Previous colloquia

Complex organic molecules (COMs) are characteristic of the chemical complexification of the star forming gas, yet we still have a poor understanding about the chemical evolution of the collapsing gas. The ALMA-IMF Large program targets 15 of the most prominent Galactic protoclusters over various evolutionary stages. Beyond the rich core population uncovered by ALMA-IMF, we identified a sample of ~70 hot core candidates using methyl formate lines. I will discuss our main results about the statistics of these chemically active sites obtained from ALMA-IMF. Our findings suggest that the most massive cores are all associated with methyl formate emission, demonstrating that all massive cores undergo a chemically active phase. Our hot core candidates exhibit emission in a variety of COMs underlying the complex chemistry associated with sites where hot cores emerge. Furthermore, I will introduce the recently accepted NASCENT-Stars large program that offers a more complete view on the molecular composition of the star forming gas using the NOEMA interferometer. I will put in context these results with our understanding of the global molecular diversity of hot cores and hot corino like objects, and discuss the origin of COMs.
(Cologne, Host: Peter Schilke)

The first deep images with the James Webb Space Telescope (JWST) have transformed our view of the Universe. With its unparalleled imaging and spectroscopic capabilities, JWST finally provides deep restframe optical observations to z=10 — a huge leap from the current z=3. Additionally, JWST immediately extended our cosmic horizon into uncharted territory, with galaxy candidates now identified out to z~14-16, only ~250-300 Myr after the Big Bang. We are thus at the brink of finding the first galaxies that ended the cosmic Dark Ages and started the reionization of the Universe. In this talk, I will show how far we have come in understanding early galaxy build-up over the last years. I will start with the state of knowledge from three decades of Hubble and Spitzer Space Telescope datasets before JWST, and will then present an overview of our current understanding of early galaxies based on early results from the first year of JWST observations.
(Bonn, Host: Cristiano Porciani)

Astronomical observations of molecules are buoyed by laboratory astrophysics investigations of a variety of processes. Observations of the interstellar medium need spectral line positions to find molecules, rates of reaction to explain to feed chemical models, and collisional (de)excitation rates to predict the abundance of molecules under the peculiar conditions of space. Laboratory astrophysics measurements or predictions can provide all this information using a wide variety of techniques. Given the strong link between rotational spectroscopy and astrochemistry through several microwave, millimeter, and sub-millimeter telescopes, the role of rotational spectroscopy can be expanded beyond its traditional role of providing spectral line positions in laboratory measurements. I will discuss new experiments that push rotational spectroscopy into the detection of products of reaction and validation of collisional (de)excitation rates all in support of astrochemistry.
(Cologne, Host: Stephan Schlemmer)

A couple of decades ago it has been realized that energy injections from stars and super massive black holes (SMBHs) are essential processes to model galaxies that resemble observed ones. Modern large-volume cosmological simulations of galaxies, such as Illustris, EAGLE, HorizonAGN and others, are now capable of producing more or less realistic galaxies, especially in relation to their stellar components. However, feedback mechanisms are known to leave more direct imprints on the properties of the gas, rather than on the stars. And so, in turn, the cosmic gas is expected to provide more stringent constraints on such feedback processes. In fact, current and future observations are providing progressively more inputs on the thermodynamical, ionization, chemical, magnetic, and kinematical properties of the gaseous atmospheres in and around galaxies. In this talk, I will give an overview on the ever more quantitative and plausible evidences of the role that SMBH feedback has in shaping the gaseous haloes from Milky Way-like galaxies to the most massive galaxy clusters in the Univers. I will do so starting from the outcome of the IllustrisTNG simulations in combination with current and future observational data, e.g. with SDSS, HST, eROSITA and XRISM, and I will introduce a new ambitious project: TNG-Cluster. I will hence discuss and showcase e.g. eROSITA-like bubbles, azimuthal-dependent properties of the circum-galactic medium, jellyfish galaxies, radio relics, turbulence and X-ray surface brightness fluctuations in the intra-cluster medium.
(Cologne, Host: Dominik Riechers)

Astronomical observations of molecules are buoyed by laboratory astrophysics investigations of a variety of processes. Observations of the interstellar medium need spectral line positions to find molecules, rates of reaction to explain to feed chemical models, and collisional (de)excitation rates to predict the abundance of molecules under the peculiar conditions of space. Laboratory astrophysics measurements or predictions can provide all this information using a wide variety of techniques. Given the strong link between rotational spectroscopy and astrochemistry through several microwave, millimeter, and sub-millimeter telescopes, the role of rotational spectroscopy can be expanded beyond its traditional role of providing spectral line positions in laboratory measurements. I will discuss new experiments that push rotational spectroscopy into the detection of products of reaction and validation of collisional (de)excitation rates all in support of astrochemistry.
(Cologne, Host: Stephan Schlemmer)

In my talk I will present recent results from state-of-the-art simulations of molecular clouds and star formation. I will focus on the interplay of magnetic fields, turbulence and chemistry and their effect on the structure evolution in clouds and the subsequent star formation process. Specifically, I will show how magnetic field lead to a stabilisation of clouds on larger scales, whereas on smaller scales gravity takes over. I will discuss how this effect is reflected in the chemical composition of the clouds and the structure of magnetic fields. Furthermore, I will present a novel analysis of the 3D morphology of substructures contained in the clouds, which show a intriguing transition from sheet-like structures to filamentary structures, in excellent agreement with recent observations. Lastly, I will connect the results of these simulations to actual observations by discussing synthetic observations created from the simulations. Specifically I will focus on dust polarisation maps and discuss what we can learn from them about the underlying 3D magnetic field structure and how accurately magnetic field properties can be inferred from such observations.

