adsabs/SciX_UAT_keywords huggingface dataset:
The Simons Observatory: Galactic Science Goals and Forecasts

Observing in six frequency bands from 27 to 280 GHz over a large sky area, the Simons Observatory (SO) is poised to address many questions in Galactic astrophysics in addition to its principal cosmological goals. In this work, we provide quantitative forecasts on astrophysical parameters of interest for a range of Galactic science cases. We find that SO can: constrain the frequency spectrum of polarized dust emission at a level of Δβ d ≲ 0.01 and thus test models of dust composition that predict that β d in polarization differs from that measured in total intensity; measure the correlation coefficient between polarized dust and synchrotron emission with a factor of two greater precision than current constraints; exclude the nonexistence of exo-Oort clouds at roughly 2.9σ if the true fraction is similar to the detection rate of giant planets; map more than 850 molecular clouds with at least 50 independent polarization measurements at 1 pc resolution; detect or place upper limits on the polarization fractions of CO(2-1) emission and anomalous microwave emission at the 0.1% level in select regions; and measure the correlation coefficient between optical starlight polarization and microwave polarized dust emission in 1° patches for all lines of sight with N H ≳ 2 × 1020 cm-2. The goals and forecasts outlined here provide a roadmap for other microwave polarization experiments to expand their scientific scope via Milky Way astrophysics. 37 37 A supplement describing author contributions to this paper can be found at https://simonsobservatory.org/wp-content/uploads/2022/02/SO_GS_Contributions.pdf.

Keywords: interstellar medium; interstellar magnetic fields; interstellar molecules; interstellar dust; polarimetry; interstellar synchrotron emission; oort cloud objects; cosmic microwave background radiation; magnetohydrodynamics; starlight polarization
High Molecular Gas Masses in Absorption-selected Galaxies at z ≈ 2

We have used the Atacama Large Millimeter/submillimeter Array (ALMA) to carry out a search for CO (3-2) or (4-3) emission from the fields of 12 high-metallicity ([M/H] ≥ -0.72 dex) damped Lyα absorbers (DLAs) at z ≈ 1.7-2.6. We detected CO emission from galaxies in the fields of five DLAs (two of which have been reported earlier), obtaining high molecular gas masses, ${M}_{\mathrm{mol}}\approx (1.3\mbox{--}20.7)\times ({\alpha }_{\mathrm{CO}}/4.36)\times {10}^{10}\ {M}_{\odot }$ . The impact parameters of the CO emitters to the QSO sight line lie in the range b ≈ 5.6-100 kpc, with the three new CO detections having $b\lesssim 15\,\mathrm{kpc}$ . The highest CO line luminosities and inferred molecular gas masses are associated with the highest-metallicity DLAs, with [M/H] ≳ -0.3 dex. The high inferred molecular gas masses may be explained by a combination of a stellar mass-metallicity relation and a high molecular gas-to-star mass ratio in high-redshift galaxies; the DLA galaxies identified by our CO searches have properties consistent with those of emission-selected samples. None of the DLA galaxies detected in CO emission were identified in earlier optical or near-IR searches and vice versa; DLA galaxies earlier identified in optical/near-IR searches were not detected in CO emission. The high ALMA CO and C[II] 158 μm detection rate in high-z, high-metallicity DLA galaxies has revolutionized the field, allowing the identification of dusty, massive galaxies associated with high-z DLAs. The H I-absorption criterion identifying DLAs selects the entire high-z galaxy population, including dusty and UV-bright galaxies, in a wide range of environments.

Keywords: high-redshift galaxies; damped lyman-alpha systems; molecular gas
Cosmological Model-independent Constraints on Spatial Curvature from Strong Gravitational Lensing and SN Ia Observations

Applying the distance sum rule in strong gravitational lensing (SGL) and SN Ia observations, one can provide an interesting cosmological model-independent method to determine the cosmic curvature parameter Ωk. In this paper, with the newly compiled data sets including 161 galactic-scale SGL systems and 1048 SN Ia data, we place constraints on Ωk within the framework of three types of lens models extensively used in SGL studies. Moreover, to investigate the effect of different mass lens samples on the results, we divide the SGL sample into three subsamples based on the center velocity dispersion of intervening galaxies. In the singular isothermal sphere (SIS) and extended power-law lens models, a flat universe is supported with an uncertainty of about 0.2, while a closed universe is preferred in the power-law lens model. We find that the choice of lens models and the classification of SGL data actually can influence the constraints on Ωk significantly.

