adsabs/SciX_UAT_keywords huggingface dataset:
Systematic KMTNet Planetary Anomaly Search. XII. Complete Sample of 2017 Subprime Field Planets

We report the analysis of four unambiguous planets and one possible planet from the subprime fields (Γ ≤ 1 hr‑1) of the 2017 Korea Microlensing Telescope Network (KMTNet) microlensing survey, to complete the KMTNet AnomalyFinder planetary sample for the 2017 subprime fields. They are KMT-2017-BLG-0849, KMT-2017-BLG-1057, OGLE-2017-BLG-0364, and KMT-2017-BLG-2331 (unambiguous), as well as KMT-2017-BLG-0958 (possible). For the four unambiguous planets, the mean planet–host mass ratios, q, are (1.0, 1.2, 4.6, 13) × 10‑4, the median planetary masses are (6.4, 24, 76, 171) M ⊕, and the median host masses are (0.19, 0.57, 0.49, 0.40) M ⊙, respectively, found from a Bayesian analysis. We have completed the Anomaly Finder planetary sample from the first 4 yr of KMTNet data (2016–2019), with 112 unambiguous planets in total, which nearly tripled the microlensing planetary sample. The "sub-Saturn desert" ( ) found in the 2018 and 2019 KMTNet samples is confirmed by the 2016 and 2017 KMTNet samples.

Keywords: gravitational microlensing exoplanet detection; gravitational microlensing
The LCO Outbursting Objects Key Project: Overview and Year 1 Status

The LCO Outbursting Objects Key (LOOK) Project uses the telescopes of the Las Cumbres Observatory (LCO) Network to (1) systematically monitor a sample of previously discovered over the whole sky, to assess the evolutionary state of these distant remnants from the early solar system, and (2) use alerts from existing sky surveys to rapidly respond to and characterize detected outburst activity in all small bodies. The data gathered on outbursts helps to characterize each outburst's evolution with time, helps to assess the frequency and magnitude distribution of outbursts in general, and contributes to the understanding of outburst processes and volatile distribution in the solar system. The LOOK Project exploits the synergy between current and future wide-field surveys such as ZTF, Pan-STARRS, and LSST, as well as rapid-response telescope networks such as LCO, and serves as an excellent test bed for what will be needed for the much larger number of objects coming from Rubin Observatory. We will describe the LOOK Project goals, the planning and target selection (including the use of NEOexchange as a Target and Observation Manager or "TOM"), and results from the first phase of observations, including the detection of activity and outbursts on the giant comet C/2014 UN271 (Bernardinelli-Bernstein) and the discovery and follow-up of 28 outbursts on 14 comets. Within these outburst discoveries, we present a high-cadence light curve of 7P/Pons-Winnecke with 10 outbursts observed over 90 days, a large outburst on 57P/duToit-Neujmin-Delporte, and evidence that comet P/2020 X1 (ATLAS) was in outburst when discovered.

Keywords: comets; long period comets; comet volatiles; asteroids; centaur group; broad band photometry; narrow band photometry; optical observation; short period comets; oort cloud objects; automated telescopes
How Sublimation Delays the Onset of Dusty Debris Disk Formation around White Dwarf Stars

Although numerous white dwarf stars host dusty debris disks, the temperature distribution of these stars differs significantly from the white dwarf population as a whole. Dusty debris disks exist exclusively around white dwarfs cooler than 27,000 K. This is all the more enigmatic given that the formation processes of dusty debris disks should favor younger, hotter white dwarfs, which likely host more dynamically unstable planetary systems. Here we apply a sophisticated material sublimation model to white dwarf systems to show that these statistics are actually a natural result of the interplay of thermal and tidal forces and how they define the circumstellar regions where dusty debris disks can form. We demonstrate that these processes tend to prevent stability against both sublimative destruction and reaccretion into planetesimals for rocky materials until white dwarfs cool to below ∼25,000-32,000 K, in agreement with the observed limit of ∼27,000 K. For pure water ice, this critical temperature is less than 2700 K (requiring a cooling age older the universe); this precludes pure water ice-rich debris disks forming through the accepted two-step mechanism. The critical temperature is size-dependent; more massive white dwarfs could potentially host dusty debris disks at warmer temperatures. Our model suggests that the location of the disks within the PG 0010+280, GD 56, GD 362, and PG 1541+651 systems are consistent with a forsterite-dominated olivine composition. We also find that very cool white dwarfs may simultaneously host multiple, independently formed dusty debris disks, consistent with observations of the LSPM J0207+3331 system.

