adsabs/SciX_UAT_keywords huggingface dataset:
The Dark Energy Camera Plane Survey 2 (DECaPS2): More Sky, Less Bias, and Better Uncertainties

Deep optical and near-infrared imaging of the entire Galactic plane is essential for understanding our Galaxy's stars, gas, and dust. The second data release of the Dark Energy Camera (DECam) Plane Survey extends the five-band optical and near-infrared survey of the southern Galactic plane to cover 6.5% of the sky, ∣b∣ ≤ 10°, and 6° > ℓ > -124°, complementary to coverage by Pan-STARRS1. Typical single-exposure effective depths, including crowding effects and other complications, are 23.5, 22.6, 22.1, 21.6, and 20.8 mag in g, r, i, z, and Y bands, respectively, with around 1″ seeing. The survey comprises 3.32 billion objects built from 34 billion detections in 21,400 exposures, totaling 260 hr open shutter time on the DECam at Cerro Tololo. The data reduction pipeline features several improvements, including the addition of synthetic source injection tests to validate photometric solutions across the entire survey footprint. A convenient functional form for the detection bias in the faint limit was derived and leveraged to characterize the photometric pipeline performance. A new postprocessing technique was applied to every detection to debias and improve uncertainty estimates of the flux in the presence of structured backgrounds, specifically targeting nebulosity. The images and source catalogs are publicly available at http://decaps.skymaps.info/.

Keywords: astronomy data reduction; catalogs; sky surveys
A Simple Code for Rotational Broadening of Broad Wavelength Range High-Dispersion Spectra

In high dispersion spectra of rotating bodies such as stars and planets, the rotation contributes significantly to, and sometimes dominates, the line broadening. We present a simple method for rotationally broadening large wavelength ranges of high-dispersion spectra. The broadening is rapid and scales linearly with the length of the spectrum array. For large wavelength ranges, the method is much faster than the popular convolution-based broadening. We provide the code implementation of this method in a publicly accessible repository.

Keywords: high resolution spectroscopy; stellar rotation; astronomy data modeling
Kinematic Structure of the Large Magellanic Cloud Globular Cluster System from Gaia eDR3 and Hubble Space Telescope Proper Motions

We have determined bulk proper motions (PMs) for 31 LMC GCs from Gaia eDR3 and Hubble Space Telescope data using multiple independent analysis techniques. Combined with literature values for distances, line-of-sight velocities, and existing bulk PMs, we extract full 6D phase-space information for 32 clusters, allowing us to examine the kinematics of the LMC GC system in detail. Except for two GCs (NGC 2159 and NGC 2210) whose high velocities suggest they are not long-term members of the LMC system, the data are consistent with a flattened configuration that rotates like the stellar disk. The one-dimensional velocity dispersions are on the order of 30 km s-1, similar to that of old stellar populations in the LMC disk. Similarly to the case for Milky Way disk clusters, the velocity anisotropy is such that the dispersion is smallest in the azimuthal direction; however, alternative anisotropies cannot be ruled out, due to distance uncertainties. The data are consistent with a single multidimensional Gaussian velocity distribution. Given the non-collisional nature of the LMC disk, this suggests that most, if not all, of the LMC GCs are formed by a single formation mechanism in the stellar disk, despite a significant spread in age and metallicity. Any accreted halo GC population is absent or far smaller in the LMC compared to the Milky Way.

Keywords: proper motions; large magellanic cloud; globular star clusters
Universal Conditional Distribution Function of [O II] Luminosity of Galaxies, and Prediction for the [O II] Luminosity Function at Redshift z < 3

