adsabs/SciX_UAT_keywords huggingface dataset:
Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with Cosmic Microwave Background Anisotropy and 21 cm Global Signals

The global history of reionization was shaped by the relative amounts of starlight released by three halo mass groups: the first two groups are atomic-cooling halos (ACHs) with virial temperatures Tvir > 104 K, either (1) massive enough to form stars even after reionization (high-mass ACHs, ≳ 109 M⊙) or (2) less massive (low-mass ACHs), subject to star formation suppression when overtaken by reionization, and the third group comprises (3) H2-cooling mini-halos (MHs) with Tvir < 104 K, whose star formation is predominantly suppressed by the H2-dissociating Lyman-Werner background. Our previous work showed that including MHs caused two-stage reionization-early rise to x ≲ 0.1, driven by MHs, followed by a rapid rise, late, to x ~ 1, driven by ACHs-with a signature in cosmic microwave background (CMB) polarization anisotropy predicted to be detectable by the Planck satellite. Motivated by this prediction, we model global reionization semi-analytically for comparison with Planck CMB data and the Experiment to Detect the Global Epoch of Reionization (EDGES) global 21 cm absorption feature, for models with: (1) ACHs, no feedback; (2) ACHs, self-regulated; and (3) ACHs and MHs, self-regulated. Model (3) agrees well with Planck E-mode polarization data, even with a substantial tail of high-redshift ionization, beyond the limit proposed by the Planck Collaboration. No model reproduces the EDGES feature. For model (3), $\left|\delta {T}_{b}\right|\lesssim 60\,\mathrm{mK}$ across the EDGES trough, an order of magnitude too shallow, and absorption starts at higher z but is spectrally featureless. Early onset reionization by Population III stars in MHs is compatible with current constraints, but only if the EDGES interpretation is discounted, or else other processes we did not include account for it.

Keywords: cosmic microwave background radiation; population iii stars; h i line emission; reionization
Measuring Solar Differential Rotation with an Iterative Phase Correlation Method

A reliable inference of the differential rotation rate of the solar photosphere is essential for models of the solar interior. The work presented here is based on a novel iterative phase correlation technique, which relies on the measurement of the local shift, at the central meridian, between two images separated by a given time interval. Consequently, it does not require any specific reference features, such as sunspots or supergranules, nor extended observations spanning several months. The reliability of the method is demonstrated by applying it to high spatial and temporal resolution continuum images of the solar photosphere, at 6173 Å, acquired by the Solar Dynamics Observatory Helioseismic and Magnetic Imager over one complete Carrington rotation. The data selected covers the time period of 2020 January 1 to February 2. The method was applied to one day, and to the full time interval. The differential rotation rate derived using this feature-independent technique yields values that fall in the middle of the range of those published to date. Most importantly, the method is suited for the production of detailed rotation maps of the solar photosphere. It also enables the visual and quantitative identification of the north-south asymmetry in the solar differential rotation rate, when present.

Keywords: solar rotation; solar differential rotation; astronomical techniques; astronomical models; analytical mathematics; computational methods; direct imaging; astrometry; astronomical methods; astronomy software; astronomy data analysis; astronomy data visualization
TOI-481 b and TOI-892 b: Two Long-period Hot Jupiters from the Transiting Exoplanet Survey Satellite

We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii (0.99 ± 0.01 ${R}_{{\rm{J}}}$ and 1.07 ± 0.02 ${R}_{{\rm{J}}}$ , respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53 ± 0.03 ${M}_{{\rm{J}}}$ versus 0.95 ± 0.07 ${M}_{{\rm{J}}}$ , respectively). Both planets orbit metal-rich stars ( $[\mathrm{Fe}/{\rm{H}}]$ = $+0.26\pm 0.05$ dex and $[\mathrm{Fe}/{\rm{H}}]$ = $+0.24\pm 0.05$ for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a ${M}_{\star }$ = 1.14 ± 0.02 ${M}_{\odot }$ , ${R}_{\star }$ = 1.66 ± 0.02 ${R}_{\odot }$ G-type star ( ${T}_{\mathrm{eff}}$ = $5735\pm 72$ K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star ( ${T}_{\mathrm{eff}}$ = $6261\pm 80$ K), which has a mass of ${M}_{\star }$ = 1.28 ± 0.03 ${M}_{\odot }$ and a radius of ${R}_{\star }$ = 1.39 ± 0.02 ${R}_{\odot }$ . TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.