Keywords: strong gravitational lensing; cosmological parameters; cosmology; gravitational lensing
The Spitzer-HETDEX Exploratory Large-Area Survey. IV. Model-based Multiwavelength Photometric Catalog

We present a 0.3-4.5 μm 16-band photometric catalog for the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers an ~27 deg2 field within the footprint of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). Here we present new DECam imaging and an rizK s band-selected catalog of four million sources extracted using a fully model-based approach. We validate our photometry by comparing with the model-based DECam Legacy Survey. We analyze the differences between model-based and aperture photometry by comparing with the previous SHELA catalog, finding that our model-based photometry can measure point sources to fainter fluxes and better capture the full emission of resolved sources. The catalog is 80% (50%) complete at riz ~ 24.7 (25.1) AB mag, and the optical photometry reaches a 5σ depth of ~25.5 AB mag. We measure photometric redshifts and achieve a 1σ scatter of Δz/(1 + z) of 0.04 with available spectroscopic redshifts at 0 ≤ z ≤ 1. This large-area, multiwavelength photometric catalog, combined with spectroscopic information from HETDEX, will enable a wide range of extragalactic science investigations.

Keywords: surveys; catalogs; galaxies; photometry
First-principles-integrated Study of Blazar Synchrotron Radiation and Polarization Signatures from Magnetic Turbulence

Blazar emission is dominated by nonthermal radiation processes that are highly variable across the entire electromagnetic spectrum. Turbulence, which can be a major source of nonthermal particle acceleration, can widely exist in the blazar emission region. The Turbulent Extreme Multi-Zone (TEMZ) model has been used to describe turbulent radiation signatures. Recent particle-in-cell (PIC) simulations have also revealed the stochastic nature of the turbulent emission region and particle acceleration therein. However, radiation signatures have not been systematically studied via first-principles-integrated simulations. In this paper, we perform combined PIC and polarized radiative transfer simulations to study synchrotron emission from magnetic turbulence in the blazar emission region. We find that the multiwavelength flux and polarization are generally characterized by stochastic patterns. Specifically, the variability timescale and average polarization degree (PD) are governed by the correlation length of the turbulence. Interestingly, magnetic turbulence can result in polarization angle swings with arbitrary amplitudes and duration, in either direction, that are not associated with changes in flux or PD. Surprisingly, these swings, which are stochastic in nature, can appear either bumpy or smooth, although large-amplitude swings (>180°) are very rare, as expected. Our radiation and polarization signatures from first-principles-integrated simulations are consistent with the TEMZ model, except that in the latter, there is a weak correlation, with zero lag, between flux and degree of polarization.

Keywords: blazars; spectropolarimetry; plasma astrophysics; non-thermal radiation sources
A Reemerging Bright Soft X-Ray State of the Changing-look Active Galactic Nucleus 1ES 1927+654: A Multiwavelength View

1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio variability of the source in its postflare state (2022 January-2023 May). First, we detect an increase in the soft X-ray (0.3-2 keV) flux from 2022 May to 2023 May by almost a factor of 5, which we call the bright soft state. The hard X-ray 2-10 keV flux increased by a factor of 2, while the UV flux density did not show any significant changes (≤30%) in the same period. The integrated energy pumped into the soft and hard X-rays during this period of 11 months is ~3.57 × 1050 erg and 5.9 × 1049 erg, respectively. From the energetics, it is evident that whatever is producing the soft excess (SE) is pumping out more energy than either the UV or hard X-ray source. Since the energy source presumably is ultimately the accretion of matter onto the supermassive black hole, the SE-emitting region must be receiving the majority of this energy. In addition, the source does not follow the typical disk-corona relation found in AGNs, neither in the initial flare (from 2017 to 2019) nor in the current bright soft state (2022-2023). We found that the core (<1 pc) radio emission at 5 GHz gradually increased until 2022 March, but showed a dip in 2022 August. The Güdel-Benz relation (L radio/L X-ray ~ 10-5), however, is still within the expected range for radio-quiet AGNs, and further follow-up radio observations are currently being undertaken.