The star-forming emission line galaxies (ELGs) with a strong [O II] doublet are one of the main spectroscopic targets for the ongoing and upcoming fourth-generation galaxy redshift surveys. In this work, we measure the [O II] luminosity L[O II] and the absolute magnitude in the near-ultraviolet (NUV) band MNUV for a large sample of galaxies in the redshift range 0.6 ≤ z < 1.45 from the Public Data Release 2 (PDR-2) of the VIMOS Public Extragalactic Redshift Survey (VIPERS). We aim to construct the intrinsic relationship between L[O II] and MNUV through Bayesian analysis. In particular, we develop two different methods to properly correct for the incompleteness effect and observational errors in the [O II] emission line measurement. Our results indicate that the conditional distribution of L[O II] at a given MNUV can be well described by a universal probability distribution function (PDF), which is independent of MNUV and redshift. Convolving the L[O II] conditional PDF with the NUV luminosity function (LF) available in the literature, we make a prediction for [O II] LFs at z < 3. The predicted [O II] LFs are in good agreement with the observational results from the literature. Finally, we utilize the predicted [O II] LFs to estimate the number counts of [O II] emitters for the Subaru Prime Focus Spectrograph survey. This universal conditional PDF of L[O II] provides a novel way to optimize the source targeting strategy for [O II] emitters in future galaxy redshift surveys, and to model [O II] emitters in theories of galaxy formation.

Keywords: emission line galaxies; luminosity function; redshift surveys; dark energy
Model-independent Estimation of H0 and ΩK from Strongly Lensed Fast Radio Bursts

Model-independent estimation of H0 and ΩK can provide clues about the origin of the intractable Hubble constant tension and the current cosmic-curvature crisis. Strongly lensed fast radio bursts (FRBs) have been proposed as precision probes of the universe since the time delay ~ ${ \mathcal O }$ (10 days) between images could be precisely measured due to short durations ~ ${ \mathcal O }({ms})$ of this kind of bright radio pulses. Here, on the basis of the distance sum rule, we investigate the capacity of model-independently estimating these two parameters from time-delay distances of strongly lensed FRBs and luminosity distances of the upcoming Wide Field InfraRed Survey Telescope (WFIRST) type Ia supernovae observations. Considering the expected FRB detection rate of upcoming facilities, we find that H0 could be determined to a ~1% precision and ΩK could be constrained to ~0.1 simultaneously from 10 lensed FRBs. These estimations, which are independent of the energy contents of the universe and validity of Einstein's equation on cosmological scales, will be complementary to popular probes and of great importance for clarifying the current crises of cosmology.

Keywords: strong gravitational lensing; cosmological parameters; radio bursts
Dynamical Effects of Cosmic Rays on the Medium Surrounding Their Sources

Cosmic rays (CRs) leave their sources mainly along the local magnetic field; in doing so they excite both resonant and nonresonant modes through streaming instabilities. The excitation of these modes leads to enhanced scattering and in turn to a large pressure gradient that causes the formation of bubbles of gas, CRs, and self-generated magnetic fields expanding into the interstellar medium. By means of hybrid particle-in-cell simulations, we show that, by exciting the nonresonant instability, CRs excavate a cavity around their source where the diffusivity is strongly suppressed. This finding invalidates the so far largely adopted flux-tube assumption, under which particles move along magnetic lines even in the nonlinear regime. This phenomenon is general and is expected to occur around any sufficiently powerful CR source in the Galaxy. Our results might provide a physical explanation of the numerous claims of suppressed CR diffusion around Galactic sources such as supernova remnants, pulsar wind nebulae, and stellar clusters.

Keywords: cosmic ray sources; magnetic fields; cosmic rays
The Host Galaxy of OJ 287 Revealed by Optical and Near-infrared Imaging

The BL Lacertae object OJ 287 (z = 0.306) has unique double-peaked optical outbursts every ∼12 yr, and it presents one of the best cases for a small-separation binary supermassive black hole (SMBH) system, with an extremely massive primary $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })\sim 10.3$ . However, the host galaxy is unresolved or only marginally detected in all optical studies so far, indicating a large deviation from the bulge mass—SMBH mass relation. We have obtained deep, high spatial resolution i-band and K-band images of OJ 287 when the target was in a low state, which enable us to detect the host galaxy. We find the broadband photometry of the host to be consistent with an early-type galaxy with MR = -22.5 and MK = -25.2, placing it in the middle of the host galaxy luminosity distribution of BL Lacertae objects. The central supermassive black hole is clearly overmassive for a host galaxy of that luminosity, but not unprecedented, given some recent findings of other "overmassive" black holes in nearby galaxies.

