; asteroids; infrared spectroscopy; spectroscopy
Particle-in-cell Simulation of Whistler Heat-flux Instabilities in the Solar Wind: Heat-flux Regulation and Electron Halo Formation

We present results of a two-dimensional fully kinetic particle-in-cell simulation in order to shed light on the role of whistler waves in the scattering of strahl electrons and in the heat-flux regulation in the solar wind. We model the electron velocity distribution function as initially composed of core and strahl populations as typically encountered in the near-Sun solar wind as observed by Parker Solar Probe. We demonstrate that, as a consequence of the evolution of the electron velocity distribution function (VDF), two branches of the whistler heat-flux instability can be excited, which can drive whistler waves propagating in the direction oblique or parallel to the background magnetic field. First, oblique whistler waves induce pitch-angle scattering of strahl electrons, toward higher perpendicular velocities. This leads to the broadening of the strahl pitch-angle distribution and hence to the formation of a halo-like population at the expense of the strahl. Later on, the electron VDF experiences the effect of parallel whistler waves, which contributes to the redistribution of the particles scattered in the perpendicular direction into a more symmetric halo, in agreement with observations. Simulation results show a remarkable agreement with the linear theory of the oblique whistler heat-flux instability. The process is accompanied by a significant decrease of the heat flux carried by the strahl population.

Keywords: solar wind; space plasmas; plasma astrophysics
The Fine-scale Structure of Polar Coronal Holes

Coronal holes are thought to be composed of relatively broad columnar structures known as plumes. Here, we demonstrate that the plumes (and interplumes) in polar coronal holes are composed of fine-scale filamentary structure, with average scales of 2″-10″. The fine structure is the off-limb analog of the previously found "plumelets" of Uritsky et al. The off-limb observations enable an examination of the fine structure without the influence of the underlying atmosphere along the line of sight. Hence, we show that the fine-scale structure is present at least until the edge of the field of view of the Solar Dynamics Observatory. The fine structure is found to have spatial distribution that follows a k -1 power law perpendicular to the inferred magnetic field direction. For a small sample of the fine structure, the cross-sectional profiles are measured as a function of height. In some cases, the measurements indicate that the fine structure expands super-radially, consistent with existing models of polar field expansion and the expansion of the plumes. We discuss the implications of the presence of the fine structure with respect to understanding wave propagation in the coronal holes and their contribution to powering the solar wind.

Keywords: solar coronal holes; solar corona; solar coronal plumes; the sun
The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations

The scaling of the turbulent spectra provides a key measurement that allows us to discriminate between different theoretical predictions of turbulence. In the solar wind, this has driven a large number of studies dedicated to this issue using in situ data from various orbiting spacecraft. While a semblance of consensus exists regarding the scaling in the magnetohydrodynamic (MHD) and dispersive ranges, the precise scaling in the transition range and the actual physical mechanisms that control it remain open questions. Using the high-resolution data in the inner heliosphere from the Parker Solar Probe mission, we find that the sub-ion scales (i.e., at the frequency f ∼ [2, 9] Hz) follow a power-law spectrum fα with a spectral index α varying between -3 and -5.7. Our results also show that there is a trend toward an anticorrelation between the spectral slopes and the power amplitudes at the MHD scales, in agreement with previous studies: the higher the power amplitude the steeper the spectrum at sub-ion scales. A similar trend toward an anticorrelation between steep spectra and increasing normalized cross helicity is found, in agreement with previous theoretical predictions about the imbalanced solar wind. We discuss the ubiquitous nature of the ion transition range in solar wind turbulence in the inner heliosphere.

Keywords: solar wind; interplanetary turbulence; solar coronal heating
Staring at the Shadows of Archaic Galaxies: Damped Lyα and Metal Absorbers Toward a Young z ∼ 6 Weak-line Quasar

We characterize the Lyα halo and absorption systems toward PSO J083+11, a unique z = 6.3401 weak-line quasar, using Gemini Near-infrared Spectrograph, Magellan Folded-port Infrared Echellette, and Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) data. Strong absorptions by hydrogen and several metal lines (e.g., C II, Mg II, and O I) are discovered in the spectrum, which indicates the presence of: (i) a proximate subdamped Lyα (sub-DLA) system at z = 6.314 and (ii) a Mg II absorber at z = 2.2305. To describe the observed damping wing signal, we model the Lyα absorption with a combination of a sub-DLA with the neutral hydrogen column density of $\mathrm{log}{N}_{\mathrm{HI}}\,=\,20.03\pm 0.30\,{\mathrm{cm}}^{-2}$ and absorption from the intergalactic medium with a neutral fraction of around 10%. The sub-DLA toward PSO J083+11 has an abundance ratio of [C/O] = -0.04 ± 0.33 and metallicity of [O/H] = -2.19 ± 0.44, similar to those of low-redshift metal-poor DLAs. These measurements suggest that the sub-DLA might truncate PSO J083+11's proximity zone size and complicate the quasar lifetime measurement. However, this quasar shows no sign of a Lyα halo in the MUSE data cube, where the estimated 1σ limit of surface brightness is $2.76\times {10}^{-18}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\mathrm{arcsec}}^{-2}$ at an aperture size of 1″, or equivalent to a Lyα luminosity of ≤43.46 erg s-1. This nondetection, while being only weak independent evidence on its own, is at least consistent with a young quasar scenario, as expected for a quasar with a short accretion timescale.

