Sazuna/UAT_keywords huggingface dataset:
Revisiting Active Galactic Nucleus Placement on the Baldwin, Phillips, and Terlevich Diagram: A Spectral Decomposition Approach. Traditional single-fiber spectroscopy provides a single galaxy spectrum, forming the basis for crucial parameter estimation. However, its accuracy can be compromised by various sources of contamination, such as the prominent Hα emission line originating from both star-forming (SF) regions and non-star-forming (NonSF) regions, including active galactic nuclei. The potential to dissect a spectrum into its SF and NonSF constituents holds the promise of significantly enhancing precision in parameter estimates. In contrast, integral field unit (IFU) surveys present a solution to minimize contamination. These surveys examine spatially localized regions within galaxies, reducing the impact of mixed sources. Although an IFU survey's resulting spectrum covers a smaller region of a galaxy than single-fiber spectroscopy, it can still encompass a blend of heterogeneous sources. Our study introduces an innovative model informed by insights from the Mapping Nearby Galaxies at Apache Point Observatory IFU survey. This model enables the decomposition of galaxy spectra, including those from the Sloan Digital Sky Survey, into SF and NonSF components. Applying our model to these survey data sets produces two distinct spectra, one for SF and another for NonSF components, while conserving flux across wavelength bins. When these decomposed spectra are visualized on a Baldwin, Phillips, and Terlevich (BPT) diagram, interesting patterns emerge. There is a significant shift in the placement of the NonSF decomposed spectra, as well as the emergence of two distinct clusters in the Low-ionization Nuclear Emission-line Region and the Seyfert region. This shift highlights the key role of SF "contamination" in influencing the positioning of NonSF spectra within the BPT diagram.

Keywords: Astronomy data analysis, Galaxy abundances, Star formation, Active galactic nuclei, Galaxy spectroscopy
Nonthermal Observations of a Flare Loop-top Using IRIS Fe XXI: Implications for Turbulence and Electron Acceleration. The excess broadening of high-temperature spectral lines, long observed near the tops of flare arcades, is widely considered to result from magnetohydrodynamic turbulence. According to different theories, plasma turbulence is also believed to be a candidate mechanism for particle acceleration during solar flares. However, the degree to which this broadening is connected to the acceleration of nonthermal electrons remains largely unexplored outside of recent work, and many observations have been limited by limited spatial resolution and cadence. Using the Interface Region Imaging Spectrometer, we present spatially resolved observations of loop-top (LT) broadenings using hot (≈11 MK) Fe XXI 1354.1 Å line emission at ≈9 s cadence during the 2022 March 30 X1.3 flare. We find nonthermal velocities upward of 65 km s‑1 that decay linearly with time, indicating the presence and subsequent dissipation of plasma turbulence. Moreover, the initial Fe XXI signal was found to be cospatial and cotemporal with microwave emission measured by the Expanded Owens Valley Solar Array, placing a population of nonthermal electrons in the same region as the LT turbulence. Evidence of electron acceleration at this time is further supported by hard X-ray measurements from the Spectrometer/Telescope for Imaging X-rays on board Solar Orbiter. Using the decay of nonthermal broadenings as a proxy for turbulent dissipation, we found the rate of energy dissipation to be consistent with the power of nonthermal electrons deposited into the chromosphere, suggesting a possible connection between turbulence and electron acceleration.

Keywords: Solar flares, Solar extreme ultraviolet emission, Solar flare spectra, Non-thermal radiation sources, Solar radio flares
Probing the Connection between IceCube Neutrinos and MOJAVE AGN. Active galactic nuclei (AGN) are prime candidate sources of the high-energy, astrophysical neutrinos detected by IceCube. This is demonstrated by the real-time multimessenger detection of the blazar TXS 0506+056 and the recent evidence of neutrino emission from NGC 1068 from a separate time-averaged study. However, the production mechanism of the astrophysical neutrinos in AGN is not well established, which can be resolved via correlation studies with photon observations. For neutrinos produced due to photohadronic interactions in AGN, in addition to a correlation of neutrinos with high-energy photons, there would also be a correlation of neutrinos with photons emitted at radio wavelengths. In this work, we perform an in-depth stacking study of the correlation between 15 GHz radio observations of AGN reported in the MOJAVE XV catalog, and 10 yr of neutrino data from IceCube. We also use a time-dependent approach, which improves the statistical power of the stacking analysis. No significant correlation was found for both analyses, and upper limits are reported. When compared to the IceCube diffuse flux, at 100 TeV and for a spectral index of 2.5, the upper limits derived are ∼3% and ∼9% for the time-averaged and time-dependent cases, respectively.

