adsabs/SciX_UAT_keywords huggingface dataset:
Pulsar Candidate Sifting Using Multi-input Convolution Neural Networks

Pulsar candidate sifting is an essential process for discovering new pulsars. It aims to search for the most promising pulsar candidates from an all-sky survey, such as the High Time Resolution Universe (HTRU), Green Bank Northern Celestial Cap (GBNCC), Five-hundred-meter Aperture Spherical Radio Telescope, etc. Recently, machine learning (ML) has become a hot topic in investigations of pulsar candidate sifting. However, one typical challenge in ML for pulsar candidate sifting comes from the learning difficulty arising from the high class imbalance between the observed numbers of pulsars and non-pulsars. Therefore, this work proposes a novel framework for candidate sifting, named Multi-input Convolutional Neural Networks (MICNN). MICNN is an architecture of deep learning with four diagnostic plots of a pulsar candidate as its inputs. To train our MICNN on a highly class-imbalanced data set, a novel image augmentation technique is proposed, as well as a three-stage training strategy. Experiments on observations from HTRU and GBNCC show the effectiveness and robustness of these proposed techniques. In the experiments on HTRU, our MICNN model achieves a recall rate of 0.962 and a precision rate of 0.967 even in a highly class-imbalanced test data set.

Keywords: pulsars; astronomy data analysis; convolutional neural networks
An Updated Small Magellanic Cloud and Magellanic Bridge Catalog of Star Clusters, Associations, and Related Objects

We present a catalog of star clusters, associations, and related extended objects in the Small Magellanic Cloud (SMC) and the Magellanic Bridge with 2741 entries, a factor 2 more than a previous version from a decade ago. Literature data up until 2018 December are included. The identification of star clusters was carried out with digital atlases in various bands currently available in the Digitized Sky Survey and the Machine Automatique à Mésurer pour l'Astronomie. imaging surveys. In particular, we cross-identified recent cluster samples from the Visible and Infrared Survey Telescope for Astronomy near-infrared YJKs survey of the Magellanic System, Optical Gravitational Lensing Experiment IV, and Survey of the MAgellanic Stellar History surveys, confirming new clusters and pointing out equivalencies. A major contribution of the present catalog consists of the accurate central positions for clusters and small associations, including a new sample of 45 clusters or candidates in the SMC and 19 in the Magellanic Bridge, as well as a compilation of the most reliable age and metallicity values from the literature. A general catalog must also deal with the recent discoveries of 27 faint and ultra-faint star clusters and galaxies projected on the far surroundings of the Clouds, most of them from the Dark Energy Survey. The information on these objects has been complemented with photometric, spectroscopic, and kinematical follow-up data from the literature. The underluminous galaxies around the Magellanic System, still very few as compared to the predictions from Λ Cold Dark Matter simulations, can bring constraints to galaxy formation and hierarchical evolution. Furthermore, we provide diagnostics, when possible, of the nature of the ultra-faint clusters, searching for borders of the Magellanic System extensions into the Milky Way gravitational potential.

Keywords: celestial objects catalogs; small magellanic cloud; star clusters; galaxy interactions
Asteroid Diameters and Albedos from NEOWISE Reactivation Mission Years Six and Seven

We present diameters and albedos computed for the near-Earth and main belt asteroids (MBAs) observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of 199 near-Earth objects (NEOs) and 5851 MBAs detected during the sixth year of the survey and 175 NEOs and 5861 MBAs from the seventh year. Comparisons of the NEO diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a ~30% relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter-wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the MBAs that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of 1415 unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to 1845 from WISE's launch to the present.

