adsabs/SciX_UAT_keywords huggingface dataset:
CANDELS Meets GSWLC: Evolution of the Relationship between Morphology and Star Formation Since z = 2

Galaxy morphology and its evolution over the cosmic epoch hold important clues for understanding the regulation of star formation (SF). However, studying the relationship between morphology and SF has been hindered by the availability of consistent data at different redshifts. Our sample, combining CANDELS (0.8 < z < 2.5) and the GALEX-SDSS-WISE Legacy Catalog (GSWLC; z ∼ 0), has physical parameters derived using consistent SED fitting with flexible dust attenuation laws. We adopt visual classifications from Kartaltepe et al. and expand them to z ∼ 0 using SDSS images matching the physical resolution of CANDELS rest-frame optical images and deep FUV GALEX images matching the physical resolution of the CANDELS rest-frame FUV images. Our main finding is that disks with SF clumps at z ∼ 0 make a similar fraction (∼15%) of star-forming galaxies as at z ∼ 2. The clumpy disk contribution to the SF budget peaks at z ∼ 1, rather than z ∼ 2, suggesting that the principal epoch of disk assembly continues to lower redshifts. Star-forming spheroids ("blue nuggets"), though less centrally concentrated than quenched spheroids, contribute significantly (∼15%) to the SF budget at z ∼ 1-2, suggesting that compaction precedes quenching. Among green valley and quiescent galaxies, the pure spheroid fraction drops after z ∼ 1, whereas spheroids with disks (S0-like) become dominant. Mergers at or nearing coalescence are enhanced in SFR relative to the main sequence at all redshifts by a factor of ∼2, but contribute ≲5% to the SF budget, with their contribution remaining small above the main sequence.

Keywords: galaxies; galaxy classification systems; high-redshift galaxies; galaxy mergers; quenched galaxies; late-type galaxies; disk galaxies; galaxy quenching; star formation; galaxy formation; galaxy evolution
A New Multichannel Parallel Real-time FFT Algorithm for a Solar Radio Observation System Based on FPGA

The real-time fast Fourier transform (FFT) is the essential algorithm for signal processing in a solar radio receiver. However, field-programmable gate array (FPGA) computation resources have become the limitation of real-time processing of signals with increasing time and spectral resolutions. It is necessary to design a real-time parallel FFT algorithm with reduced resource occupation in the development of future receiving systems. In this paper, we developed a multichannel parallel FFT algorithm named the multichannel parallel real-time fast Fourier transform (MPR-FFT), which can greatly reduce FPGA resource occupation while increasing the real-time processing speed. In this algorithm, the 4L simultaneous N-point FFTs are first converted into L simultaneous 4N-point FFTs. Fusion processing is then performed to obtain the 4 ∗ L ∗ N-point spectrum. This method has been used in developing a solar radio spectrometer, which works in the frequency range of 0.5-15 GHz in the Chashan Observatory. In this spectrometer, 16 channel MPR-FFT with 8k-point data is realized in a Xilinx UltraScale KU115 FPGA. The MPR-FFT algorithm reduced the computational resources to a large extent compared to the Cooley-Tukey-based parallel FFT method; for instance, the Look-Up-Table, Look-Up-Table RAM, Flip-Flop, and Digital Signal Process slices were reduced by 37%, 50%, 17%, and 2.48%, respectively. Although the MPR-FFT consumes 14 block RAM resources more than the Cooley-Tukey-based parallel FFT, the MPR-FFT algorithm presents an overall reduction in resource usage.