Keywords: elliptical galaxies; agn host galaxies; bl lacertae objects; supermassive black holes
Time-variable Jet Ejections from RW Aur A, RY Tau, and DG Tau

We present Gemini-NIFS, Very Large Telescope-SINFONI, and Keck-OSIRIS observations of near-IR [Fe II] emission that are associated with well-studied jets from three active T Tauri stars-RW Aur A, RY Tau, and DG Tau-taken from 2012 to 2021. We primarily cover the redshifted jet from RW Aur A and the blueshifted jets from RY Tau and DG Tau, in order to investigate long-term time variabilities that are potentially related to the activities of mass accretion and/or the stellar magnetic fields. All of these jets consist of several moving knots, with tangential velocities of 70-240 km s-1, which were ejected from the star with different velocities and at irregular time intervals. Via comparisons with the literature, we identify significant differences in the tangential velocities between 1985-2008 and 2008-2021 for the DG Tau jet. The sizes of the individual knots appear to increase with time, and, in turn, their peak brightnesses in the 1.644 μm emission decreased by up to a factor of ~30 during the epochs of our observations. The variety of decay timescales measured in the [Fe II] 1.644 μm emission could be attributed to different preshock conditions should the moving knots be unresolved shocks. However, our data do not exclude the possibility that these knots are due to nonuniform density/temperature distributions with another heating mechanism, or, in some cases, due to stationary shocks without proper motions. Spatially resolved observations of these knots with significantly higher angular resolutions will be necessary to better understand their physical nature. * Based on observations obtained at the Gemini Observatory, the European Southern Observatory (under ESO program 2100.C-5015), and the W. M. Keck Observatory.

Keywords: stellar jets; t tauri stars
Scientific CMOS Sensors in Astronomy: IMX455 and IMX411

Scientific complementary metal-oxide-semiconductor (CMOS) detectors have developed quickly in recent years thanks to their low cost and high availability. They also have some advantages over charge-coupled devices (CCDs), such as high frame rate or typically lower readout noise. These sensors started to be used in astronomy following the development of the first back-illuminated models. Therefore, it is worth studying their characteristics, advantages, and weaknesses. One of the most widespread CMOS sensors are those from the Sony IMX series, which are included in large astronomical survey projects based on small and fast telescopes because of their low cost, and capability for wide-field and high-cadence surveys. In this paper, we aim to characterize the IMX455M and IMX411M sensors, which are integrated into the QHY600 and QHY411 cameras, respectively, for use in astronomical observations. These are large (36 × 24 and 54 × 40 mm) native 16 bit sensors with 3.76 μm pixels and are sensitive in the optical range. We present the results of the laboratory characterization of both cameras. They showed a very low dark current of 0.011 and 0.007 e- px-1 s-1 @-10°C for the QHY600 and QHY411 cameras, respectively. They also show the presence of warm pixels, ~0.024% in the QHY600 and 0.005% in the QHY411. Warm pixels proved to be stable and linear with exposure time, and are therefore easily corrected using dark frames. Pixels affected by the Salt & Pepper noise are ~2% of the total and a method to correct for this effect is presented. Both cameras were attached to night telescopes and several on-sky tests were performed to prove their capabilities. On-sky tests demonstrate that these CMOS behave as well as CCDs of similar characteristics and (for example) they can attain photometric accuracies of a few mili-magnitudes.

Keywords: astronomical detectors; astronomical instrumentation
Galactic Interstellar Sulfur Isotopes: A Radial 32S/34S Gradient?

We present observations of 12C32S, 12C34S, 13C32S, and 12C33S J = 2-1 lines toward a large sample of massive star-forming regions by using the Arizona Radio Observatory 12 m telescope and the IRAM 30 m. Taking new measurements of the carbon 12C/13C ratio, the 32S/34S isotope ratio was determined from the integrated 13C32S/12C34S line intensity ratios for our sample. Our analysis shows a 32S/34S gradient from the inner Galaxy out to a galactocentric distance of 12 kpc. An unweighted least-squares fit to our data yields 32S/34S = (1.56 ± 0.17)DGC + (6.75 ± 1.22) with a correlation coefficient of 0.77. Errors represent 1σ standard deviations. Testing this result by (a) excluding the Galactic center region, (b) excluding all sources with C34S opacities >0.25, (c) combining our data and old data from previous study, and (d) using different sets of carbon isotope ratios leads to the conclusion that the observed 32S/34S gradient is not an artifact but persists irrespective of the choice of sample and carbon isotope data. A gradient with rising 32S/34S values as a function of galactocentric radius implies that the solar system ratio should be larger than that of the local interstellar medium. With the new carbon isotope ratios, we indeed obtain a local 32S/34S isotope ratio about 10% below the solar system one, as expected in the case of decreasing 32S/34S ratios with time and increased amounts of stellar processing. However, taking older carbon isotope ratios based on a lesser amount of data, such a decrease is not seen. No systematic variation of 34S/33S ratios along galactocentric distance was found. The average value is 5.9 ± 1.5, the error denoting the standard deviation of an individual measurement.

