We present a theoretical model of the near-surface shear layer (NSSL) of the Sun. Convection cells deeper down are affected by the Sun’s rotation, but this is not the case in a layer just below the solar surface due to the smallness of the convection cells there. Based on this idea, we show that the thermal wind balance equation (the basic equation in the theory of the meridional circulation which holds inside the convection zone) can be solved to obtain the structure of the NSSL, matching observational data remarkably well.

Planetary nebulae (PNe) are known to be extreme radiation environments. However, these extreme conditions do not preclude the presence of different types of molecules. PNe appear as unique laboratories where atoms and simple and complex molecules, including radicals and ions, coexist. Our recent high-resolution radio observations of the C-rich PNe IC 418 and NGC 7027 and proto-PN (pPN) IRAS 22272+5435 have provided us with a precise database of the molecular content of these three objects. In our aim to study the organic molecules in the radio domain, we have found very deep radio recombination lines (RRLs) of neutral and ionized atoms never observed before. These new detected RRLs, along with the molecular content, will give information on the evolutionary state of the sources, as well as the chemical reactions taking place in such complex astrophysical environments.

Triaxial dynamical models of massive galaxies observed in the ATLAS3D project can provide new insights into the complex evolutionary processes that shape galaxies. The ATLAS3D survey is ideal as the sample comprises a good mix of fast and slow rotators with vastly different mass assembly histories. We present a detailed dynamical study with our triaxial modelling code DYNAMITE, which models galaxies as a superposition of their stellar orbits. The models allow us to constrain the intrinsic shape of the stellar component, the distributions of the visible and invisible matter and the orbit distribution in these nearby early-type galaxies and to relate it with different evolutionary scenarios. Triaxial modelling is essential for these galaxies to understand their complex kinematical features.

Planetary influence on a stellar convective shell can result in a periodic modulation of stellar dynamo drivers. Similar modulation can arise in stellar binary systems. Using the Parker low-mode dynamo model we investigate the properties of nonlinear parametric resonance. This model is a system of four ordinary differential equations and, in the first approximation, describes the processes of generation and oscillation of large-scale magnetic fields in stellar systems. In the absence of nonlinear suppression effects, the problem, by analogy with a system of harmonic oscillations, allows an asymptotic selection of multiple resonant frequencies. Despite the fact that at first glance at these frequencies it is reasonable to expect an increase in the amplitude, the behavior of the system can be just the opposite. All this stuff deserves a systematic analysis of swing excitation in the dynamo sistems in comparison with classical swing excitation in the framework of the Mathieu equation.

An accurate description of the center-to-limb variation (CLV) of stellar spectra is becoming an increasingly critical factor in both stellar and exoplanet characterization. In particular, the CLV of spectral lines is extremely challenging as its characterization requires highly detailed knowledge of the stellar physical conditions. To this end, we present the Numerical Empirical Sun-as-a-Star Integrator (NESSI) as a tool for translating high-resolution solar observations of a partial field of view into disk-integrated spectra that can be used to test common assumptions in stellar physics.

We have measured zonal and meridional components of subsurface flows up to a depth of 30 Mm below the solar surface by applying the technique of ring diagram on Dopplergrams which are constructed from the spherical harmonic (SH) coefficients. The SH coefficients are obtained from the Helioseismic and Magnetic Imager (HMI) full-disk Dopplergrams. We find a good agreement and some differences between the flows obtained in this study with those from the traditional methods using direct Dopplergrams.

Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the underlying stellar population. In recent years, it has also been found that PNe in the metal-poor halos of galaxies have different properties (specific frequency, luminosity function), than PNe in the more metal-rich galaxy centers. A more quantitative understanding of the role of age and metallicity in these relations would turn PNe into valuable stellar-population tracers. In order to do that, a full characterization of PNe in regions where the stellar light can also be analysed in detail is necessary. In this work, we make use of integral-field spectroscopic data covering the central regions of galaxies, which allow us to measure both stellar ages and metallicities as well as to detect PNe. This analysis is fundamental to calibrate PNe as stellar population tracers and to push our understanding of galaxy properties at unprecedented galactocentric distances.

The Milky Way satellite dwarf galaxy Antlia II is one of the lowest surface brightness galaxies known. It has a size comparable to the Large Magellanic Cloud, but only 106 solar masses of stars. We present kinematic and chemical measurements from the Southern Stellar Stream Spectroscopic Survey using the AAT/2dF that clearly demonstrate that Antlia II is tidally disrupting. The orbit and velocity gradient also clearly shows that the Milky Way has moved in response to the Large Magellanic Cloud. However, Antlia II currently lies on the galaxy mass-metallicity relation, suggesting that it has not lost too much stellar mass. These measurements illustrate the importance of full dynamic models when interpreting the masses of local group galaxies.