Keywords: exoplanet dynamics; exoplanet astronomy; circumstellar dust; white dwarf stars; circumstellar grains; debris disks
Geometric Support for Dark Matter by an Unaligned Einstein Ring in A3827

The nondetection of dark matter (DM) particles in increasingly stringent laboratory searches has encouraged alternative gravity theories where gravity is sourced only from visible matter. Here, we consider whether such theories can pass a two-dimensional test posed by gravitational lensing—to reproduce a particularly detailed Einstein ring in the core of the galaxy cluster A3827. We find that when we require the lensing mass distribution to strictly follow the shape (ellipticity and position angle) of the light distribution of cluster member galaxies, intracluster stars, and the X-ray emitting intracluster medium, we cannot reproduce the Einstein ring, despite allowing the mass-to-light ratios of these visible components to freely vary with radius to mimic alternative gravity theories. Alternatively, we show that the detailed features of the Einstein ring are accurately reproduced by allowing a smooth, freely oriented DM halo in the lens model, with relatively small contributions from the visible components at a level consistent with their observed brightnesses. This dominant DM component is constrained to have the same orientation as the light from the intracluster stars, indicating that the intracluster stars trace the gravitational potential of this component. The Einstein ring of A3827 therefore presents a new challenge for alternative gravity theories: not only must such theories find agreement between the total lensing mass and visible mass, but they must also find agreement between the projected sky distribution of the lensing mass and that of the visible matter, a more stringent test than has hitherto been posed by lensing data.

Keywords: strong gravitational lensing; dark matter distribution; galaxy clusters
Linking Cause and Effect: Nanoscale Vibrational Spectroscopy of Space Weathering from Asteroid Ryugu

Airless bodies are subjected to space-weathering effects that modify the first few microns of their surface. Therefore, understanding their impact on the optical properties of asteroids is key to the interpretation of their color variability and infrared reflectance observations. The recent Hayabusa2 sample return mission to asteroid Ryugu offers the first opportunity to study these effects, in the case of the most abundant spectral type among the main-asteroid belt, C-type objects. This study employs vibrational electron energy-loss spectroscopy in the transmission electron microscope to achieve the spatial resolution required to measure the distinct mid-infrared spectral signature of Ryugu's space-weathered surface. The comparison with the spectrum of the pristine underlying matrix reveals the loss of structural -OH and C-rich components in the space-weathered layers, providing direct experimental evidence that exposure to the space environment tends to mask the optical signatures of phyllosilicates and carbonaceous matter. Our findings should contribute to rectifying potential underestimations of water and carbon content of C-type asteroids when studied through remote sensing with new-generation telescopes.

Keywords: space weather; asteroid surfaces; remote sensing; small solar system bodies; vibrational spectroscopy; infrared spectroscopy; impact gardening; planetary mineralogy
Velocity-resolved Reverberation Mapping of Changing-look AGN NGC 2617

NGC 2617 attracted a lot of attention after the detection of changes in its spectral type; the geometry and kinematics of the broad-line region (BLR) are still ambiguous. In this paper, we present the high cadence (∼2 days) reverberation mapping campaign of NGC 2617 from 2019 October to 2020 May undertaken at the Lijiang 2.4 m telescope. For the first time, the velocity-resolved reverberation signature of the object was successfully detected. Both Hα and Hβ show an asymmetrical profile with a peak in the velocity-resolved time lags. For both of the lines, the lag of the line core is longer than those of the relevant wings, and the peak of the velocity-resolved lags is slightly blueshifted. These characteristics are not consistent with the theoretical prediction of the inflow, outflow or Keplerian disk model. Our observations give the time lags of Hα, Hβ, Hγ, and He I, with a ratio of τHα: τHβ: τHγ: τHe I = 1.27:1.00:0.89:0.20, which indicates a stratified structure in the BLR of the object. It is the first time that the lags of Hα and He I are obtained. Assuming a virial factor of f = 5.5 for the dispersion width of the line, the masses of the black holes derived from Hα and Hβ are ${23.8}_{-2.7}^{+5.4}$ and ${21.1}_{-4.4}^{+3.8}\times {10}^{6}{M}_{\odot }$ , respectively. Our observed results indicate the complexity of the BLR of NGC 2617.