Keywords: active galactic nuclei; x-ray active galactic nuclei; seyfert galaxies
Multidimensional Parameter Study of Double Detonation Type Ia Supernovae Originating from Thin Helium Shell White Dwarfs

Despite the importance of Type Ia supernovae (SNe Ia) throughout astronomy, the precise progenitor systems and explosion mechanisms that drive SNe Ia are still unknown. An explosion scenario that has gained traction recently is double detonation, in which an accreted shell of He detonates and triggers a secondary detonation in the underlying white dwarf. Our research presents a number of high-resolution, multidimensional, full-star simulations of thin-He-shell, sub-Chandrasekhar-mass white dwarf progenitors that undergo a double detonation. This suite of thin-shell progenitors incorporates He shells that are thinner than those in previous multidimensional studies. We confirm the viability of the double detonation across a range of He-shell parameter space, as well as present bulk yields and ejecta profiles for each progenitor. The yields obtained are generally consistent with previous works and indicate the likelihood of producing observables that resemble SNe Ia. The dimensionality of our simulations allow us to examine features of the double detonation more closely, including the details of the off-center secondary ignition and asymmetric ejecta. We find considerable differences in the high-velocity extent of postdetonation products across different lines of sight. The data from this work will be used to generate predicted observables and may further support the viability of the double detonation scenario as an SN Ia channel, as well as show how the properties of the progenitor or viewing angle may influence trends in observable characteristics.

Keywords: type ia supernovae; white dwarf stars; supernova dynamics; explosive nucleosynthesis
Is there a Radio Excess from the Decoupling of Pre-recombination Bremsstrahlung?

Recently it has been suggested that thermal bremsstrahlung emission, when it decouples prior to recombination, creates an excess over the Planck cosmic microwave background spectrum at sub-GHz frequencies. Remarkable by itself, this would also explain a long-standing unexplained deficit in the predictions of the extragalactic radio background. In this brief note, I reiterate that no such non-thermal component can arise by itself when matter and radiation remain kinetically coupled.

Keywords: cosmic microwave background radiation; radiative processes
870 μm Dust Continuum of the Youngest Protostars in Ophiuchus

We present a 0.15 arcsec resolution (21 au) ALMA 870 μm continuum survey of 25 pointings containing 31 young stellar objects in the Ophiuchus molecular clouds. Using the dust continuum as a proxy for dust mass and circumstellar disk radius in our sample, we report mean masses of ${2.8}_{-1.3}^{+2.1}$ and ${2.5}_{-1.1}^{+9.2}$ M⊕ and mean radii of ${23.5}_{-1.2}^{+1.8}$ and ${16.5}_{-0.9}^{+2.8}$ au, for Class I and Flat spectrum protostars, respectively. In addition, we calculate the multiplicity statistics of the dust surrounding young stellar objects in Ophiuchus. The multiplicity fraction and companion star fraction of the combined Class I and Flats based solely on this work are 0.25 ± 0.09 and 0.33 ± 0.10, respectively, which are consistent with the values for Perseus and Orion. While we see clear differences in mass and radius between the Ophiuchus and Perseus/Orion protostellar surveys, we do not see any significant differences in the multiplicities of the various regions. We posit that there are some differences in the conditions for star formation in Ophiuchus that strongly affect disk size (and consequently disk mass), but does not affect system multiplicity, which could imply important variation in planet formation processes.

