839. WE-Heraeus-Seminar: Charting the Cosmos: From Cosmic Stellar Nurseries to Evolved Stars using High Powered Telescopes

Aug 18, 2025, 10:30 AM → Aug 22, 2025, 2:00 PM Europe/Berlin

Wasem Kloster Engelthal

Despite playing a central role as the building blocks of cosmic structures, the processes governing star formation and evolution remain among the least understood phenomena in the Universe. Key questions range from what mechanisms drive the transition from diffuse atomic to molecular clouds to form stars and how the evolution of stars shape their environment on both local and on global scales. The aim of the 839 WE-Heraeus-Seminar is to foster collaborative discussions and showcase groundbreaking research in this field.

Highlights will include new observations from high-powered telescopes, along with theoretical and computational results using state-of-the-art simulations. Furthermore, as we enter an era of highly sensitive instrumentation, bringing together communities representing the main pillars of modern astronomy will enable us to address the complexities of star-formation and stellar evolution more effectively. 

This seminar will also honour the life and work of Prof. Dr. Karl M. Menten, our dear friend, esteemed mentor, and wonderful colleague, whose sudden and unexpected passing has left us heartbroken. However, his legacy endures. His contributions over the past forty years have been a driving force and a source of inspiration for countless researchers in the field of Astornomy and Astrophysics.

The program consists of the following six sessions, each featuring invited reviews, invited presentations, and numerous contributed talks and poster presentations:

• Cool Evolved Stars
• Galactic Surveys
• Star Formation
• Instrumentation Landscape
• Interstellar medium & Spectroscopy
• Galactic Centre

 

 

 

 

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Mon, August 18

10:30 AM Registration

11:30 AM Welcome Note WE.-Heraeus Foundation

11:40 AM Opening Remarks

12:00 PM Lunch

Cool Evolved Stars: Session I: Cool Evolved Stars

1 Cool Evolved Stars

The end stages of the lives of cool, low-to-intermediate mass
stars ($0.8\le M_{\star}\le 8 M_{\odot}$) are marked by the onset of a range of
complex and dynamic atmospheric phenomena, including radial
pulsations, large-scale convection, and the onset of
intense mass loss through dense, low-velocity winds. These winds
expel up to 80% of the star's initial mass back into the
interstellar medium, resulting in the formation of extensive
circumstellar envelopes of gas and dust, and serving as a
primary source of dust and heavy element enrichment in the Galaxy.
I will review recent advances in our understanding of late-stage
stellar evolution and mass loss, with a focus on some of the latest
insights being provided by centimeter, millimeter, and
submillimeter observations.

Speaker: Lynn Matthews (MIT Haystack Observatory)

2 Imaging sub-millimetre HCN lasers in carbon-rich AGB stars

HCN is one of the most abundant molecules in the circumstellar envelopes of carbon-rich AGB stars. Recent single-dish observations have revealed the widespread presence of its emission lines in vibrationally excited states. These include two intense sub-millimetre laser lines at 805 and 891 GHz that originate from a system of two Coriolis-coupled vibrationally excited states at an excitation energy of $E/k > 4000$ K.

We observed both transitions with ALMA in Band 10 and obtained a high detection rate for the laser lines. The flux density of the 891 GHz laser is typically an order of magnitude higher than that of the 805 GHz. High-resolution images revealed that the laser emission comes from the innermost regions of the mass loss, consistent with previous analyses on single-dish data. The bright and relatively compact laser emission allows self-calibration that has significantly improved the imaging dynamic ranges. We also observed time variability in transitions with multi-epoch observations. Thermal emission lines from the ground and vibrationally excited states of HCN were also detected.

Speaker: Ka Tat Wong

3 Mergers of stars, young and old

I am going to review the last two decades of studies of objects undergoing a stellar collision or recovering from a coalescence. Among them are transients known as red novae. These objects produce dusty circumstellar remnants rich in molecules. I am going to present observations of these remnants that are helping us to decode the merger process, its causes, and final products.

Speaker: Tomasz Kaminski (CAMK Toruń)

4 Explosive Outflows and Bow Shocks: Radio Evidence of Stellar Encounters

High-angular-resolution radio observations offer a unique opportunity to identify young stars inside ultracompact HII regions and study their dynamic interactions in early phases of star formation. In this work, I will present recent results from Karl G. Jansky VLA observations targeting two different environments. In NGC 6334A, we conducted a multi-epoch, multi-frequency study of the arc-shaped source CKR02A, revealing a clear bow shock morphology and a nonthermal spectral index ($\alpha = -0.68 \pm 0.17$). Preliminary proper motion measurements suggest a runaway velocity of approximately 120 km s$^{-1}$, consistent with CKR02A being either the bow shock of a massive runaway star or the colliding-wind region of an embedded massive binary. In a separate study of the explosive molecular outflows (EMOs) in DR 21 and G5.89, we conducted a census of compact radio sources (CRS) in search of runaway stars associated with past dynamical events. Eighteen CRS were detected in DR 21, several near the ejection center of the molecular filaments, making them excellent candidates for future astrometric follow-up. These results highlight the potential of high-resolution radio observations to uncover the hidden population of massive stars and dynamical histories within deeply embedded star-forming regions.