Keywords: active galaxies; photometry; reverberation mapping; seyfert galaxies; spectroscopy; supermassive black holes
Galactic Magnetic Fields. I. Theoretical Model and Scaling Relations

Galactic dynamo models have generally relied on input parameters that are very challenging to constrain. We address this problem by developing a model that uses observable quantities as input: the galaxy rotation curve, the surface densities of the gas, stars and star formation rate, and the gas temperature. The model can be used to estimate parameters of the random and mean components of the magnetic field, as well as the gas scale height, root-mean-square velocity and the correlation length and time of the interstellar turbulence, in terms of the observables. We use our model to derive theoretical scaling relations for the quantities of interest, finding reasonable agreement with empirical scaling relations inferred from observation. We assess the dependence of the results on different assumptions about turbulence driving, finding that agreement with observations is improved by explicitly modeling the expansion and energetics of supernova remnants. The model is flexible enough to include alternative prescriptions for the physical processes involved, and we provide links to two open-source PYTHON programs that implement it.

Keywords: spiral galaxies; galaxy magnetic fields; interstellar magnetic fields; interstellar medium; disk galaxies
The Negative Polarization Branch of Asteroid 47 Aglaja

The degree of linear polarization of the main-belt asteroid 47 Aglaja was measured at low phase angles. The data obtained made it possible to construct a complete branch of the negative polarization. Comparison with asteroids of the same spectral type and having equally high albedo values showed that asteroid 47 Aglaja has a much smaller negative polarization branch, which indicates a possible difference in the chemical composition or structure of matter on the surface.

Keywords: asteroids; polarimetry
The Quasar SDSS J140821.67+025733.2 Does Not Contain a 196 Billion Solar Mass Black Hole

The black hole in the quasar SDSS J140821.67+025733.2 has been reported to have a mass of 1.96 × 1011 M⊙ based on measurements from the SDSS DR12 Quasar Catalog. As a result, references to this object as the most massive known black hole in the universe have recently appeared in scientific articles and in popular media including Wikipedia. We show that this extremely high mass estimate is incorrect, resulting from a faulty measurement of the C IV line width. From a new measurement of the Mg II line width, we derive an estimate of MBH ≈ 8 × 109 M⊙.

Keywords: black hole physics; supermassive black holes; quasars
JWST/NIRSpec Measurements of the Relationships between Nebular Emission-line Ratios and Stellar Mass at z 3-6

We analyze the rest-optical emission-line ratios of star-forming galaxies at 2.7 ≤ z < 6.5 drawn from the Cosmic Evolution Early Release Science (CEERS) Survey and their relationships with stellar mass (M *). Our analysis includes both line ratios based on the [N II] λ6583 feature ([N II] λ6583/Hα, ([O III] λ5007/Hβ)/([N II] λ6583/Hα) (O3N2), and [N II] λ6583/[O II] λ3727) and those featuring α-elements ([O III] λ5007/Hβ, [O III] λ5007/[O II] λ3727 (O32), ([O III] λλ4959, 5007 + [O II] λ3727)/Hβ (R23), and [Ne III] λ3869/[O II] λ3727). Given the typical flux levels of [N II] λ6583 and [Ne III] λ3869, which are undetected in the majority of individual CEERS galaxies at 2.7 ≤ z < 6.5, we construct composite spectra in bins of M * and redshift. Using these composite spectra, we compare the relationships between emission-line ratios and M * at 2.7 ≤ z < 6.5 with those observed at lower redshift. While there is significant evolution toward higher excitation (e.g., higher [O III] λ5007/Hβ, O32, O3N2) and weaker nitrogen emission (e.g., lower [N II] λ6583/Hα and [N II] λ6583/[O II] λ3727) between z ~ 0 and z ~ 3, we find in most cases that there is no significant evolution in the relationship between line ratio and M * beyond z ~ 3. The [Ne III] λ3869/[O II] λ3727 ratio is anomalous in showing evidence for significant elevation at 4.0 ≤ z < 6.5 at fixed mass, relative to z ~ 3.3. Collectively, however, our empirical results suggest no significant evolution in the mass-metallicity relationship at 2.7 ≤ z < 6.5. Representative galaxy samples and metallicity calibrations based on existing and upcoming JWST/NIRSpec observations will be required to translate these empirical scaling relations into ones tracing chemical enrichment and gas cycling and to distinguish among descriptions of feedback in galaxy formation simulations at z > 3.

