Ralf S. Klessen
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View article: What is the contribution of gravitational infall on the mass assembly of star-forming clouds? A case study in a numerical simulation of the interstellar medium
What is the contribution of gravitational infall on the mass assembly of star-forming clouds? A case study in a numerical simulation of the interstellar medium Open
Star formation in galaxies is a complex phenomenon occurring on a very wide range of scales, and molecular clouds are at the heart of this process. The formation of these structures and the subsequent collapse of the gas within them to for…
View article: How is cold, star-forming gas in galaxies affected by magnetic fields?
How is cold, star-forming gas in galaxies affected by magnetic fields? Open
Numerical simulations provide a unique opportunity to improve our understanding of the role of magnetic fields in the interstellar medium of galaxies and in star formation. However, many existing galaxy-scale numerical simulations impose a…
View article: Masses, Star Formation Efficiencies, and Dynamical Evolution of 18,000 H <scp>ii</scp> Regions
Masses, Star Formation Efficiencies, and Dynamical Evolution of 18,000 H <span>ii</span> Regions Open
We present measurements of the masses associated with ∼18,000 H ii regions across 19 nearby star-forming galaxies by combining data from JWST, Hubble Space Telescope, MUSE, Atacama Large Millimeter/submillimeter Array, Very Large Arra…
View article: Predictive modelling of galactic star and planet formation
Predictive modelling of galactic star and planet formation Open
Predictive modelling of galactic star and planet formation This article details advancements in our understanding of star and planet formation within galaxies, emphasising the transition from steady-state models to recognising the dynamic …
View article: Tiny dust particles in space are the seeds of life
Tiny dust particles in space are the seeds of life Open
Tiny dust particles in space are the seeds of life Dr Stefan Reissl and Prof Dr Ralf S. Klessen introduce tiny dust particles in space, the seeds of life, in this intriguing field of astronomy research. Life on Earth owes its existence to …
View article: Characterization of Two Cool Galaxy Outflow Candidates Using Mid-infrared Emission from Polycyclic Aromatic Hydrocarbons
Characterization of Two Cool Galaxy Outflow Candidates Using Mid-infrared Emission from Polycyclic Aromatic Hydrocarbons Open
We characterize two candidate cool galactic outflows in two relatively low-mass, highly inclined Virgo cluster galaxies: NGC 4424 and NGC 4694. Previous analyses of observations using the Atacama Large Millimeter/submillimeter Array carbon…
View article: JWST Observations of Starbursts: PAHs Closely Trace the Cool Phase of M82's Galactic Wind
JWST Observations of Starbursts: PAHs Closely Trace the Cool Phase of M82's Galactic Wind Open
Stellar feedback drives multiphase gas outflows from starburst galaxies, but the interpretation of dust emission in these winds remains uncertain. To investigate this, we analyze new JWST mid-infrared images tracing polycyclic aromatic hyd…
View article: Quantification of the Age Dependence of Mid-infrared Star Formation Rate Indicators
Quantification of the Age Dependence of Mid-infrared Star Formation Rate Indicators Open
We combine James Webb Space Telescope images of the nearby galaxy NGC 5194 in the hydrogen recombination line Pa α (1.8756 μ m) from the Cycle 1 program JWST-FEAST with 21 μ m dust continuum images from the Cycle 2 Treasury program JWGT to…
View article: M3DIS -- A grid of 3D radiation-hydrodynamics stellar atmosphere models for stellar surveys. II. Carbon-enhanced metal-poor stars
M3DIS -- A grid of 3D radiation-hydrodynamics stellar atmosphere models for stellar surveys. II. Carbon-enhanced metal-poor stars Open
Understanding the origin and evolution of carbon-enhanced metal-poor (CEMP) stars is key to tracing the Galaxy's early chemical enrichment. We investigate how realistic 3D radiation-hydrodynamics (RHD) model atmospheres affect carbon abund…
View article: Masses, Star-Formation Efficiencies, and Dynamical Evolution of 18,000 HII Regions
Masses, Star-Formation Efficiencies, and Dynamical Evolution of 18,000 HII Regions Open