Speaker: Sergio Abraham Dzib Quijano (Max Planck Institute for Radio Astronomy)

5 Probing Stellar Evolution through SMA Spectral-Line Surveys: A Tribute to Karl Menten's Legacy

We conducted spectral-line surveys of surveys of five evolved
stars---IRC+10216, CRL 618, CRL 2688, VY Canis Majoris (VY CMa),
and NGC 7027--- using Submillimeter Array (SMA). These studies aimed
to elucidate the chemical and morphological transformations that
occur: (i) in the transition from the asymptotic giant branch (AGB)
phase to planetary nebulae (PN); and (ii) in oxygen-rich supergiant
environments.

In IRC+10216 (293.9--354.8 GHz), we detected 442 lines (200+ new)
including vibrationally excited transitions from compact regions
(<1$''$) close to the star. The CRL 618 (281.9--359.4 GHz) survey
revealed over 1100 lines, dominated by HC$_3$N and c-C$_3$H$_2$,
tracing both fast outflows and a compact molecular core. CRL 2688
(224--266 GHz) showed weaker Si-bearing species and a striking
S-shaped morphology in CS and HCN, indicating a precessing jet. In
VY CMa (279--355 GHz), 223 lines from 19 molecules were detected,
including TiO, TiO$_2$, and AlCl for the first time in this source.
The hot molecular gas is spatially offset from the dust continuum,
and several features coincide with known IR and optical structures.
SMA observations of NGC 7027 (290--359 GHz) mapped CO, HCO$^{+}$
and H recombination lines, providing physical conditions in both
the ionized region and expanding molecular shell.

Future directions include monitoring time variability in high-excitation
transitions from regions within a few stellar radii and simultaneous
observation of maser and thermal SiO transitions, enabled by the
SMA’s wide bandwidth.

Karl Menten was a major collaborator on all of these projects. His
mentorship and scientific insight were foundational to the success
and direction of this work.

Speaker: Nimesh Patel (Center for Astrophysics | Harvard & Smithsonian)

3:00 PM Coffee Break

6 High-resolution view of the inhomogeneous, dynamical atmosphere of the AGB star W Hya with ALMA, VLT/SPHERE, and VLTI/MATISSE

The mass-loss mechanism in asymptotic giant branch (AGB) stars is not yet fully understood. It is of paramount importance to spatially resolve the region within several stellar radii, where the stellar wind accelerates. We present high-angular-resolution ALMA imaging of the well-studied AGB star W Hya, combined with contemporaneous visible polarimetric imaging with VLT/SPHERE-ZIMPOL and thermal-IR imaging with VLTI/MATISSE. The angular resolution of these observations (20 mas with ALMA, 26 mas with SPHERE-ZIMPOL, and 10 mas with VLTI/MATISSE) allows us to spatially resolve W Hya's extended atmosphere in great details.

ALMA's high angular resolution allowed us to resolve the stellar disk of W Hya and clumpy, irregularly shaped emission extending to ~100 mas with a plume in the NNW, a tail in the SSE, and the extended atmosphere elongated in the ENE--WSW direction with semimajor and semiminor axes of ~70 and 40 mas (~3.4 and 1.9 stellar radii), respectively. Our ALMA data taken at phase 0.53 (minimum light) indicate global, accelerating infall within ~75 mas (3.6 stellar radii) but also with local outflows close to the local escape velocity. We identified 59 lines, which include SiO, H2O, SO2, SO, HCN, AlO, AlOH, TiO, TiO2, and OH. The images in the different molecular lines reveal highly inhomogeneous molecular chemistry in the extended atmosphere. Surprisingly, we detected non-thermal emission on top of the continuum over the stellar disk--instead of pure absorption as expected--in about 2/3 of the identified lines, including SiO, H2O, SO2, and AlO. The surface emission seen in the 29SiO (v=2, 253 GHz) and vibrationally excited H2O (v2=2, 268 GHz) lines is particularly strong, indicating (likely) maser actions.

