The magnetic network is a typical magnetic structure of the quiet Sun. Investigating its cycle dependence is crucial for understanding its evolution. We aim to identify and analyze the spatial scales of the magnetic network within magnetic power spectra derived from high-resolution Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic Imager (HMI) synoptic magnetograms. The data sets cover the entirety of solar cycles 23, 24, and part of cycle 25. We find that the identified magnetic network sizes identified range from 26 Mm to 41 Mm. There seems to be no obvious dependence on the solar cycle, and the sizes are distributed uniformly within the identification range.

We present new high-spectral resolution échelle spectra of IC 4997 obtained in 2023 June to study the evolution of its recently reported variable Hα emission line profile. Compared with similar spectra from 2020 September, the new ones also show a single-peaked profile but the full velocity width of the Hα wings has increased by a factor of; 1.2. Besides, we use our high-resolution échelle spectra to investigate the internal kinematics of the nebula. Preliminary analysis suggests that the two shells of IC 4997 are kinematically resolved: the outer shell expands at; 10–14 km s-1 and the inner shell at; 25 km s-1.

Prolate rotation is characterized by a significant stellar rotation around a galaxy’s major axis, which contrasts with the more common oblate rotation. Prolate rotation is thought to be due to major mergers and thus studies of prolate-rotating systems can help us better understand the hierarchical process of galaxy evolution. Dynamical studies of such galaxies are important to find their gravitational potential profile, total mass, and dark matter fraction. Recently, it has been shown in a cosmological simulation that it is possible to form a prolate-rotating dwarf galaxy following a dwarf-dwarf merger event. The simulation also shows that the unusual prolate rotation can be time enduring. In this particular example, the galaxy continued to rotate around its major axis for at least 7.4 Gyr (from the merger event until the end of the simulation). In this project, we use mock observations of the hydro-dynamically simulated prolate-rotating dwarf galaxy to fit various stages of its evolution with Jeans dynamical models. The Jeans models successfully fit the early oblate state before the major merger event, and also the late prolate stages of the simulated galaxy, recovering its mass distribution, velocity dispersion, and rotation profile. We also ran a prolate-rotating N-body simulation with similar properties to the cosmologically simulated galaxy, which gradually loses its angular momentum on a short time scale ∼ 100 Myr. More tests are needed to understand why prolate rotation is time enduring in the cosmological simulation, but not in a simple N-body simulation.

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.

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.

Using hydrodynamic simulations and photoionization calculations, we demonstrate that quasar emission line spectra contain information on the driving mechanism of galaxy-scale outflows. Outflows driven by a hot shocked bubble are expected to exhibit LINER-like optical line ratios, while outflows driven by radiation pressure are expected to exhibit Seyfert-like line ratios. Driving by radiation pressure also has a distinct signature in the narrow UV lines, which is detected in an HST-COS spectrum of a nearby quasar hosting a large-scale wind.

The recent acquisition of high-quality deep images of planetary nebulae (PNe) in world-class telescopes has allowed the detection for the first time of a wealth of small-scale morphological features and structures that highlight the complexity of their formation history and the physical processes modeling them. In this work we present the discovery of a series of clumps embedded within the ionized nebular shell of the evolved PN NGC 3587, the Owl Nebula, that had escaped previous detections. The multi-wavelength analysis provided by GEMINI, NOT and Aristarchos in the optical and CFHT and Spitzer infrared images indicates that these clumps are formed by denser and colder material, with a notable content of molecular H2.

Bipolar or multipolar lobes in pre-planetary nebulae (pPNe) often exhibit intertwined outer whorled patterns, resulting from stellar wind matter accumulation during the asymptotic giant branch (AGB) phase. These structures are likely triggered by stellar or substellar companions. We regard that CW Leonis currently stands at a critical transition moment, providing a vivid illustration of the progression from an AGB star in a binary system to a pPN. We have found that CW Leonis has shown significant enhancements in its optical and near-infrared light curves over the past two decades, with the recent Hubble Space Telescope image finally revealing the long-awaited central star. Utilizing an eccentric-orbit binary model, we can reproduce the position-angle dependence of the expansion velocity in the whorled pattern around CW Leonis, suggesting a nearly face-on orbital inclination. Its contradiction to the features in the innermost circumstellar envelope, corresponding to a nearly edge-on inclination, may imply the presence of an additional companion. Our updated theoretical framework explores the complexity of the whorled pattern. Further identifying and monitoring phase-transition candidates at the tip of the AGB will provide valuable insights into the AGB-pPN transition and the role of companions in shaping the morphological evolution of these stellar objects.