Keywords: exoplanet detection methods; transit photometry; radial velocity; exoplanet astronomy
Outflowing Helium from a Mature Mini-Neptune

We announce the detection of escaping helium from TOI 2134b, a mini-Neptune a few gigayears old. The average in-transit absorption spectrum shows a peak of 0.37% ± 0.05% and an equivalent width of W avg = 3.3 ± 0.3 mÅ. Among all planets with helium detections, TOI 2134b is the only mature mini-Neptune, has the smallest helium signal, and experiences the lowest X-ray and ultraviolet (XUV) flux. Putting TOI 2134b in the context of all other helium detections, we report the detection of a strong (p = 3.0 × 10-5) and theoretically expected correlation between F XUV/ρ XUV (proportional to the energy-limited mass-loss rate) and R * W avg (roughly proportional to the observationally inferred mass-loss rate). Here W avg is the equivalent width of the helium absorption, and ρ XUV is the density of the planet within the XUV photosphere, but the correlation is similarly strong if we use the optical photosphere. Having the lowest value on both axes, TOI 2134b anchors the relation. We encourage further observations to fill in the missing regions of this parameter space and improve estimates of F XUV.

Keywords: mini neptunes; exoplanet atmospheric evolution; exoplanet atmospheres
Spectroscopic Analysis of Milky Way Outer Halo Satellites: Aquarius II and Boötes II

In this paper, we present a chemical and kinematic analysis of two ultrafaint dwarf galaxies (UFDs), Aquarius II (Aqu II) and Boötes II (Boo II), using Magellan/IMACS spectroscopy. We present the largest sample of member stars for Boo II (12), and the largest sample of red giant branch members with metallicity measurements for Aqu II (eight). In both UFDs, over 80% of targets selected based on Gaia proper motions turned out to be spectroscopic members. In order to maximize the accuracy of stellar kinematic measurements, we remove the identified binary stars and RR Lyrae variables. For Aqu II, we measure a systemic velocity of -65.3 ± 1.8 km s-1 and a metallicity of [Fe/H] = $-{2.57}_{-0.17}^{+0.17}$ . When compared with previous measurements, these values display a ~6 km s-1 difference in radial velocity and a decrease of 0.27 dex in metallicity. Similarly for Boo II, we measure a systemic velocity of $-{130.4}_{-1.1}^{+1.4}$ km s-1, more than 10 km s-1 different from the literature, a metallicity almost 1 dex smaller at [Fe/H] = $-{2.71}_{-0.10}^{+0.11}$ , and a velocity dispersion 3 times smaller at ${\sigma }_{{v}_{\mathrm{hel}}}={2.9}_{-1.2}^{+1.6}$ km s-1. Additionally, we derive systemic proper-motion parameters and model the orbits of both UFDs. Finally, we highlight the extremely dark-matter-dominated nature of Aqu II and compute the J-factor for both galaxies to aid searches of dark matter annihilation. Despite the small size and close proximity of Boo II, it is an intermediate target for the indirect detection of dark matter annihilation due to its low-velocity dispersion and corresponding low dark matter density.

Keywords: dwarf galaxies; dark matter; stellar kinematics; milky way galaxy; spectroscopy; binary stars
Time-delay Measurement of Mg II Broad-line Response for the Highly Accreting Quasar HE 0413-4031: Implications for the Mg II-based Radius-Luminosity Relation