The SPHERE-ZIMPOL visible polarimetric images taken just nine days before our ALMA data reveal the formation of clumpy dust clouds within 2 stellar radii, which coincide well with the strong surface emission of the vibrationally excited H2O line as well as the emission of the SiO, AlO, TiO, TiO2, SO, and SO2 lines. This lends support to that SiO, H2O, and AlO are directly involved in grain nucleation.

The VLTI/MATISSE data taken contemporaneously with the ALMA data allow us to probe the region slightly closer to the star than studied with ALMA and SPHERE-ZIMPOL. Our preliminary imaging shows irregularly shaped atmosphere extending to ~40 mas (~2 stellar radii) with significant inhomogeneities over the stellar disk. The object appears to be slightly more extended in the 4 micron SiO band. The combined view with ALMA, SPHERE-ZIMPOL, and MATISSE enables us to constrain the physical properties of the complex atmosphere, which are crucial for better understanding the dust formation physics and wind acceleration mechanism.

Speaker: Keiichi Ohnaka (Universidad Andres Bello)

7 Investigating feedback from dusty RSG outflows with 3D Hydrodynamic simulations

Recent JWST observations towards Westerlund 1 have revealed extensive nebular emission associated with the cluster. Given the age of the region and proximity of that material to massive stars it cannot be primordial star forming gas and the origin is uncertain. One explanation for the nebulosity is ablation flows from Red Supergiant (RSG) stars embedded in the cluster wind driven by the Wolf-Rayet (WR) stars in the cluster core. In this talk, I will present 3D hydrodynamic simulations with the PION code to study the interaction between the cluster and RSG winds. In this work, we compare with the JWST observations by generating synthetic dust emission maps. We find that the ablation flow morphology is consistent with the observations towards Westerlund 1, with clumps and instabilities. Synthetic observations at 11 μm predict fluxes in the ablation flow of ∼ 1000 − 6000 MJy ster$^{−1}$ which is consistent with the unsaturated components of the JWST F1130W observations in the vicinity of the red supergiants in the region. This good agreement is achieved without any consideration of polycyclic aromatic hydrocarbons (PAHs), which have a known 11.3 $\mu$m feature that appears in the F1130W band. This suggests that the ablation flow is PAH depleted. I will also give an overview of the implications of this work for constraining the feedback from RSGs to later generations of star formation. I will conclude with how future observations of the RSG-cluster wind interactions could constrain both the properties of the cluster wind itself, and the physical processes occurring in the turbulent mixing here.

Speaker: Cormac Larkin (MPI Kernphysik & ZAH/ARI)

8 Old stars and recent enigmas in the light of atomic fine-structure emissions

Evolved stars, as cosmic carbon and dust factories or progenitors of supernovae, play an essential role in the cosmic cycle of matter, yet they are far from being fully understood. This contribution will give two examples.

The photochemistry of their envelopes is thought to be almost exclusively driven by the interstellar radiation field (ISRF). While the line-profile modeling of emissions of CO and its photodissociation product C$^0$ from the prototypical carbon star IRC+10216 can be understood by modeling the exposure of a constant mass-loss wind to the ISRF, the emergence of C$^+$ emission close to the stellar photosphere is an unsolved enigma. Rather expected from the outer shells and from the termination shock at the contact surface between the wind and the ISM, an ionizing source in the inner envelope is required to produce the time-variable observed C$^+$ emission. Potential candidates are a so far undetected companion star, shocks forming in response to the convective motions underneath the photosphere, interstellar photons travelling through a patchy envelope, or FUV emissions generated by cosmic rays.

Likewise, the strength of the [CII] emission from the red supergiant (RSG) $\mu$ Cephei is not predicted by equilibrium-chemistry models. With a warm, thick envelope, the observed line-flux ratio of the [OI] emissions from the $^3$P ground-state triplet is reproduced by the model, but the absolute fluxes call for a near distance of 440 pc. Interferometric near-infrared data can be reconciled with this requirement if one accounts for significant emissions from star spots (as observed, for other RSGs, with the VLTI, and attributed to upwelling large convection cells). The mid-infrared fine-structure line ratio of [S I] and [Fe II] is reproduced by the model. However, here the line fluxes are over-predicted, which is attributed to the limitations of the chemical model.

This contribution presents SOFIA data from the GREAT instrument suite and EXES, along with data from APEX and ISO. The analysis is carried out through NLTE radiative transfer. The underlying opacity tables account for atomic, molecular and collision-induced absorptions, but the optical depths are generally dominated by self-absorption, especially in the [OI] lines. For the mid-infrared, dust extinction is treated as a foreground veil condensing in response to the chemistry in the inner envelope.