Keywords: galaxy formation; galaxy evolution; high-redshift galaxies
The Intrinsic Scatter of the Broad Lines-Narrow Line Correlation in Type I AGN

A correlation between the FWHM of the broad Balmer lines and the narrow [O III]/Hβ line ratio was recently applied to the black hole (BH) mass estimation in type II active galactic nuclei (AGN), where only the narrow lines are visible to the observer. The correlation was initially quantified with type I AGN using stacked spectra, in groups automatically created using a machine-learning algorithm. Such an analysis does not provide information about the intrinsic scatter of the correlation. In addition, it does not necessarily reproduce the true underlying correlation, for example, due to the stacking of spectra with different properties. Testing these two issues requires measurements of individual objects. In this work, we perform such a test by fitting the broad and narrow lines for 8302 type I AGN from the Sloan Digital Sky Survey. Due to the difficulty in reliably measuring the narrow Balmer lines in such objects, which are, in many cases, a small contribution on top of the broad lines, we visually inspect all of the fits and identify 1561 objects with robust measurements. Using these measurements, we find that while a correlation does exist, it shows a large scatter and is not well described by a linear relation. This should be taken into account when using the broad Hβ FWHM versus narrow [O III]/Hβ correlation for type II AGN BH mass estimation.

Keywords: active galactic nuclei; active galaxies; supermassive black holes
High-resolution Hubble Space Telescope Imaging Survey of Local Star-forming Galaxies. I. Spatially Resolved Obscured Star Formation with Hα and Paschen-β Recombination Lines

We present a sample of 24 local star-forming galaxies observed with broadband and narrowband photometry from the Hubble Space Telescope (HST) that are part of the Great Observatories All-sky Luminous Infrared Galaxies Survey of local luminous and ultraluminous infrared galaxies. With narrowband filters around the emission lines Hα (and [N II]) and Paβ, we obtain robust estimates of the dust attenuation affecting the gas in each galaxy, probing higher attenuation than can be traced by the optical Balmer decrement Hα/Hβ alone by a factor of >1 mag. We also infer the dust attenuation toward the stars via a spatially resolved spectral energy distribution fitting procedure that uses all available HST imaging filters. We use various indicators to obtain the star formation rate (SFR) per spatial bin and find that Paβ traces star-forming regions where the Hα and the optical stellar continuum are heavily obscured. The dust-corrected Paβ SFR recovers the 24 μm inferred SFR with a ratio of -0.14 ± 0.32 dex and the SFR inferred from the 8 to 1000 μm infrared luminosity at -0.04 ± 0.23 dex. Both in a spatially resolved and integrated sense, rest-frame near-infrared recombination lines can paint a more comprehensive picture of star formation across cosmic time, particularly with upcoming JWST observations of Paschen-series line emission in galaxies as early as the epoch of reionization.