Keywords: young stellar objects; radio interferometry; protoplanetary disks; pre-main sequence stars
Kinematic Evidence for an Embedded Planet in the IM Lupi Disk

We test the hypothesis that an embedded giant planet in the IM Lupi protostellar disk can produce velocity kinks seen in CO line observations as well as the spiral arms seen in scattered light and continuum emission. We inject planets into 3D hydrodynamics simulations of IM Lupi, generating synthetic observations using Monte Carlo radiative transfer. We find that an embedded planet of 2-3 M Jup can reproduce non-Keplerian velocity perturbations, or "kinks", in the 12CO J = 2-1 channel maps. Such a planet can also explain the spiral arms seen in 1.25 mm dust continuum emission and 1.6 μm scattered-light images. We show that the wake of the planet can be traced in the observed peak velocity map, which appears to closely follow the morphology expected from our simulations and from analytic models of planet-disk interaction.

Keywords: exoplanet formation; exoplanet migration; protoplanetary disks; planet formation; circumstellar disks; hydrodynamical simulations; planetary-disk interactions
Solar Radio Burst Detection Based on the MobileViT-SSDLite Lightweight Model

Real-time detection of solar radio bursts is crucial in solar physics research and space weather forecasting. However, current research on the automatic detection of solar radio bursts is limited to identifying the presence or absence of solar radio bursts or recognizing only a single type of burst, such as type II or III. Furthermore, existing methods cannot learn spectral and temporal features and often suffer from the drawbacks of large network models, resulting in slow speeds. This paper proposes an automatic recognition and localization method based on a lightweight object detection model for solar radio burst events. We collected observation data from e-CALLISTO and established a data set containing type II, III, IV, and V solar radio bursts. To address the real-time requirements of practical applications and consider the temporal and frequency domain information of spectrogram images, we improved a vision transformer with a self-attention mechanism and adopted a lightweight model for detection. The experimental results demonstrate that our proposed method achieves an average precision at a 50% intersection-over-union threshold of 78.2% and a recall rate of 92% on the established solar radio burst data set. Additionally, the model operates at a detection speed of 54.8 frames s-1, where a frame refers to a spectral image with a duration of 15 minutes, enabling efficient automated detection and localization of type II, III, IV, and V solar radio bursts.

Keywords: neural networks; solar physics; detection
Quantifying Non-parametric Structure of High-redshift Galaxies with Deep Learning

At high redshift, due to both observational limitations and the variety of galaxy morphologies in the early universe, measuring galaxy structure can be challenging. Non-parametric measurements such as the CAS system have thus become an important tool due to both their model-independent nature and their utility as a straightforward computational process. Recently, convolutional neural networks (CNNs) have been shown to be adept at image analysis, and are beginning to supersede traditional measurements of visual morphology and model-based structural parameters. In this work, we take a further step by extending CNNs to measure well known non-parametric structural quantities: concentration (C) and asymmetry (A). We train CNNs to predict C and A from individual images of ~150,000 galaxies at 0 < z < 7 in the CANDELS fields, using Bayesian hyperparameter optimization to select suitable network architectures. Our resulting networks accurately reproduce measurements compared with standard algorithms. Furthermore, using simulated images, we show that our networks are more stable than the standard algorithms at low signal-to-noise. While both approaches suffer from similar systematic biases with redshift, these remain small out to z ~ 7. Once trained, measurements with our networks are >103 times faster than previous methods. Our approach is thus able to reproduce standard measures of non-parametric morphologies and shows the potential of employing neural networks to provide superior results in substantially less time. This will be vital for making best use of the large and complex data sets provided by upcoming galaxy surveys, such as Euclid and Rubin-LSST.