During minima of solar activity, it is possible to estimate the influence of convection zone turbulence on the magnetic flux tubes forming active regions (ARs), because the toroidal field of the old cycle weakens, and the new toroidal field is still weak. We analyzed ARs of solar minima between 23-24 and 24-25 solar cycles. ARs were classified as regular, irregular and unipolar spots. Regular ARs follow the empirical laws consistent with the Babcock–Leighton dynamo theory. We found that regular ARs dominate by flux and by number during the solar minima. Irregular ARs are mainly represented by bipolar structures of deformed orientation and contribute only one-third in the total flux and one-third in the total number. Very complex multipolar ARs are extremely rare. So, during solar minima the global dynamo still guides the formation of ARs, whereas the turbulence only slightly affects the toroidal flux tubes orientation.

Solar activity shows an 11-year (quasi)periodicity with a pronounced, but limited variability of the cycle amplitudes. The properties of active region (AR) emergence play an important role in the modulation of solar cycles and are our central concern in building a model for predicting future cycle(s) in the framework of the Babcock–Leighton (BL)-type dynamo. The emergence of ARs has the property that strong cycles tend to have higher mean latitudes and lower tilt angle coefficients. Their non-linear feedbacks on the solar cycle are referred to as latitudinal quenching and tilt quenching, respectively. Meanwhile, the stochastic properties of AR emergence, e.g., rogue ARs, limit the scope of the solar cycle prediction. For physics-based prediction models of the solar cycle, we suggest that uncertainties in both the observed magnetograms assimilated as the initial field and the properties of the AR emergence should be taken into account.

Blind spectroscopy of massive lensing galaxy clusters with MUSE has revealed large numbers of gravitationally-lensed Lyman-α emitters exhibiting asymmetric profiles at 2.9 < z < 6.7, suggesting abundant outflows from low-mass star-forming galaxies in the early universe. Are these primaeval galaxies experiencing their first bursts of star formation, or established galaxies experiencing rejuvenation? With JWST rest-frame optical/NIR continuum imaging now available for many of these objects, we can search for older stellar populations. Here, we search for spectroscopic confirmation of outflows from these galaxies, finding a few high-signal-to-noise cases in which blueshifted interstellar absorption lines are detected. Next, we analyse the star formation histories with combined HST + JWST photometry. We find most them to be well characterised by very young, low metallicity stellar populations. However, despite the rest-frame optical/NIR coverage of JWST, we cannot place strict upper bounds on the mass in old stars (age > 100 Myr).

Understanding the origin of the stellar streams around the Milky Way can be of great relevance to learn about the history of the Milky Way and the formation of its substructures. A previous study on the Milky Way streams (Pawlowski et al. 2012) showed that many of these (7 out of 14) present a similar orientation to that of the disk of satellite galaxies (DoS) and the young globular clusters of the Milky Way. This suggests that the DoS, the young globular clusters and a large fraction of the Milky Way streams have a correlated origin. The authors proposed that these substructures could have formed as a result of a past interaction between the Milky Way and the Andromeda galaxy. In this work, we revise the distribution of the orbital poles of the Milky Way streams in light of the latest stream dataset, which includes a total of 97 streams.

Lyman-α (Lyα) emitting galaxies (LAEs) have been the subject of a range of observational studies of cosmic reionization, tracing the emergence of the first ionized ‘bubbles’ and the evolution of the neutral fraction of the intergalactic medium (IGM). Here we discuss a series of works characterising the physical properties and environments of the most distant LAEs identified in the JWST Advanced Deep Extragalactic Survey (JADES). Around half of the z < 8 LAEs fall within large-scale galaxy overdensities, providing strong evidence for enhanced Lyα transmission in these environments. Despite findings of strong Lyα absorption at the redshift frontier (z > 9) exceeding that expected only by the IGM, several LAEs are discovered at z > 8, including one at redshift z = 13.0 that shows highly exceptional properties. These observations firmly establish LAEs as powerful probes of the unfolding of cosmic reionisation out to the earliest stages of galaxy evolution.