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Speaker: Helmut Wiesemeyer (Max-Planck-Institut für Radioastronomie)

9 Big grains in Red Rectangle's flat rotating disk

The transformation of the circumstellar envelopes of asymptotic giant branch stars (AGB-CSEs) into first pre-planetary nebulae (pPNe) and later on planetary nebulae (PNe) is one of the most intriguing problems in modern Astrophysics. After more than 30 years of research, the community is convinced that the large variety of bizarre geometries of pPNe and PNe can only be explained by the presence of binary/multiple systems at their centres. In this context, a particular class of sources arises: the so-called post-AGB binaries with rotating disks. These sources systematically consist of a post-AGB primary and a main sequence (MS) secondary surrounded by a circumbinary rotating disk. A poster child of this class is the system HD 44179 at the centre of the "Red Rectangle" nebula. Here, we present our latest (14 AU resolution) ALMA observations of Red rectangle's rotating disk. These data show that the dust has settled towards the equatorial plane and that grain growth takes place in this stable structure. Very recent MeerKAT observations have just confirmed this picture. The characteristics of the rotating disk resemble those of proto-planetary disks very much. We further argue that the Red Rectangle is rather the rule than the exception, making post-AGB binaries ideal candidates to study grain growth on short timescales and for the search of planet formation in stars beyond the MS.

Speaker: Javier Alcolea (Observatorio Astronómico Nacional (IGN/CNIG, Spain))

10 ALMA and APEX observations of the bipolar outflow around HR3126

HR3126 is a bright M-star surrounded by an extensive E-W bipolar (10' x 3') outflow seen in optical/infrared/CO-emission. VLTI observations show the central star and the presence of a central disk with a size of about 5 mas. We will present the results of ALMA observations of the outflow in the CO (1-0) line over a region of 5' x 5' at a resolution of 2.5". The CO emission traces the inner 3' x 3' of the bipolar outflow showing an hourglass shaped E-W bipolar outflow and N-S emission tracing what appears to be an expanding toroidal structure. All features have a similar velocity field with the velocity increasing linearly with the distance from the star, and expansion time scales of about 6500 yr. The CO emission also shows what are possibly shocked interaction regions inside the two lobes of the bipolar outflow. Their positions are consistent with the direction of a putative jet directed perpendicularly to the central disk seen in the VLTI observations. We did not, however, detect emission in the interaction regions from shock tracers such as SiO and HCO+ using APEX.

Speaker: Lars Nyman (Chalmers University of Technology)

5:00 PM Discussion I: Tomasz Kaminski

11 Karl's contributions to EHT

Speaker: Anton Zensus

5:50 PM Postcards for Karl

Tue, August 19

Galactic Surveys: Session II: Galactic and Extragalactic Surveys

12 Galactic Plane Surveys: A Multi-Wavelength View of Star Formation

Over the past two decades, there has been a major international effort to create high-resolution, multi-wavelength maps of the Galactic plane. These surveys span radio, submillimetre, and near-infrared wavelengths from ground-based observatories, as well as mid- and far-infrared wavelengths from space-based missions (e.g., SPITZER, HERSHEL).

The APEX telescope has played a central role in this endeavour through landmark surveys such as ATLASGAL, SEDIGISM, and OGHReS, and by supporting complementary programmes with targeted follow-up observations (e.g., ALMAGAL and FEEDBACK).

By combining these datasets with radio and infrared surveys, we have been able to chart the distribution of dense gas and star formation activity across the Milky Way's disc in unprecedented detail. This comprehensive view is now enabling us to investigate how different environments influence the star formation process.

In this talk, I will present an overview of these surveys and highlight some of the key scientific results they have delivered.

Speaker: James Urquhart (University of Kent)

13 The BeSSeL Survey: Mapping the Spiral Structure of the Milky Way

The Bar and Spiral Structure Legacy (BeSSeL) Survey has yielded
about 200 parallax and proper motion measurements of masers
associated with young massive stars. Recently the use of
3-dimensional kinematic distances, in addition to parallaxes,
have significantly improved the locations of stars more distant
than about 5 kpc, leading to a more accurate tracing of the
spiral structure of the Milky Way. These measurements also
provide full spatial and kinematic information, which
constrain fundamental Galactic parameters, including the
distance to the Galactic center and the rotation curve.
In this talk, I will present our updated picture of the
Milky Way.