Keywords: asteroids; near-earth objects; infrared astronomy
Turbulence Regulates the Rate of Planetesimal Formation via Gravitational Collapse

We study how the interaction between the streaming instability (SI) and intrinsic gas-phase turbulence affects planetesimal formation via gravitational collapse in protoplanetary disks. Turbulence impedes the formation of particle clumps by acting as an effective turbulent diffusivity, but it can also promote planetesimal formation by concentrating solids, for example, in zonal flows. We quantify the effect of turbulent diffusivity using numerical simulations of the SI in small local domains, forced with velocity perturbations that establish approximately Kolmogorov-like turbulence. We find that planetesimal formation is suppressed by turbulence once velocity fluctuations exceed $\langle \delta {v}^{2}\rangle $ ≃ (10-3.5-10-3) ${c}_{s}^{2}$ . Turbulence whose strength is just below the threshold reduces the rate at which solids are bound into clumps. Our results suggest that the well-established turbulent thickening of the midplane solid layer is the primary mechanism by which turbulence influences planetesimal formation and that planetesimal formation requires a midplane solid-to-gas ratio ɛ ≳ 0.5. We also quantify the initial planetesimal mass function using a new clump-tracking method to determine each planetesimal mass shortly after collapse. For models in which planetesimals form, we show that the mass function is well described by a broken power law, whose parameters are robust to the inclusion and strength of imposed turbulence. Turbulence in protoplanetary disks is likely to substantially exceed the threshold for planetesimal formation at radii where temperatures T ≳ 103 K lead to thermal ionization. Planetesimal formation may therefore be unviable in the inner disk out to 2-3 times the dust sublimation radius.

Keywords: stellar accretion disks; protoplanetary disks; planetesimals; planet formation
Extreme Variation in Star Formation Efficiency across a Compact, Starburst Disk Galaxy

We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using ~200 pc resolution CO(2 - 1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 108 yr inside the half-light radius. This translates to a star formation efficiency per freefall time that also changes by 2 orders-of-magnitude, reaching 50%-100%, different than local spiral galaxies and the typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has a star formation rate 10× above the z = 0 main sequence; Toomre Q ≈ 0.5-0.7 and high gas velocity dispersion (σ mol ≈ 25 km s-1). We find that IRAS08 is similar to other rotating, starburst galaxies from the literature in the resolved ${{\rm{\Sigma }}}_{\mathrm{SFR}}\propto {{\rm{\Sigma }}}_{\mathrm{mol}}^{N}$ relation. By combining resolved literature studies we find that the distance from the main sequence is a strong indicator of the Kennicutt-Schmidt power-law slope, with slopes of N ≈ 1.6 for starbursts from 100 to 104 M ⊙ pc-2. Our target is consistent with a scenario in which violent disk instabilities drive rapid inflows of gas. It has low values of Toomre-Q, and also at all radii, the inflow timescale of the gas is less than the depletion time, which is consistent with the flat metallicity gradients in IRAS08. We consider these results in light of popular star formation theories; in general observations of IRAS08 find the most tension with theories in which star formation efficiency is a constant. Our results argue for the need of high-spatial-resolution CO observations for a larger number of similar targets.

Keywords: starburst galaxies
A Dynamical Survey of the Trans-Neptunian Region. I. Mean-motion Resonances with Neptune

In this paper, we present a large-scale dynamical survey of the trans-Neptunian region, with particular attention to mean-motion resonances (MMRs). We study a set of 4121 trans-Neptunian objects (TNOs), a sample far larger than in previous works. We perform direct long-term numerical integrations that enable us to examine the overall dynamics of the individual TNOs as well as to identify all MMRs. For the latter purpose, we apply an own-developed FAIR method that allows the semi-automatic identification of even very high-order MMRs. Apart from searching for the more frequent eccentricity-type resonances that previous studies concentrated on, we set our method to allow the identification of inclination-type MMRs, too. Furthermore, we distinguish between TNOs that are locked in a given MMR throughout the whole integration time span (108 yr) and those that are only temporarily captured in resonances. For a more detailed dynamical analysis of the trans-Neptunian space, we also construct dynamical maps using test particles. Observing the fine structure of the 34-80 au region underlines the stabilizing role of the MMRs, with the regular regions coinciding with the positions of real TNOs.

