adsabs/SciX_UAT_keywords huggingface dataset:
Exploring NGC 2345: A Comprehensive Study of a Young Open Cluster through Photometric and Kinematic Analysis

We conducted a photometric and kinematic analysis of the young open cluster NGC 2345 using CCD UBV data from 2 m Himalayan Chandra Telescope, Gaia Data Release 3, Two Micron All-Sky Survey, and the Photometric All-Sky Survey data sets. We found 1732 most probable cluster members with membership probability higher than 70%. The fundamental and structural parameters of the cluster are determined based on the cluster members. The mean proper motion of the cluster is estimated to be ${\mu }_{\alpha }\cos \delta $ = ‑1.34 ± 0.20 and μ δ = 1.35 ± 0.21 mas yr‑1. Based on the radial density profile, the estimated radius is ∼12.'8 (10.37 pc). Using color–color and color–magnitude diagrams, we estimate the reddening, age, and distance to be 0.63 ± 0.04 mag, 63 ± 8 Myr, and 2.78 ± 0.78 kpc, respectively. The mass function slope for main-sequence stars is determined as 1.2 ± 0.1. The mass function slope in the core, halo, and overall region indicates a possible hint of mass segregation. The cluster's dynamical relaxation time is 177.6 Myr, meaning ongoing mass segregation, with complete equilibrium expected in 100–110 Myr. Apex coordinates are determined as ‑40.°89 ± 0.12, ‑ 44.°99 ± 0.15. The cluster's orbit in the Galaxy suggests early dissociation into field stars due to its close proximity to the Galactic disk.

Keywords: open star clusters; orbits; initial mass function; interstellar extinction
Hyperfine Structure Constants for Levels of 175Lu+

Accurate and complete atomic data are required for the determination of accurate stellar photospheric abundances. This includes hyperfine structure (HFS) for some elements—those with high nuclear spin and/or large nuclear magnetic moments. Lutetium is one such element. In this study, spectra of a commercial Lu-Ne hollow cathode lamp operating at a low current were recorded with the high-resolution University of Wisconsin 3 m focal length echelle spectrograph. These spectra of resolved and partially resolved hyperfine patterns for 35 ultraviolet and blue transitions of Lu II have been studied for the purpose of extracting hyperfine constants. We present HFS constants for 16 levels of singly ionized lutetium, 10 of which have been measured for the first time.

Keywords: atomic spectroscopy; stellar abundances; laboratory astrophysics
Energy Dissipation in Coronal Loops: Statistical Analysis of Intermittent Structures in Magnetohydrodynamic Turbulence

The power-law energy distribution observed in dissipation events ranging from flares down to nanoflares has been associated either to intermittent turbulence or to self-organized criticality. Despite the many studies conducted in recent years, it is unclear whether these two paradigms are mutually exclusive or they are complementary manifestations of the complexity of the system. We numerically integrate the magnetohydrodynamic equations to simulate the dynamics of coronal loops driven at their bases by footpoint motions. After a few photospheric turnover times, a stationary turbulent regime is reached, displaying a broadband power spectrum and a dissipation rate consistent with the cooling rates of the plasma confined in these loops. Our main goal is to determine whether the intermittent features observed in this turbulent flow can also be regarded as manifestations of self-organized criticality. A statistical analysis of the energy, area, and lifetime of the dissipative structures observed in these simulations displays robust scaling laws. We calculated the critical exponents characterizing the avalanche dynamics, and the spreading exponents that quantify the growth of these structures over time. In this work we also calculate the remaining critical exponents for several activity thresholds and verify that they satisfy the conservation relations predicted for self-organized critical systems. These results can therefore be regarded as a bona fide test supporting that the stationary turbulent regimes characterizing coronal loops also correspond to states of self-organized criticality.

