adsabs/SciX_UAT_keywords huggingface dataset:
Recent Formation of a Spiral Disk Hosting Progenitor Globular Clusters at the Center of the Perseus Brightest Cluster Galaxy. I. Spiral Disk

We address the nature and origin of a spiral disk at the center of NGC 1275, the giant elliptical galaxy at the center of the Perseus cluster, that spans a radius of ~5 kpc. By comparing stellar absorption lines measured in long-slit optical spectra with synthetic spectra for single stellar populations, we find that fitting of these lines requires two stellar populations: (i) a very young population that peaks in radial velocity at ±250 km s-1 of the systemic velocity within a radius of ~720 pc of the nucleus, a 1σ velocity dispersion significantly lower than 140 km s-1, and an age of 0.15 ± 0.05 Gyr; and (ii) a very old population having a constant radial velocity with a radius corresponding to the systemic velocity, a much broader velocity dispersion of ~250 km s-1, and an age of around 10 Gyr. We attribute the former to a post-starburst population associated with the spiral disk, and the latter to the main stellar body of NGC 1275 along the same sight line. If the spiral disk is the remnant of a cannibalized galaxy, then its progenitor would have had to retain an enormous amount of gas in the face of intensive ram-pressure stripping so as to form a total initial mass in stars of ~3 × 109 M ⊙. More likely, the central spiral originally comprised a gaseous body accreted over the distant past from a residual cooling flow, before experiencing a starburst ~0.15 Gyr ago to form its stellar body.

Keywords: galaxy spectroscopy; optical astronomy; cooling flows; post-starburst galaxies; spectral index; stellar populations; brightest cluster galaxies
One-dimensional Force-free Numerical Simulations of Alfvén Waves around a Spinning Black String

We performed one-dimensional force-free magnetodynamic numerical simulations of the propagation of Alfvén waves along magnetic field lines around a spinning black-hole-like object, the Banados-Teitelboim-Zanelli black string, to investigate the dynamic process of wave propagation and energy transport with Alfvén waves. We considered an axisymmetric and stationary magnetosphere and perturbed the background magnetosphere to obtain the linear wave equation for the Alfvén wave mode. The numerical results show that the energy of Alfvén waves monotonically increases as the waves propagate outwardly along the rotating curved magnetic field line around the ergosphere, where energy seems not to be conserved, in the case of energy extraction from the black string by the Blandford-Znajek mechanism. The apparent breakdown of energy conservation suggests the existence of a wave induced by the Alfvén wave. Considering the additional fast magnetosonic wave induced by the Alfvén wave, the energy conservation is confirmed. Similar relativistic phenomena, such as the amplification of Alfvén waves and induction of fast magnetosonic waves, are expected around a spinning black hole.

Keywords: black hole physics; general relativity; plasma astrophysics; alfven waves; magnetic fields; active galactic nuclei; computational methods
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary System

We report the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ 287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ± 0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ 287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ 287 as well as the dense monitoring sample of Krakow.

Keywords: high energy astrophysics
CEERS Key Paper. VIII. Emission-line Ratios from NIRSpec and NIRCam Wide-Field Slitless Spectroscopy at z > 2

We use James Webb Space Telescope Near-Infrared Camera Wide Field Slitless Spectroscopy (NIRCam WFSS) and the Near-Infrared spectrograph (NIRSpec) in the Cosmic Evolution Early Release survey to measure rest-frame optical emission-line ratios of 155 galaxies at z > 2. The blind NIRCam grism observations include a sample of galaxies with bright emission lines that were not observed on the NIRSpec masks. We study the changes of the Hα, [O III]/Hβ, and [Ne III]/[O II] emission lines in terms of redshift by comparing to lower-redshift SDSS, CLEAR, and MOSDEF samples. We find a significant (>3σ) correlation between [O III]/Hβ with redshift, while [Ne III]/[O II] has a marginal (2σ) correlation with redshift. We compare [O III]/Hβ and [Ne III]/[O II] to stellar mass and Hβ SFR. We find that both emission-line ratios have a correlation with Hβ SFR and an anticorrelation with stellar mass across the redshifts 0 < z < 9. Comparison with MAPPINGS V models indicates that these trends are consistent with lower metallicity and higher ionization in low-mass and high-SFR galaxies. We additionally compare to IllustrisTNG predictions and find that they effectively describe the highest [O III]/Hβ ratios observed in our sample, without the need to invoke MAPPINGS models with significant shock ionization components.

