On August 25 2013 Dana Patchick from the “Deep Sky Hunters” (DSH) amateur astronomer group discovered a diffuse nebulosity in the Wide-field Infrared Survey Explorer (WISE) mid-IR image archive that had no optical counterpart but appeared similar to many Planetary Nebulae (PNe) in WISE. As his 30th discovery he named it Pa 30 and it was added to the HASH PN database as a new PN candidate. Little did he know how important his discovery would become. 10 years later this object is the only known bound remnant of a violent double WD merger accompanied by a rare Type Iax SN, observed and recorded by the ancient Chinese and Japanese in 1181 AD. This makes Pa 30 and its central star IRAS 00500+6713 (WD J005311) the only SN Iax remnant in our Galaxy, the only known bound remnant of any SN, and based on the central star’s spectrum the only Wolf-Rayet star known that neither has a massive progenitor nor is the central star of a Planetary Nebula. We cover this story and our key role in it.

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.

We performed numerical simulations of the common envelope (CE) interaction between two intermediate-mass asymptotic giant branch (AGB) stars and their low-mass companions. For the first time, formation and growth of dust in the envelope is calculated explicitly. We find that the first dust grains appear as early as ∼1–3 yrs after the onset of the CE, and are smaller than grains formed later. As the simulations progress, a high-opacity dusty shell forms, resulting in the CE photosphere being up to an order of magnitude larger than it would be without the inclusion of dust. At the end of the simulations, the total dust yield is ∼8.2×10−3 M⊙ (∼2.2×10−2 M⊙) for a CE with a 1.7 M⊙ (3.7 M⊙) AGB star. Dust formation does not substantially lead to more mass unbinding or substantially alter the orbital evolution.

In the late 80s of the 20th century, Crimean astronomers, studying the structure of transverse magnetic fields in active regions (ARs), discovered signs of the presence of large-scale vertical electric currents – global electric currents (Abramenko, Gopasyuk 1987). In 2018–2020, we finalized and adapted the method for detecting large-scale electric currents to the data of modern instruments for studying the Sun, and began studying their dynamics on time scales of 3–5 days (Fursyak et. al 2020). Our researches carried out during 2020–2023 showed that: 1) Large-scale electric currents with values of the order of ~ 1013 A exist in ARs with nonzero flare activity. 2) Large-scale electric currents extend to the upper layers of the solar atmosphere in one part of the AR, and close through the chromosphere and corona in the remaining part of the AR. This assumption for the AR NOAA 12192 is confirmed by the results of numerical simulations performed in 2016 (Jiang et al. 2016). 3) The greater the magnitude of the large-scale electric current, the higher the probability of occurrence of M- and X- class solar flares in the AR. 4) At the final stages of AR evolution, a nonzero large-scale electric current can have a stabilizing effect on the sunspot, preventing its decay by its own magnetic field. 5) Large-scale electric currents are involved in coronal heating processes. Ohmic dissipation of a large-scale electric current is one of the mechanisms of quasi-stationary heating of coronal plasma above the AR. Our research on large-scale electric currents and the processes in which they take part continues.

We study disks and jets in various accretion states (SANE and MAD) using novel, GPU-accelerated general-relativistic magneto-hydrodynamic (GR-MHD) code which we developed, based on HARM. This code, written in CUDA-c and uses OpenMP to parallelize multi-GPU setups, allows high resolution simulations of accretion disks and the formation and structure of jets without the need of multi-node supercomputer infrastructure. A 2563 simulation is well within the reach of an Nvidia DGX-V100 server, with the computation being a factor about 100 times faster if only the CPU was used.

We use this code to examine several disk structures, wind and jet properties in the MAD and SANE states. In the MAD state, we find that the magnetic flux threading the horizon mostly depends on the spin of the BH. This implies that the jet structure and power are strong functions of the spin, with non-spinning BHs have the widest jets.

Low-lying loops in the quiet Sun are a reliable source of energy for atmospheric heating, but the mechanisms by which they evolve are somewhat enigmatic. To address the origins of atmospheric heating events in the quiet Sun, we utilize our stratified, convection-driven, 3D MHD simulation Bifrost to explore the evolution and eventual major reconnection between several magnetic features; one of which is a magnetic flux rope. We zoom in on the buildup of the magnetic flux rope, which self-orders in the corona via an inverse cascade of helicity. We also discover that the flux rope attempts to relax to a linear force-free field according to Taylor’s theory, but cannot do so completely. Finally, we demonstrate that the eventual nanoflare-scale reconnection event could potentially be observed in the 171 Å channels of SDO/AIA and the future MUSE mission. We also determine that the spectral resolution of MUSE is sensitive enough to capture the kinematics of the bi-directional plasma jets emanating from the reconnection region.