Speaker: Mark Reid (Center for Astrophysics | Harvard & Smithsonian)

10:10 AM Coffee Break

14 Constraining the Spiral Arm Structure in the Outer Galaxy

Over the past decades, our understanding of the Milky Way’s large-scale spiral structure has significantly improved through parallax maser distance measurements. The locations and the morphology of the Outer and Outer-Scutum-Centaurus arms, however, remain poorly constrained. As an extension to the BeSSeL survey, we measure parallaxes of water masers at 22 GHz in high-mass star forming regions in the Outer Galaxy, which are tracers of spiral structure. We present results on the parallax of several of the sources. We discuss the source's location with respect to the Outer and Outer-Scutum-Centaurus arms, as well as implications on spiral arm models.

Speaker: Michael Rugel (NRAO)

15 Should Perseus and Sagittarius be merged?

The Galactic structure has been a fundamental and longstanding challenge in astronomy. Over the past two decades, advancements in accurate distance measurements have provided an unprecedented opportunity to address this issue. Using the most reliable data available, we developed a new model of the Milky Way’s spiral arm structure (Xu+2023). This model suggests that the Milky Way features two spiral arms in its inner regions and transitions to multiple arms in its outer regions, contrasting with the widely accepted model of a four-arm spiral galaxy with continuous arms extending from the inner to the outer regions. Statistical analyses of Milky Way-like galaxies support our model as typical, while the mainstream four-arm model appears anomalous and unobserved in similar galaxies. However, our proposed model predominantly relies on data from the northern sky, highlighting the need for comprehensive observations in the Southern sky.

Speaker: Ye Xu (中国科学院紫金山天文台)

16 Evolution of the Local Spiral Structure Revealed by OB-type Stars in Gaia DR3

The structure and evolution of the spiral arms of the Milky Way have long been an important yet controversial issue. The wide age range of OB-type stars, coupled with the large amount of high-precision astrometric data provided by Gaia DR3, presents us with an opportunity to explore this issue. After constructing overdensity maps and examining the variations of overdensities with Galactocentric distance along the Galactic azimuth, we compare the spiral structures traced by B3–B5, B6–B7, B8, and B9 stars with those of young O–B2 stars in the vicinity of the Sun. We find that as the ages of the OB tracer stars increase, the Perseus Arm traced by them gradually shifts toward the anti-Galactic center direction, and the pitch angle of the Carina Arm gradually decreases. These results will help us to understand better the evolutionary properties of nearby spiral arms.

Speaker: Jingjing Li (PMO)

11:30 AM Discussion Session I: Andreas Brunthaler

12:00 PM Lunch

17 The Global View of Star Formation in the Milky (GLOSTAR) Project: status and future prospects

The Global View of Star Formation in the Milky Way (GLOSTAR) project is a large, unbiased and sensitive radio-wavelength survey mapping a significant part of the Galactic mid-plane. Using the Very Large Array in both the B and D configurations and the 100-m Effelsberg telescope, GLOSTAR observed the 4–8 GHz radio continuum and several spectral lines: seven hydrogen radio recombination lines (RRLs), the 4.8 GHz formaldehyde absorption line (H2CO), and the 6.7 GHz transition of methanol (CH3OH), an exclusive tracer of high-mass young stellar objects.
In the last years, our team has produced several catalogs that in total contain thousands of radio continuum sources detected in the 2$^{\rm o}$ < ℓ < 40$^{\rm o}$, 56$^{\rm o}$ < ℓ < 60$^{\rm o}$; |b|< 1$^{\rm o}$ region and the Cygnus X region. For a significant fraction of the sources, we provided a source classification based on their emission properties at infrared and submillimeter wavelengths. In addition, over 150 supernova remnants (SNRs) candidates were found in the D-configuration radio continuum images, of which 3 are confirmed to be SNRs based on their spectral index, polarization properties and morphology.
As for the spectral lines, the RRLs allowed us to identify more than two thousand individual Galactic HII regions and derived their physical properties while the formaldehyde absorption line was used to study the structure and kinematics of the molecular gas in the Cygnus X region. The Class II methanol maser line was detected in more than five hundred Galactic sources, of which ~15% are new.
In this talk, I will review the status of the project, present our main results and discuss some prospects for the future.

Speaker: Gisela Ortiz-Leon (Instituto Nacional de Astrofisica, Optica y Electronica)

18 ALMAGAL: a census of high-mass cluster forming regions in the Galaxy

The Large ALMA Program ALMAGAL observed more than 1000 high-mass cluster forming regions in the Galaxy with a spatial resolution of about 1000 au. I will present the first results from it, concentrating on the characterization of the temperature structures. At these resolutions, it is not straightforward any more to use established techniques such a single component fitting of lines. Instead, the large temperature gradients present at these small scales make it necessary to use novel methods, such as structure modeling either with optimizing algorithms or with machine learning methods such as neural networks. This is essential to get a handle on the luminosities at these small scales, and characterize the exact nature of the central sources, inaccessible in the IR because of they are very deeply embedded.