We present the monitoring of the active galactic nuclei continuum and Mg II broad-line emission for the quasar HE 0413-4031 (z = 1.38) based on the six-year monitoring by the South African Large Telescope (SALT). We manage to estimate a time-delay of ${302.6}_{-33.1}^{+28.7}$ days in the rest frame of the source using seven different methods: interpolated cross-correlation function, discrete correlation function (DCF), z-transformed DCF, JAVELIN, two estimators of data regularity (Von Neumann, Bartels), and χ2 method. This time-delay is below the value expected from the standard radius-luminosity relation. However, based on the monochromatic luminosity of the source and the spectral energy distribution modeling, we interpret this departure as the shortening of the time-delay due to the higher accretion rate of the source, with the inferred Eddington ratio of ∼0.4. The Mg II line luminosity of HE 0413-4031 responds to the continuum variability as ${L}_{\mathrm{line}}\propto {L}_{\mathrm{cont}}^{0.43\pm 0.10}$ , which is consistent with the light-travel distance of the location of Mg II emission at Rout ∼ 1018 cm. Using the data of 10 other quasars, we confirm the radius-luminosity relation for the broad Mg II line, which was previously determined for the broad Hβ line for lower-redshift sources. In addition, we detect a general departure of higher-accreting quasars from this relation in analogy to the Hβ sample. After the accretion-rate correction of the light-travel distance, the Mg II-based radius-luminosity relation has a small scatter of only 0.10 dex.

Keywords: radio loud quasars
ALMA Observations of the Sub-kpc Structure of the Host Galaxy of a z = 6.5 Lensed Quasar: A Rotationally Supported Hyper-Starburst System at the Epoch of Reionization

We report Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the dust continuum and [C II] emission of the host galaxy of J0439+1634, a gravitationally lensed quasar at z = 6.5. Gravitational lensing boosts the source-plane resolution to ~0"15 (~0.8 kpc). The lensing model derived from the ALMA data is consistent with the fiducial model in Fan et al. based on HST imaging. The host galaxy of J0439+1634 can be well-fitted by a Sérsic profile consistent with an exponential disk, both in the far-infrared (FIR) continuum and the [C II] emission. The overall magnification is 4.53 ± 0.05 for the continuum and 3.44 ± 0.05 for the [C II] line. The host galaxy of J0439+1634 is a compact ultraluminous infrared galaxy, with a total star formation rate (SFR) of 1.56 × 103M⊙ yr-1 after correcting for lensing and an effective radius of 0.74 kpc. The resolved regions in J0439+1634 follow the "[C II] deficit," where the [C II]-to-FIR ratio decreases with FIR surface brightness. The reconstructed velocity field of J0439+1634 appears to be rotation-like. The maximum line-of-sight rotation velocity is 130 km s-1 at a radius of 2 kpc. However, our data cannot be fit by an axisymmetric thin rotating disk, and the inclination of the rotation axis, i, remains unconstrained. We estimate the dynamical mass of the host galaxy to be $7.9{\sin }^{-2}(i)\times {10}^{9}{M}_{\odot }$ . J0439+1634 is likely to have a high gas-mass fraction and an oversized SMBH compared to local relations. The SFR of J0439+1634 reaches the maximum possible values, and the SFR surface density is close to the highest value seen in any star-forming galaxy currently known in the universe.

Keywords: quasars; galaxies
The Calibration of theta-phi Fiber Positioners Based on the Differential Evolution Algorithm

Robotic fiber positioner (RFP) arrays are commonly adopted in multiobject spectroscopic instruments. The positioning accuracy is a common but vital issue for RFP as inaccurate fiber placement may heavily affect the observation performance. The calibration of RFP can effectively improve the positioning accuracy. Least-square is a widely used calibration method. However, it has disadvantages, such as sensitivity to the initial values and calculation complexity. To improve the positioning accuracy and reduce the iteration moves, we propose a new calibration method based on the differential evolution algorithm and verify it by calibrating the RFP of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope. We first build the kinematic models of the RFP based on the Denavit–Hartenberg matrix and geometry relationship. Then, we analyze the error components and present the proposed calibration algorithms. The experiments are done with the digital universal tool microscope 19JC and the errors are calculated using the distance between the positions of achieved and target. Results show that the proposed algorithm can achieve higher accuracy than the least-square method and the average positioning accuracy is improved by 78.94% after calibration. Combined with the "pulse reduction" strategy and close-loop compensation, after two moves, the positioners can place the fiber ends within 40 μm of the intended location. The proposed calibration method is also suitable for other similar theta-phi positioners.