Keywords: interplanetary turbulence; solar coronal heating
Spectroscopic Constraints on the Buildup of Intracluster Light in the Coma Cluster

The stellar content of the intracluster light (ICL) provides unique insight into the hierarchical assembly process of galaxy clusters. We present optical spectra of three ICL regions (μg ≈ 25.3-26.2 mag arcsec-2) in the Coma cluster, located between 100 and 180 kpc from their nearest brightest cluster galaxies (BCGs): NGC 4889 and NGC 4874. Integral-field unit (IFU) spectroscopy with 13.5 hr on-source integration was acquired in an ancillary program within the Sloan Digital Sky Survey-IV MaNGA survey. We stacked the 127 individual fiber spectra in each IFU to achieve a 1σ limiting surface brightness of 27.9 mag arcsec-2, corresponding to a mean signal-to-noise ratio in the optical of 21.7, 9.0, and 11.7 Å-1, for each ICL region. We apply stellar population models to the stacked spectra. Our results show that the velocity dispersions of ICL regions are very high (σ ∼ 630 km s-1), indicating the stars in these regions are tracing the gravitational potential of the cluster, instead of any individual galaxy. The line-of-sight velocities are different from each other by ∼700 km s-1, while the velocity of each region is similar to the closest BCG. This suggests that the ICL regions are associated with two distinct subclusters centered on NGC 4889 and NGC 4874. The stellar populations of these regions are old and metal-poor, with ages of ${12.7}_{-3.4}^{+1.0}$ , ${6.7}_{-2.0}^{+2.9}$ , and ${9.7}_{-3.5}^{+3.5}$ Gyr, and [Fe/H] of $-{1.0}_{-0.3}^{+0.2}$ , $-{0.6}_{-0.5}^{+0.3}$ , and $-{0.8}_{-0.4}^{+0.3}$ . From the derived age and metallicity, the buildup of ICL in Coma is likely to be through the accretion of low-mass galaxies or the tidal stripping of the outskirts of massive galaxies that have ended their star formation early on, instead of directly from major mergers of massive galaxies.

Keywords: coma cluster; galaxy evolution
Kepler Problem under Repulsive Inverse-square Central Forces

In this article, I present important results of the Kepler problem under repulsive inverse-square central forces. While motions of this type have been discussed thoroughly in the classical scattering theory, I do not find available literature that treats the problem as an analog of the Kepler problem under an attractive central force. My results are applicable to motions of dust particles subject to solar radiation pressure accelerations exceeding the solar gravitational acceleration in the two-body problem.

Keywords: comets; comet dust tails; two-body problem; orbital motion
Dropouts of Fully Stripped Ions in the Solar Wind: A Diagnostic for Wave Heating versus Reconnection

The SWICS instrument on board the ACE satellite has detected frequent intervals in the slow solar wind and interplanetary coronal mass ejections in which C6+ and other fully stripped ions are strongly depleted, though the ionization states of elements such as Si and Fe indicate that those ions should be present. It has been suggested that these "outlier" or "dropout" events can be explained by the resonant cyclotron heating process, because these ions all have the same cyclotron frequency as He2+. We investigate the region in the corona where these outlier events form. It must be above the ionization freeze-in height and the transition to collisionless plasma conditions, but low enough that the wind still feels the effects of solar gravity. We suggest that the dropout events correspond to relatively dense blobs of gas in which the heating is reduced because local variations in the Alfvén speed change the reflection of Alfvén waves and the turbulent cascade. As a result, the wave power at the cyclotron frequency of the fully stripped ions is absorbed by He2+ and may not be able to heat the other fully stripped ions enough to overcome solar gravity. If this picture is borne out, it may help to discriminate between resonant cyclotron heating and stochastic heating models of the solar wind.

Keywords: slow solar wind; solar coronal mass ejections; alfven waves; solar magnetic reconnection; ionization
HST/COS Observations of Quasar Outflows in the 500-1050 ŠRest Frame. VII. Distances and Energetics for 11 Outflows in Five Quasars

From Hubble Space Telescope/Cosmic Origins Spectrograph spectra of five quasars, 16 outflows are detected. For 11 outflows, we are able to constrain their distances to the central source (R) and their energetics. In instances of multiple electron number density determinations (used in the calculation of R) for the same outflow, the values are consistent within errors. For the 11 outflows, eight have measurements for R (between 10 and 1000 pc), one has a lower limit, another has an upper limit, and the last has a range in R. There are two outflows that have enough kinetic luminosity to be major contributors to active galactic nucleus feedback. The outflowing mass is found primarily in a very high-ionization phase, which is probed using troughs from, e.g., Ne VIII, Na IX, Mg X, and Si XII. Such ions connect the physical conditions of these ultraviolet outflows to the X-ray warm absorber outflows seen in nearby Seyfert galaxies. The ion Cl VII and several new transitions from Ne V have been detected for the first time. * Based on observations 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, Incorporated, under NASA contract NAS5-26555.

