We report on recent results from our successful and pioneering observational program with ALMA to study emerging ultracompact HII regions of pre-planetary nebulae (pPNe) using mm-wavelength recombination lines (mRRLs) as new optimal tracers. We focus on our study of two poster-child pPNe, namely, M 2-9 and CRL 618. We reveal the structure and kinematics of the enigmatic inner nebular regions of these objects with an unprecedented angular resolution down to 20-30 mas (∼15-30 AU linear scales). For both targets, the ionized central regions are elongated along the main symmetry axis of the large-scale nebulae, consistent with bipolar winds, and show notable axial velocity gradients with expansion velocities of up to ∼100 kms. The intensity and width of the H30α profiles are found to be time variable, denoting changes on scales of a few years of the physical properties and kinematics of the present-day post-AGB ejections. Our ongoing analysis involves 3D, non-LTE radiative transfer modeling of the mRRLs and free-free continuum emission. This approach allows us to provide an exceptionally detailed description of the physical conditions in the innermost layers of these well known pPNe.

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.

Red novae are transients powered by collisions of non-compact stars. Among their progenitors are systems of evolved subgiants and giants stars. Remnants of such red novae display bipolar structures which have remarkably close characteristics to many post-AGB or pre-PN systems. It is important to ask (and eventually verify) whether some of the less known post-main-sequence objects (mis-)classified as pre-PNe can be merger remnants similar to the red nova remnants.

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.

I examine the morphologies of the brightest planetary nebulae (PNe) in the Milky Way Galaxy and conclude that violent binary interaction processes eject the main nebulae of the brightest PNe. The typical morphologies of the brightest PNe are multipolar, namely have been shaped by two or more major jet-launching episodes at varying directions, and possess small to medium departures from pure point symmetry. I discuss some scenarios, including a rapid onset of a common envelope interaction and the merger of the companion, mainly a white dwarf, with the asymptotic giant branch core at the termination of the common envelope. Some of these might be progenitors of type Ia supernovae (SNe Ia), as I suggest for SNR G1.9+0.3, the youngest SN Ia in the Galaxy.

The carbon-rich star V Hydrae is known to be in its transition from the asymptotic giant branch phase to a bipolar planetary nebula. However, the origin of its bipolar shape, as well as its long-term periodic obscuration, are not well understood. Using high-resolution spectra from the HERMES/Mercator spectrograph spanning over 10-yr monitoring, we disentangled the orbital signal from the intrinsic Mira-like variations of V Hya. The orbital solution obtained is compatible with the light-curve modulation, which we interpret as an obscuration caused by an extended dusty environment surrounding the unseen companion. Additionally, we report high-velocity phase-dependent absorption features in the sodium doublet and explain them by the presence of a conical jet ejected from the (accretion disc of the) companion. We confront our binary scenario with previous radio observations and discuss how this jet could shape the large-scale bipolar outflow of the system.

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 way we look at the sky is connected to the cosmological paradigm embraced by the society we live in. On the other hand, several astronomical concepts reinforce the idea of a common humanity. Yet, scientific outreach is frequenty reaching out only to a specific part of the world population, often excluding people living in extreme social vulnerability, victims of violence and prejudice, fighting for their lives and for the right of living according to their traditions. We present two outreach projects, developed in Brazil, funded by the Office of Astronomy for Development (OAD) of the International Astronomical Union (IAU), i.e. “Under Other Skies” & “OruMbya”, which tackle the importance of ethno-astronomy, and the collaboration with leaders and cultural agents of marginalised communities. We also describe an educational project born in the favela of Cantagalo Pavão Pavãozinho (PPG), in Rio de Janeiro, during the COVID19 pandemic, which started a collaboration with local educators and artists to offer classes of astronomy and English language to children in the favela.

