A comparative analysis of sub-THz emission of stellar flares from red dwarfs has been carried out. ALMA observations indicate that the sub-THz emission flux from stellar flares with a duration of 10 s is an order of magnitude greater than for solar flares. The sub-THz emission is linearly polarized and decreases with frequency. The degree of polarization can reach tens of percent. We show that these types of spectrum slopes and linear polarization can be caused by the synchrotron emission of ultrarelativistic electrons. The origin of the observed relationships between sub-THz, low frequency radio, and X-ray emissions of stellar flares are discussed.

We present an analysis of high resolution spectra in the optical and near infrared wavelength region for cool protoplanetary nebulae with the goal to identify lines of carbon bearing molecules and some less studied neutron capture elements. The site of formation of CN and C2 lines in the spectra of IRAS 22272+5435 and IRAS Z02229+6208 appears to be an extended stellar atmosphere and inner/outer CSE. The abundance of thulium was estimated for the first time in the photosphere of IRAS22272+5435, log ε(Tm) ≃ 1.5.

We analyzed VLT/MUSE data for 20 galaxies in the ESO public archive to identify their systems’ planetary nebulae (PNe). Using the differential emission line filter (DELF) technique, we performed photometry of the galaxies’ PNe and determined their distances via the planetary nebula luminosity function (PNLF). Of the 16 galaxies for which a quality PNLF could be formed, two are isolated and more distant than 30 Mpc and therefore, relatively unaffected by Hubble Flow peculiar velocities. Using these data, we derived a Hubble Constant of 74.2 ± 7.2 (stat) ±3.7 (sys) km s−1 Mpc−1, a value that is similar to that found from other quality indicators (e.g., Cepheids, the tip of the red giant branch, and surface brightness fluctuations), but with a larger uncertainty due to the small number of galaxies. We describe how to improve PNLF measurements so that the precision of the technique is comparable to that of other quality distance indicators. We also describe a path forward in the era of ELTs that supersedes current techniques.

Flows originating from black hole magnetospheres via Blandford-Znajek (BZ) process start highly relativistically, with very large Lorentz factors γ01, imprinted into the flow during pair production within the gaps. As a result, BZ-driven outflows would produce spine-brightened images, contrary to observations of the edge-brightened jet in M87. We conclude that M87 jet is not BZ-driven.

The field of Galactic archaeology in the Milky Way (MW) has been significantly transformed by the advent of proper motions (PMs), but PM studies are still in their early stages in the M31 system. Measuring PMs in the M31 system poses a challenge for Gaia, limiting HST and JWST as the only reliable options. PM measurements of M31 satellites enable the estimation of M31’s total mass, examination of the dynamical stability of the Great Plane of Andromeda, and establishing connections to M31 substructures. We have successfully measured the PMs of NGC 147 and NGC 185 using multiepoch HST imaging data. Recently, we have obtained second-epoch HST imaging data for seven additional satellites through the HST program GO-16273. We present preliminary results from the PM measurements of these galaxies along with the implications. Finally, we discuss the future prospects of measuring PMs at the distance of M31.

Stellar streams unveil galactic histories through gravitational interactions, mergers, and tidal disruptions. To explore the complex morphology of streams, we use a ∼47 million halo main sequence stars catalogue using Gaia DR3 proper motion and photometry information, the combination of which renders the reduced proper motion parameter. This sample with reliable photometric distances reaches out to ∼21 kpc thereby probing much further out than would be possible using reliable Gaia parallaxes. Binned velocity moments on-sky pop up several known streams in the inner halo - particularly retrograde structures, due to the kinematic selection. We select and characterise the streams GD-1, Jhelum and Phlegethon. The faint signs of disequilibrium in the form of kinks and density variations in these thin streams will paint a more detailed picture of the existence and properties of the dark matter sub-haloes that perturb them and in turn, the mass distribution of our Galaxy.

Directly observing “Pop III” or zero-metallicity galaxies has long been a goal in our quest to find the first galaxies that formed in the Universe. These objects, however, have remained elusive even with 2.5 years of JWST observations. We present spectroscopy on the lowest metallicity systems yet confirmed with JWST, including the most extreme Lyman-alpha emitters at MUV = −15 (0.01L*) detected with MUSE at z =3 −7 as well as a photometrically-selected sample at z =4 −9 from the JADES survey. While these objects show significantly lower metallicities than more UV-luminous objects at the same redshifts, we find a consistent metallicity floor at ≍ 2% Zȯ. This indicates rapid chemical enrichment must be taking place in systems with light-weighted ages less than 5 Myr. However, many typical selections involving photometric redshifts and/or UV continuum slopes are biased against identification of even lower metallicities. Therefore, it is currently not possible to establish if this “floor” is real or an observational artifact. Spectroscopy of larger samples selected in less restrictive ways will be required to fully determine the answer.