Keywords: galaxy kinematics; active galaxies; broad-absorption line quasar; interstellar absorption; quasar absorption line spectroscopy; active galactic nuclei; quasars
The ALMA Spectroscopic Survey Large Program: The Infrared Excess of z = 1.5-10 UV-selected Galaxies and the Implied High-redshift Star Formation History

We make use of sensitive (9.3 μJy beam-1 rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field (ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range z = 1.5-10 (to ∼7-28 M⊙ yr-1 at 4σ over the entire range). We find that the fraction of ALMA-detected galaxies in our z = 1.5-10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 109.0 M⊙ to ${85}_{-18}^{+9}$ % at >1010 M⊙. Moreover, on stacking all 1253 low-mass (<109.25 M⊙) galaxies over the ASPECS footprint, we find a mean continuum flux of -0.1 ± 0.4 μJy beam-1, implying a hard upper limit on the obscured star formation rate of <0.6 M⊙ yr-1 (4σ) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies (LIR/LUV) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at > ${10}^{9.5}\,{M}_{\odot }$ and an SMC-like relation at lower masses. Using stellar mass and β measurements for z ∼ 2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between β and stellar mass and then use this correlation to show that our IRX-β and IRX-stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of β and stellar mass. Finally, we present updated estimates of star formation rate density determinations at z > 3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at z > 2.

Keywords: lyman-break galaxies; infrared excess; high-redshift galaxies; dust continuum emission; far infrared astronomy
Structure and Spectroscopic Properties of Hydrocalcium Isocyanide Isomers: Plausible Astronomical Ca-bearing Molecules

Recently, the first Ca-bearing molecule discovered in space, calcium isocyanide, CaNC, has been detected in the IRC+10216 circumstellar envelope. Related to CaNC are closed-shell stable molecules of [C, Ca, H, N] composition. One of the isomers with this composition is hydrocalcium isocyanide, HCaNC, which belongs to the hydrometal isocyanide/cyanide group of compounds, among which hydromagnesium isocyanide, HMgNC, is, to date, the only one detected in space. In this work, we have performed a study of the [C, Ca, H, N] isomers that are systems of possible interstellar interest by using quantum theoretical methodologies. The analysis of the relative energies predicts three low-lying isomers: c-HCa-NC (1A'), hydrocalcium isocyanide, HCaNC (1Σ), and hydrocalcium cyanide, HCaCN (1Σ). At the composite level, HCaNC (1Σ) and HCaCN (1Σ) were located 0.87 and 4.84 kcal mol-1, respectively, above the c-HCa-NC (1Σ) isomer. Interconversion processes between these isomers have been studied to analyze their stability. Isomer HCaNC is characterized as a transition state and thus directly isomerizes to the c-HCa-NC minimum. The isomerization process of HCaCN → c-HCa-NC shows a small barrier of about 0.76 kcal mol-1 (∼382 K) above HCaCN, at the highest level of theory employed in this work, suggesting that HCaCN could easily isomerize into the most stable isomer, c-HCa-NC. Our results predict two low-lying isomers, namely, c-HCa-NC (1A') and hydrocalcium cyanide, HCaCN (1Σ), as possible candidates for experimental or radioastronomical detection. For these isomers, we provide predictions for their vibrational and rotational spectroscopic parameters that could aid in their eventual characterization in the laboratory or in space.