Keywords: astronomical techniques; astronomy software; radio astronomy; radio receivers; radio spectroscopy; solar instruments; solar radio telescopes
A Comprehensive Model of Morphologically Realistic Cosmic Dust Particles: An Application to Mimic the Unusual Polarization Properties of the Interstellar Comet 2I/Borisov

The cosmic dust particles found in space are mainly porous aggregates of smaller grains. Theoretically, these aggregates are replicated using fractal geometry, assuming a cluster of spheres. Although the light scattering response of cosmic dust aggregates has been thoroughly studied using clusters of spherical grains in the past few decades, the effect of irregularities on the surface of each grain in an entire aggregate has mostly been neglected. We introduce, for the first time, a visually realistic cosmic dust model that incorporates a mixture of rough fractal aggregates (RFA) and agglomerated debris (Solids) to replicate the unusual polarization-phase curve observed in the case of the interstellar comet 2I/Borisov at multiple wavelengths. The authenticity of the RFA structures has been verified by replicating light scattering results of circumstellar dust analogs from the Granada Amsterdam Light Scattering Database. We demonstrate that the light scattering response from the RFA structures has a very close resemblance to the experimental values. Finally, we model the observed polarization-phase curve of the interstellar comet 2I/Borisov using a mixture of RFA and solid particles. The best-fit data indicate the presence of a higher percentage of porous RFA structures (80%) owing to the fact that the comet carries a higher percentage of small and highly porous pristine cosmic dust particles. Further, the model indicates that the unusually steep polarimetric slope and the high dust-to-gas ratio in newer comets are mainly due to a higher porous-to-compact ratio.

Keywords: comets; interstellar objects; coma dust; polarimetry; radiative transfer simulations
Rapid Rotation of Kepler Field Dwarfs and Subgiants: Spectroscopic v sin i from APOGEE

We use 5337 spectroscopic $v\sin i$ measurements of Kepler dwarfs and subgiants from the APOGEE survey to study stellar rotation trends. We find a detection threshold of 10 km s-1, which allows us to explore the spindown of intermediate-mass stars leaving the main sequence, merger products, young stars, and tidally synchronized binaries. We see a clear distinction between blue stragglers and the field turnoff in α-rich stars, with a sharp rapid rotation cutoff for blue stragglers consistent with the Kraft break. We also find rapid rotation and radial velocity variability in a sample of red straggler stars, considerably cooler than the giant branch, lending credence to the hypothesis that these are active, tidally synchronized binaries. We see clear evidence for a transition between rapid and slow rotation on the subgiant branch in the domain predicted by modern angular momentum evolution models. We find substantial agreement between the spectroscopic and photometric properties of KIC targets added by Huber et al. based on Two Micron All Sky Survey photometry. For the unevolved lower main sequence, we see the same concentration toward rapid rotation in photometric binaries as that observed in rotation period data, but at an enhanced rate. We attribute this difference to unresolved near-equal-luminosity spectroscopic binaries with velocity displacements on the order of the APOGEE resolution. Among cool unevolved stars we find an excess rapid rotator fraction of 4% caused by pipeline issues with photometric binaries.

Keywords: late-type stars; subgiant stars; stellar rotation; spectroscopy
Suprathermal H+ Pickup Ion Tails in the Outer Heliosphere

This study provides a detailed analysis of five distant interplanetary shocks observed by the Solar Wind Around Pluto instrument on board New Horizons, which exhibit the signature of a suprathermal H+ pickup ion (PUI) tail in the downstream distribution. These shocks were observed with a PUI data cadence of approximately 24 hr, covering a heliocentric distance range of 23.71-36.75 au. The shock compression ratio varies between approximately 1.4 and 3.2. The H+ PUI density and temperature show a gradual increase across the shock, while the H+ solar wind density shows erratic behavior without a distinct downstream compression. The H+ PUI cooling index variation across the shock displays different characteristics in each shock. This study demonstrates, for the first time, the variation of the number density of downstream H+ PUI tails with the shock compression ratio, revealing an increase in tail density with stronger shocks. Additionally, theoretical estimates of reflected PUI number densities derived from the electrostatic cross-shock potential agree very well with the observed H+ PUI tail densities for stronger shocks.

