HeH+ is a very simple molecule, consisting only of an alpha-particle (the He nucleus), a proton (the H nucleus), and two electrons. In addition, it is thought to be the very first diatomic molecule formed when the early universe cooled down, and it has even been detected in our galaxy.Therefore, we investigated the fundamental rotational …

Read more “B7/B8/C4: Exploring the fundamental molecular ion HeH+ (Oskar Asvany, Urs Graf, Weslley Silva)”

In our latest SILCC paper, we perform magneto-hydrodynamic simulations to investigate the impact of metallicity on the interstellar medium (ISM). In fact, gas-phase metallicity affects heating and cooling processes in the star-forming ISM as well as ionising luminosities, wind strengths, and lifetimes of massive stars. Our simulations include non-equilibrium chemistry, a space- and time-variable far-UV background and cosmic ray ionisation rate, metal-dependent stellar tracks, the formation of HII regions, stellar winds, type II supernovae, and cosmic ray injection and transport.

Infrared- or submillimeter-bright dusty star-forming galaxies (DSFGs) are key contributors to the cosmic star formation rate density in the early universe, preserving the imprint of its star formation history [1-2]. We are at the forefront of observations, having secured spectroscopic redshifts for about 400 DSFGs up to redshift z ~ 7. Among these, the NOEMA z-GAL is the largest sample of 135 meaningfully selected high-z DSFGs (S500µm > 80 mJy) from the Herschel fields, whose spectroscopic redshifts are robustly measured mainly using higher-J CO lines [3].

In our recent Astronomy & Astrophysics paper, we explore the prospects of using [CII] line intensity mapping (LIM) observational technique with the upcoming FYST / Prime-Cam instrument to study galaxies that formed about 0.5–1.5 billion years after the Big Bang. LIM measures the cumulative emission from many faint galaxies without resolving them individually, offering a powerful way to trace the contribution of sources too faint to be detected even with state-of-the-art telescopes. The [CII] 158 µm line is a key tracer of star formation in these early systems, but its signal is strongly contaminated by foreground CO emission from later galaxies along the line of sight.

In our recent A&A paper (Dannhauer et al., subm.), we investigated the “Diamond Ring” in Cygnus X, a striking 6 pc wide  ring-like structure seen in [C II] 158 μm and dust emission. Unlike the three-dimensional [C II] shells discovered in recent years, the Diamond Ring reveals itself as the first pure ring, slowly expanding at only ~1.3 km/s. 

The process that brings galaxies to reduce and definitely halt to form stars (the star formation quenching) is the result of a complex interplay of phenomena that are difficult to disentangle without an adequate and statistically significant sample of galaxies. Given this, we have assembled the integrated Extragalactic Database for Galaxy Evolution (iEDGE), collecting stellar continuum, nebular emission lines, and molecular gas information for hundreds of galaxies in the local Universe.  iEDGE is, to date, the most comprehensive and extensive database of (CO-based) integrated galaxy properties. 

In recent years, the fine-structure line of C+ at 158 microns – the [CII] line – has gained significant attention as a molecular gas tracer, particularly at z ≳ 4.  Being one of the brightest emission lines in galaxies, it offers a unique window into the molecular ISM of distant galaxies, where conventional tracers like CO become observationally expensive. 

In our recent A&A Letter, we studied ionized carbon emission (C⁺, [C II]) at 158 μm in S144, a C⁺ bubble on the southeastern edge of the ring-shaped star-forming region RCW79. S144 hosts a compact H II region ionized by a single O7.5–9.5 V/III star. Using SOFIA/upGREAT maps with high angular and spectral resolution, we identified the first bubble that remains mostly filled with C⁺ gas – an indicator of an exceptionally early evolutionary stage. All previously characterized C⁺ bubbles exhibit shell-like rings with central cavities carved by stellar winds, marking more advanced phases.

Massive stars (M > 8 solar masses) significantly affect the surrounding medium during their life through stellar winds and ionising radiation. These processes shape the circumstellar medium (CSM) into complex structures, including cavities. When a massive star explodes as a supernova (SN), the resulting shock wave expands into this non-uniform medium, generating bright X-ray emission. As a result, X-ray observations of SN remnants (SNRs) provide insights into the stellar evolution of a progenitor massive star and the interstellar medium (ISM) nearby.