Keywords: astrochemistry; interstellar medium; molecular spectroscopy
Solar Cycle 25 Prediction Using N-BEATS

Solar activities lead to Sun variation with an 11 yr periodicity. The periodic variation affects space weather and heliophysics research. So it is important to accurately predict solar cycle variations. In this paper, we predicted the ongoing Solar Cycle 25 using neural basis expansion analysis for the interpretable time series deep learning method. 13 months of smoothed monthly total sunspot numbers taken by sunspot Index and Long-term Solar Observations are selected to train and evaluate our model. We used root mean square error (RMSE) and mean absolute time lag (MATL) to evaluate our model performance. RMSE and MATL measure the difference between our predicted values and the actual values along the Y- and X-axis, respectively. The RMSE value is 26.62 ± 1.56 and the MATL value is 1.34 ± 0.35, demonstrating that our model is able to better predict sunspot number variation. Finally, we predicted the variation of the sunspot numbers for Solar Cycle 25 using the model. The sunspot number of Solar Cycle 25 will peak around 2024 February with an amplitude of 133.9 ± 7.2. This means that Solar Cycle 25 will be slightly more intense than Solar Cycle 24.

Keywords: solar cycle
Energetics and 3D Structure of Elementary Events in Solar Coronal Heating

Parker first proposed (1972) that coronal heating was the necessary outcome of an energy flux caused by the tangling of coronal magnetic field lines by photospheric flows. In this paper we discuss how this model has been modified by subsequent numerical simulations outlining in particular the substantial differences between the "nanoflares" introduced by Parker and "elementary events," defined here as small-scale spatially and temporally isolated heating events resulting from the continuous formation and dissipation of field-aligned current sheets within a coronal loop. We present numerical simulations of the compressible 3D MHD equations using the HYPERION code. We use two clustering algorithms to investigate the properties of the simulated elementary events: an IDL implementation of a density-based spatial clustering of applications with noise technique, and our own physical distance clustering algorithm. We identify and track elementary heating events in time, both in temperature and in Joule heating space. For every event we characterize properties such as density, temperature, volume, aspect ratio, length, thickness, duration, and energy. The energies of the events are in the range of 1018-1021 erg, with durations shorter than 100 s. A few events last up to 200 s and release energies up to 1023 erg. While high temperatures are typically located at the flux tube apex, the currents extend all the way to the footpoints. Hence, a single elementary event cannot at present be detected. The observed emission is due to the superposition of many elementary events distributed randomly in space and time within the loop.

Keywords: solar coronal heating; magnetohydrodynamical simulations
LISC Catalog of Star Clusters. II. High Galactic Latitude Open Clusters in Gaia EDR3

It is well known that there are few open clusters (OCs) in the high-latitude region of the Milky Way galaxy, because most star formation takes place in the thin disk. It is therefore crucial to look for high Galactic latitude OCs, in order to understand OCs and the Galactic parts outside the plane well. This work looks for high Galactic latitude OCs in Gaia Early Data Release 3, and determines their basic parameters from color-magnitude diagrams (CMDs) if the main sequence is included in CMDs. The friend-of-friend method is applied to the determination of the membership of stars. Star groups with more than 20 bright (G < 18 mag) stars are taken as OC candidates, and these candidates are finally verified by the observed CMDs including stars fainter than 18 mag in the G band. After crossmatching with previous catalogs, 56 new OC candidates are found in the high Galactic latitude region with ∣b∣ ≥ 25°, in which 35 have somewhat clear CMDs and are suggested as newly discovered OCs. Finally, eight of the new OCs are confirmed again by the pyUPMASK technique. The new sample increases the total number of known high Galactic latitude OC candidates significantly. The distance modulus, color excess, metallicity, age, and binary fraction of 35 newly discovered OCs are determined by fitting their observed CMDs to the ASPS stellar population models. All the results are included in the new star cluster catalog, LISC, as its second part (LISC II).

Keywords: globular star clusters; open star clusters; galaxy stellar content; fundamental parameters of stars
A NuSTAR and Chandra Investigation of the Misaligned Outflow of PSR J1101-6101 and the Lighthouse Pulsar Wind Nebula