Keywords: interplanetary shocks; pickup ions; solar wind; heliosphere; interplanetary particle acceleration; space plasmas; plasma physics
Uncovering a Massive z 7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web

In this Letter, we report the discovery of the highest redshift, heavily obscured, radio-loud (RL) active galactic nucleus (AGN) candidate selected using JWST NIRCam/MIRI, mid-IR, submillimeter, and radio imaging in the COSMOS-Web field. Using multifrequency radio observations and mid-IR photometry, we identify a powerful, RL, growing supermassive black hole with significant spectral steepening of the radio spectral energy distribution (f 1.28 GHz ~ 2 mJy, q 24 μm = -1.1, α 1.28-3 GHz = - 1.2, Δα = - 0.4). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/near-infrared (NIR) data and thus infer heavy amounts of obscuration (N H > 1023 cm-2). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo-z of z phot = ${7.7}_{-0.3}^{+0.4}$ and estimate an extremely massive host galaxy $(\mathrm{log}{M}_{\star }=11.92\pm 0.5{M}_{\odot})$ hosting a powerful, growing supermassive black hole (L Bol = 4-12x × 1046 erg s-1). This source represents the farthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs.

Keywords: quasars; radio loud quasars; active galactic nuclei; supermassive black holes; reionization; high-redshift galaxies
Spectropolarimetric Measurements of Hidden Broad Lines in Nearby Megamaser Galaxies: A Lack of Clear Evidence for a Correlation between Black Hole Masses and Virial Products

High-accuracy black hole (BH) masses require excellent spatial resolution that is only achievable for galaxies within ~100 Mpc using present-day technology. At larger distances, BH masses are often estimated with single-epoch scaling relations for active galactic nuclei. This method requires only luminosity and the velocity dispersion of the broad-line region (BLR) to calculate a virial product, and an additional virial factor, f, to determine the BH mass. The accuracy of these single-epoch masses, however, is unknown, and there are few empirical constraints on the variance of f between objects. We attempt to calibrate single-epoch BH masses using spectropolarimetric measurements of nine megamaser galaxies from which we measure the velocity distribution of the BLR. We do not find strong evidence for a correlation between the virial products used for single-epoch masses and dynamical mass, either for the megamaser sample alone or when it is combined with dynamical masses from reverberation mapping modeling. Furthermore, we find evidence that the virial parameter f varies between objects, but we do not find strong evidence for a correlation with other observable parameters such as luminosity or broad-line width. Although we cannot definitively rule out the existence of any correlation between dynamical mass and virial product, we find tension between the allowed f-values for masers and those widely used in the literature. We conclude that the single-epoch method requires further investigation if it is to be used successfully to infer BH masses. * Based on observations made with the Southern African Large Telescope.

Keywords: active galactic nuclei; reverberation mapping; megamasers
Significant Dust-obscured Star Formation in Luminous Lyman-break Galaxies at z 7-8

We make use of Atacama Large Millimeter/submillimeter Array continuum observations of 15 luminous Lyman-break galaxies at z ~ 7-8 to probe their dust-obscured star formation. These observations are sensitive enough to probe obscured star formation rates (SFRs) of 20 M ⊙ yr-1 (3σ). Six of the targeted galaxies show significant (≥3σ) dust-continuum detections, more than doubling the number of known dust-detected galaxies at z > 6.5. Their IR luminosities range from 2.7 × 1011 L ⊙ to 1.1 × 1012 L ⊙, equivalent to obscured SFRs of 25 to 101 M ⊙ yr-1. We use our results to quantify the correlation of the infrared excess (IRX) on the UV-continuum slope β UV and stellar mass. Our results are most consistent with a Small Magellanic Cloud (SMC) attenuation curve for intrinsic UV-slopes ${\beta }_{\mathrm{UV},\mathrm{intr}}$ of -2.63 and most consistent with an attenuation curve in between SMC and Calzetti for ${\beta }_{\mathrm{UV},\mathrm{intr}}$ slopes of -2.23, assuming a dust temperature T d of 50 K. Our fiducial IRX-stellar mass results at z ~ 7-8 are consistent with marginal evolution from z ~ 0. We then show how both results depend on T d . For our six dust-detected sources, we estimate their dust masses and find that they are consistent with dust production from supernovae if the dust destruction is low (<90%). Finally we determine the contribution of dust-obscured star formation to the SFR density for UV luminous (H<-21.5 mag: ≳1.7 L * UV) z ~ 7-8 galaxies, finding that the total SFR density at z ~ 7 and z ~ 8 from bright galaxies is ${0.20}_{-0.10}^{+0.10}$ dex and ${0.23}_{-0.09}^{+0.06}$ dex higher, respectively; i.e., ~ $\tfrac{1}{3}$ of the star formation in ≳1.7 L * UV galaxies at z ~ 7-8 is obscured by dust.