Speaker: Peter Schilke (University of Cologne)

19 The Milky Way ISM at low frequency: an uGMRT perspective

Low radio frequency observations are extremely useful to study the properties of various components (e.g. diffuse multi-phase ISM, star-forming regions, HII regions, photo-dissociation regions, supernova remnants) of the interstellar medium. The recent upgrade of the Giant Metrewave Radio Telescope has resulted in an enhanced sensitivity over a wider accessible frequency range, larger instantaneous bandwidth, and better spectral resolution. These, in turn, have enabled us not only to start a low frequency Galactic plane survey complementary to the THOR and the GLOSTAR survey, but also to take up search for less explored spectral lines at these frequencies. In this presentation, I will report some of the recent results from our group, focusing mainly on the uGMRT "band-3" and "band-4" observations of the Orion nebula and the W43-W44 region. In particular, multi-wavelength study of the Orion region, along with careful quantification of the spectral index reliability at different signal to noise ratio, clearly bring out the presence of non-thermal emission associated with M42. I will discuss the plausible implications of these findings, and the lessons learned on the unique challenges and opportunities of low radio frequency observations.

Speaker: Nirupam Roy (Indian Institute of Science)

2:20 PM Discussion Session II: Friedrich Wyrowski

2:50 PM Postcards for Karl

3:00 PM Coffee Break

20 Molecules in the Magellanic clouds

Metal enrichment is a fundamental tracer of stellar nucleosynthesis, stellar populations, and galactic chemical evolution. While extensively studied in the Milky Way, its role in metal-poor galaxies remains largely unexplored. The Magellanic Clouds, as nearby low-metallicity systems, provide a unique opportunity to investigate these processes under conditions analogous to those in high-redshift galaxies. Here, we present first results from a deep spectral line survey of N113 in the Large Magellanic Cloud (LMC), offering new constraints on elemental enrichment. We report the first accurate determination of the $^{34}$S/$^{33}$S ratio and the first detection of CF$^{+}$ in the LMC, shedding light on sulfur nucleosynthesis and interstellar fluorine chemistry in metal-poor galaxies. Additionally, using ACA observations, we derive the first $^{18}$O/$^{17}$O ratio in the Small Magellanic Cloud (SMC), providing key insights into oxygen enrichment. In this talk, I will discuss the implications of these findings for our understanding of chemical evolution in metal-poor galaxies.

Speaker: Yan Gong (Purple Moutain observatory)

21 APEX Legacy Survey of the molecular gas in the LMC

The Large Magellanic Cloud (LMC) is a unique laboratory for extragalactic studies of star formation. From 2019 to the end of 2023, we observed the LMC in the 12CO(3–2) and 13CO(3–2) lines with the APEX telescope. In total, the resulting survey covered 23.4 sq. deg. (17.8 pc^2) of the LMC disk at a spatial resolution of 5 pc. The derived map of the molecular gas distribution is unpreceded in terms of the spatial resolution and mass surface density limit compared with any extragalactic study of the molecular gas done until today for a whole galaxy. In addition, the stellar mass of the LMC (~2.7 \times 10^9 M_solar) places our study well below the knee of the stellar mass function which, in general, is not well investigated. In this talk, I will introduce the survey and present our analysis of the cloud luminosity and mass functions in the LMC, the scaling relations between selected cloud properties in the galaxy, and the 12CO(3–2) / 12CO(1–0) line ratio that highlights the LMC regions with potentially extreme excitations.

Speaker: Konstantin Grishunin (MPIfR)

22 Millimeter emission of nearby galaxies: NIKA2/30m observations

I will present new results from IMEGIN, a large program conducted with
the IRAM 30-meter telescope aimed at mapping the continuum emission of
nearby galaxies at 1 mm and 2 mm using the NIKA2 camera. The
millimeter regime remains one of the least explored regions of a
galaxy's spectral energy distribution (SED), yet it hosts crucial
emission from three fundamental physical processes: thermal dust
emission, free-free emission from ionized gas, and synchrotron
emission from cosmic ray electrons spiraling in magnetic fields.

By combining these high-resolution millimeter maps with extensive
ancillary datasets, we are constructing spatially resolved SEDs across
our target galaxies. This enables us to disentangle the relative
contributions of the three emission mechanisms, investigate their
connection to star formation activity, probe the dust emissivity index
(β), and explore how these properties vary with galactic environment.