Keywords: Neutrino astronomy, Radio astronomy, High energy astrophysics
Three-dimensional Thermodynamic Structures of the Intracluster Medium across Edges in the X-Ray Surface Brightness of Massive, Bright, Dynamically Active Galaxy Clusters. We present a detailed study of three-dimensional (3D) thermodynamic structures of the intracluster medium (ICM) across edges in the X-ray surface brightness of four massive, bright, dynamically active galaxy clusters (A3667, A2319, A520, and A2146), with the Chandra X-ray Observatory. Based on a forward modeling approach developed in previous work, we extend this approach with more generalized ICM density and temperature profiles, allowing us to apply uniformly to the observed X-ray surface brightness profiles to detect edges and measure the 3D thermodynamic profiles of the ICM simultaneously and self-consistently. With the forward modeling analysis, we find, in agreement with previous works, that the obtained 3D thermodynamic structures of the ICM across the edges in A3667 and A2319 are consistent with the characteristics of cold fronts, whereas those in A520 and A2146 are consistent with the nature of shock fronts. We find that the azimuthal distribution of the pressure ratio at the cold front in A3667 shows a different trend from that in A2319. For the shock fronts in A520 and A2146, the observed 3D temperature profiles of the ICM indicate that the temperature is highest at the position of the shock front. In the case of the sector exhibiting  M=2.4  in A520, the ICM temperature appears isothermal with a temperature of ∼10 keV until ∼300 kpc away from the shock front in the post-shock region, being consistent with the hypothesis of the instant-equilibration model for shock heating.

Keywords: Galaxy clusters, Intracluster medium, X-ray astronomy
Ne VIII in the Warm-hot Circumgalactic Medium of FIRE Simulations and in Observations. The properties of warm-hot gas around ∼L * galaxies can be studied with absorption lines from highly ionized metals. We predict Ne VIII column densities from cosmological zoom-in simulations of halos with masses in ∼1012 and ∼1013 M ☉ from the Feedback in Realistic Environments (FIRE) project. Ne VIII traces the volume-filling, virial-temperature gas in ∼1012 M ☉ halos. In ∼1013 M ☉ halos the Ne VIII gas is clumpier, and biased toward the cooler part of the warm-hot phase. We compare the simulations to observations from the COS Absorption Survey of Baryon Harbors (or CASBaH) and COS Ultraviolet Baryon Survey (or CUBS). We show that when inferring halo masses from stellar masses to compare simulated and observed halos, it is important to account for the scatter in the stellar-mass–halo-mass relation, especially at M ⋆ ≳ 1010.5 M ☉. Median Ne VIII columns in the fiducial FIRE-2 model are about as high as observed upper limits allow, while the simulations analyzed do not reproduce the highest observed columns. This suggests that the median Ne VIII profiles predicted by the simulations are consistent with observations, but that the simulations may underpredict the scatter. We find similar agreement with analytical models that assume a product of the halo gas fraction and metallicity (relative to solar) ∼0.1, indicating that observations are consistent with plausible circumgalactic medium temperatures, metallicities, and gas masses. Variants of the FIRE simulations with a modified supernova feedback model and/or active galactic nuclei feedback included (as well as some other cosmological simulations from the literature) more systematically underpredict Ne VIII columns. The circumgalactic Ne VIII observations therefore provide valuable constraints on simulations that otherwise predict realistic galaxy properties.