Keywords: resonant kuiper belt objects; n-body problem
Massive Molecular Gas Companions Uncovered by Very Large Array CO(1-0) Observations of the z = 5.2 Radio Galaxy TN J0924-2201

We present Karl G. Jansky Very Large Array K-band (19 GHz) observations of the redshifted CO(1-0) line emission toward the radio galaxy TN J0924-2201 at z = 5.2, which is one of the most distant radio galaxies with CO detected. With an angular resolution of ~2″, the CO(1-0) line emission is resolved into three clumps, within ±500 km s-1 relative to its redshift, which is determined by Lyα. We find that the clumps are located off-center and 12-33 kpc away from the center of the host galaxy, which has counterparts in the Hubble Space Telescope i band, Spitzer/IRAC, and the Atacama Large Millimeter/submillimeter Array (ALMA) band 6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate the infrared luminosity L IR and the star formation rate (SFR) of the host galaxy to be (9.3 ± 1.7) × 1011 L ⊙ and 110 ± 20 M ⊙ yr-1, respectively. We also derive the 3σ upper limit of ${M}_{{{\rm{H}}}_{2}}\lt 1.3\times {10}^{10}$ M ⊙ at the host galaxy. The detected CO(1-0) line luminosities of the three clumps, $L{{\prime} }_{\mathrm{CO}(1-0)}$ = (3.2-4.7) × 1010 K km s-1 pc2, indicate the presence of three massive molecular gas reservoirs, with ${M}_{{{\rm{H}}}_{2}}$ = (2.5-3.7) × 1010 M ⊙, assuming a CO-to-H2 conversion factor of α CO = 0.8 ${M}_{\odot }{({\rm{K}}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{pc}}^{2})}^{-1}$ , although the SFR is not elevated due to the nondetection of the ALMA 1.3 mm continuum (SFR < 40 M ⊙ yr-1). From the host galaxy, the nearest molecular gas clump, labeled "clump A," is apparently in alignment with the radio jet axis, showing radio-CO alignment. The origins of these three clumps around TN J0924-2201 can possibly be interpreted as outflows, mergers, or jet-induced metal enrichment.

Keywords: high-redshift galaxies; radio galaxies; radio active galactic nuclei; agn host galaxies
Experimental Phase Function and Degree of Linear Polarization Curves of Millimeter-sized Cosmic Dust Analogs

We present laboratory measurements of the phase functions and degree of linear polarization (DLP) curves of a selection of millimeter-sized cosmic dust analog particles. The set includes particles with similar sizes but diverse internal structure (compact and porous) and absorbing properties. The measured phase functions are found to be in all cases very different from those of micron-sized particles. They show a monotonic decrease with increasing phase angle from the back- to the side-scattering region, reaching a minimum at large phase angles before a steep increase of the forward peak. This is in stark contrast to the phase functions of micron-sized particles, which are rather flat at low and intermediate phase angles. The maximum of the DLP for millimeter-sized compact particles is shifted toward larger phase angles (∼130°) compared to that of micron-sized particles (∼90°). Porosity plays an important role in the measured DLP curves: the maximum significantly decreases for increasing porosity as a result of multiple scattering within the particle. Large porous particles with highly absorbing inclusions can reproduce both the OSIRIS/Rosetta phase functions and ground-based DLP observations of comet 67P/Churyumov-Gerasimenko.

Keywords: circumstellar dust; polarimetry; circumstellar disks; debris disks; comets; experimental techniques; protoplanetary disks
Occurrence and Evolution of Switchbacks in the Inner Heliosphere: Parker Solar Probe Observations