Keywords: emission line galaxies; galaxy evolution; galaxies; active galaxies
Parent Volatile Outgassing Associations in Cometary Nuclei: Synthesizing Rosetta Measurements and Ground-based Observations

Comets, as remnants of the solar system's formation, vary in volatile-refractory content. In situ comet studies, such as the Rosetta mission to 67P/Churyumov–Gerasimenko, provide detailed volatile composition insights, while ground-based studies offer broader comet samples but in fewer species. Comparing 67P's volatile correlations during the 2 yr Rosetta mission with those from remote sensing gives insights into volatile distribution in the nucleus and factors influencing their release. Our goal is to identify associations between volatiles seen from the ground and those in 67P. Given 67P's seasonal variations, we segmented the Rosetta mission around 67P into six epochs, reflecting different insolation conditions. It has been suggested that there are at least two different ice matrices, H2O and CO2 ice, in which the minor species are embedded in different relative abundances within them. We employed various methodologies to establish associations among volatiles, such as volatile production rates, spatial distributions, patterns in mixing ratio, and local outgassing source locations. We note that different techniques of grouping molecules with respect to H2O and CO2 may yield different results. Earth's atmosphere blocks CO2; however, due to observed differences between H2O and C2H6 from the ground and between H2O and CO2 from comet missions, C2H6 is suggested to be a CO2 proxy. Our study delves into cometary coma molecular correlations, highlighting their associations with H2O and CO2 matrices and advancing our understanding of the early solar system comet formation and evolution.

Keywords: comet nuclei; remote sensing; comet volatiles
Magnetic Helicity Associated with the Proton Temperature Anisotropy Instabilities in the Presence of an Imbalanced Solar Wind Turbulence

Some of the most common processes in the solar wind, such as turbulence and wave generation by instabilities, are associated with spectral magnetic helicity. Therefore, the helicity is a convenient tool to investigate these processes. We use three-dimensional nonlinear kinetic simulations with particle ions and fluid electrons to analyze the magnetic helicity produced by proton temperature anisotropy instabilities coexisting with an ambient turbulence. The symmetry of the unstable system is violated by alpha-particle streaming with respect to protons along the mean magnetic field. At the same time, the turbulent fluctuations are also imbalanced by a nonzero cross-helicity. We show that in the nonlinear phase of the instability the resulting helicity structure is different from the prediction of the linear theory. In particular, it contains sign reversals and multiple domains of nonzero helicity. The turbulence generates its own magnetic helicity signature, which extends over a wide range of angles around the direction perpendicular to the mean magnetic field, and can have a sign the same as or opposite to that of the instability. These findings are consistent with the observed helicity spectra in the solar wind.

Keywords: space plasmas; interplanetary turbulence; solar wind
Electrostatic Turbulence and Debye-scale Structures in Collisionless Shocks

We present analysis of more than 100 large-amplitude bipolar electrostatic structures in a quasi-perpendicular supercritical Earth's bow shock crossing, measured by the Magnetospheric Multiscale spacecraft. The occurrence of the bipolar structures is shown to be tightly correlated with magnetic field gradients in the shock transition region. The bipolar structures have negative electrostatic potentials and spatial scales of a few Debye lengths. The bipolar structures propagate highly oblique to the shock normal with velocities (in the plasma rest frame) of the order of the ion-acoustic velocity. We argue that the bipolar structures are ion phase space holes produced by the two-stream instability between incoming and reflected ions. This is the first identification of the ion two-stream instability in collisionless shocks.