Keywords: high-redshift galaxies; galaxies; lyman-break galaxies; interstellar dust; interstellar dust extinction; galaxy evolution
Fuzzy Dark Matter and Dark Matter Halo Cores

Whereas cold dark matter (CDM) simulations predict central dark matter cusps with densities that diverge as ρ(r) ∼ 1/r, observations often indicate constant-density cores with finite central densities ρ0 and a flat density distribution within a core radius r0. This paper investigates whether this core-cusp problem can be solved by fuzzy dark matter (FDM), a hypothetical particle with a mass of the order of m ≈ 10-22 eV and a corresponding de Broglie wavelength on astrophysical scales. We show that galaxies with CDM halo virial masses Mvir ≤ 1011M⊙ follow two core-scaling relations. In addition to the well-known universal core column density Σ0 ≡ ρ0 × r0 = 75 ${M}_{\odot }$ pc-2, core radii increase with virial masses as r0 ∼ ${M}_{\mathrm{vir}}^{\gamma }$ with γ of order unity. Using the simulations by Schive et al. we demonstrate that FDM can explain the r0-Mvir scaling relation if the virial masses of the observed galaxy sample scale with the formation redshift z as Mvir ∼ (1 + z)-0.4. The observed constant Σ0 is however in complete disagreement with FDM cores which are characterized by a steep dependence Σ0 ∼ r ${}_{0}^{-3}$ , independent of z. More high-resolution simulations are now required to confirm the simulations of Schive et al. and explore the transition region between the soliton core and the surrounding halo. If these results hold, FDM can be ruled out as the origin of observed dark matter cores and other physical processes are required to account for their formation.

Keywords: cold dark matter; dark matter distribution; galaxies; cosmology
Finding Quasars behind the Galactic Plane. I. Candidate Selections with Transfer Learning

Quasars behind the Galactic plane (GPQs) are important astrometric references and useful probes of Milky Way gas. However, the search for GPQs is difficult due to large extinctions and high source densities in the Galactic plane. Existing selection methods for quasars developed using high Galactic latitude (high-b) data cannot be applied to the Galactic plane directly because the photometric data obtained from high-b regions and the Galactic plane follow different probability distributions. To alleviate this data set shift problem for quasar candidate selection, we adopt a transfer-learning framework at both the data and algorithm levels. At the data level, to make a training set in which a data set shift is modeled, we synthesize quasars and galaxies behind the Galactic plane based on SDSS sources and the Galactic dust map. At the algorithm level, to reduce the effect of class imbalance, we transform the three-class classification problem for stars, galaxies, and quasars into two binary classification tasks. We apply the XGBoost algorithm to Pan-STARRS1 (PS1) and AllWISE photometry for classification and an additional cut on Gaia proper motion to remove stellar contaminants. We obtain a reliable GPQ candidate catalog with 160,946 sources located at ∣b∣ ≤ 20° in the PS1-AllWISE footprint. Photometric redshifts of GPQ candidates achieved with the XGBoost regression algorithm show that our selection method can identify quasars in a wide redshift range (0 < z ≲ 5). This study extends the systematic searches for quasars to the dense stellar fields and shows the feasibility of using astronomical knowledge to improve data mining under complex conditions in the big-data era.