Since its launch in 2018, the Parker Solar Probe (PSP) mission revealed the presence of numerous fascinating phenomena occurring closer to the Sun, such as the presence of ubiquitous switchbacks (SBs). The SBs are large magnetic field deflections of the local magnetic field relative to a background field. We investigated the statistical properties of the SBs during the first 10 encounters between 13.28 and 58 solar radii (R ⊙) using data from the SWEAP and FIELDS suites on board PSP. We find that the occurrence percentage of small deflections with respect to the Parker spiral decreases with radial distance (R). In contrast, the occurrence percentage of the large deflections (SBs) increases with R, as does the SB patches. We also find that the occurrence of SBs correlates with the bulk velocity of the solar wind, i.e., the higher the solar wind velocity, the higher the SB occurrence. For V sw ≤ 400 km s-1, the SB occurrence percentage shows a constantly increasing trend between 13 and 58 R ⊙. However, for V sw > 400 km s-1, the occurrence percentage saturates beyond 35 R ⊙. The occurrence percentage of mini SB patches (<60 s) shows a decreasing trend with R, while the occurrence percentage of long-duration SB patches (>200 s) increases with R. Sub-Alfvénic regions that we analyzed during Encounters 8-10 have not shown any SBs. This analysis of the PSP data hints that some of the SBs are decaying and some are being created in situ.

Keywords: solar wind; interplanetary magnetic fields
The Hα and [O III] λ5007 Luminosity Functions of 1.2 < z < 1.9 Emission-line Galaxies from Hubble Space Telescope (HST) Grism Spectroscopy

Euclid and the Roman Space Telescope (Roman) will soon use grism spectroscopy to detect millions of galaxies via their Hα and [O III] λ5007 emission. To better constrain the expected galaxy counts from these instruments, we use a vetted sample of 4239 emission-line galaxies from the 3D Hubble Space Telescope survey to measure the Hα and [O III] λ5007 luminosity functions between 1.16 < z < 1.90; this sample is ~4 times larger than previous studies at this redshift. We find very good agreement with previous measurements for Hα, but for [O III], we predict a higher number of intermediate-luminosity galaxies than from previous works. We find that, for both lines, the characteristic luminosity, ${{ \mathcal L }}_{* }$ , increases monotonically with redshift, and use the Hα luminosity function to calculate the epoch's cosmic star formation rate density. We find that Hα-visible galaxies account for ~81% of the epoch's total star formation rate, and this value changes very little over the 1.16 < z < 1.56 redshift range. Finally, we derive the surface density of galaxies as a function of limiting flux and find that previous predictions for galaxy counts for the Euclid Wide Survey are unchanged, but there may be more [O III] galaxies in the Roman High Latitude Survey than previously estimated.

Keywords: galaxy evolution; luminosity function; spectral energy distribution; high-redshift galaxies
SPLUS J142445.34-254247.1: An r-process-enhanced, Actinide-boost, Extremely Metal-poor Star Observed with GHOST

We report on a chemo-dynamical analysis of SPLUS J142445.34-254247.1 (SPLUS J1424-2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process (r-process). This star was first selected as a metal-poor candidate from its narrowband S-PLUS photometry and followed up spectroscopically in medium resolution with Gemini-South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini-South, allowing for the determination of the chemical abundances for 36 elements, from carbon to thorium. At [Fe/H] = -3.39, SPLUS J1424-2542 is one of the lowest-metallicity stars with measured Th and has the highest $\mathrm{log}\epsilon (\mathrm{Th}/\mathrm{Eu})$ observed to date, making it part of the "actinide-boost" category of r-process-enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424-2542 formed must have been enriched by at least two progenitor populations. The light-element (Z ≤ 30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3-13.4 M ⊙, and the heavy-element (Z ≥ 38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66 M ⊙ and 1.27 M ⊙) event. A kinematical analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a likely in situ origin, not associated with any known early merger events in the Milky Way.

Keywords: high resolution spectroscopy; stellar atmospheres; narrow band photometry; chemical abundances; metallicity
Discovery of a Low-mass Companion Embedded in the Disk of the Young Massive Star MWC 297 with VLT/SPHERE

We report the discovery of a low-mass stellar companion around the young Herbig Be star MWC 297. We performed multi-epoch high-contrast imaging in the near-infrared with the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. The companion is found at a projected separation of 244.7 ± 13.2 au and a position angle of 176.4 ± 0.1 deg. The large separation supports formation via gravitational instability. From the spectrum, we estimate a mass of 0.1-0.5 M⊙, the range conveying uncertainties in the extinction of the companion and in evolutionary models at young ages. The orbit coincides with a gap in the dust disk inferred from the spectral energy distribution. The young age (≲1 Myr) and mass ratio with the central star (∼0.01) makes the companion comparable to PDS 70 b, suggesting a relation between formation scenarios and disk dynamics.

