adsabs/SciX_UAT_keywords huggingface dataset:
Little Red Dots: An Abundant Population of Faint Active Galactic Nuclei at z ∼ 5 Revealed by the EIGER and FRESCO JWST Surveys

Characterizing the prevalence and properties of faint active galactic nuclei (AGNs) in the early Universe is key for understanding the formation of supermassive black holes (SMBHs) and determining their role in cosmic reionization. We perform a spectroscopic search for broad Hα emitters at z ≈ 4–6 using deep JWST/NIRCam imaging and wide field slitless spectroscopy from the EIGER and FRESCO surveys. We identify 20 Hα lines at z = 4.2–5.5 that have broad components with line widths from ∼1200–3700 km s‑1, contributing ∼30%–90% of the total line flux. We interpret these broad components as being powered by accretion onto SMBHs with implied masses ∼107–8 M ⊙. In the UV luminosity range M UV,AGN+host = ‑21 to ‑18, we measure number densities of ≈10‑5 cMpc‑3. This is an order of magnitude higher than expected from extrapolating quasar UV luminosity functions (LFs). Yet, such AGN are found in only <1% of star-forming galaxies at z ∼ 5. The number density discrepancy is much lower when compared to the broad Hα LF. The SMBH mass function agrees with large cosmological simulations. In two objects, we detect complex Hα profiles that we tentatively interpret as caused by absorption signatures from dense gas fueling SMBH growth and outflows. We may be witnessing early AGN feedback that will clear dust-free pathways through which more massive blue quasars are seen. We uncover a strong correlation between reddening and the fraction of total galaxy luminosity arising from faint AGN. This implies that early SMBH growth is highly obscured and that faint AGN are only minor contributors to cosmic reionization.

Keywords: high-redshift galaxies; quasars; active galactic nuclei; reionization
The Ratio of Perpendicular and Parallel Diffusion Coefficients of Low-energy Particles in Turbulent Space Plasmas

Recently an improved nonlinear theory for the transport of energetic particles across a mean magnetic field has been developed. The latter theory is called the field line-particle decorrelation theory and is the first analytical theory that agrees with test-particle simulations without the need of a correction parameter, nor does the theory contain any other free parameter. In the current paper we derive analytical forms for the ratio of perpendicular and parallel spatial diffusion coefficients κ ⊥/κ ∥ of low-energy particles. In the considered limit the latter ratio is constant meaning that it does not depend on particle energy or rigidity. It is shown that the ratio always has the form ${\kappa }_{\perp }/{\kappa }_{\parallel }={a}^{2}\delta {B}_{x}^{2}/{B}_{0}^{2}$ if a two-dimensional turbulence model is employed. Furthermore, the parameter a 2 depends only on the shape of the turbulence spectrum but not on the magnetic fields. The obtained results can be important for a variety of applications such as studies of solar modulation and diffusive shock acceleration.

Keywords: interplanetary turbulence; cosmic rays
Galactic Winds and Bubbles from Nuclear Starburst Rings

Galactic outflows from local starburst galaxies typically exhibit a layered geometry, with cool 104 K flow sheathing a hotter 107 K, cylindrically collimated, X-ray-emitting plasma. Here we argue that winds driven by energy injection in a ring-like geometry can produce this distinctive large-scale multiphase morphology. The ring configuration is motivated by the observation that massive young star clusters are often distributed in a ring at the host galaxy's inner Lindblad resonance, where larger-scale spiral arm structure terminates. We present parameterized three-dimensional radiative hydrodynamical simulations that follow the emergence and dynamics of energy-driven hot winds from starburst rings. In this letter, we show that the flow shocks on itself within the inner ring hole, maintaining high 107 K temperatures, while flows that emerge from the wind-driving ring unobstructed can undergo rapid bulk cooling down to 104 K, producing a fast hot biconical outflow enclosed by a sheath of cooler nearly comoving material without ram pressure acceleration. The hot flow is collimated along the ring axis, even in the absence of pressure confinement from a galactic disk or magnetic fields. In the early stages of expansion, the emerging wind forms a bubble-like shape reminiscent of the Milky Way's eROSITA and Fermi bubbles and can reach velocities usually associated with active-galactic-nucleus-driven winds. We discuss the physics of the ring configuration, the conditions for radiative bulk cooling, and the implications for future X-ray observations.