The Sun’s meridional circulation is a crucial component for understanding the Sun’s dynamo and its interior dynamics. However, the determination of meridional circulation is affected by a systematic center-to-limb (CtoL) effect, which introduces systematic errors 5–10 times stronger than the meridional-flow-induced travel-time shifts in deep-flow measurements. Recently, it was found that the CtoL effect has a significant acoustic-frequency dependence, while flow-induced travel-time shifts show little frequency dependence (Chen & Zhao 2018). This discovery forms the basis for designing a new method to remove the CtoL effect. We therefore propose a frequency-dependent approach to measure the CtoL effect and the flow-induced signals in the Fourier domain. In this work, we present this new method and compare time–distance measurements in different frequency bands with those obtained by previous time-domain methods. The results demonstrate consistency with conventional time-domain fitting methods in the dominant frequency range, promising the potential for conducting meridional flow inversion across a broader frequency spectrum.

We compare different estimates of distances to planetary nebulae (PNe), namely, Gaia parallaxes and statistical values, in order to determine the most reliable distance for each PN. In numerous instances, we find that the distances derived from the Gaia parallaxes are not the most reliable, and that better estimates can be obtained from the median of the available statistical values. Our resulting distances imply that the distributions of distances from the Galactic plane of PNe with [WR] central stars is different from the distributions of both non-[WR] hydrogen-poor central stars and hydrogen-rich central stars.

Coronal rain is formed in the post-impulsive phase of solar flares due to the thermal instability of coronal plasma in EUV loops. As a result, the sub-terahertz (sub-THz) emission flux in the post-impulsive phase of solar flares can be increased due to the increasing of the optical thickness of the thermal source. This suggests that sub-THz observations can be used as a diagnostic tool for coronal rain.

This work is aimed to analyse the relationship between the sub-THz radiation and variations of the temperature and the emission measure of the EUV coronal plasma during the post-impulsive phase of the SOL2022-05-04T08:45 solar flare.

Based on the two-dimensional temperature and emission measure distributions obtained from the AIA/SDO EUV intensity data, it was found that the temperature decreases whereas the emission measure reaches the maximum near the sub-THz flare peak. This circumstance and peculiarities of the radiation time profiles in different wave ranges show evidence in favor of the significant contribution of the thermal coronal loop plasma to the flare sub-THz radiation at least for some flare events. The sub-THz emission may be associated with a coronal condensation, accompanied by the formation of coronal rain.

To create early warning capabilities for upcoming Space Weather disturbances, we have selected a dataset of 61 emerging active regions, which allows us to identify characteristic features in the evolution of acoustic power density to predict continuum intensity emergence. For our study, we have utilized Doppler shift and continuum intensity observations from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The local tracking of 30.66 × 30.66-degree patches in the vicinity of active regions allowed us to trace the evolution of active regions starting from the pre-emergence state. We have developed a machine learning model to capture the acoustic power flux density variations associated with upcoming magnetic flux emergence. The trained Long Short-Term Memory (LSTM) model is able to predict 5 hours ahead whether, in a given area of the solar surface, continuum intensity values will decrease. The performed study allows us to investigate the potential of the machine learning approach to predict the emergence of active regions using acoustic power maps as input.

The Satellite Plane Problem (SPP) has been a hotly discussed topic for the past two decades. During which, a diametric discussion has begun, between papers that suggest that satellite galaxy planes represent an exception of, and papers which suggest that they are consistent with ΛCDM simulations. However, this discussion has not moved far beyond analysis and re-analysis of galaxies in the Local Group which is a roadblock in producing a more complete and robust analysis. This is motivating an effort to characterise satellite galaxy systems in the wider local universe. We present here initial results of an extensive optical survey of NGC2683 and M104, with the purpose of identifying optical elusive satellite galaxy candidates for follow up observations. These systems are among the first that will allow us to control for mechanisms which are suggested to create or otherwise explain the significance of satellite planes.

We present early results from our program of ALMA Band 6 (1.3mm) molecular line mapping of a sample of nearby, well-studied examples of high-excitation, bipolar/pinched-waist and molecule-rich planetary nebulae (Hubble 5 and NGC 2440, 2818, 2899, 6302, and 6445). We have mapped these planetary nebulae (PNe) in isotopologues of CO as well as various molecular line tracers of high-energy irradiation, such as HCN, CN, HNC, and HCO+, with the complementary goals of establishing nebular kinematics as well as the zones of UV-heated and X-ray-ionized molecular gas within each nebula. The resulting high-resolution ALMA molecular emission-line maps reveal the regions of high-excitation bipolar PNe in which molecular gas, presumably ejected during asymptotic giant branch stages of the PN progenitor stars, survives and evolves chemically. We present a summary of molecular species detected to date in the sample nebulae, and we use example results for one PN (NGC 6455) to demonstrate the power of the ALMA data in revealing the structures, kinematics, and compositions of the equatorial molecular tori that are a common feature of the sample objects.