Keywords: ae stars; star formation; binary stars
Quantifying the Stellar Halo's Response to the LMC's Infall with Spherical Harmonics

The vast majority of the mass in the Milky Way (MW) is in dark matter (DM); we therefore cannot directly observe the MW mass distribution and have to use tracer populations in order to infer properties of the MW DM halo. However, MW halo tracers do not only feel the gravitational influence of the MW itself. Tracers can also be affected by MW satellites; Garavito-Camargo et al. (2109) demonstrate that the Large Magellanic Cloud (LMC) induces a density wake in the MW DM, resulting in large-scale kinematic patterns in the MW stellar halo. In this work, we use spherical harmonic expansion (SHE) of the velocity fields of simulated stellar halos in an effort to disentangle perturbations on large scales (e.g., due to the LMC itself, as well as the LMC-induced DM wake) and small scales (due to substructure). Using the Garavito-Camargo et al. simulations, we demonstrate how the different terms in the SHE of the stellar velocity field reflect the different wake components and show that these signatures are a strong function of the LMC mass. An exploration of model halos built from accreted dwarfs suggests that stellar debris from massive, recent accretion events can produce much more power in the velocity angular power spectra than the perturbation from the LMC-induced wake. We therefore consider two models for the Sagittarius (Sgr) stream—the most recent, massive accretion event in the MW apart from the LMC—and find that the angular power on large scales is generally dominated by the LMC-induced wake, even when Sgr is included. We conclude that SHE of the MW stellar halo velocity field may therefore be a useful tool in quantifying the response of the MW DM halo to the LMC's infall.

Keywords: milky way dark matter halo; milky way dynamics; milky way stellar halo; milky way galaxy
A Census of Thermally Pulsing AGB Stars in the Andromeda Galaxy and a First Estimate of Their Contribution to the Global Dust Budget

We present a near-complete catalog of the metal-rich population of thermally pulsing asymptotic giant branch (AGB) stars in the northwest quadrant of M31. This metal-rich sample complements the equally complete metal-poor Magellanic Cloud AGB catalogs produced by the SAGE program. Our catalog includes Hubble Space Telescope (HST) wide-band photometry from the Panchromatic Hubble Andromeda Treasury survey, HST medium-band photometry used to chemically classify a subset of the sample, and Spitzer mid- and far-IR photometry that we have used to isolate dust-producing AGB stars. We have detected 346,623 AGB stars; these include 4802 AGB candidates producing considerable dust, and 1356 AGB candidates that lie within clusters with measured ages, and in some cases metallicities. Using the Spitzer data and chemical classifications made with the medium-band data, we have identified both carbon- and oxygen-rich AGB candidates producing significant dust. We have applied color-mass-loss relations based on dusty-AGB stars from the LMC to estimate the dust injection by AGB stars in the PHAT footprint. Applying our color relations to a subset of the chemically classified stars producing the bulk of the dust, we find that ~97.8% of the dust is oxygen-rich. Using several scenarios for the dust lifetime, we have estimated the contribution of AGB stars to the global dust budget of M31 to be 0.9%-35.5%, which is in line with previous estimates in the Magellanic Clouds. Follow-up observations of the M31 AGB candidates with the JWST will allow us to further constrain stellar and chemical evolutionary models, and the feedback and dust production of metal-rich evolved stars.

Keywords: asymptotic giant branch stars; andromeda galaxy; circumstellar dust; extreme carbon stars; stellar mass loss; local group; star clusters; late stellar evolution; spectral energy distribution