Based on RR Lyrae with accurate proper motions and classification in Gaia DR3, we determine the Milky Way mass distribution from fitting dynamical models to the gravitational force field and the Galactic rotation curve. Applying Gaussian Mixture Model to the intrinsic velocity distribution, we present the result of a multi-component kinematic model of RR Lyrae in the inner regions 5 ≲ r ≲ 20 kpc. Considering the early accretion history of the MW and thus the stellar halo may not be in equilibrium, we separate the halo population into an isotropic stellar halo and the radially-anisotropic population relevant to a merge event. With a Bayesian approach, we fit the potential model parameters, including the density flattening of the dark matter (DM) halo. Our best-fitting dynamical model suggests a nearly spherical spheroid shape of , a DM halo mass of , total MW mass of .

Understanding the epoch of reionization (EoR) is one of the frontier goals of modern astronomy. Lyα emission from the high-redshift galaxies has proved to be a useful tool for probing cosmic reionization. The launch of JWST has enabled the ultraviolet and optical spectroscopic studies of Lyα emitters (LAE) in the EoR. In this contribution, we present the results based on the stacking analysis of JWST/NIRSpec spectra of galaxies taken as part of the JWST GTO program JADES. The sample consists of > 250 galaxies at redshifts of ∼5-10. We divide this sample into six different sub-samples of galaxies based on the strengths of Lyα emission and redshifts and create composite spectra. We then estimate emission line ratios of optical and UV emission lines, and various physical quantities such as dust extinction, electron temperatures, ionization parameters, and ionizing photon production efficiencies to characterize the populations of LAEs and non-LAEs.

We investigated chromospheric activities of pre-main-sequence (PMS) stars. First, we studied the Ca II infrared triplet emission lines with Subaru/HDS and other spectroscopic instruments. Most PMS stars have narrow Ca II lines whose intensities are as large as the maximum of the zero-age main-sequence (ZAMS) stars. The chromosphere of PMS stars is suggested to be filled by the Ca II emitting region. Second, we found many faint chromospheric emission lines such as Mg I and Fe I for more than half of the ZAMS stars. Third, we searched the periodic light variation caused by a starspot for the 26 PMS stars. Their TESS light variations and Ca II emission line strengths show the positive correlation, and are located on the extensions of the superflare stars. In summary, PMS stars have very active chromosphere driven by strong dynamo process due to the fast rotation and the long convection timescale.

In this contribution, I will review a few of the key characteristics of the stellar populations and interstellar medium (ISM) of high-redshift galaxies as revealed by James Webb Space Telescope (JWST) spectroscopy. Specifically, I will discuss recent evidence for nitrogen enhancement and proposed mechanisms to explain it, the existence of galaxies with very blue UV continuum slopes, and the ionization state of emission-line galaxies. I will then focus on some recent work to understand the connection between ionization parameter, gas density, and metallicity, showing that the gas density is an important factor in modulating the ionization parameter across a large range of redshift.

Ram-pressure stripping (RPS) is a process known to remove gas from satellite galaxies. Recent observational studies have found an increased ratio of active galactic nuclei (AGN) among the population of RPS galaxies compared to regular galaxies in the field. To test whether ram pressure (RP) can trigger an AGN, we perform a suite of hydrodynamical wind-tunnel simulations of a massive (Mstar = 1011 Mȯ) galaxy, with inclusion of star formation, stellar feedback and high resolution up to 39 pc. We find that RP increases the inflow of gas to the galaxy centre, which in turn can result in the enhanced BH accretion, as measured by the Bondi-Hoyle model. We also estimate pressure of outflows from our accretion rates and show that AGN feedback would play an important role on the early stages of stripping, while RP itself is not so strong.