I have performed numerical hydrodynamical calculations of outflows driven by the evaporation of a pseudo-barotropic ring around a luminous central star. The outflow shapes and internal structures resemble known cylindrical nebulae. Some of the corresponding synthetic spectra show ‘Hubble’ type outflow.

. Post-starburst galaxies (PSBs) have quenched (significant decline in star formation rate) both recently and rapidly (≲Gyr). They are thus promising in providing insights into activities that are happening at the early stage of quenching. While studies have suggested that black hole feedback in the form of active galactic nuclei (AGN) and outflows play important roles in quenching, the details of how they impact the host galaxies and their interplay with other quenching mechanisms are still not fully understood. We find that PSBs commonly show signatures of AGN activity but they appear to be weak and/or heavily obscured. These AGN might be able to drive outflows but they are likely not strong enough to remove gas from the host galaxy. Direct evidence of AGN quenching the star formation of the host galaxy is still missing and AGN likely quench by disturbing rather than expelling the gas.

Globular clusters in the nearby universe were formed in the first chapter of our cosmic history, but they show only the current chapter. However, the JWST enables us to see the younger phase of the globular clusters in the distant universe. Galaxy clusters host both galaxy globular clusters and intracluster globular clusters. We present a wide field photometric survey of globular clusters in the nearby to distant galaxy clusters. We discuss the photometric properties of these globular clusters in relation with the structure and assembly history of their host galaxy clusters.

Recent James Webb Space Telescope (JWST) observations with superb angular resolution have revealed the existence of clumpy galaxies at high redshift through the detection of rest-frame optical emission lines. The formation of clumpy galaxies at lower redshift (z ≲ 4) has been investigated both observationally and theoretically, and violent disk instability driven by cold gas accretion is proposed as one of the main mechanisms. However, the formation of clumpy galaxies at z > 6 is not well understood theoretically.

In order to study the properties of (sub-)galactic clumps around the epoch of reionization (z ≳ 6), we use FirstLight, a suite of zoom-in high-resolution (∼20 pc) cosmological simulations. We devise a physical model of Hii regions and calculate spatially resolved [Oiii] line emission. We identify the giant clumps that are bright in [Oiii] 5007Å line with flux greater than ∼ 10−18 ergs−1 cm−2, to be detected by JWST. Among 62 simulated galaxies that have stellar masses of (0.5 – 6) × 1010 M⊙ at z = 5, we find clumps in 1828 snapshots in the redshift range z = 5.5 – 9.5. About one-tenth of the snapshots show the existence of clumpy systems with two or more components. Most of the clumps are formed by mergers and can be characterized by their ages; central clumps dominated by stellar populations older than 50 Myr, and off-centered clumps dominated by younger stellar populations with specific star formation rates of ∼ 50 Gyr−1. The latter type of young clumps is formed from gas debris in the tidal tails of major mergers. The merger-induced clumps are short-lived, and merge within a dynamical time of several tens million years. The number density of the clumpy systems is estimated to be ∼ 10−5 cMpc−3, which is large enough to be detected in recent JWST surveys.

Recent panoramic maps of the Magellanic system have revealed a wealth of low-surface-brightness stellar substructures surrounding both the Large and Small Magellanic Clouds (LMC/SMC); clear evidence of tidal interactions between the two Clouds, as well as with the Milky Way. The Magellanic Edges Survey (MagES), a spectroscopic survey that targets red clump and red giant branch stars across the outskirts of both Clouds, aims to characterise these features and shed light on their formation. We summarise recent results from MagES, which suggest multiple previous LMC-SMC interactions are required to fully explain the observed dynamical properties of the Clouds.

Dwarf satellite galaxies in our Milky Way and different galaxy systems in the Local Volume appear to be arranged in thin, vast planes. It has been argued that these phase-space correlations cannot be explained to a satisfactory degree by the ΛCDM paradigm but it is unclear whether these planes in our neighborhood are statistical outliers, or if they are perhaps a common phenomenon in the Universe. Recent deep imaging surveys have significantly increased the number of known dwarf galaxies and allow us to advance such small-scale tensions beyond the Local Volume. We present our study analyzing the spatial distribution of 2210 dwarf galaxies identified in the MATLAS survey as well as results from follow-up observations with the MUSE instrument on the VLT. Spectral information for 56 of these dwarf galaxies allow for a deeper dive into their properties and for a comparison to the Local Volume dwarfs.