Keywords: astronomical instrumentation
Linear Mode Decomposition in Magnetohydrodynamics Revisited

Small-amplitude fluctuations in the magnetized solar wind are measured typically by a single spacecraft. In the magnetohydrodynamics (MHD) description, fluctuations are typically expressed in terms of the fundamental modes admitted by the system. An important question is how to resolve an observed set of fluctuations, typically plasma moments such as the density, velocity, pressure, and magnetic field fluctuations, into their constituent fundamental MHD modal components. Despite its importance in understanding the basic elements of waves and turbulence in the solar wind, this problem has not yet been fully resolved. Here, we introduce a new method that identifies between wave modes and advected structures such as magnetic islands or entropy modes and computes the phase information associated with the eligible MHD modes. The mode-decomposition method developed here identifies the admissible modes in an MHD plasma from a set of plasma and magnetic field fluctuations measured by a single spacecraft at a specific frequency and an inferred wavenumber k m . We present data from three typical intervals measured by the Wind and Solar Orbiter spacecraft at ~1 au and show how the new method identifies both propagating (wave) and nonpropagating (structures) modes, including entropy and magnetic island modes. This allows us to identify and characterize the separate MHD modes in an observed plasma parcel and to derive wavenumber spectra of entropic density, fast and slow magnetosonic, Alfvénic, and magnetic island fluctuations for the first time. These results help identify the fundamental building blocks of turbulence in the magnetized solar wind.

Keywords: solar wind
Searching for a Hypervelocity White Dwarf SN Ia Companion: A Proper-motion Survey of SN 1006

Type Ia supernovae (SNe Ia) are securely understood to come from the thermonuclear explosion of a white dwarf as a result of binary interaction, but the nature of that binary interaction and the secondary object is uncertain. Recently, a double white dwarf model known as the dynamically driven double-degenerate double-detonation (D6) model has become a promising explanation for these events. One realization of this scenario predicts that the companion may survive the explosion and reside within the remnant as a fast moving (V peculiar > 1000 km s-1), overluminous (L > 0.1 L ⊙) white dwarf. Recently, three objects that appear to have these unusual properties have been discovered in the Gaia survey. We obtained photometric observations of the SN Ia remnant SN 1006 with the Dark Energy Camera over four years to attempt to discover a similar star. We present a deep, high-precision astrometric proper-motion survey of the interior stellar population of the remnant. We rule out the existence of a high-proper-motion object consistent with our tested realization of the D6 scenario (V transverse > 600 km s-1 with m r < 21 corresponding to an intrinsic luminosity of L > 0.0176 L ⊙). We conclude that such a star does not exist within the remnant or is hidden from detection by either strong localized dust or the unlikely possibility of ejection from the binary system almost parallel to the line of sight.

Keywords: type ia supernovae; white dwarf stars; supernovae; supernova remnants; astrometry
CHAOS V: Recombination Line Carbon Abundances in M 101

The CHemical Abundances Of Spirals (CHAOS) project is building a large database of Large Binocular Telescope (LBT) H II region spectra in nearby spiral galaxies to use direct abundances to better determine the dispersion in metallicity as a function of galactic radius. Here, we present CHAOS LBT observations of C II λ4267 emission detected in 10 H II regions in M 101, and using a new photoionization model-based ionization correction factor, we convert these measurements into total carbon abundances. A comparison with M 101 C II recombination line observations from the literature shows excellent agreement, and we measure a relatively steep gradient in log(C/H) of -0.37 ± 0.06 dex ${R}_{e}^{-1}$ . The C/N observations are consistent with a constant value of log(C/N) = 0.84 with a dispersion of only 0.09 dex, which, given the different nucleosynthetic sources of C and N, is challenging to understand. We also note that when plotting N/O versus O/H, all of the H II regions with detections of C II λ4267 present N/O abundances at the minimum of the scatter in N/O at a given value of O/H. If the high surface brightness necessary for the detection of the faint recombination lines is interpreted as an indicator of H II region youth, then this may point to a lack of nitrogen pollution in the youngest H II regions. In the future, we anticipate that the CHAOS project will significantly increase the total number of C II λ4267 measurements in extragalactic H II regions.