Keywords: starburst galaxies; active galaxies; hydrodynamical simulations; astronomical simulations; active galactic nuclei; galactic winds; galaxy evolution; stellar feedback
Edge-of-the-Multis: Evidence for a Transition in the Outer Architectures of Compact Multiplanet Systems

Although the architectures of compact multiple-planet systems are well characterized, there has been little examination of their "outer edges," or the locations of their outermost planets. Here we present evidence that the observed high-multiplicity Kepler systems truncate at smaller orbital periods than can be explained by geometric and detection biases alone. To show this, we considered the existence of hypothetical planets orbiting beyond the observed transiting planets with properties dictated by the "peas-in-a-pod" patterns of intrasystem radius and period ratio uniformity. We evaluated the detectability of these hypothetical planets using (1) a novel approach for estimating the mutual inclination dispersion of multitransiting systems based on transit chord length ratios, and (2) a model of transit probability and detection efficiency that accounts for the impacts of planet multiplicity on completeness. Under the assumption that the "peas-in-a-pod" patterns continue to larger orbital separations than observed, we find that ≳35% of Kepler compact multis should possess additional detected planets beyond the known planets, constituting a ~7σ discrepancy with the lack of such detections. These results indicate that the outer (~100-300 days) regions of compact multis experience a truncation (i.e., an "edge-of-the-multis") or a significant breakdown of the "peas-in-a-pod" patterns, in the form of systematically smaller radii or larger period ratios. We outline future observations that can distinguish these possibilities, and we discuss implications for planet formation theories.

Keywords: exoplanets; super earths; mini neptunes; exoplanet systems; exoplanet dynamics; exoplanet formation
Turbulence in Milky Way Star-forming Regions Traced by Young Stars and Gas

The interstellar medium (ISM) is turbulent over vast scales and in various phases. In this paper, we study turbulence with different tracers in four nearby star-forming regions: Orion, Ophiuchus, Perseus, and Taurus. We combine the APOGEE-2 and Gaia surveys to obtain the full six-dimensional measurements of positions and velocities of young stars in these regions. The velocity structure functions (VSFs) of the stars show a universal scaling of turbulence. We also obtain Hα gas kinematics in these four regions from the Wisconsin H-Alpha Mapper. The VSFs of the Hα are more diverse compared to those of stars. In regions with recent supernova activities, they show characteristics of local energy injections and higher amplitudes compared to the VSFs of stars and of CO from the literature. Such difference in amplitude of the VSFs can be explained by the different energy and momentum transport from supernovae into different phases of the ISM, thus resulting in higher levels of turbulence in the warm ionized phase traced by Hα. In regions without recent supernova activities, the VSFs of young stars, Hα, and CO are generally consistent, indicating well-coupled turbulence between different phases. Within individual regions, the brighter parts of the Hα gas tend to have a higher level of turbulence than the low-emission parts. Our findings support a complex picture of the Milky Way ISM, where turbulence can be driven at different scales and inject energy unevenly into different phases.

Keywords: molecular clouds; stellar dynamics; young star clusters; interstellar medium; stellar feedback; supernova dynamics; supernova remnants; stellar motion; warm ionized medium
Iterative Phase Correlation Algorithm for High-precision Subpixel Image Registration

Many astrophysical observations and measurement techniques that rely on data from images include an image registration step. The results of such techniques thus heavily rely on the precision of the registration. We present an Iterative Phase Correlation (IPC) algorithm, which is an extension of the well-known phase correlation method of image registration and is ideally suited for problems, where the subpixel registration accuracy plays a crucial role. Furthermore, a sophisticated and reliable method of optimal IPC parameter estimation is described. The paper includes examples of such optimized parameters for Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager, SDO/Atmospheric Imaging Assembly, and Solar Terrestrial Relations Observatory A/B Sun Earth Connection Coronal and Heliospheric Investigation images. The new method (both with or without the parameter optimization step) significantly outperforms standard image registration methods, such as (non-iterative) phase correlation or (normalized) cross correlation in the sense of subpixel accuracy. A step-by-step pseudocode implementation is also included.