This study focuses on investigating planetary nebulae (PNe) within the dwarf galaxy VCC 1249, located in the halo of the early-type galaxy (ETG) M49, by utilizing data obtained from the Multi-Unit Spectroscopic Explorer (MUSE). The integral-field spectroscopy capabilities of MUSE enable the identification of individual planetary nebulae. The interaction of VCC 1249 with the cluster-dominant galaxy M49 in the Virgo Subcluster B is driving this project, as it offers a unique opportunity to explore how high-density environments influence the properties and fate of low-mass galaxies. To identify potential PNe candidates within VCC 1249, the method proposed by Roth et al. (2021) is employed. Through this approach, ten candidates exhibiting features consistent with PNe properties have been identified.

Planetary nebulae (PNe) represent the final link in the chain of the gas and dust enrichment of low- and intermediate-mass stars. We present a comprehensive study of the relevant observational data of 10 PNe of the Large Magellanic Cloud (LMC). Analysing them from the UV to the IR, we characterise the nature of the central star (CS) and the dust contribution. We link these results to the evolutionary history of these sources.

AI and deep learning techniques are beginning to play an increasing role in astronomy as a necessary tool to deal with the data avalanche. We describe an application for finding resolved Planetary Nebulae (PNe) in crowded, wide-field, narrow-band Hα survey imagery in the Galactic plane.

The diagnostic diagrams are fundamental tools that require an upgrade, and this research marks the initial steps toward the development of advanced N-dimensional diagnostic charts by combining integral field spectroscopy and clustering techniques. Using this potent combination of methodologies, the preliminary findings have facilitated the precise differentiation of morphological components within NGC 3242, NGC 6369, NGC 6778, and NGC 7009 within a five-dimensional framework.

Gaia DR3 parallaxes of a sample of post-AGB candidates have allowed us to unequivocally establish their evolutionary stage. Making use of the available photometry, interstellar extinction, and parallax-derived distance, their spectral Energy Distributions (SED) were fitted. From this, luminosity and effective temperature were worked out, placing them in the Hertzsprung-Russell (HR) diagram. This allows direct comparison with updated post-AGB evolutionary tracks, and estimation of their masses and evolutionary ages. As a result of that they were classified as post-AGB, YSO, and supergiant. From a sample of 146 candidates, 63 are post-AGB, 27 YSO, 5 supergiants, and 51 unconfirmed candidates. In addition, there were HST images for some of them, finding that very few post-AGB show a bipolar or multipolar structure.

We have found strong evidence that an extended bipolar planetary nebula (PN), lying in the line-of-sight of the Galactic open cluster M37, is actually its physical member. We estimated both the PN physical properties and the properties of its progenitor from cluster studies. The progenitor mass has been found to be around 2.8 M⊙. There are only a handful of such confirmed associations and each of them provides valuable additional data to the initial-to-final-mass relation. The nebula has a major axis of 445 arcsec and a kinematical age of around 80 kyrs -the largest ever determined for a PN- suggesting that PNe in clusters do not dissipate as fast as field PNe.

We study the physics of the ionized gas in the last stages of evolution of low- and intermediate-mass stars that end their lives as planetary nebulae (PNe). Specifically, those that are in the earliest stages of the PN phase. For this purpose, we observed with the Australia Telescope Compact Array the spectra at radio frequencies of a sample of (H2O and/or OH) maser-emitting PNe. We determined the spectral index of the radio continuum emission of these sources and the turnover frequency of the emission, which could be tied to the age of the sources.

Radiative transfer in spherical circumstellar silicate dust envelope was modelled with and without accounting for polarization, using the code RADMC-3D. It was found that the influence of polarization on dust temperature and the mean intensity of shortwave radiation in spherically symmetric case is negligible, but neglecting for polarization does not give sensible economy of the computing time for the given signal to noise ratio. Construction of good virtual polarization images of the object can require much more computing time than good intensity images.

Due to the contamination from omnipresent interstellar 21 cm emission, atomic hydrogen (H <sc>i</sc>) associated with planetary nebulae (PNe) has been insufficiently investigated. In this proceeding we report a project of searching for H i surrounding PNe using the Five hundred-meter Aperture Spherical radio Telescope (FAST), which is the most sensitive single-dish telescope at L-band. The observations may offer new insights into the interaction processes between PNe and the interstellar medium.

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 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.

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.