Speaker: Carsten Kramer (IRAM)

23 Star-formation quenching of nearby galaxies

The mechanisms that lead galaxies to strongly reduce their star formation activity (star-formation quenching) are complex and still poorly understood. To address this challenge, we developed a new star-formation quenching classification scheme based on the ionised gas distribution in galaxies. The classification suggests a more detailed understanding of the galaxy quenching process by focusing on transitional phases, rather than relying on a binary categorisation of galaxies as either quenching or star-forming. Studying the molecular and hydrogen gas within these transitional phases is fundamental to understanding how star formation is suppressed—whether due to the absence of gas or dynamical effects.
Our results from single-dish and resolved molecular gas surveys (such as CARMA-EDGE and APEX-EDGE) indicate a strong correlation between the molecular gas distribution and the quenching stage of galaxies. For example, galaxies with quiescent nuclear rings exhibit a large fraction of molecular gas in the centre (probably due to a bar-quenching mechanism, which drives gas toward the centre of the galaxy), while centrally quiescent galaxies lack molecular gas in the centre (probably due to a bulge-quenching mechanism that exhausts the central molecular gas by turning it into stars). Interestingly, there are some nearly-retired galaxies that do not form stars intensively, yet they exhibit a vast amount of molecular and neutral gas.
Complementary single-dish and resolved HI data (from GBT and VLA/GMRT instruments) show that neutral hydrogen gas is much more extended than molecular gas. Galaxies below the Main Sequence of star-formation—those beginning to quench or already quenched—show patchy or ring-like HI distributions, in contrast to the well-defined, fast-rotating disks of star-forming galaxies on the Main Sequence.
This indicates that galaxies with different quenching patterns have likely been shaped by different—and possibly multiple—quenching mechanisms. Further multi-wavelength investigations and a closer look at the transformation of the baryon cycle in galaxies will shed more light on the quenching process and help answer how galaxies evolve—whether through inside-out, outside-in quenching, or both.

Speaker: Veselina Kalinova (Max Planck Institute for Radioastronomy)

Poster Session

Wed, August 20

Star Formation: Session III: Star Formation

24 The Orion Radio All-Stars: Probing Extreme Space Weather in Young Stellar Objects

The Orion Nebula Cluster (ONC), the nearest region of high-mass star formation, hosts a rich population of low-mass young stellar objects (YSOs). While X-ray studies have long revealed high-energy activity in YSOs, only recent advances in radio instrumentation - particularly wideband VLA receivers and the VLBA software correlator - have enabled detailed, complementary insights into their centimetric emission, both thermal and nonthermal.

Radio detections in the ONC date back to early VLA observations, which revealed compact sources later identified as YSOs and proplyds. Upgrades to the VLA and VLBA have since expanded the YSO sample, allowing in-band spectral index measurements and variability studies. Unlike the faint solar radio output (undetectable at Orion's distance), YSO radio flares reflect extreme space weather that shapes disk irradiation and potentially influences planet formation.

In this talk, I will review Karl's foundational radio studies of the ONC, including pioneering VLBI work that yielded a high-precision parallax for the cluster (414±7 pc), a major improvement over prior estimates. I'll then present current results from the Orion Radio All-Stars project, which uses VLA, VLBA, and ALMA data to constrain YSO radio emission and its broader implications.

Speaker: Jan Forbich

25 Methanol as a diagnostic of the interstellar medium: From Karl Menten’s pioneering work to recent applications

Methanol (CH₃OH) has emerged as one of the most versatile molecular tracers of the physical and chemical conditions in the interstellar medium, offering insights into gas temperature, density, kinematics, and evolutionary stage. This contribution pays tribute to the pivotal work of Prof. Dr. Karl M. Menten, whose pioneering studies on methanol in star-forming regions paved the way for much of what we understand today about CH₃OH emission in these regions.

Karl’s early identification and interpretation of methanol masers—particularly Class II masers—opened new windows into the study of massive star formation providing the comunity with a tool to identify early phases of massive young stellar objects when not much else than UCHii regions where available, and, later, performing high-precision astrometry to probe galactic structure and dynamics.

Building on his legacy, several works expanded our understanding of CH₃OH in a broad range of environments—from cold prestellar cores to protostellar disks and extragalactic sources. This talk will highlight Karl Menten’s fundamental role in establishing methanol as a tracer of molecular astrophysics, and present new results that underscore its value as a diagnostic of the ISM across different environments.