Keywords: astronomical techniques; direct imaging; astronomy software; ccd observation; publicly available software; fast fourier transform; astrometry; algorithms; astronomical methods; astronomy data analysis; computational methods; analytical mathematics
Impact of Pycnonuclear Fusion Uncertainties on the Cooling of Accreting Neutron Star Crusts

The observation of X-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. This, however, requires extensive modeling of the crusts and matching the results to observations. The pycnonuclear fusion reaction rates implemented in these models are theoretically calculated by extending phenomenological expressions and have large uncertainties spanning many orders of magnitude. We present the first sensitivity studies of these pycnonuclear fusion reactions in realistic network calculations. We also couple the reaction network with the thermal evolution code dStar to further study their impact on the neutron star cooling curves in quiescence. Varying the pycnonuclear fusion reaction rates alters the depth at which nuclear heat is deposited although the total heating remains constant. The enhancement of the pycnonuclear fusion reaction rates leads to an overall shallower deposition of nuclear heat. The impurity factors are also altered depending on the type of ashes deposited on the crust. These total changes correspond to a variation of up to 9 eV in the modeled cooling curves. While this is not sufficient to explain the shallow heat source, it is comparable to the observational uncertainties and can still be important for modeling the neutron star crust.

Keywords: nuclear astrophysics; neutron stars; degenerate matter; x-ray transient sources
An Upper Limit on the Charge of the Black Hole Sgr A* from EHT Observations

The Event Horizon Telescope (EHT) recently released an image of the supermassive black hole Sgr A* showing an angular shadow diameter d sh = 48.7 ± 7 μas and Schwarzschild shadow deviation $\delta =-{0.08}_{-0.09}^{+0.09}\,(\mathrm{VLTI})$ , $-{0.04}_{-0.10}^{+0.09}\,(\mathrm{Keck})$ using a black hole mass $M={4.0}_{-0.6}^{+1.1}\times {10}^{6}\,{M}_{\odot }$ . The EHT image of Sgr A* is consistent with a Kerr black hole's expected appearance, and the results directly prove the existence of a supermassive black hole at the center of the Milky Way. Here, we use the EHT observational results for Sgr A* to investigate the constraints on its charge with the aid of Kerr-like black holes, paying attention to three leading rotating models, namely Kerr-Newman, Horndeski, and hairy black holes. Modeling the supermassive black hole Sgr A* as these Kerr-like black holes, we observe that the EHT results for Sgr A* place stricter upper limits on the parameter space of Kerr-Newman and Horndeski black holes than those placed by the EHT results for M87*. A systematic bias analysis reveals that observational results from future EHT experiments will place more precise limits on the charge of the black hole Sgr A*. Thus, the Kerr-like black holes and Kerr black holes are indiscernible in a substantial region of the EHT-constrained parameter space; the claim is substantiated by our bias analysis.

Keywords: astrophysical black holes; black hole physics; galactic center; gravitation; gravitational lensing
The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at z = 0.27

We present ZTF18abvkwla (the "Koala"), a fast blue optical transient discovered in the Zwicky Transient Facility (ZTF) One-Day Cadence (1DC) Survey. ZTF18abvkwla has a number of features in common with the groundbreaking transient AT 2018cow: blue colors at peak ( $g-r\approx -0.5$ mag), a short rise time from half-max of under two days, a decay time to half-max of only three days, a high optical luminosity ( ${M}_{g,\mathrm{peak}}\approx -20.6$ mag), a hot (≳40,000 K) featureless spectrum at peak light, and a luminous radio counterpart. At late times ( ${\rm{\Delta }}t\gt 80\,\mathrm{days}$ ), the radio luminosity of ZTF18abvkwla ( $\nu {L}_{\nu }\gtrsim {10}^{40}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ at 10 $\mathrm{GHz}$ , observer-frame) is most similar to that of long-duration gamma-ray bursts (GRBs). The host galaxy is a dwarf starburst galaxy ( $M\approx 5\times {10}^{8}\,{M}_{\odot }$ , $\mathrm{SFR}\approx 7\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ ) that is moderately metal-enriched ( $\mathrm{log}[{\rm{O}}/{\rm{H}}]\approx 8.5$ ), similar to the hosts of GRBs and superluminous supernovae. As in AT2018cow, the radio and optical emission in ZTF18abvkwla likely arise from two separate components: the radio from fast-moving ejecta ( ${\rm{\Gamma }}\beta c\gt 0.38c$ ) and the optical from shock-interaction with confined dense material (<0.07 M⊙ in $\sim {10}^{15}\,\mathrm{cm}$ ). Compiling transients in the literature with ${t}_{\mathrm{rise}}\lt 5\,\mathrm{days}$ and ${M}_{\mathrm{peak}}\lt -20$ mag, we find that a significant number are engine-powered, and suggest that the high peak optical luminosity is directly related to the presence of this engine. From 18 months of the 1DC survey, we find that transients in this rise-luminosity phase space are at least two to three orders of magnitude less common than CC SNe. Finally, we discuss strategies for identifying such events with future facilities like the Large Synoptic Survey Telescope, as well as prospects for detecting accompanying X-ray and radio emission.