Keywords: active galactic nuclei; astrostatistics techniques; classification; catalogs; quasars; galactic and extragalactic astronomy
ALMA Observations of the Extraordinary Carina Pillars: A Complementary Sample

We present a study of six dusty and gaseous pillars (containing the Herbig-Haro (HH) objects HH 1004 and HH 1010) and globules (that contain the HH 666, HH 900, HH 1006, and HH 1066 objects) localized in the Carina Nebula using sensitive and high-angular-resolution (~0.″3) Atacama Large Millimeter/submillimeter Array observations. This is a more extensive study that the one presented in Cortes-Rangel et al. As in this former study, we also analyzed the 1.3 mm continuum emission and C18O(2-1), N2D+(3-2), and 12CO(2-1) spectral lines. These new observations revealed the molecular outflows emanating from the pillars, the dusty envelopes+disks that are exciting them, and the extended HH objects far from their respective pillars. We reveal that the masses of the disks+envelopes are in the range of 0.02-0.38 M ⊙, and those for the molecular outflows are of the order of 10-3 M ⊙, which suggest that their exciting sources might be low- or intermediate-mass protostars as already revealed in recent studies at infrared and submillimeter bands. In the regions associated with the objects HH 900 and HH 1004, we report multiple millimeter continuum sources, from where several molecular outflows emanate.

Keywords: protostars; interstellar medium; stellar jets; herbig-haro objects
Forward Modeling of Particle Acceleration and Transport in an Individual Solar Flare

The aim of this study is to generate maps of the hard X-ray emission produced by energetic electrons in a solar flare and compare them with observations. The ultimate goal is to test the viability of the combined MHD/test-particle approach for data-driven modeling of active events in the solar corona and their impact on the heliosphere. Based on an MHD model of X-class solar flare observed on 2017 September 8, we calculate trajectories of a large number of electrons and protons using the relativistic guiding-center approach. Using the obtained particle trajectories, we deduce the spatial and energy distributions of energetic electrons and protons, and calculate bremsstrahlung hard X-ray emission using the "thin-target" approximation. Our approach predicts some key characteristics of energetic particles in the considered flare, including the size and location of the acceleration region, energetic particle trajectories and energy spectra. Most importantly, the hard X-ray bremsstrahlung intensity maps predicted by the model are in good agreement with those observed by RHESSI. Furthermore, the locations of proton and electron precipitation appear to be close to the sources of helioseismic response detected in this flare. Therefore, the adopted approach can be used for observationally driven modeling of individual solar flares, including manifestations of energetic particles in the corona, as well as the inner heliosphere.

Keywords: solar flares; solar x-ray flares; solar energetic particles; computational methods
New Observational Constraints on the Winds of M dwarf Stars

High-resolution UV spectra of stellar H I Lyα lines from the Hubble Space Telescope (HST) provide observational constraints on the winds of coronal main-sequence stars, thanks to an astrospheric absorption signature created by the interaction between the stellar winds and the interstellar medium. We report the results of a new HST survey of M dwarf stars, yielding six new detections of astrospheric absorption. We estimate mass-loss rates for these detections and upper limits for nondetections. These new constraints allow us to characterize the nature of M dwarf winds and their dependence on coronal activity for the first time. For a clear majority of the M dwarfs, we find winds that are weaker than or comparable in strength to that of the Sun, i.e., $\dot{M}\leqslant 1\,{\dot{M}}_{\odot }$ . However, two of the M dwarfs have much stronger winds: YZ CMi (M4 Ve; $\dot{M}=30\,{\dot{M}}_{\odot }$ ) and GJ 15AB (M2 V+M3.5 V; $\dot{M}=10\,{\dot{M}}_{\odot }$ ). Even these winds are much weaker than expectations if the solar relation between flare energy and coronal mass ejection (CME) mass extended to M dwarfs. Thus, the solar flare/CME relation does not appear to apply to M dwarfs, with important ramifications for the habitability of exoplanets around M dwarfs. There is evidence for some increase in $\dot{M}$ with coronal activity as quantified by X-ray flux, but with much scatter. One or more other factors must be involved in determining wind strength besides spectral type and coronal activity, with magnetic topology being one clear possibility. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-15326.

Keywords: stellar coronae; stellar phenomena; stellar winds; astrospheres; ultraviolet astronomy