Keywords: high-redshift galaxies; galaxies; convolutional neural networks
The Relative Role of Bars and Galaxy Environments in AGN Triggering of SDSS Spirals

We quantify the relative role of galaxy environment and bar presence on AGN triggering in face-on spiral galaxies using a volume-limited sample with 0.02 < z < 0.055, Mr < 19.5, and σ > 70 $\,\mathrm{km}\,{{\rm{s}}}^{-1}$ selected from Sloan Digital Sky Survey (SDSS) Data Release 7. To separate their possible entangled effects, we divide the sample into bar and non-bar samples, and each sample is further divided into three environment cases of isolated galaxies, interacting galaxies with a pair, and cluster galaxies. The isolated case is used as a control sample. For these six cases, we measure AGN fractions at a fixed central star formation rate and central velocity dispersion, σ. We demonstrate that the internal process of the bar-induced gas inflow is more efficient in AGN triggering than the external mechanism of the galaxy interactions in groups and cluster outskirts. The significant effects of bar instability and galaxy environments are found in galaxies with a relatively less massive bulge. We conclude that from the perspective of AGN-galaxy coevolution, a massive black hole is one of the key drivers of spiral galaxy evolution. If it is not met, a bar instability helps the evolution, and in the absence of bars, galaxy interactions/mergers become important. In other words, in the presence of a massive central engine, the role of the two gas inflow mechanisms is reduced or almost disappears. We also find that bars in massive galaxies are very decisive in increasing AGN fractions when the host galaxies are inside clusters.

Keywords: galaxy evolution; galaxy nuclei; galaxy quenching; galaxy interactions; galaxy clusters
Calibrating X-Ray Binary Luminosity Functions via Optical Reconnaissance. II. The High-mass XLF and Globular Cluster Population of X-Ray Binaries in the Low Star-forming Spiral M81

We characterize the optical counterparts to the compact X-ray source population within the nearby spiral galaxy M81 using multiband Hubble Space Telescope (HST) imaging data. By comparing the optical luminosities and colors measured for candidate donor stars and host clusters to stellar and cluster evolutionary models, respectively, we estimate the likely masses and upper age limits of the field and cluster X-ray binaries. We identify 15 low-mass X-ray binaries (i.e., donor star mass ≲ 3 M ⊙) within ancient globular clusters, as well as 42 candidate high-mass X-ray binaries (i.e., donor star mass ≳ 8 M ⊙). To estimate the likelihood of misclassifications, we inject 4000 artificial sources into the HST mosaic image and conclude that our classifications of globular clusters and high-mass X-ray binaries are reliable at the >90% level. We find that globular clusters that host X-ray binaries are on average more massive and more compact than globular clusters that do not. However, there is no apparent correlation between the X-ray brightness of the clusters and their masses or densities, nor are X-ray binary hosts more X-ray luminous than the general field population of low-mass X-ray binaries. This work represents one of the first in-depth analyses of the population of X-ray binaries within globular clusters in a spiral galaxy.

Keywords: x-ray binary stars; globular star clusters
Limitations of the Ca II 8542 Å Line for the Determination of Magnetic Field Oscillations

Chromospheric umbral oscillations produce periodic brightenings in the core of some spectral lines, known as umbral flashes. They are also accompanied by fluctuations in velocity, temperature, and, according to several recent works, magnetic field. In this study, we aim to ascertain the accuracy of the magnetic field determined from inversions of the Ca II 8542 Å line. We have developed numerical simulations of wave propagation in a sunspot umbra. Synthetic Stokes profiles emerging from the simulated atmosphere were computed and then inverted using the NICOLE code. The atmospheres inferred from the inversions have been compared with the original parameters from the simulations. Our results show that the inferred chromospheric fluctuations in velocity and temperature match the known oscillations from the numerical simulation. In contrast, the vertical magnetic field obtained from the inversions exhibits an oscillatory pattern with a ~300 G peak-to-peak amplitude, which is absent in the simulation. We have assessed the error in the inferred parameters by performing numerous inversions with slightly different configurations of the same Stokes profiles. We find that when the atmosphere is approximately at rest, the inversion tends to favor solutions that underestimate the vertical magnetic field strength. On the contrary, during umbral flashes, the values inferred from most of the inversions are concentrated at stronger fields than those from the simulation. Our analysis provides a quantification of the errors associated with the inversions of the Ca II 8542 Å line and suggests caution with the interpretation of the inferred magnetic field fluctuations.

Keywords: solar chromosphere; sunspots; solar atmosphere; solar oscillations; computational methods