Star formation is ubiquitous in the Galaxy, but the physical and chemical conditions in star-forming sites might differ as a function of galactocentric radius. Due to the negative metallicity gradient, the efficiency of gas cooling and dust shielding decreases in more distant regions. A lower interstellar radiation field and a decrease in cosmic-ray fluxes lead to a decrease in gas heating and ultimately cause lower gas and dust temperatures in the outer Galaxy. The balance between these processes sets the physical conditions of the gas and dust and likely affects star-formation rates and efficiencies. In this talk, we will present the first research highlights of the recently completed APEX legacy survey “Outer Galaxy High Resolution Survey” (OGHReS), which covers 100 deg^2 in the 3rd Galactic quadrant in the 2-1 transition of CO and its rare isotopologues. We will discuss important characteristics of the structure of the outer Galaxy, highlighting the differences with the inner Galaxy. We observed that large-scale filaments in the outer Galaxy are fundamentally quiescent objects, with a mass one order of magnitude lower compared to similar size filaments in the inner Galaxy. Additionally, outer galaxy filaments are found exclusively in inter-arm regions, which might point towards a different formation mechanism with respect to the inner Galaxy. The most prominent filament in the outer Galaxy, Falcor, is the only exception, being a site of efficient star formation and a host of the hot core candidate. Finally, we will present preliminary results of the follow-up studies of selected  star-forming clumps in additional molecular and atomic lines, and discuss their gradients across the Milky Way. We will initiate the discussion to what extent the outer Galaxy can act as a laboratory of star formation in a low-metallicity environment, and propose the next steps necessary to interpret star formation in diverse ecosystems.

High-resolution spectroscopic measurements performed in the laboratory enable the determination of molecular parameters and the identification of molecular species in different environments. The detection of new species and an estimation of its density allow in a second step to constrain astrophysical/chemical models. Very precise laboratory measurements may also challenge our understanding of quantum chemistry and fundamental physics.

Several high-resolution spectrometers were built recently in Louvain-la-Neuve. Those instruments work in different spectral ranges, microwave, near-infrared and UV to measure different molecular systems such as isolated molecules, neutral van der Waals complexes and molecular ions. During this talk, we will introduce a buffer gas cooling cell (20K) which is combined to a cavity ringdown spectrometer working in the near-infrared range. The set-up is illustrated in Figure 1. This instrument has been specifically designed to obtain reference measurements on complex molecules such as CH₃OH probed in the overtone range. Our recent results concerning methanol will be shown and the tools developed to tackle the complex spectral signature will be detailed. Part of the complex spectral signature of methanol is also illustrated in Figure 1. Several potential upgrades of this instrument, for instance combining it with a home-built femtosecond laser to reach higher precision will be presented. Further, I will present action photodissociation spectroscopy measurements and the associated analysis concerning ionic species such as N₂O⁺. To finish, our results concerning the study of molecular aggregation at the molecular scale will be presented. 

Figure 1: The Experimental set-up combining a buffer gas cooling cell and a cavity ringdown spectrometer is presented in the upper panel. Laser light is injected in a high-finesse optical cavity and the lifetime of the photons inside this cavity is measured as a function of the laser frequency. The lower panel presents the spectrum of methanol measured in the 2OH overtone range at a temperature of 25 K. 

(Cologne, Host: Oskar Asvany)

The high incidence of multiples and particularly close binaries among main sequence massive stars, challenges current understanding of their formation. To understand how such close systems are built, we need to obtain strong constrains on the origin of the pairing mechanism and the birth orbital properties. Different scenarios operating at different scales try to explain the formation of these multiples such as turbulent/core fragmentation, disk fragmentation (in which inward migration can occur) and the capture of an unbound body or similar dynamical effects that may happen later on in the formation process. With the ultimate goal to better understand multiplicity origins and properties at birth, I will demonstrate the crucial role of high-angular observations such as interferometry (VLTI/GRAVITY and PIONIER) and high-contrast imaging (VLT/NACO) to investigate key ingredients in massive star formation processes. The combination of these techniques provides valuable statistics on young high-mass multiple systems with physical separations ranging from 1 to 35,000 AU.
By determining physical properties such as multiplicity frequencies, mass ratios, and physical separation distributions, we can link our findings to the most promising pathways for the formation of massive multiples. In our quest to understand the origins of multiplicity, we compare our results with those of other stellar populations across different mass regimes and evolutionary stages, within a consistent parameter space. Finally, in the context of the SFB1601, this talk will also highlight some of our team’s latest and early results on multiplicity in young massive stars.