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.

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.

The number density of extragalactic 21-cm radio sources as a function of their spectral line-widths – the H i width function (H i WF) – is a tracer of the dark matter halo mass function. The ALFALFA 21-cm survey measured the H i WF in northern and southern Galactic fields finding a systematically higher number density in the north; an asymmetry which is in tension with Λ cold dark matter models which predicts the H i WF should be identical everywhere if sampled in sufficiently large volumes. We use the Sibelius-DARK N-body simulation and semi-analytical galaxy formation model GALFORM to create mock ALFALFA surveys to investigate survey systematics. We find the asymmetry has two origins: the sensitivity of the survey is different in the two fields, and the algorithm used for completeness corrections does not fully account for biases arising from spatial galaxy clustering. Once survey systematics are corrected, cosmological models can be tested against the H i WF.

The combination of kinematic and chemical information from Galactic stars has revealed in great detail the structure, dynamics and history of our own Galaxy. In external galaxies, it is impossible to map the distribution of individual stars, but high signal-to-noise integral field unit (IFU) spectroscopy data at various wavelengths, together with sophisticated dynamical models, give us the opportunity to gather information on the structure, dynamics and formation history of these systems. The Schwarzschild method models galaxies through the superposition of stellar orbits, and is equipped to deal with very detailed kinematic measurements, allowing us to take full advantage of high-quality IFU datasets of nearby galaxies. Here we present an implementation of this method called DYNAMITE. We provide an overview of the modelling technique, introduce applications to observations and simulations, and anticipate our future plans for DYNAMITE.

Gaia EDR3 has provided proper motions of Milky Way (MW) dwarf galaxies with an unprecedented accuracy, which allows us to investigate their orbital properties. We found that the total energy and angular momentum of MW dwarf galaxies are much larger than that of MW K-giant stars, Sagittarius stream stars and globular clusters. It suggests that many MW dwarf galaxies have had a recent infall into the MW halo. We confirmed that MW dwarf galaxies lie near their pericenters, which suggests that they do not behave like satellite systems derived from Lambda-Cold-Dark-Matter cosmological simulations. These new results require revisiting the origin of MW dwarf galaxies, e.g., if they came recently, they were likely to have experienced gas removal due to the ram pressure induced by MW’s hot gas, and to be affected by MW tides. We will discuss the consequences of these processes on their mass estimation.

We do know that planetary nebulae (PNe) are ionized gaseous clouds of material ejected by evolved dying stars. The intense ultraviolet radiation field of these stars leads to the dissociation of the cold molecular gas and then to the ionization/excitation of the resultant atomic gas. The chemical composition, ionization structure, physical conditions and formation process of nebular shells, rims, and halos are well comprehended. On the contrary, the origin of low-ionization structures (LISs) frequently found in PNe break the overall picture, and it still remains poorly understood. The latest discoveries of molecular hydrogen (H2) in LISs have changed how we think about their origin. Besides the detection of H2 emission, the [Fe ii] 1.644μm and [C i] 8727Å lines have also been detected in LISs. These results add new pieces to the puzzling problem of LISs opening a new window to enrich our knowledge and understanding on these microstructures.

Classical and recurrent novae are luminous eruptions taking place in binary star systems in which a white dwarf accretes material from a non-degenerate stellar companion. After the nova event, a shell of gas is expelled and expands into the surrounding environment at hundreds to thousands of km s−1. This shell, the so-called nova remnant, experiences interactions with the binary system, the accretion disk, the surrounding environment, and very notably with continuous winds from the white dwarf powered by radiation from nuclear burning on its surface. The similarities with the formation of planetary nebulae are obvious, yet the shaping of nova remnants occurs on much shorter time-scales. This results in the prevalent round to mild elliptical 3D shape of nova remnants. Here we describe the morphology, kinematics and dynamics of nova remnants based on our multi-epoch imaging and long-slit and integral field spectroscopic studies and compare them with those of planetary nebulae.