Keywords: radio transient sources; high energy astrophysics; supernovae; core-collapse supernovae; jets; sky surveys
X-Ray Studies of the Pulsar PSR J1420-6048 and Its TeV Pulsar Wind Nebula in the Kookaburra Region

We present a detailed analysis of broadband X-ray observations of the pulsar PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra, XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we detected 68 ms pulsations of the pulsar and characterized its X-ray pulse profile, which exhibits a sharp spike and a broad bump separated by ~0.5 in phase. A high-resolution Chandra image revealed a complex morphology of the PWN: a torus-jet structure, a few knots around the torus, one long (~7') and two short tails extending in the northwest direction, and a bright diffuse emission region to the south. Spatially integrated Chandra and NuSTAR spectra of the PWN out to 2.'5 are well-described by a power-law model with a photon index Γ ≈ 2. A spatially resolved spectroscopic study, as well as NuSTAR radial profiles of the 3-7 keV and 7-20 keV brightness, showed a hint of spectral softening with increasing distance from the pulsar. A multiwavelength spectral energy distribution (SED) of the source was then obtained by supplementing our X-ray measurements with published radio, Fermi-LAT, and H.E.S.S. data. The SED and radial variations of the X-ray spectrum were fit with a leptonic multizone emission model. Our detailed study of the PWN may be suggestive of (1) particle transport dominated by advection, (2) a low magnetic-field strength (B ~ 5 μG), and (3) electron acceleration to ~PeV energies.

Keywords: pulsar wind nebulae; pulsars; spectral energy distribution; high energy astrophysics; gamma-ray sources; radiative processes; x-ray astronomy
Calibration of Transition-edge Sensor (TES) Bolometer Arrays with Application to CLASS

The current and future cosmic microwave background (CMB) experiments fielding kilopixel arrays of transition-edge sensor (TES) bolometers require accurate and robust gain calibration methods. We simplify and refactor the standard TES model to directly relate the detector responsivity calibration and optical time constant to the measured TES current I and the applied bias current I b. The calibration method developed for the Cosmology Large Angular Scale Surveyor (CLASS) TES bolometer arrays relies on current versus voltage (I-V) measurements acquired daily prior to CMB observations. By binning Q-band (40 GHz) I-V measurements by optical loading, we find that the gain calibration median standard error within a bin is 0.3%. We test the accuracy of this I-V bin detector calibration method by using the Moon as a photometric standard. The ratio of measured Moon amplitudes between the detector pairs sharing the same feedhorn indicates a TES calibration error of 0.5%. We also find that, for the CLASS Q-band TES array, calibrating the response of individual detectors based solely on the applied TES bias current accurately corrects TES gain variations across time but introduces a bias in the TES calibration from data counts to power units. Since the TES current bias value is set and recorded before every observation, this calibration method can always be applied to the raw TES data and is not subject to I-V data quality or processing errors.