Keywords: active galactic nuclei; active galaxies; damped lyman-alpha systems; early universe; high-redshift galaxies; metal line absorbers; quasar absorption line spectroscopy; quasars; reionization; supermassive black holes
Challenges in Scientific Data Communication from Low-mass Interstellar Probes

An optical downlink for the return of scientific data from space probes at interstellar distances is studied. The context is probes moving at relativistic speed using a terrestrial directed-energy beam for propulsion, necessitating very low mass probes. Achieving simultaneous communication from a swarm of probes launched at regular intervals to a target at the distance of Proxima Centauri is addressed. The analysis focuses on fundamental physical and statistical communication limitations on downlink performance rather than a concrete implementation. Transmission time/distance and probe mass are chosen to achieve the best data latency versus volume trade-off. Challenges in targeting multiple probe trajectories with a single receiver are addressed, including multiplexing, parallax, and target-star proper motion. Constraints on transmit aperture size make a compelling argument in favor of free-space optical communications, and this is the assumed approach for our baseline analysis. Relevant sources of background radiation, including cosmic, atmospheric, and receiver dark count, are identified and estimated. Direct detection enables high photon efficiency and incoherent aperture combining. A novel burst pulse-position modulation (BPPM) beneficially expands the optical bandwidth and ameliorates receiver dark counts. A canonical receive optical collector combines minimum transmit power with constrained swarm-probe coverage. Theoretical limits on reliable data recovery and sensitivity to the various BPPM model parameters are applied, including a wide range of total collector areas. Significant near-term technological obstacles are identified. Enabling innovations include a high peak-to-average power ratio, a large source extinguishing factor, the shortest atmosphere-transparent wavelength to minimize target-star interference, adaptive optics for atmospheric turbulence, very selective bandpass filtering (possibly with multiple passbands), very low dark count single-photon superconducting detectors, and very accurate attitude control and pointing mechanisms.

Keywords: exoplanets; exoplanet astronomy; deep space probes; flyby missions; space probes
CME-induced Thermodynamic Changes in the Corona as Inferred from Fe XI and Fe XIV Emission Observations during the 2017 August 21 Total Solar Eclipse

We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 R⊙. Measurements of the Fe XI (789.2 nm) and Fe XIV (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse (TSE). Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe XI and Fe XIV emission relative to continuum scattering, as well as the relative abundance of Fe10+ and Fe13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is (1.1-1.2) × 106 K in coronal holes and (1.2-1.4) × 106 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength TSE observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 R⊙.

Keywords: total eclipses; solar eclipses; solar particle emission; solar e corona; solar k corona; solar f corona; solar abundances; solar coronal mass ejections; solar coronal mass ejection shocks; solar coronal transients; solar coronal streamers; solar coronal holes
The Physical Properties of Massive Green Valley Galaxies as a Function of Environments at 0.5 < z < 2.5 in 3D-HST/Candels Fields

To investigate the effects of environment in the quenching phase, we study the empirical relations for green valley (GV) galaxies between overdensity and other physical properties (i.e., effective radius r e , Sérsic indices n, and specific star formation rate (sSFR)). Based on five 3D-HST/CANDELS fields, we construct a large sample of 2126 massive (M ⋆ > 1010 M ☉) GV galaxies at 0.5 < z < 2.5 and split it into the higher overdensity quarter and the lower overdensity quarter. The results shows that GV galaxies in denser environments have higher n values and lower sSFR at 0.5 < z < 1, while there is no discernible distinction at 1 < z < 2.5. No significant enlarging or shrinking is found for GV galaxies in different environments within the same redshift bin. This suggests that a dense environment would promote the growth of bulges and suppress star formation activity of GV galaxies at 0.5 < z < 1.5 but would not affect the galaxy size. We also study the dependence of the fraction of three populations (blue cloud, GV, and red sequence) on both environments and M ⋆. At a given M ⋆, blue cloud fraction goes down with increasing environment density, while red sequence fraction is opposite. For the most massive GV galaxies, a sharp drop appears in the denser environment. Coupled with the mass dependence of three fractions in different redshift bins, our result implies that stellar mass and environments jointly promote the quenching process. Such a dual effect is also confirmed by recalculating the new effective GV fraction as the number of GV galaxies over the number of nonquiescent galaxies.

Keywords: green valley galaxies; galaxy environments; star formation; galaxy quenching; stellar properties
Molecules with ALMA at Planet-forming Scales (MAPS). IV. Emission Surfaces and Vertical Distribution of Molecules

The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a unique opportunity to study the vertical distribution of gas, chemistry, and temperature in the protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. By using the asymmetry of molecular line emission relative to the disk major axis, we infer the emission height (z) above the midplane as a function of radius (r). Using this method, we measure emitting surfaces for a suite of CO isotopologues, HCN, and C2H. We find that 12CO emission traces the most elevated regions with $z/r\gt 0.3$ , while emission from the less abundant 13CO and C18O probes deeper into the disk at altitudes of $z/r\,\lesssim \,0.2$ . C2H and HCN have lower opacities and signal-to-noise ratios, making surface fitting more difficult, and could only be reliably constrained in AS 209, HD 163296, and MWC 480, with $z/r\,\lesssim \,0.1$ , i.e., relatively close to the planet-forming midplanes. We determine peak brightness temperatures of the optically thick CO isotopologues and use these to trace 2D disk temperature structures. Several CO temperature profiles and emission surfaces show dips in temperature or vertical height, some of which are associated with gaps and rings in line and/or continuum emission. These substructures may be due to local changes in CO column density, gas surface density, or gas temperatures, and detailed thermochemical models are necessary to better constrain their origins and relate the chemical compositions of elevated disk layers with those of planet-forming material in disk midplanes. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: protoplanetary disks; interstellar molecules; astrochemistry; high angular resolution; circumstellar disks; planet formation