As AGB stars evolve to planetary nebulae (PNe), the geometry of the ejected mass transforms from nearly spherical to extremely aspherical. The mechanisms governing this transformation are plausibly linked to binarity and the associated production of disks and jets during the transitional (post-AGB) evolutionary stage. We are carrying out an ALMA survey of a representative sample of bipolar/multipolar post-AGB objects to obtain high angular-resolution (0″.11) observations of the CO(3–2) and 6–5 emission and study the collimated outflows and central disks. We present highlights from our ongoing survey – e.g., the presence of bipolar or multipolar high-velocity outflows, dense toroidal waists, and in one case, a circular ring around the central bipolar nebula. We will use radiative transfer modeling to derive accurate outflow momenta, masses, and mass-loss rates for our sample, thereby constraining different classes of binary PN-shaping models.

We study the m = 1 high-latitude inertial mode and its contribution to the latitudinal transport of the Sun’s angular momentum. Ring-diagram helioseismology applied to 5° tiles is used to obtain the horizontal flows near the surface of the Sun. Using 10 years of data from SDO/HMI, we report on the horizontal eigenfunction and Reynolds stress $\[{Q_{\theta \phi }} = \langle {u'_\theta }{u'_\phi }\rangle \]$ for the m = 1 high-latitude inertial mode (frequency –86.3 nHz, critical latitudes ±58°). We find that Qθφ takes significant values above the critical latitude and is positive (negative) in the northern (southern) hemisphere, implying equatorward transport of angular momentum. The Qθφ peaks above latitude 70° with a value of 38 m2/s2.

We used the OGLE data to search for binary central stars of planetary nebulae (CSPNe) in the Large Magellanic Cloud (LMC). Nine binary CSPNe with periods between 0.24 and 23.6 days were discovered. The obtained fraction of binary CSPNe for the LMC PNe is without correcting for incompleteness.

We use nearly two decades of helioseismic data obtained from the GONG (2002–2020) and HMI (2010–2020) ring-diagram pipelines to examine the temporal variations of the properties of individual equatorial Rossby modes with azimuthal orders in the range 6 ≤ m ≤ 10. We find that the mode parameters obtained from GONG and HMI are consistent during the data overlapping period of 2010–2020. The power and the frequency of each mode exhibit significant temporal variations over the full observing period. Using the GONG data during solar cycles 23 and 24, we find that the mode power averaged over 6 ≤ m ≤ 10 shows a positive correlation with the sunspot number (0.42), while the averaged frequency shift is anti-correlated (–0.91). The anti-correlation between the average mode power and frequency shift is –0.44.

The connection between X-ray weakness and powerful X-ray outflows is both expected in a scenario where outflows are connected with radiation-driven winds, and observed in several sources, both in the local Universe and at high redshift. Here I present the first results of a new study of this possible connection based on a search for SDSS quasars with weak X-ray emission in serendipitous XMM-Newton observations. The selected objects have a “normal” optical/UV blue continuum, but a flat and extraordinarily weak X-ray spectrum. The availability of rest-frame optical/UV spectra allows to check for the signature of outflows in the absorption lines and/or in the profiles of the emission lines. This method could reveal the presence of a population of so-far overlooked outflowing quasars and confirm the connection between winds and X-ray weakness in quasars.

The newly discovered inertial modes in the Sun offer the opportunity to probe the solar convective zone down to the tachocline. While linear analysis predicts the frequencies and eigenfunctions of the modes, it gives no information about their excitation or their amplitudes. We present here a theoretical formalism for the stochastic excitation of the solar inertial modes by turbulent convection. The amplitudes predicted by our model are in complete agreement with observations, thus supporting the assumption that they are stochastically excited. Our work also uncovers a qualitative transition in the shape of the inertial mode spectrum, between m ≲ 5 where the modes are clearly resolved in frequency, and m ≳ 5 where the modes overlap. This complicates the interpretation of the high-m data, and suggests that a model for the whole shape of the power spectrum is necessary to exploit the full seismic potential of solar inertial modes.