Keywords: cmbr detectors; observational cosmology; early universe; cosmic microwave background radiation
The Effects of Self-interacting Bosonic Dark Matter on Neutron Star Properties

We propose a model of asymmetric bosonic dark matter (DM) with self-repulsion. By adopting the two-fluid formalism, we study different DM distribution regimes, either, fully condensed inside the core of a star, or, otherwise, distributed in a dilute halo around a neutron star (NS). We show that for a given total gravitational mass, DM condensed in a core leads to a smaller radius and tidal deformability compared to a pure baryonic star. This effect may be interpreted as an effective softening of the equation of state. On the other hand, the presence of a DM halo increases the tidal deformability and total gravitational mass. As a result, an accumulated DM inside compact stars could mimic an apparent softening/stiffening of strongly interacting matter EoS and constraints we impose on it at high densities. We limit the model parameter space by confronting the cross section of the DM self-interaction to the constraint extracted from the analysis of the Bullet Cluster. Furthermore, from the analysis of the effect of DM particles, interaction strength, and relative DM fractions inside NSs we obtained a rigorous constraint on model parameters. To identify its impact on NSs we consider the DM fraction may reach up to 5%, which could be considered too high in several scenarios. Finally, we discuss several pieces of smoking gun evidence of the presence of DM that is free from the abovementioned degeneracy between the effect of DM and properties of strongly interacting matter. These signals could be probed with future and ongoing astrophysical and gravitational wave surveys.

Keywords: neutron stars; dark matter; gravitational waves
Magnetar as the Central Engine of AT2018cow: Optical, Soft X-Ray, and Hard X-Ray Emission

AT2018cow is the most extensively observed and widely studied fast blue optical transient to date; its unique observational properties challenge all existing standard models. In this paper, we model the luminosity evolution of the optical, soft X-ray, and hard X-ray emission, as well as the X-ray spectrum of AT2018cow with a magnetar-centered engine model. We consider a two-zone model with a striped magnetar wind in the interior and an expanding ejecta outside. The soft and hard X-ray emission of AT2018cow can be explained by the leakage of high-energy photons produced by internal gradual magnetic dissipation in the striped magnetar wind, while the luminous thermal UV/optical emission results from the thermalization of the ejecta by the captured photons. The two-component energy spectrum yielded by our model with a quasi-thermal component from the optically thick region of the wind superimposed on an optically thin synchrotron component well reproduces the X-ray spectral shape of AT2018cow. The Markov Chain Monte Carlo fitting results suggest that in order to explain the very short rise time to peak of the thermal optical emission, a low ejecta mass M ej ≈ 0.1 M ⊙ and high ejecta velocity ${v}_{\mathrm{SN}}\approx 0.17c$ are required. A millisecond magnetar with P 0 ≈ 3.7 ms and B p ≈ 2.4 × 1014 G is needed to serve as the central engine of AT2018cow.

Keywords: magnetars; x-ray transient sources; supernovae; core-collapse supernovae
Dissecting Nearby Galaxies with piXedfit. II. Spatially Resolved Scaling Relations among Stars, Dust, and Gas

We study spatially resolved scaling relations among stars, dust, and gas in ten nearby spiral galaxies. In a preceding paper, we have derived spatially resolved properties of the stellar population and dust by a panchromatic spectral energy distribution fitting using piXedfit. Now, we investigate resolved star formation ( ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ -ΣSFR-Σ*) and dust scaling relations. While the relations with all subgalactic regions of the galaxies are reasonably tight (σ ≲ 0.3 dex), we find that most of the scaling relations exhibit galaxy-to-galaxy variations in normalization and shape. Only two relations of Σdust-Σgas and Σdust- ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ do not show noticeable galaxy-to-galaxy variations among our sample galaxies. We further investigate the correlations among the scaling relations. We find significant correlations among the normalization of the ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ -ΣSFR-Σ* relations, which suggest that the galaxies with higher levels of resolved H2 fraction ( ${f}_{{{\rm{H}}}_{2}}$ ) tend to have higher levels of resolved star formation efficiency (SFE) and specific star formation rate (sSFR). We also observe that the galaxies with higher levels of resolved dust-to-stellar mass ratios tend to have higher levels of resolved sSFR, SFE, and ${f}_{{{\rm{H}}}_{2}}$ . Moreover, we find that the galaxies with higher global sSFR and less compact morphology tend to have higher levels of the resolved sSFR, SFE, and ${f}_{{{\rm{H}}}_{2}}$ , which can explain the variations in the normalization of the ${{\rm{\Sigma }}}_{{{\rm{H}}}_{2}}$ -ΣSFR-Σ* relationships. Overall, we observe indications of the contributions of both global and local factors in governing the star formation process in galaxies.

Keywords: galaxy evolution; spiral galaxies; interstellar medium; gas-to-dust ratio