I review methods and techniques to build mass models of disk galaxies from gas dynamics. I focus on two key steps: (1) the derivation of rotation curves using 3D emission-line datacubes from H I, CO, and/or Hαobservations, and (2) the calculation of the gravitational field from near-infrared images and emission-line maps, tracing the stellar and gas mass distributions, respectively. Mass models of nearby galaxies led to the establishment of the radial acceleration relation (RAR): the observed centripetal acceleration from rotation curves closely correlates with that predicted from the baryonic distribution at each galaxy radius, even when dark matter supposedly dominates the gravitational field. I conclude by discussing the (uncertain) location of Local Group dwarf spheroidal galaxies on the RAR defined by more massive disk galaxies.

We present the spatially resolved star formation history (SFH) of a shell-like structure located in the northeastern Small Magellanic Cloud (SMC). We quantitatively obtain the SFH using unprecedented deep photometric data (g ∼ 24 magnitude) from the SMASH survey and colour-magnitude diagram (CMD) fitting techniques. We consider, for the first time, the SMC’s line-of-sight depth and its optical effects on the CMDs. The SFH presents higher accuracy when a line-of-sight depth of ∼ 3 kpc is simulated.

We find young star formation enhancements at ∼150 Myr, ∼200 Myr, ∼450 Myr, ∼650 Myr, and ∼1 Gyr. Comparing the structure’s SFH with the Large Magellanic Cloud’s northern arm SFH we show strong evidence of synchronicity from at least the past ∼2.8 Gyr, possibly ∼3.5 Gyr. Our results place constraints on the orbital history of the Magellanic Clouds which, potentially, have implications on their dynamical mass estimates.

Despite model predictions, many planetary nebulae appear to have a relatively rich molecular content. Observational studies of over 30 such objects show the presence of a variety of gas-phase molecules, from simple species such as CN and CS, to more complex organics including H2CO, HC3N, c-C3H2, and CH3CN. Other PNe contain fullerenes; carbonaceous and silicate dust features are also found. Molecular abundances also do not appear to vary with nebular age. Remnant material from the asymptotic giant branch appears to undergo chemical processing in the protoplanetary nebula phase and then is frozen out in planetary nebulae. PN ejecta are thus in part molecular in content and may account for the observation of complex molecules in diffuse clouds.

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.

Photon-driven flows have been studied for almost a century, and a quantitative description of the radiative forces on atoms and ions is important for understanding a wide variety of systems, including active galactic nuclei (AGN). The colloquially-termed “radiation pressure” of line-driven winds plays an important role in driving outflows in these environments. Quantifying the associated forces is crucial to understanding how these flows enable interactive mechanisms within these environments, such as AGN feedback. Here we provide new calculations of the dimensionless line strength parameter due to radiation driving. For representative AGN, we calculate the photoionization balance at each step along the line of sight (LOS) to the proposed wind-launching region above the accretion disk. We then use a recently compiled database of approximately 5.6 million spectral lines to compute the strength of the line-driving force on the gas and the mass-loss rates resulting from these outflows. We also introduce a “shielding factor’’ that increases the magnitude of the accretion disk column density prior to the launch radius. This shielding factor simulates a proposed inner “failed wind” region that is thought to shield the outflowing gas from becoming over-ionized by the central source. We also revisit and formalize the role of the commonly-used ionization parameter in setting the properties of the accelerating gas.

OH masers are signpost of planetary nebulae (PNe) at a very young stage. In particular, Vy 2-2 was the first OH maser-emitting PN ever identified. It consists of a bright compact shell and a faint bipolar structure. The reported values for its O+2/H+ abundance discrepancy factor (ADF) are inconsistent:; 4.3, and; 11.8. To characterize the ionized gas and to redetermine the ADF(O+2), we have obtained medium-resolution optical spectra. We found that the ionized gas is oxygen-rich (C/O; 0.15), and an ADF(O+2); 13.6. Also, the N/O abundance ratio is; 0.39, implying a low-mass progenitor (Mi ≤ 1.5 Me). Unexpectedly, the detection of stellar weak emission lines (wels) suggests that the central star is carbon-rich. Alternatively, the wels may be emitted by an irradiated companion in a post-common envelope system. We have also obtained high-resolution optical spectroscopy on Vy 2-2. Our spectra kinematically resolve the bright shell and bipolar structure. We found that these expand at: 10 and: 20 km s-1, respectively.

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.

A family of unidentified infrared emission (UIE) bands is widely observed in planetary nebulae. We suggest that the carriers of the UIE bands are mixed aromatic/aliphatic organic nanoparticles (MAONs) synthesized over thousand-year time scales in the nebulae. The possible chemical pathways of synthesis is discussed. These organics are ejected into the interstellar medium and could have enriched the primordial Solar System, leading to the reservoir of complex organics in comets, asteroids, planetary satellites, and interplanetary dust particles.