We present measurements of the masses associated with $\sim18,000$ HII regions across 19 nearby star-forming galaxies by combining data from JWST, HST, MUSE, ALMA, VLA, and MeerKAT from the multi-wavelength PHANGS survey. We report 10 pc-s…
View article: Characterization of Two Cool Galaxy Outflow Candidates Using Mid-Infrared Emission from Polycyclic Aromatic Hydrocarbons
Characterization of Two Cool Galaxy Outflow Candidates Using Mid-Infrared Emission from Polycyclic Aromatic Hydrocarbons Open
We characterize two candidate cool galactic outflows in two relatively low mass, highly inclined Virgo cluster galaxies: NGC4424 and NGC4694. Previous analyses of observations using the Atacama Large Millimeter Array (ALMA) carbon monoxide…
View article: The Resolved Structure of a Low-metallicity Photodissociation Region
The Resolved Structure of a Low-metallicity Photodissociation Region Open
Photodissociation regions (PDRs) are key to understanding the feedback processes that shape interstellar matter in galaxies. One important type of PDR is the interface between H ii regions and molecular clouds, where far-ultraviolet radiat…
View article: The SWAN view of dense gas in the Whirlpool. A cloud-scale comparison of N2H+, HCO+, HNC, and HCN emission in M51
The SWAN view of dense gas in the Whirlpool. A cloud-scale comparison of N2H+, HCO+, HNC, and HCN emission in M51 Open
Tracing dense molecular gas, the fuel for star formation, is essential for understanding the evolution of molecular clouds and star-formation processes. We compared the emission of HCN (1-0), HNC (1-0), and with the emission of at cloud sc…
View article: Azimuthal offsets in spiral arms of nearby galaxies
Azimuthal offsets in spiral arms of nearby galaxies Open
Spiral arms play a central role in disc galaxies, but their dynamical nature remains a long-standing open question. Azimuthal offsets between molecular gas and star formation are expected if gas crosses spiral arms, as predicted by quasi-s…
View article: PHANGS-HST Catalogs for ∼100,000 Star Clusters and Compact Associations in 38 Galaxies. II. Physical Properties from Decision-tree-based Spectral Energy Distribution Fitting of NUV-<i>U</i>-<i>B</i>-<i>V</i> <i>-</i> <i>I</i> Photometry with Categorical Priors Set by H<i>α</i> Emission, Cluster Morphology, and Other Auxiliary Information
PHANGS-HST Catalogs for ∼100,000 Star Clusters and Compact Associations in 38 Galaxies. II. Physical Properties from Decision-tree-based Spectral Energy Distribution Fitting of NUV-<i>U</i>-<i>B</i>-<i>V</i> <i>-</i> <i>I</i> Photometry with Categorical Priors Set by H<i>α</i> Emission, Cluster Morphology, and Other Auxiliary Information Open
This paper is the second in a series presenting the catalogs and properties of the largest sample to date of ∼100,000 star clusters and compact associations, in 38 spiral galaxies observed by the PHANGS-HST Treasury survey. Here, we presen…
View article: A normalizing flow approach for the inference of star cluster properties from unresolved broadband photometry I: Comparison to spectral energy distribution fitting
A normalizing flow approach for the inference of star cluster properties from unresolved broadband photometry I: Comparison to spectral energy distribution fitting Open
Estimating properties of star clusters from unresolved broadband photometry is a challenging problem that is classically tackled by spectral energy distribution (SED) fitting methods that are based on simple stellar population (SSP) models…
View article: The Rosetta Stone Project
The Rosetta Stone Project Open
Context . The evolution of massive star-forming clumps that are progenitors of high-mass young stellar objects are often classified based on a variety of observational indicators ranging from near-infrared to radio wavelengths. Among them,…
View article: The accretion luminosity of Class I protostars
The accretion luminosity of Class I protostars Open
Context . The value of the accretion luminosity during the early phases of star formation is crucial information that aids in understanding how stars form, but it is still very difficult to obtain. Aims . We have developed a new methodolog…
View article: The Rosetta Stone project. III. ALMA synthetic observations of fragmentation in high-mass star-forming clumps