Keywords: Hydrodynamical simulations, Galaxy formation, Quasar absorption line spectroscopy, Galaxy groups, Circumgalactic medium
Mapping the Distribution of the Magnetic Field Strength along the NGC 315 Jet. We study magnetic field strengths along the jet in NGC 315. First, we estimated the angular velocity of rotation in the jet magnetosphere by comparing the measured velocity profile of NGC 315 with the magnetohydrodynamic jet model proposed by Tomimatsu and Takahashi. Similar to the case of M87, we find that the model can reproduce the logarithmic feature of the velocity profile and suggest a slowly rotating black hole magnetosphere for NGC 315. By substituting the estimated Ω F  into the jet power predicted by the Blandford–Znajek mechanism, we estimate the magnetic field strength near the event horizon of the central black hole as 5 × 103 G ≲ B  H  ≲ 2 × 104 G. We then estimate magnetic field strengths along the jet by comparing the spectral index distribution obtained from very long baseline interferometry (VLBI) observations with a synchrotron-emitting jet model. Then we constrain the magnetic field strength at a deprojected distance z from the black hole to be in the range 0.06 G ≲ B(z) ≲ 0.9 G for 5.2 × 103 r  g  ≲ z ≲ 4.9 × 104 r  g , where r  g  represents the gravitational radius. By combining the obtained field strengths at the event horizon and the downstream section of the jet, we find that the accretion flow at the jet base is consistent with a magnetically arrested disk. We discuss a comparison of the jet power and the magnetic flux anchored to the event horizon in NGC 315 and M87.

Keywords: AGN host galaxies, Black hole physics, Magnetohydrodynamics, Radio jets
Coupled Disk-star Evolution in Galactic Nuclei and the Lifetimes of QPE Sources. A modest fraction of the stars in galactic nuclei fed toward the central supermassive black hole (SMBH) approach on low-eccentricity orbits driven by gravitational-wave radiation (extreme mass ratio inspiral (EMRI)). In the likely event that a gaseous accretion disk is created in the nucleus during this slow inspiral (e.g., via an independent tidal disruption event (TDE)), star–disk collisions generate regular short-lived flares consistent with the observed quasiperiodic eruption (QPE) sources. We present a model for the coupled star-disk evolution, which self-consistently accounts for mass and thermal energy injected into the disk from stellar collisions and associated mass ablation. For weak collision/ablation heating, the disk is thermally unstable and undergoes limit-cycle oscillations, which modulate its properties and lead to accretion-powered outbursts on timescales of years to decades, with a time-averaged accretion rate ∼0.1Ṁ Edd. Stronger collision/ablation heating acts to stabilize the disk, enabling roughly steady accretion at the EMRI-stripping rate. In either case, the stellar destruction time through ablation, and hence the maximum QPE lifetime, is ∼102–103 yr, far longer than fallback accretion after a TDE. The quiescent accretion disks in QPE sources may at the present epoch be self-sustaining and fed primarily by EMRI ablation. Indeed, the observed range of secular variability broadly matches those predicted for collision-fed disks. Changes in the QPE recurrence pattern following such outbursts, similar to that observed in GSN 069, could arise from temporary misalignment between the EMRI-fed disk and the SMBH equatorial plane as the former regrows its mass after a state transition.

Keywords: X-ray transient sources, Supermassive black holes, Tidal disruption, Gravitational waves
Accurate Measurement of the Lensing Magnification by BOSS CMASS Galaxies and Its Implications for Cosmology and Dark Matter. Magnification serves as an independent and complementary gravitational lensing measurement to shear. We develop a novel method to achieve an accurate and robust magnification measurement around BOSS CMASS galaxies across physical scales of 0.016h ‑1 Mpc &lt; r p &lt; 10h ‑1 Mpc. We first measure the excess total flux density δ M of the source galaxies in the deep DECaLS photometric catalog that are lensed by CMASS galaxies. We convert δ M to magnification μ by establishing the δ μ–δ M relation using a deeper photometric sample. By comparing magnification measurements in three optical bands (grz), we constrain the dust attenuation curve and its radial distribution, discovering a steep attenuation curve in the circumgalactic medium of CMASS galaxies. We further compare dust-corrected magnification measurements to model predictions from high-resolution dark matter-only (DMO) simulations in Wilkinson Microwave Anisotropy Probe (WMAP) and Planck cosmologies, as well as the hydrodynamic simulation TNG300-1, using precise galaxy–halo connections from the Photometric objects Around Cosmic webs method and the accurate ray-tracing algorithm P3MLens. For r p &gt; 70h ‑1 kpc, our magnification measurements are in good agreement with both WMAP and Planck cosmologies, resulting in an estimation of the matter fluctuation amplitude of S 8 = 0.816 ± 0.024. However, at r p &lt; 70h ‑1 kpc, we observe an excess magnification signal, which is higher than the DMO model in Planck cosmology at 2.8σ and would be exacerbated if significant baryon feedback is included. Implications of the potential small scale discrepancy for the nature of dark matter and for the processes governing galaxy formation are discussed.