Keywords: astrophysical processes
GOALS-JWST: Revealing the Buried Star Clusters in the Luminous Infrared Galaxy VV 114

We present the results of a James Webb Space Telescope NIRCam investigation into the young massive star cluster (YMC) population in the luminous infrared galaxy VV 114. We identify 374 compact YMC candidates with signal-to-noise ratios ≥ 3, 5, and 5 at F150W, F200W, and F356W, respectively. A direct comparison with our HST cluster catalog reveals that ~20% of these sources are undetected at optical wavelengths. Based on yggdrasil stellar population models, we identify 17 YMC candidates in our JWST imaging alone with F150W - F200W and F200W - F356W colors suggesting they are all very young, dusty (A V = 5-15), and massive (105.8 < M ⊙ < 106.1). The discovery of these "hidden" sources, many of which are found in the "overlap" region between the two nuclei, quadruples the number of t < 3 Myr clusters and nearly doubles the number of t < 6 Myr clusters detected in VV 114. Now extending the cluster age distribution ( ${dN}/d\tau \propto {\tau }^{\gamma }$ ) to the youngest ages, we find a slope of γ = -1.30 ± 0.39 for 106 < τ(yr) < 107, which is consistent with the previously determined value from 107 < τ(yr) < 108.5, and confirms that VV 114 has a steep age distribution slope for all massive star clusters across the entire range of cluster ages observed. Finally, the consistency between our JWST- and HST-derived age distribution slopes indicates that the balance between cluster formation and destruction has not been significantly altered in VV 114 over the last 0.5 Gyr.

Keywords: young star clusters; luminous infrared galaxies; star forming regions; interacting galaxies
Constraining Cosmic-Ray Acceleration in the Magnetospheric Gaps of Sgr A*

Sagittarius A* (Sgr A*) is a potential very high energy (VHE) γ-ray and cosmic-ray source. We examine limits to gap-type particle acceleration in the magnetosphere of Sgr A*, showing that in the current phase of activity proton acceleration to PeV energies is possible, with injection powers into the environment usually limited to several 1036 erg s-1. Compton upscattering of ambient soft photons by gap-accelerated electrons could yield TeV emission compatible with the detected VHE point source. We explore the dependency of the results on changes in the accretion rate showing that higher stages in the past are unlikely to increase the power output unless the inner accretion flows itself changed its configuration.

Keywords: high energy astrophysics; black hole physics; galactic cosmic rays; galactic center
Constraints on Stellar Flare Energy Ratios in the NUV and Optical from a Multiwavelength Study of GALEX and Kepler Flare Stars

We present a multiwavelength study of stellar flares on primarily G-type stars using overlapping time domain surveys in the near-ultraviolet (NUV) and optical regimes. The NUV (the Galaxy Evolution Explorer; GALEX) and optical (Kepler) wavelength domains are important for understanding energy fractionations in stellar flares, and for constraining the associated incident radiation on a planetary atmosphere. We follow up on the NUV flare detections presented in Brasseur et al., using coincident Kepler long (1557 flares) and short (two flares) cadence light curves. We find no evidence of optical flares at these times, and place limits on the flare energy ratio between the two wave bands. We find that the energy ratio is correlated with GALEX band energy, and extends over a range of about 3 orders of magnitude in the ratio of the upper limit of Kepler band flare energy to NUV flare energy at the same time for each flare. The two flares with Kepler short-cadence data indicate that the true Kepler band energy may be much lower than the long-cadence-based upper limit. A similar trend appears for the bulk flare energy properties of nonsimultaneously observed flares on the same stars. We provide updated models to describe the flare spectral energy distribution from the NUV through the optical including continua and emission lines to improve upon blackbody-only models. The spread of observed energy ratios is much larger than encompassed by these models and suggests new physics is at work. These results call for a better understanding of NUV flare physics and provide a cautionary tale about using only optical flare measurements to infer the UV irradiation of close-in planets.