We present a study of the evolution of two types of coronal holes (CHs) in the solar minimum of 24/25, which was preceded by a prolonged minimum of 23/24 and a weak 24 solar cycle. The goal of the study is to clarify whether the behavior of CHs during this period is also unusual? The study is based on the material of observations obtained by SDO/AIA/193. The Heliophysics Events Knowledgebase was used to localize the CHs and calculate their areas. Analysis of the evolution of the areas of polar and non-polar CHs in solar minimum 24/25 revealed a number of features. The hemispheric asymmetry is evident both in solar activity indices and in the localization of maxima of polar and non-polar CH areas. The hemispheric area imbalance is minimal for polar CHs and pronounced in the regions of non-polar CHs and sunspots. This is consistent with the general concept of polar CHs as the main source of the Sun’s dipole magnetic field. The areas of polar CHs significantly exceed the areas of non-polar CHs and make a significant contribution to the total area of all CHs in the solar disk. It is concluded that the dynamics of polar and nonpolar CHs suggests that the 24/25 minimum is rather close to earlier minima than to the 23/24 minimum.

Cosmological simulations predict dark matter shapes that deviate from spherical symmetry. The exact shape depends on the prescription of the simulation and the interplay between dark matter and baryons. This signature is most pronounced in the diffuse galactic haloes that can be observationally probed with planetary nebulae and globular clusters (GCs). The kinematic observations of these halo tracers support intrinsic triaxial shape for the mass generating the gravitational potential. With discrete axisymmetric modelling of GCs as the halo tracers of NGC 5128 we investigate the overall mass distribution of this nearby giant elliptical galaxy. Our modelling approach constrains c200, (M/L)*,B and inclination. We derive a preliminary M200 ∼ 1 × 1012 M⊙ and flattening qDM ∼ 1.3 indicative of prolate/triaxial halo for NGC 5128.

A striking feature of the solar cycle is that at the beginning, sunspots appear around mid-latitudes, and over time the latitudes of emergences migrate towards the equator. The maximum level of activity varies from cycle to cycle. For strong cycles, the activity begins early and at higher latitudes with wider sunspot distributions than for weak cycles. The activity and the width of sunspot belts increase rapidly and begin to decline when the belts are still at high latitudes. However, in the late stages of the cycles, the level of activity, and properties of the butterfly wings all have the same statistical properties independent of the peak strength of the cycles. We have modelled these features using Babcock–Leighton type dynamo model and shown that the toroidal flux loss from the solar interior due to magnetic buoyancy is an essential nonlinearity that leads to all the cycles decline in the same way.

Using the superb capabilities of JWST, we investigate the structure of thin and thick disks in galaxies beyond the local universe for the first time. We found evidence of sequential formation, where most galaxies initially form a thick disk, followed by the formation of a thin disk. Thin disk formation occurred around 8 Gyr ago in high-mass galaxies, earlier than 4 Gyr ago in low-mass galaxies, aligning with the onset of thin disk formation in the Milky Way. We propose that this downsizing thin disk formation—delayed in low-mass galaxies—can be naturally explained by stability-regulated disk formation by evolving gas fractions. As gas fractions decrease over time, turbulence in the gas disk declines, allowing a thin disk to form. High-mass galaxies, which efficiently convert gas into stars, achieve lower gas fractions, supporting earlier thin disk formation.

The REBELS ALMA large program has obtained, to date, the largest number of [C ii] and dust continuum observations of massive galaxies at z 6-8. We present results from a now complete JWST NIRSpec/IFU program (GO-1626, PI Stefanon) targeting 12 of these galaxies at 0.6-5.3μm. Due to the incredible sensitivity of the NIRSpec prism, key optical emission lines between [O ii] and [S ii] are detected for the majority of the sample, enabling metallicity constraints from a range of different calibrations. One surprising finding of this dataset is the near-solar oxygen abundances for several of these galaxies. We focus on an extension of the mass-metallicity relations at high-z to higher stellar masses, in comparison to the typical galaxies observed in e.g., JADES and CEERS. These relations provide fundamental information on how stellar mass is assembled in galaxies, and how star formation enriches and dilutes the interstellar medium.

Ionized nebulae are key to understanding the chemical composition and evolution of the Universe. Among these nebulae, H ii regions and planetary nebulae are particularly important as they provide insight into the present and past chemical composition of the interstellar medium, along with the nucleosynthetic processes involved in the chemical evolution of the gas. However, the heavy-element abundances derived from collisionally excited lines (CELs) and recombination lines (RLs) do not align. This longstanding abundance discrepancy problem calls into question our absolute abundance determinations. Which of the lines (if any) provides the correct heavy element abundances? Recently, it has been shown that there are temperature inhomogeneities concentrated within the highly ionized gas of the H ii regions, causing the reported discrepancy. However, planetary nebulae do not exhibit the same trends as the H ii regions, suggesting a different origin for the abundance discrepancy. In this proceedings, we briefly discuss the state-of-the-art of the abundance discrepancy problem in both H ii regions and planetary nebulae.