Keywords: interstellar medium; h ii regions; chemical abundances; spiral galaxies
Constraining the Fluctuating Gunn-Peterson Approximation using Lyα Forest Tomography at z = 2

The fluctuating Gunn-Peterson approximation (FGPA) is a commonly used method to generate mock Lyα forest absorption skewers at Cosmic Noon (z ≳ 2) from the matter density field of N-body simulations without running expensive hydrodynamical simulations. Motivated by recent developments in 3D intergalactic medium (IGM) tomography observations as well as matter density field reconstruction techniques applied to galaxy redshift samples at z ~ 2, we examine the possibility of observationally testing FGPA by directly examining the relationship between Lyα transmission and the underlying matter density field. Specifically, we analyze the EAGLE, Illustris, IllustrisTNG, and Nyx cosmological hydrodynamic simulations that were run with different codes and sub-grid models. While the FGPA is an excellent description of the IGM in lower-density regions, the slope of the transmission-density distribution at higher densities is significantly affected by feedback processes causing the FGPA to break down in that regime. Even without added feedback, we find significant deviations caused by hydrodynamical effects arising from nonlinear structure growth. We then proceed to make comparisons using realistic mock data assuming the sightline sampling and spectral properties of the recent CLAMATO survey, and find that it would be challenging to discern between the FGPA and hydrodynamical models with current data sets. However, the improved sightline sampling from future extremely large telescopes or large volumes from multiplexed spectroscopic surveys such as Subaru PFS should allow for stringent tests of the FGPA, and make it possible to detect the effect of galaxy feedback on the IGM.

Keywords: intergalactic medium; lyman alpha forest; hydrodynamical simulations
The Hard-to-soft Transition of GX 339-4 as Seen by Insight-HXMT

We present an analysis of the relativistic reflection spectra of GX 339-4 during the hard-to-soft transition of its 2021 outburst observed by Insight-HXMT. The strong relativistic reflection signatures in the data suggest a high black hole spin (a * > 0.86) and an intermediate disk inclination angle (i ≈ 35°-43°) of the system. The transition is accompanied by an increasing temperature of the disk and a softening of the corona emission, while the inner disk radius remains stable. Assuming a lamppost geometry, the corona height is also found to stay close to the black hole across the state transition. If we include the Comptonization of the reflection spectrum, the scattering fraction parameter is found to decrease during the state transition. We also perform an analysis with a reflection model designed for hot accretion disks of stellar mass black holes where the surface of the innermost accretion disk is illuminated by emission from the corona and the thermal disk below. Our results support the scenario in which the state transition is associated with variations in the corona properties.

Keywords: astrophysical black holes; stellar mass black holes; x-ray astronomy; x-ray sources
The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda

The inner kiloparsec regions surrounding sub-Eddington (luminosity less than 10-3 in Eddington units, L Edd) supermassive black holes (BHs) often show a characteristic network of dust filaments that terminate in a nuclear spiral in the central parsecs. Here we study the role and fate of these filaments in one of the least accreting BHs known, M31 (10-7 L Edd) using hydrodynamical simulations. The evolution of a streamer of gas particles moving under the barred potential of M31 is followed from kiloparsec distance to the central parsecs. After an exploratory study of initial conditions, a compelling fit to the observed dust/ionized gas morphologies and line-of-sight velocities in the inner hundreds of parsecs is produced. After several million years of streamer evolution, during which friction, thermal dissipation, and self-collisions have taken place, the gas settles into a disk tens of parsecs wide. This is fed by numerous filaments that arise from an outer circumnuclear ring and spiral toward the center. The final configuration is tightly constrained by a critical input mass in the streamer of several 103 M ☉ (at an injection rate of 10-4 ${M}_{\odot }\,{{\rm{yr}}}^{-1}$ ); values above or below this lead to filament fragmentation or dispersion respectively, which are not observed. The creation of a hot gas atmosphere in the region of ~106 K is key to the development of a nuclear spiral during the simulation. The final inflow rate at 1 pc from the center is ~1.7 × 10-7 M ☉ yr-1, consistent with the quiescent state of the M31 BH.

Keywords: interstellar medium; andromeda galaxy; supermassive black holes; interstellar filaments; astronomical simulations; hydrodynamical simulations