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment designed to characterize our cosmic dawn using the redshifted 21 cm line of neutral hydrogen from the epoch of reionization. The bright extragalactic foreground emission dominates the extremely faint 21-cm line signal from the epoch of reionization. Along with the foreground emission, the antenna systematics make it challenging to accurately measure the extremely weak signal. The systematics result in high or low power, abnormal bandpass shape, excess correlation, and temporal structure. We examine the temporal discontinuity issues, which are the main source of temporal structure.

V510 Pup (IRAS 08005-2356) is a binary post-AGB system with a fast molecular outflow that has been noted for its puzzling mixture of carbon- and oxygen-rich features in the optical and infrared. To explore this chemical dichotomy and relate it to the kinematics of the source, we present an ACA spectral line survey detailing fourteen newly detected molecules in this pre-planetary nebula. The simultaneous presence of CN/C2H/HC3N and SO/SO2 support the previous conclusion of mixed chemistry, and their line profiles indicate that the C- and O-rich material trace distinct velocity structures in the outflow. This evidence suggests that V510 Pup could harbor a dense O-rich central waist from an earlier stage of evolution, which persisted after a fast C-rich molecular outflow formed. By studying the gas phase composition of this unique source, we aim to reveal new insights into the interplay between dynamics and chemistry in rapidly evolving post-AGB systems.

Even after decades of usage as an extragalactic standard candle, the universal bright end of the planetary nebula luminosity function (PNLF) still lacks a solid theoretical explanation. Until now, models have modeled planetary nebulae (PNe) from artificial stellar populations, without an underlying cosmological star formation history. We present PICS (PNe In Cosmological Simulations), a novel method of modeling PNe in cosmological simulations, through which PN populations for the first time naturally occur within galaxies of diverse evolutionary pathways. We find that only by using realistic stellar populations and their metallicities is it possible to reproduce the bright end of the PNLF for all galaxy types. In particular, the dependence of stellar lifetimes on metallicity has to be accounted for to produce bright PNe in metal-rich populations. Finally, PICS reproduces the statistically complete part of the PNLF observed around the Sun, down to six orders of magnitude below the bright end.

The modelling of the evolutionary phases beyond the asymptotic giant branch attracts the interest of the astrophysical community because it allows the determination of the properties of progenitor stars and to deduce the efficiency of the mechanisms able to alter the surface chemistry of the stars evolving through the asymptotic giant branch. This has been possible since improvements in the modelling of these phases, which allow a reliable determination of the luminosity with which stars evolve after the termination the asymptotic giant branch evolution.

The surface chemistry of post-asymptotic giant branch stars and planetary nebulae is shown to be tightly correlated to the various processes taking place during the asymptotic giant branch evolution. The possibility of using the observed infrared excess of these evolved stars to derive information on the dust formation process during the previous evolutionary phases is also discussed.

To understand the formation and evolution of the Universe, it is crucial to understand how and when the first stars formed. The latest observational data reveal unprecedented information about the chemical enrichment of the early Universe, which seems to behave differently from the local Universe. The first stars, being very massive, enrich their metal-poor environment in an uncertain way. In order to predict the abundances of the first galaxies, we include nucleosynthesis yields from Population III stars up to 300M⊙, including faint supernovae, Wolf-Rayet (WR) stars and Pair-Instability Supernovae (PISN) into our state-of-the-art hydrodynamical cosmological simulations. Our code (based on Gadget-3) also includes the latest nucleosynthesis yields from population II stars (from Kobayashi et al. 2020) for all stellar mass ranges. We predict the chemical abundance evolution of galaxies for different elements from the early Universe to the local Universe. We first test the modelling of stellar feedback by comparing the observed evolution of mass–metallicity relations (MZR) and metallicity gradients of the interstellar medium. We then compare our model including Population III stars with observational data from the James Web Space Telescope (JWST). For elemental abundances, we find that the N/O abundance gives a systematically higher value, comparable to the observational data of very high-redshift galaxies such as GN-z11.

Since the mid 70ies it is known that the dwarf galaxies around the Milky Way are arranged in a thin, polar structure. The arrangement and motion within this structure has been identified as a severe challenge to the standard model of cosmology, dubbed as the plane of satellites problem. More observational evidence for such structures has been put forward around other galaxies, such as the Andromeda galaxy, Cen A or NGC 253, among others, adding to the previously identified tensions. Solutions to the plane of satellite problem should therefore not only be tailored to the Milky Way, but need to explain all these different observed systems and environments.