Keywords: Observational cosmology, Gravitational lensing, Dark matter, Intergalactic dust clouds
Three-dimensional Simulations of the Magnetorotational Instability in Eccentric Disks. Previously we demonstrated that the magnetorotational instability (MRI) grows vigorously in eccentric disks, much as it does in circular disks, and we investigated the nonlinear development of the eccentric MRI without vertical gravity. Here we explore how vertical gravity influences the magnetohydrodynamic (MHD) turbulence stirred by the eccentric MRI. Similar to eccentric disks without vertical gravity, the ratio of Maxwell stress to pressure, or the Shakura–Sunyaev α parameter, remains ∼10‑2, and the local sign flip in the Maxwell stress persists. Vertical gravity also introduces two new effects. Strong vertical compression near pericenter amplifies reconnection and dissipation, weakening the magnetic field. Angular momentum transport by MHD stresses broadens the mass distribution over eccentricity at much faster rates than without vertical gravity; as a result, spatial distributions of mass and eccentricity can be substantially modified in just ∼5 to 10 orbits. MHD stresses in the eccentric debris of tidal disruption events may power emission ≳1 yr after disruption.

Keywords: Accretion, Black hole physics, Gravitation, Magnetohydrodynamical simulations
An Untargeted Search for Radio-emitting Tidal Disruption Events in the VAST Pilot Survey. We present a systematic search for tidal disruption events (TDEs) using radio data from the Variables and Slow Transients (VAST) Pilot Survey conducted using the Australian Square Kilometre Array Pathfinder. Historically, TDEs have been identified using observations at X-ray, optical, and ultraviolet wavelengths. After discovery, a few dozen TDEs have been shown to have radio counterparts through follow-up observations. With systematic time-domain radio surveys becoming available, we can now identify new TDEs in the radio regime. A population of radio-discovered TDEs has the potential to provide several key insights including an independent constraint on their volumetric rate. We conducted a search to select variable radio sources with a single prominent radio flare and a position consistent within 2σ of the nucleus of a known galaxy. While TDEs were the primary target of our search, sources identified in this search may also be consistent with active galactic nuclei exhibiting unusual flux density changes at the timescales probed, uncharacteristically bright supernovae, or a population of gamma-ray bursts. We identify a sample of 12 radio-bright candidate TDEs. The timescales and luminosities range from ∼6 to 230 days and ∼1038 to 1041 erg s‑1, respectively, consistent with models of radio emission from TDEs that launch relativistic jets. After calculating the detection efficiency of our search using a Monte Carlo simulation of TDEs, and assuming all 12 sources are jetted TDEs, we derive a volumetric rate for jetted TDEs of  0.80‑0.23+0.31  Gpc‑3 yr‑1, consistent with previous empirically estimated rates.