PSR J1101-6101 is an energetic young pulsar that powers the remarkable Lighthouse pulsar wind nebula (PWN). The pulsar belongs to the rare type of radio- and gamma-ray-quiet pulsars that are bright in hard X-rays. Moreover, the Lighthouse PWN is remarkable for its misaligned outflow (which gave rise to the PWN's nickname). Also known as "pulsar filaments," these collimated parsec-scale X-ray structures have been recently discovered in the vicinity of a handful of fast-moving pulsars, and they appear unaffected by the ram pressure that confines pulsar tails. We report on NuSTAR observations of PSR J1101-6101 and its misaligned outflow-the first observation of such a structure above ~10 keV. We detect the outflow up to 25 keV, spatially resolve its spectral evolution with distance from the pulsar, find unambiguous evidence of spectral cooling with distance from the pulsar, and infer physical properties of the particles and magnetic field in the outflow. We also reanalzye archival Chandra data and discuss the outflow's small-scale structure. We detect pulsations from PSR J1101-6101 up to 20 keV, present the X-ray pulse profile, confirm its period derivative, and perform phase-resolved spectroscopy. Finally, we discuss the X-ray source 2CXO J110158.4-605649 = 2XMM J110158.5-605651 (a serendipitously observed blazar) and suggest it may be the X-ray counterpart to the GeV source 4FGL J1102.0-6054.

Keywords: pulsar wind nebulae; pulsars; x-ray astronomy; relativistic fluid dynamics; interstellar medium; interstellar magnetic fields; magnetohydrodynamics
Preacceleration in the Electron Foreshock. I. Electron Acoustic Waves

To undergo diffusive shock acceleration, electrons need to be preaccelerated to increase their energies by several orders of magnitude, else their gyroradii will be smaller than the finite width of the shock. In oblique shocks, where the upstream magnetic field orientation is neither parallel nor perpendicular to the shock normal, electrons can escape to the shock upstream, modifying the shock foot to a region called the electron foreshock. To determine the preacceleration in this region, we undertake particle-in-cell simulations of oblique shocks while varying the obliquity and in-plane angles. We show that while the proportion of reflected electrons is negligible for θ Bn = 74.°3, it increases to R ~ 5% for θ Bn = 30°, and that, via the electron acoustic instability, these electrons power electrostatic waves upstream with energy density proportional to R 0.6 and a wavelength ≈2λ se, where λ se is the electron skin length. While the initial reflection mechanism is typically a combination of shock-surfing acceleration and magnetic mirroring, we show that once the electrostatic waves have been generated upstream, they themselves can increase the momenta of upstream electrons parallel to the magnetic field. In ≲1% of cases, upstream electrons are prematurely turned away from the shock and never injected downstream. In contrast, a similar fraction is rescattered back toward the shock after reflection, reinteracts with the shock with energies much greater than thermal, and crosses into the downstream.

Keywords: shocks
Outflows, Shocks, and Coronal Line Emission in a Radio-selected AGN in a Dwarf Galaxy

Massive black holes (BHs) in dwarf galaxies can provide strong constraints on BH seeds; however, reliably detecting them is notoriously difficult. High-resolution radio observations were recently used to identify accreting massive BHs in nearby dwarf galaxies, with a significant fraction found to be non-nuclear. Here we present the first results of our optical follow-up of these radio-selected active galactic nuclei (AGNs) in dwarf galaxies using integral field unit (IFU) data from Gemini-North. We focus on the dwarf galaxy J1220+3020, which shows no clear optical AGN signatures in its nuclear Sloan Digital Sky Survey spectrum covering the radio source. With our new IFU data, we confirm the presence of an active BH via the AGN coronal line [Fe X] and enhanced [O I] emission coincident with the radio source. Furthermore, we detect broad Hα emission and estimate a BH mass of MBH = 104.9M⊙. We compare the narrow emission line ratios to standard BPT diagnostics and shock models. Spatially resolved BPT diagrams show some AGN signatures, particularly in [O I]/Hα, but overall do not unambiguously identify the AGN. A comparison of our data to shock models clearly indicates shocked emission surrounding the AGN. The physical model most consistent with the data is an active BH with a radiatively inefficient accretion flow that both photoionizes and shock-excites the surrounding gas. We conclude that feedback is important in radio-selected BHs in dwarf galaxies and that radio surveys may probe a population of low accretion rate BHs in dwarf galaxies that cannot be detected through optical surveys alone.

Keywords: dwarf galaxies; active galaxies; low-luminosity active galactic nuclei; radio jets; black holes