Seminars and Colloquia at ESO Garching and on the campus

Planetary nebulae (PNe) are powerful probes of their host galaxies; however, their detection outside the Milky Way is significantly more challenging. We investigate the PN population of M33 using data from the J-PLUS survey (DR3), a 12-band photometric dataset well suited for identifying Hα emitters. While only 13 of the 143 known PNe in M33 have photometry available in the J-PLUS catalog, by performing source extraction directly on the J-PLUS images we recovered photometry for over one hundred PNe, including the 13 already cataloged, thus revealing the hidden population.
Color-color diagrams allowed us to identify possible PN candidates, most consistent with emission-line sources, and even a potential halo PN when combining radial velocities from the literature with criteria previously applied to Milky Way halo PNe.
This work represents the first attempt to explore extragalactic PNe with multi-band photometric surveys such as J-PLUS, S-PLUS, and J-PAS, highlighting their strong potential for PN research in nearby galaxies.

A recent paper on archive (https://arxiv.org/abs/2509.12551) explores Observatories as an example of Large-scale research infrastructures.

The authors pose several questions, for instance (paraphrasing): does a culture of open archives or open telescope time calls guarantee progress

towards equality in the distribution of knowledge and leadership in science? Are there temporal evolutions on the role of leadership experienced

by telescope host countries? I will try to summarize their many pieces of analysis and, if the audience is up for it, discuss the different strategies

at place right now in Chile regarding host access to telescope time / data.

Quasar studies with Herschel/SPIRE often report host luminosities ranging from 10^{12} to 10^{14} solar luminosities, suggestive of star formation rates of up to several thousand solar masses per year. However, due to the limited spatial resolution of SPIRE, it is uncertain whether the far-infrared (FIR) emission originates from the quasar itself, nearby sources, or unrelated sources within the SPIRE beam. High-resolution observations at wavelengths close to the SPIRE coverage are needed to pinpoint the true source of the FIR emission. In this talk, I will discuss the unambiguous identification of ALMA Band 7 counterparts of a statistical sample of 152 FIR-bright SDSS quasars and subsequent multiplicity rates among these systems. Based on the multiplicities, the importance of mergers as triggers for concomitant accretion onto supermassive black holes and extreme star formation will be addressed. The multiplicities will be assessed as a function of redshift, IR properties and "balnicity". I will also report on the serendipitous detection of two CO(6-5) and three CO(7-6) transitions out of the eight such transitions expected based on the spectral setup and the redshifts of the objects in the sample.

Our eyes are our window to the world but they can only perceive a tiny fraction of the radiation emitted by celestial objects. For centuries, astronomy relied on optical telescopes that observed only this “visible light.” Yet to truly understand the Universe, we must look beyond: we need to explore the entire electromagnetic spectrum, from radio waves to infrared, and even the high-energy ultraviolet, X-rays, and gamma rays – which require space telescopes, since our atmosphere blocks them from reaching the ground.

In this one-hour talk, I will take the audience on a journey through the often unexpected milestones that led to the development of modern astronomy, explaining along the way which cosmic sources shine in each part of the spectrum. I will conclude by discussing the “cosmic light background” – the combined glow of all celestial objects that have ever existed in cosmic history — an ancient, diffuse radiation that tells the story of the Universe’s evolution.

The Milky Way is still evolving. The accretion of gas and stars from our surroundings in the Local Group continues to shape and build the Galaxy. Multi-phase gas flows play essential roles in cycling baryons and metals through the Galactic ecosystem and fueling the Galactic gas supply. In this colloquium I will review recent work on the gas flows around the Milky Way, based on UV/optical absorption-line observations from HST and VLT, H I 21 cm observations, and hydrodynamic simulations. After introducing the use of high-velocity clouds (HVCs) as tracers of Galactic inflow and outflow, I will discuss the Galaxy’s cool nuclear outflow and the giant Fermi and eROSITA Bubbles found on either side of the Galactic Center. I will then discuss the gas content of the Magellanic System, which is interacting with the Milky Way and slowly transferring large amounts of gas to the Galaxy. This will include new results on the LMC’s gaseous halo and the distance to the Magellanic Stream. 

The discovery of high ionization emission lines in both high-redshift galaxies and nearby, metal-poor dwarf galaxies has questioned the origin of He II ionizing radiation. Current stellar population synthesis models consistently fail to reproduce the necessary ionizing fluxes, pointing to a fundamental gap in our understanding of stellar feedback and its role in cosmic reionization. Classical Wolf-Rayet (WR) stars are hot, evolved massive stars with depleted hydrogen. WR stars with prominent Nitrogen emission lines in their spectra are called WN type, further sub-divided as 'early' (WNE) when showing emission from high ionization species (e.g., He II, N V). WNE stars at low metallicity are huge contributors to the HeII ionizing flux of their host galaxy. However, the presence of WNE stars in integrated environments can be diluted, making their direct spectroscopic detection challenging. In this talk, I will directly compare stellar spectral diagnostics for the resolved WNE stars in our nearest low-metallicity dwarf galaxy, the SMC, with integrated nebular diagnostics from the Local Volume Mapper integral field survey. I will discuss the implications of our unexpected findings for population synthesis models and galaxy evolution.

This study presents a unified high-resolution spectroscopic analysis of stars in the Galactic center, aiming to characterize the chemical evolution and formation history of this complex environment. By focusing on the nuclear star cluster (NSC), including stars in very close proximity to the supermassive black hole, we explore α-element (e.g., magnesium, silicon, and calcium) abundance trends as key diagnostics for star formation rates and gas-infall history. High-resolution, near-infrared spectra are compared to a control sample of solar-neighborhood M giants to minimize systematic uncertainties and provide a robust framework for chemical analysis. Our results reveal that the NSC stars exhibit enhanced α-element abundances, particularly in the predominantly metal-rich regime. Notably, the high-resolution observations of stars very near the supermassive black hole show surprising abundance signatures that challenge conventional scenarios of nuclear star formation, suggesting that the stars may have experienced unique enrichment processes that cannot be solely explained by traditional accretion events or capture from dwarf galaxies.