Keywords: interstellar medium; stellar nucleosynthesis; abundance ratios; radio astronomy; stellar abundances; galaxy chemical evolution; interstellar molecules; milky way galaxy
Improving z ∼ 7-11 Galaxy Property Estimates with JWST/NIRCam Medium-band Photometry

The past decade has seen impressive progress in the detection of z > 7 galaxies with the Hubble Space Telescope; however, little is known about their properties. The James Webb Space Telescope will revolutionize the high-z field by providing near-IR (i.e., rest-frame optical) data of unprecedented depth and spatial resolution. Measuring galaxy quantities such as resolved stellar ages or gas metallicity gradients traditionally requires spectroscopy, as broadband imaging filters are generally too coarse to fully isolate diagnostics such as the 4000 Å (rest-frame) break, continuum emission from aged stars, and key emission lines (e.g., [O II], [O III], Hβ). However, in this paper, we show that adding NIRCam images through a strategically chosen medium-band filter to common wide-band filter sets adopted by ERS and GTO programs delivers tighter constraints on these galactic properties. To constrain the choice of filter, we perform a systematic investigation of which combinations of wide-band filters from ERS and GTO programs and single medium-band filters offer the tightest constraints on several galaxy properties at redshifts z ∼ 7-11. We employ the JAGUAR extragalactic catalogs to construct statistical samples of physically motivated mock photometry and conduct SED-fitting procedures to evaluate the accuracy of galaxy property (and photo-z) recovery with a simple star formation history model. We find that adding >4.1 μm medium filters at comparable depth to the broadband filters can significantly improve photo-zs and yield close to order-of-magnitude improvements in the determination of quantities such as stellar ages, metallicities, SF-related quantities, and emission-line fluxes at z ∼ 8. For resolved sources, the proposed approach enables the spatially resolved determination of these quantities that would be prohibitive with slit spectroscopy.

Keywords: reionization; galaxy evolution; high-redshift galaxies; galaxy photometry; star formation
Improved Orbital Constraints and Hα Photometric Monitoring of the Directly Imaged Protoplanet Analog HD 142527 B

Companions embedded in the cavities of transitional circumstellar disks have been observed to exhibit excess luminosity at Hα, an indication that they are actively accreting. We report 5 yr (2013-2018) of monitoring of the position and Hα excess luminosity of the embedded, accreting low-mass stellar companion HD 142527 B from the MagAO/VisAO instrument. We use pyklip, a Python implementation of the Karhunen-Loeve Image Processing algorithm, to detect the companion. Using pyklip forward modeling, we constrain the relative astrometry to 1-2 mas precision and achieve sufficient photometric precision (±0.2 mag, 3% error) to detect changes in the Hα contrast of the companion over time. In order to accurately determine the relative astrometry of the companion, we conduct an astrometric calibration of the MagAO/VisAO camera against 20 yr of Keck/NIRC2 images of the Trapezium cluster. We demonstrate agreement of our VisAO astrometry with other published positions for HD 142527 B, and use orbitize! to generate a posterior distribution of orbits fit to the relative astrometry of HD 142527 B. Our data suggest that the companion is close to periastron passage, on an orbit significantly misaligned with respect to both the wide circumbinary disk and the recently observed inner disk encircling HD 142527 A. We translate observed Hα contrasts for HD 142527 B into mass accretion rate estimates on the order of 4-9 × 10-10 M ⊙ yr-1. Photometric variation in the Hα excess of the companion suggests that the accretion rate onto the companion is variable. This work represents a significant step toward observing accretion-driven variability onto protoplanets, such as PDS 70 b&c.