We analyze molecules in the laboratory to find their spectroscopic “fingerprints”, which astronomers can use to identify the molecules in space. Unlike a human fingerprint, the molecular fingerprint also reveals physical properties of the molecules’ surroundings. The temperature of the astronomical regions can be determined by comparing the relative intensities of different transitions of a molecule. In an ideal case, the transitions belong to different vibrationally excited states of the molecule. Therefore, analyzing also the rotational spectra of vibrationally excited states, the so-called vibrational satellites, in the laboratory is important. However, due to the higher vibrational energy, their population usually is very much lower compared to the ground vibrational state making it harder to find their patterns in the spectrum.

Understanding how stars form and evolve is one of the most fascinating challenges in astronomy. A key piece of this puzzle is the stellar multiplicity—the frequency, separations, and mass ratios of stars that form in pairs or higher-order groups. Massive stars, which make up only 0.01% of all formed stars,  play a pivotal role in shaping galaxies and the universe. Understanding their life cycle—90% of which unfolds alongside at least one companion—is therefore of paramount importance. Yet, they are particularly difficult to study since they are heavily bloated in their dusty envelopes and are born in distant, dense, and young star clusters. These observational challenges leave significant gaps in our understanding of how their multiplicity evolves over time. 

We are currently building the CCAT Heterodyne Array Instrument (CHAI) to be operated at the FYST-telescope. CHAI is a 64-pixel high-resolution spectrometer for two frequency bands around 460 GHz (650 µm) and 800 GHz (370 µm). For optimum instrument stability, CHAI uses balanced SIS mixers, which receive their Local Oscillator (LO) signal through an input port separate from the measurement signal input.

To date, the growth mechanism of supermassive black holes (SMBHs) is a scientific mystery. If we consider the accretion rate of the SMBH in our Milky Way, Sagittarius A* (Sgr A*), and the age of the universe, a discrepancy of several magnitudes in its mass opens up. One proposed idea to overcome the mismatch of accretion rate and age of the universe is merging events between intermediate-mass black holes (IMBHs) that ultimately form SMBHs. However, only around 10 IMBHs in our entire universe have been confirmed by observations, which poses a significant challenge to the theory of merging black holes.

Stars form within molecular clouds, dense regions of cold gas primarily composed of molecular hydrogen. These clouds provide the necessary conditions for the formation of stars, including low temperatures and high densities, which allow gravitational forces to overcome thermal pressure and initiate the collapse of gas. To fully understand the process of star formation and therefore the evolution of galaxies, it is crucial to study the properties of molecular clouds—such as their mass, density, distribution, and relation to the galactic environment.

Line Intensity Mapping (LIM) is an emerging technique in radio-astronomy that scans vast fractions of the sky with a large beam and detects the integrated emission of all sources along the line of sight without resolving individual objects. This approach enables probing the high-redshift Universe including the contribution from intrinsically faint sources that traditional surveys miss due to their flux-limit thresholds. These peculiarities make LIM an ideal tool to probe the nature of dark matter (DM).

Modelling the molecular gas content of galaxies is a highly non-linear, multi-scale problem in astrophysics. On one hand, it is necessary to simulate galaxies in realistic environments as they are affected by outflows and gas accretion from the cosmic web. On the other hand, molecular-cloud chemistry is regulated by conditions on sub-parsec scales.

Many places in space are too far away to learn about them by sending spacecraft there. So they cannot be examined directly but instead, we can learn about them by analyzing their emitted light. Due to quantum mechanics, each molecule has a set of characteristic transition lines that uniquely identify it. When these transition lines are found in the emitted spectrum, we can be sure that the respective molecule appears in the observed object. However, to identify molecules in space, we first have to understand their characteristic patterns in the laboratory. We do so by measuring the rotational spectrum of the molecules in our experiment and then fitting quantum mechanical models to them. These models can then be used by astronomers to identify the molecules in space and also to infer the physical conditions of the corresponding regions in space. For example, the temperature can be deduced from intensity relations, the pressure from the lineshape, and the molecule’s abundance can be inferred from its intensity.

What is the structure and chemical composition of gas that may feed future star formation? Before interstellar gas turns dense enough to form new stars it is not fully molecular yet but in some so far unknown transitional state. A special case of such gas clouds are given by high-latitude clouds representing material that may fall onto the plane of the Milky Way.

What roles do different stellar feedback processes play in governing star formation? From ionizing and non-ionizing radiation to stellar winds and supernovae, these forces interact with the surrounding stellar nurseries. However, understanding the precise significance of each process in shaping star formation remains an ongoing challenge.

To learn more about the formation and evolution of massive stars it is important to confront simulations and observations. It is useful to interpret the observational data and to extract the cores’ physical parameters,. We can address e.g. the question how massive cores fragment and form (massive) stars, or how long the young, massive stellar objects are embedded in their parental core.