The study of resolved stellar populations in the nearest galaxies, or “near-field cosmology”, provides key constraints on the physics underlying galaxy formation and evolution. Deep, wide-field surveys of nearby groups of galaxies allow us to characterize the past and ongoing accretion processes shaping the halos of Milky Way-mass galaxies. This field is set to experience significant advancements with the current and future generations of state-of-the-art telescopes.

Feedback and outflows associated with a quasar phase are expected to be critical in quenching the most massive galaxies at high-z. Observations targeting the cool molecular and atomic phases, which dominate the mass and momentum budget of massive galaxy outflows and remove the direct fuel for star formation are, however, severely limited in high-z QSO hosts. We discuss two recent ALMA programs: one targeting molecular outflows in 3 z ∼ 6 QSO hosts using the OH 119 μm absorption line and another targeting the diffuse, predominantly atomic gas in the halos surrounding 5 QSO host between z ∼ 2 – 4 using the OH+(11 – 10) absorption line. Outflows are successfully detected in both samples and compared with outflows driven by high-z star-forming galaxies observed in the same lines. Both studies indicate that observing QSOs during the blow-out phase is crucial for studying the impact of the active nucleus on the ejection of gas from the host galaxy.

In this contribution, I present a selected overview of optical interferometry imaging results that brought insights on stellar activity and mass loss in evolved stars. I briefly introduce the STELLIM project that aims to characterize stellar surfaces and circumstellar environments by producing fast and reliable interferometric images.

Leo T is the lowest mass galaxy known to contain neutral gas and to show signs of recent star formation, which makes it a valuable laboratory for studying the nature of gas and star formation at the limits of where galaxies are found to have rejuvenating episodes of star formation.

Here we discuss a novel study of Leo T that uses data from the MUSE integral field spectrograph and photometric data from HST. The high sensitivity of MUSE allowed us to increase the number of Leo T stars observed spectroscopically from 19 to 75. We studied the age and metallicity of these stars and identified two populations, all consistent with similar metallicity of [Fe/H] ∼ − 1.5 dex, suggesting that a large fraction of metals were ejected. Within the young population, we discovered three emission line Be stars, supporting the conclusion that rapidly rotating massive stars are common in metal-poor environments. We find differences in the dynamics of young and old stars, with the young population having a velocity dispersion consistent with the kinematics of the cold component of the neutral gas. This finding directly links the recent star formation in Leo T with the cold component of the neutral gas.

This study analyzed the Doppler shift in the solar spectrum using the Interface Region Imaging Spectrograph (IRIS). Two types of oscillations were investigated: long period damp and short period damp. The researchers observed periodic perturbations in the Doppler velocity oscillations of bright points (BPs) in the chromosphere and transition region (TR). Deep learning techniques were used to examine the statistical properties of damping in different solar regions. The results showed variations in damping rates, with higher damping in coronal hole areas. The study provided insights into the damping behavior of BPs and contributed to our understanding of energy dissipation processes in the solar chromosphere and TR.

We have undertaken a deep investigation of a well defined sample of 136 PNe located in a 10×10 degree central region of the Galactic Bulge observed with the ESO VLT and supplemented by archival HST images. These studies have provided precise morphologies, major axes position angles and the most robust sample of consistently derived chemical abundances available to date. Using these data we have statistically confirmed, at 5σ, the precise PNe population that provides the PNe alignment of major axes previously suggested in the Galactic Bulge, revealed a partial solution to the sulfur anomaly and uncovered interesting morphological, abundance and kinematic features. We summarise the most significant findings here with detailed results appearing in a series of related publications.

Almost 80% of mature planetary nebulae (PNe) have non spherical symmetry. Small-scale torii, knots, filaments and jets, frequently of low-ionization, were found embedded in PNe large-scale structures. In particular, the presence of stellar jets has been investigated through morpho-kinematic studies of PNe, from narrow-band imagery and high-dispersion long-slit spectroscopic observations. However, the latter technique is limiting the understanding of the global 3D structure of the PNe. MEGARA – the optical IFU attached to the 10.4-m Gran Telescopio Canarias – provides the ideal data to study the 3D morpho-kinematic structure of PN, allowing to discover, young jets “hidden” in the nebula. The access to the early evolution and interaction of these jets with the nebular envelope give us the opportunity of elucidating the formation of the non-spherical morphologies observed in most nebulae. We will present the results obtained from the MEGARA, unveiling for the first time hidden jets embedded in the ionized nebular envelope of NGC 2392, HuBi 1, M 2-31, M 3-38.