Keywords: direct imaging; stellar accretion; accretion; star formation; orbit determination
The Study of X-Ray Flux Variability of M87

We searched for a short-term X-ray variability of the M87 core and jet from archival X-ray data with long exposure data taken by the Suzaku, Chandra, and NuSTAR telescopes. We found the intraday variability for the Suzaku data obtained in 2006, and for the Chandra core obtained in 2017. The intraday variability suggested a minute emission region about the size of the Schwarzschild radius of the M87 supermassive black hole. Suzaku could not resolve a core and HST-1; however, in 2006, HST-1 was much brighter than the core, and thus, the variability is likely due to the HST-1. Since the photon index in 2006 was 2.38, the emission was possibly synchrotron emission from the local shock region in the HST-1, indicating that the particle acceleration of TeV electrons occurred far away (~100 pc) from the core. Assuming the fading time to be equal to the synchrotron cooling time, the magnetic field is constrained to be B ~ 1.94 δ1/3 mG. Moreover, the photon index of the core in 2017 was approximately 1.96; thus, the possible emission was from the radiative inefficiency accretion flow of the core or inverse Compton scattering in the jet. Intraday time variability prefers the latter possibility.

Keywords: x-ray active galactic nuclei; radio galaxies
A Comparison of Distant and Nearby Solar Twins

Properties of solar twins at kiloparsec distances from the local standard of rest are compared to solar twins within 100 pc of the Sun. They have a velocity distribution closely similar to that of the nearby twins in addition to closely matching T eff, $\mathrm{log}(g)$ and [Fe/H]. The new twins are a kpc distant from Earth, and closer to the Galactic center. Additionally, they may be significantly older than nearby twins, and thus are useful for spectroscopic comparison with solar twins, in the search for fine structure constant variation.

Keywords: solar analogs
Resonant Absorption of Magnetohydrodynamic Body Modes under Photospheric Conditions

Observations reveal that surface and body modes exist in solar pores under photospheric conditions. While the effects of resonant absorption on photospheric surface modes are well established, its effect on body modes is not known yet. In this paper, we investigate resonant absorption for the body modes under photospheric conditions. We numerically solve the dispersion relation induced by thin boundary approximation and obtain the wave dispersion curves and damping rates of three arbitrarily chosen body modes for sausage and kink waves, respectively. The results show that resonant absorption for the body modes is weaker than for the slow surface modes in both cusp and Alfvén continua. The damping behavior of body modes is similar to slow surface modes while the higher body mode has stronger resonant absorption.

Keywords: solar physics; magnetohydrodynamics; solar photosphere; solar oscillations; alfven waves; magnetic fields; solar atmosphere
Dynamical Instabilities in Systems of Multiple Short-period Planets Are Likely Driven by Secular Chaos: A Case Study of Kepler-102

We investigated the dynamical stability of high-multiplicity Kepler and K2 planetary systems. Our numerical simulations find instabilities in ∼20% of the cases on a wide range of timescales (up to 5 × 109 orbits) and over an unexpectedly wide range of initial dynamical spacings. To identify the triggers of long-term instability in multiplanet systems, we investigated in detail the five-planet Kepler-102 system. Despite having several near-resonant period ratios, we find that mean-motion resonances are unlikely to directly cause instability for plausible planet masses in this system. Instead, we find strong evidence that slow inward transfer of angular momentum deficit (AMD) via secular chaos excites the eccentricity of the innermost planet, Kepler-102 b, eventually leading to planet-planet collisions in ∼80% of Kepler-102 simulations. Kepler-102 b likely needs a mass ≳0.1 M⊕, hence a bulk density exceeding about half Earth's, in order to avoid dynamical instability. To investigate the role of secular chaos in our wider set of simulations, we characterize each planetary system's AMD evolution with a "spectral fraction" calculated from the power spectrum of short integrations (∼5 × 106 orbits). We find that small spectral fractions (≲0.01) are strongly associated with dynamical stability on long timescales (5 × 109 orbits) and that the median time to instability decreases with increasing spectral fraction. Our results support the hypothesis that secular chaos is the driver of instabilities in many nonresonant multiplanet systems and also demonstrate that the spectral analysis method is an efficient numerical tool to diagnose long-term (in)stability of multiplanet systems from short simulations.

Keywords: exoplanets; exoplanet dynamics; exoplanet systems; orbital evolution