Keywords: Supermassive black holes, Sky surveys, Tidal disruption, Galaxy nuclei, Time domain astronomy
Time Evolution of the Synchrotron X-Ray Emission in Kepler's Supernova Remnant: The Effects of Turbulence and Shock Velocity. The maximum energy of electrons in supernova remnant (SNR) shocks is typically limited by radiative losses, where the synchrotron cooling time equals the acceleration time. The low speed of shocks in a dense medium increases the acceleration time, leading to lower maximum electron energies and fainter X-ray emissions. However, in Kepler's SNR, an enhanced electron acceleration, which proceeds close to the Bohm limit, occurs in the north of its shell, where the shock is slowed by a dense circumstellar medium (CSM). To investigate whether this scenario still holds at smaller scales, we analyzed the temporal evolution of the X-ray synchrotron flux in filamentary structures using the two deepest Chandra/ACIS X-ray observations, performed in 2006 and 2014. We examined spectra from different filaments, measured their proper motion, and calculated the acceleration to synchrotron timescale ratios. The interaction with the turbulent and dense northern CSM induces competing effects on electron acceleration: on one hand, turbulence reduces the electron mean free path enhancing the acceleration efficiency, and on the other hand, lower shock velocities increase the acceleration timescale. In most filaments, these effects compensate each other, but in one region, the acceleration timescale exceeds the synchrotron timescale, resulting in a significant decrease in nonthermal X-ray emission from 2006 to 2014, indicating fading synchrotron emission. Our findings provide a coherent understanding of the different regimes of electron acceleration observed in Kepler's SNR through various diagnostics.

Keywords: Supernova remnants, Interstellar medium
A Portrait of the Rotation of Ultra-cool Dwarfs Revealed by TESS. This study presents the results of a search for rotation signatures in 250 Gaia Data Release 3 ultra-cool dwarfs (UCDs) with TESS light curves (LCs). We identified 71 targets with unambiguous periodicities, of which 61 present rotation signatures and a single-source behavior, with periods between 0.133 and 5.81 days. Five UCDs show double-dip features, namely variations with two periods, one approximately double or half the other. The remaining 10 UCDs with unambiguous variability present a likely nonsingle behavior. We also found 20 UCDs showing complex behavior in their LCs, with noticeable fluctuations and irregular structure, with a few exhibiting apparent changes in their temporal structure. The remaining 159 targets show noisy LCs corresponding to low-amplitude signals, whose temporal variation cannot be easily identified. The distribution of the UCDs with rotation signature in a color–magnitude diagram points to a lack of rotating objects within about 11.5 &lt; M  G  &lt; 12.5 and G–G RP &lt; 1.5, separating them into two regimes, one mainly composed of less massive late-M stars with P rot ≥ 1.0 day, and another mainly composed of more massive early-M stars with P rot &lt; 1.0 day. It is important to emphasize that by separating stars into age intervals, one observes that UCDs with P rot ≥ 1.0 day tend to be located in regions of younger objects, and, in contrast, those with P rot &lt; 1.0 day are mainly concentrated in regions of older objects. Whether this trend of stars contrasting the sample separation is physical or produced by observational biases is a question to be verified in future studies.

Keywords: Stellar photometry, Brown dwarfs, Space observatories, Stellar astronomy, Low mass stars, Stellar rotation
Precise Bolometric Luminosities and Effective Temperatures of 23 Late-T and Y Dwarfs Obtained with JWST. We present infrared spectral energy distributions of 23 late-type T and Y dwarfs obtained with the James Webb Space Telescope. The spectral energy distributions consist of NIRSpec PRISM and MIRI low-resolution spectrometer spectra covering the ∼1–12 μm wavelength range at λ/Δλ ≈ 100 and broadband photometry at 15, 18, and 21 μm. The spectra exhibit absorption features common to these objects including H2O, CH4, CO, CO2, and NH3. Interestingly, while the spectral morphology changes relatively smoothly with spectral type at λ &lt; 3 μm and λ &gt; 8 μm, it shows no clear trend in the 5 μm region where a large fraction of the flux emerges. The broad-wavelength coverage of the data enables us to compute the first accurate measurements of the bolometric fluxes of cool brown dwarfs. Combining these bolometric fluxes with parallaxes from Spitzer and Hubble Space Telescope, we also obtain the first accurate bolometric luminosities of these cool dwarfs. We then used the Sonora Bobcat solar-metallicity evolutionary models to estimate the radii of the dwarfs, which results in effective temperature estimates ranging from ∼1000 to 350 K with a median uncertainty of ± 20 K, which is nearly an order of magnitude improvement over previous work. We also discuss how various portions of the spectra either do or do not exhibit a clear sequence when ordered by their effective temperatures.

Keywords: Brown dwarfs, Effective temperature, Fundamental parameters of stars, Y dwarfs, James Webb Space Telescope, Spectroscopy, Near infrared astronomy