Keywords: stellar astronomy; stellar physics; optical flares; stellar flares; near ultraviolet astronomy
A New Likely Redback Millisecond Pulsar Binary with a Massive Neutron Star: 4FGL J2333.1-5527

We present the discovery of a likely new redback millisecond pulsar (MSP) binary associated with the Fermi γ-ray source 4FGL J2333.1-5527. Using optical photometric and spectroscopic observations from the Southern Astrophysical Research telescope, we identify a low-mass, main-sequence-like companion in a 6.9 hr, highly inclined orbit around a suspected massive neutron star primary. Archival XMM-Newton X-ray observations show this system has a hard power-law spectrum Γ = 1.6 ± 0.3 and LX ∼ 5 × 1031 erg s-1, consistent with redback MSP binaries. Our data suggest that for secondary masses typical of redbacks, the mass of the neutron star is likely well in excess of ∼1.4 M⊙, but future timing of the radio pulsar is necessary to bolster this tentative conclusion. This work shows that a bevy of nearby compact binaries still await discovery, and that unusually massive neutron stars continue to be common in redbacks.

Keywords: millisecond pulsars; low-mass x-ray binary stars; gamma-rays; compact binary stars
Possible Evidence for the Gluon Condensation Effect in Cosmic Positron and Gamma-Ray Spectra

The gluon condensation (GC) effect in cosmic proton-proton collisions at high energy is used to explain an excess in the positron spectrum observed by the Alpha Magnetic Spectrometer. We find that this excess may originate from the GC effect in Tycho's supernova remnant.

Keywords: gamma-ray astronomy; high energy astrophysics; galactic cosmic rays
CLEAR: Boosted Lyα Transmission of the Intergalactic Medium in UV-bright Galaxies

Reionization is an inhomogeneous process, thought to begin in small ionized bubbles of the intergalactic medium (IGM) around overdense regions of galaxies. Recent Lyα studies during the epoch of reionization show evidence that ionized bubbles formed earlier around brighter galaxies, suggesting higher IGM transmission of Lyα from these galaxies. We investigate this problem using IR slitless spectroscopy from the Hubble Space Telescope (HST) Wide-Field Camera 3 (WFC3) G102 grism observations of 148 galaxies selected via photometric redshifts at 6.0 < z < 8.2. These galaxies have spectra extracted from the CANDELS Lyα Emission at Reionization (CLEAR) survey. We combine the CLEAR data for 275 galaxies with the Keck Deep Imaging Multi-Object Spectrograph and MOSFIRE data set from the Texas Spectroscopic Search for Lyα Emission at the End of Reionization Survey. We constrain the Lyα equivalent width (EW) distribution at 6.0 < z < 8.2, which is described by an exponential form, ${dN}/d\mathrm{EW}\propto \exp (-\mathrm{EW})/{W}_{0}$ , with the characteristic e-folding scale width (W 0). We confirm a significant drop in the Lyα strength (i.e., W 0) at z > 6. Furthermore, we compare the redshift evolution of W 0 between galaxies at different UV luminosities. UV-bright (M UV < -21 [i.e., L UV > L*]) galaxies show weaker evolution with a decrease of 0.4 ( ± 0.2) dex in W 0 at z > 6, while UV-faint (M UV > -21 [L UV < L*]) galaxies exhibit a significant drop of 0.7-0.8 (±0.2) dex in W 0 from z < 6 to z > 6. If the change in W 0 is proportional to the change in the IGM transmission for Lyα photons, then this is evidence that the transmission is "boosted" around UV-brighter galaxies, suggesting that reionization proceeds faster in regions around such galaxies.