The Rosetta Stone project. III. ALMA synthetic observations of fragmentation in high-mass star-forming clumps Open
The physical mechanisms that regulate the collapse of high-mass parsec-scale clumps and allow them to form clusters of new stars represent a crucial aspect of star formation. To investigate these mechanisms, we developed the Rosetta Stone …
View article: The dynamical impact of cosmic rays in the Rhea magnetohydrodynamic simulations
The dynamical impact of cosmic rays in the Rhea magnetohydrodynamic simulations Open
This study explores the dynamical impact of cosmic rays (CRs) in Milky Way-like galaxies using the Rhea simulation suite. Cosmic rays, with their substantial energy density, influence the interstellar medium (ISM) by supporting galactic wi…
View article: The HI-to-H2 transition in the Draco cloud
The HI-to-H2 transition in the Draco cloud Open
In recent decades, significant attention has been dedicated to analytical and observational studies of the atomic hydrogen (HI) to molecular hydrogen (H2) transition in the interstellar medium. We focussed on the Draco diffuse cloud to gai…
View article: Reconciling extragalactic star formation efficiencies with theory: Insights from PHANGS
Reconciling extragalactic star formation efficiencies with theory: Insights from PHANGS Open
New extragalactic measurements of the cloud population-averaged star formation efficiency per free-fall time, ϵ ff , from PHANGS show little sign of a theoretically predicted dependence on the gas virial level and weak variation with cloud…
View article: The MUSE view of the Sculptor galaxy: Survey overview and the luminosity function of planetary nebulae
The MUSE view of the Sculptor galaxy: Survey overview and the luminosity function of planetary nebulae Open
The Sculptor galaxy, NGC 253, is the southern massive star-forming disk galaxy that is closest to the Milky Way. We present a new 103-pointing MUSE mosaic of this galaxy that covers most of its star-forming disk up to 0.75 × R 25 . With an…
View article: Extreme cloud collisions in nearby barred galaxies
Extreme cloud collisions in nearby barred galaxies Open
The inner regions of the Milky Way are known to contain an enigmatic population of prominent molecular clouds characterized by extremely broad lines. The physical origin of these ‘extended velocity features’ (EVFs) is still debated, althou…
View article: The HI-to-H<sub>2</sub> transition in the Draco cloud
The HI-to-H<sub>2</sub> transition in the Draco cloud Open
In recent decades, significant attention has been dedicated to analytical and observational studies of the atomic hydrogen (H I ) to molecular hydrogen (H 2 ) transition in the interstellar medium. We focussed on the Draco diffuse cloud to…
View article: GULP. II. Hierarchical Distribution and Evolution of Young Stellar Structures in NGC 4449
GULP. II. Hierarchical Distribution and Evolution of Young Stellar Structures in NGC 4449 Open
We investigate the hierarchical distribution and evolution of young stellar structures in the dwarf starburst galaxy NGC 4449 using data from the GULP survey. By analyzing the spatial distribution of field stars younger than 100 Myr, we id…
View article: The accretion luminosity of Class I protostars
The accretion luminosity of Class I protostars Open
The value of the accretion luminosity during the early phases of star formation is a crucial information which helps us understand how stars form, yet it is still very difficult to obtain. We develop a new methodology to measure accretion …
View article: Simulating nearby disc galaxies on the main star formation sequence
Simulating nearby disc galaxies on the main star formation sequence Open
Recent hydrodynamical simulations of isolated barred disc galaxies have suggested a structural change in the distribution of the interstellar medium (ISM) around a stellar mass M * of 10 10 M ⊙ . In the higher-mass regime ( M ∗ ≥ 10 10 M ⊙…
View article: Black Hole - Neutron Star and Binary Neutron Star Mergers from Population III and II stars
Black Hole - Neutron Star and Binary Neutron Star Mergers from Population III and II stars Open
Population III (Pop.$~$III) stars are expected to be massive and to undergo minimal mass loss due to their lack of metals, making them ideal progenitors of black holes and neutron stars. Here, we investigate the formation and properties of…