Keywords: extragalactic astronomy; interstellar medium; star formation; interstellar dust extinction; luminous infrared galaxies
Assessment of Critical Convection and Associated Rotation States in Models of Sun-like Stars Including a Stable Layer

Recent numerical simulations of rotating stellar convection have suggested the possible existence of retrograde (slow equator, fast poles) or so-called antisolar differential rotation states in slowly rotating stars possessing a large Rossby number. We aim to understand whether such rotational states exist from the onset of convective instability or are the outcome of complex nonlinear interactions in the turbulent convective envelope. To this end, we have made a systematic linear analysis of the critical state of convection in a series of 15 numerical simulations published in Brun et al. We have assessed their degree of supercriticality and most-unstable mode properties, and computed the second-order mean zonal flow response. We find that none of the linear critical cases show a retrograde state at the onset of convection even when their nonlinear counterparts do. We also find that the presence of a stably stratified layer coupled to the convectively unstable upper layer leads to interesting gravity-wave excitation and angular momentum transport. We conclude that retrograde states of differential rotation are probably the outcome of complex mode-mode interactions in the turbulent convection layer and are, as a consequence, likely to exist in real stars.

Keywords: stellar convective zones; stellar interiors; astrophysical fluid dynamics; internal waves; stellar rotation
The Observable Properties of Galaxy Accretion Events in Milky Way-like Galaxies in the FIRE-2 Cosmological Simulations

In the Λ-Cold Dark Matter model of the universe, galaxies form in part through accreting satellite systems. Previous works have built an understanding of the signatures of these processes contained within galactic stellar halos. This work revisits that picture using seven Milky Way-like galaxies in the Latte suite of FIRE-2 cosmological simulations. The resolution of these simulations allows a comparison of contributions from satellites aboveM * ≳ 10 × 7 M ⊙, enabling the analysis of observable properties for disrupted satellites in a fully self-consistent and cosmological context. Our results show that the time of accretion and the stellar mass of an accreted satellite are fundamental parameters that in partnership dictate the resulting spatial distribution, orbital energy, and [α/Fe]-[Fe/H] compositions of the stellar debris of such mergers at present day. These parameters also govern the resulting dynamical state of an accreted galaxy at z = 0, leading to the expectation that the inner regions of the stellar halo (R GC ≲ 30 kpc) should contain fully phase-mixed debris from both lower- and higher-mass satellites. In addition, we find that a significant fraction of the lower-mass satellites accreted at early times deposit debris in the outer halo (R GC > 50 kpc) that are not fully phased-mixed, indicating that they could be identified in kinematic surveys. Our results suggest that, as future surveys become increasingly able to map the outer halo of our Galaxy, they may reveal the remnants of long-dead dwarf galaxies whose counterparts are too faint to be seen in situ in higher-redshift surveys.

Keywords: galaxy formation; milky way galaxy; milky way stellar halo; milky way dynamics
First Extragalactic Detection of Thermal Hydroxyl (OH) 18 cm Emission in M31 Reveals Abundant CO-faint Molecular Gas

The most abundant interstellar molecule, molecular hydrogen (H2), is practically invisible in cold molecular clouds. Astronomers typically use carbon monoxide (CO) to trace the bulk distribution and mass of H2 in our galaxy and many others. CO observations alone fail to trace a significant component of molecular gas known as "CO-dark" molecular gas, which can be probed with molecules such as OH and CH. We present an extremely sensitive pilot search for the 18 cm hydroxyl (OH) lines in the Andromeda galaxy (M31) with the 100 m Robert C. Byrd Green Bank Telescope. We successfully detected the 1665 and 1667 MHz OH lines in faint emission. The 1665/1667 MHz line ratio displays the characteristic 5:9 ratio predicted under conditions of local thermodynamic equilibrium. To our knowledge, this is the first detection of nonmaser 18 cm OH emission in another galaxy. We compare our OH and H I observations with archival CO (1–0) observations. Our OH detection position overlaps with the previously discovered Arp Outer Arm in CO. Our best estimates show that the amount of H2 traced by OH is 100%–140% higher than the amount traced by CO in this sight line. The amount of dark molecular gas implied by dust data supports this conclusion. We conclude that the 18 cm OH lines hold promise as a valuable tool for mapping of the "CO-dark" and "CO-faint" molecular gas phase in nearby galaxies, especially with upcoming multibeam, phased-array feed receivers on radio telescopes, which will allow for drastically improved mapping speeds of faint signals.

Keywords: andromeda galaxy; radio astronomy; interstellar medium; interstellar clouds; interstellar molecules