Keywords: reionization; early universe; intergalactic medium; high-redshift galaxies; lyman-alpha galaxies; extragalactic astronomy
Gravitational Lensing of Acoustic Charged Black Holes

We study the gravitational lensing of acoustic charged black holes in strong and weak field limit approximations. For this purpose, we first numerically obtain the deflection limit coefficients and deflection angle in the strong field limit. We observe that the strong deflection angle α D increases with increasing magnitude of the charged parameter Q and that the strong deflection angle α D of an acoustic charged black hole with tuning parameter ξ = 4 is greater than that of a standard Reissner-Nordström black hole (ξ = 0). We also study the astrophysical consequences via strong gravitational lensing by taking the example of various supermassive black holes in the center of several galaxies and observe that the acoustic charged black hole could be quantitatively distinguished from standard Reissner-Nordström (ξ = 0) and standard Schwarzschild (ξ = 0, Q = 0) black holes. Furthermore, by using the Gauss-Bonnet theorem, we derive the weak deflection angle in the background of an acoustic charged black hole in the curved spacetime. We find that, for fixed values of the charged parameter Q and the tuning parameter (ξ = 0 or 4), the weak deflection angle σ D decreases with the impact parameter b. We also observe that the weak deflection angle σ D decreases with increasing magnitude of the charged parameter Q for a fixed value of the tuning parameter (ξ = 0 or 4). Our results suggest that the observational test for an acoustic charged black hole is indeed feasible, and it is generalized to the cases of acoustic Schwarzschild (Q = 0), standard Reissner-Nordström (ξ = 0), and standard Schwarzschild (ξ = 0, Q = 0) black holes.

Keywords: weak gravitational lensing; strong gravitational lensing; gravitational lensing
Circumbinary Disk Evolution in the Presence of an Outer Companion Star

We consider a hierarchical triple system consisting of an inner eccentric binary with an outer companion. A highly misaligned circumbinary disk around the inner binary is subject to two competing effects: (i) nodal precession about the inner binary eccentricity vector that leads to an increase in misalignment (polar alignment) and (ii) Kozai-Lidov (KL) oscillations of eccentricity and inclination driven by the outer companion that leads to a reduction in the misalignment. The outcome depends upon the ratio of the timescales of these effects. If the inner binary torque dominates, then the disk aligns to a polar orientation. If the outer companion torque dominates, then the disk undergoes KL oscillations. In that case, the highly eccentric and misaligned disk is disrupted and accreted by the inner binary, while some mass is transferred to the outer companion. However, when the torques are similar, the outer parts of the circumbinary disk can undergo large eccentricity oscillations while the inclination remains close to polar orientation. The range of initial disk inclinations that evolve to a polar orientation is smaller in the presence of the outer companion. Disk breaking is also more likely, at least temporarily, during the polar alignment process. The stellar orbits in HD 98800 have parameters such that polar alignment of the circumbinary disk is expected. In the absence of gas, solid particles are unstable at much smaller radii than the gas-disk inner tidal truncation radius because KL-driven eccentricity leads to close encounters with the binary.

Keywords: accretion; stellar accretion disks; circumstellar disks; protoplanetary disks; trinary stars; binary stars; hydrodynamics; exoplanet formation; planet formation
Detecting High-energy Neutrino Minibursts from Local Supernovae with Multiple Neutrino Observatories

Growing evidence from multiwavelength observations of extragalactic supernovae (SNe) has established the presence of dense circumstellar material in Type II SNe. Interaction between the SN ejecta and the circumstellar material should lead to diffusive shock acceleration of cosmic rays and associated high-energy emission. Observation of high-energy neutrinos along with the MeV neutrinos from SNe will provide unprecedented opportunities to understand unanswered questions in cosmic-ray and neutrino physics. We show that current and future neutrino detectors can identify high-energy neutrinos from an extragalactic SN in the neighborhood of the Milky Way. We present the prospects for detecting high-energy neutrino minibursts from SNe in known local galaxies, and demonstrate how the network of multiple high-energy neutrino detectors will extend the horizon for the identification of high-energy SN neutrinos. We also discuss high-energy neutrino emission from SN 2023ixf.

Keywords: supernova neutrinos; particle astrophysics; high energy astrophysics; neutrino astronomy; neutrino telescopes