Babcock–Leighton process, in which the poloidal field is generated through the decay and dispersal of tilted bipolar magnetic regions (BMRs), is observed to be the major process behind the generating poloidal field in the Sun. Based on this process, the Babcock–Leighton dynamo models have been a promising tool for explaining various aspects of solar and stellar magnetic cycles. In recent years, in the toroidal to poloidal part of this dynamo loop, various nonlinear mechanisms, namely the flux loss through the magnetic buoyancy in the formation of BMRs, latitude quenching, tilt quenching, and inflows around BMRs, have been identified. While these nonlinearities tend to produce a stable magnetic cycle, the irregular properties of BMR, mainly the scatter around Joy’s law tilt, make a considerable variation in the solar cycle, including grand minima and maxima. After reviewing recent developments in these topics, I end the presentation by discussing the recent progress in making the early prediction of the solar cycle.

We have identified the velocity jump (shock) features in the inner 20′ × 10′ region of M31 using the data of [O III] and H I. The identified shock features are found primarily on the leading side of the potential bar, displaying a typical pattern of bar-driven gas inflow. The shock features provide independent evidence for M31 being a barred galaxy. Our preliminary gas simulations with a barred potential of M31 can reproduce these shock features.

New large observational surveys such as Gaia are leading us into an era of data abundance, offering unprecedented opportunities to discover new physical laws through the power of machine learning. Here we present an end-to-end strategy for recovering a free-form analytical potential from a mere snapshot of stellar positions and velocities. First we show how auto-differentiation can be used to capture an agnostic map of the gravitational potential and its underlying dark matter distribution in the form of a neural network. However, in the context of physics, neural networks are both a plague and a blessing as they are extremely flexible for modeling physical systems but largely consist in non-interpretable black boxes. Therefore, in addition, we show how a complementary symbolic regression approach can be used to open up this neural network into a physically meaningful expression. We demonstrate our strategy by recovering the potential of a toy isochrone system.

Ultra-diffuse galaxies (UDGs) are spatially extended, low surface brightness stellar systems with regular elliptical-like morphology found in large numbers in galaxy clusters and groups. Studies of the internal dynamics and dark matter content of UDGs have been hampered by their low surface brightnesses. We identified a sample of low-mass early-type post-starburst galaxies, ‘future UDGs’ in the Coma cluster still populated with young stars, which will passively evolve into UDGs in the next 5–10 Gyr. We collected deep observations for a sample of low-mass early-type galaxies in the Coma cluster using MMT Binospec, which includes present-day and future UDGs. We derived their dark matter content within a half-light radius (70–95 %) and total dynamical masses (M200 = 5.5 · 109 − 1.4·1011 M⊙) assuming the Burkert density profile and assess how different proposed evolutionary channels affect dark and visible matter in UDGs. We also discuss observational methodology of present and future UDG studies.

Just like the Sun, other stars also exhibit differential rotation. Currently, the rotation profile of a star that hosts a transiting planet can be estimated if during a transits, the planet occults a spot on the photosphere of the star, causing slight variations in its light curve. By detecting the same spot during a later transit, the stellar rotation period at that latitude is determined. Here, we present the results of differential rotation for 48 stars, 13 from the spot transit mapping method, while the remaining 35 stars from other techniques. The results show that the differential rotation is correlated with the stellar mean rotation period for fast rotating stars and strongly anti-correlated for slow rotators. The transition occuring at rotation period of 5 days. On the other hand, the differential shear increases with effective temperature for fast rotating stars, but the correlation is lost for the slow rotators.