Speaker: Silvia Leurini (INAF)

10:10 AM Coffee Break

26 Karl and his 6.7-GHz maser legacy: Cepheus & new perspectives

After Karl's discovery of the methanol maser transition at 6.7-GHz in the early '90, a number of young stars have gained much interest in the community being associated with the brightest masers of this kind. Among them, HW2 in Cepheus-A stands out as the closest source to the Sun and thus a preferred maser laboratory, but its story is yet to be told. The circum-stellar environment surrounding HW2 has long been the subject of much debate about the presence or not of an accretion disk, questioning our current paradigm of star formation itself. Most interestingly, 6.7-GHz methanol masers towards Cepheus-A were shown to trace gas infall associated with the gravitational collapse around HW2, at variance with the most common belief they trace slowly expanding gas in general. Recently, we have finally confirmed this collapsing scenario near HW2 by high angular resolution observations of hot ammonia, triggering the following question: can 6.7-GHz masers be identified as infall tracers and, if yes, under which conditions? Looking through the literature about HW2, I will discuss how Karl's discovery of 6.7-GHz masers still inspires new advances in star formation after more than 30 years.

Speaker: Alberto Sanna (INAF, Osservatorio Astronomico di Cagliari)

27 ​Accretion flows, fragmentation and high-mass star formation: Lessons from VLA, SMA and ALMA surveys

Massive protostars are typically born in parsec-scale molecular clumps that collapse and fragment, leading to the formation of a cluster of stellar objects. How massive molecular clumps collapse and fragment to give rise to a cluster of stellar objects has been a puzzle for decades. In this presentation,  I report systematic survey in the NH3 (1, 1) and (2, 2) inversion lines toward 62 high-mass star-forming regions using the Very Large Array (VLA). The observations revealed NH3 gas filaments  associated with protoclusters. Velocity gradients in the filaments suggest mass transport toward the central region of the clump. Follow-up observations of a subset of hub-filament systems with the Submillmeter Array (SMA) and Atacama Millimeter/submillimeter Array (ALMA) were carried out. I will present ensemble physical conditions revealed by the NH3 observations, and fragmentation properties in these protoclusters obtained with the SMA and ALMA.

Speaker: Qizhou Zhang (Center for Astrophysics | Harvard & Smithsonian)

28 Before Fragmentation: From Uniform Clouds to Stellar Clusters

Characterizing the initial stages of star cluster formation is crucial for understanding their evolution. The analysis of our systematic ALMA survey of nearby, high-mass quiescent clumps revealed a puzzle: many objects with at least hundreds of solar masses of molecular material detected in single dish dust continuum data disappeared at high resolution, indicating an extended, relatively uniform distribution of material.
To investigate the nature of these sources, we analyzed ALMA archival data for three sources in the survey. Using CH$_3$OH and N$_2$H$^+$ as density and kinematic tracers, we studied the morphology and velocity structure of these regions. Remarkably, the molecular emission, even of methanol, is very extended, filling most of the primary beam, and reveals a relatively uniform density distribution, significantly below the typical densities of established high-mass star-forming cores.
Few compact, dense cores are detected within these clumps. However, large-scale velocity gradients are observed, suggesting ongoing accretion onto the extended filamentary structures.
These findings indicate that the most extreme sources in our survey represent a very early, potentially pre-core phase of cluster formation, where mass is still being assembled from the environment before significant fragmentation occurs. Unveiling these initial conditions offers a glimpse into the very beginnings of stellar nurseries, potentially mirroring the environment where our own Sun and planet were born.

Speaker: Andrea Giannetti (INAF - IRA Bologna)

11:30 AM Discussion Session I: Thomas Henning

12:00 PM Lunch

29 Not Your Typical Disk: ALMA unveils an expanding, ring-shaped structure in G23.6

The formation of high-mass stars remains one of the key open questions in astrophysics. While structures familiar from low-mass star formation—such as outflows, jets, and rotating centroids—have been observed in massive star-forming regions, detailed studies at spatial scales of a few hundred AU are still rare and limited to only a handful of sources.
Recent ALMA observations of the high-mass protostellar object G23.6 have revealed a remarkable ring-shaped circumstellar disk—the first of its kind to be resolved with this morphology at such small scales. Proper motion measurements of methanol masers trace the ring’s expansion away from the central source. Strikingly, the ring is rich in complex organic molecules, while its center appears depleted of molecular gas and dust, except for localized emission from sulfur-bearing species. These may trace shocks at the disk-envelope interface, potentially driven by infall or outflows. A mild velocity gradient across the ring in multiple molecular lines is consistent with a slow component of rotation.
In this presentation, I will explore the unique morphology and kinematics of this circumstellar ring, present detailed analyses of its molecular content, and discuss its implications for models of massive star formation.

Speaker: Katharina Immer (ESO)

30 Testing the star formation process across the Milky Way with APEX/ArTéMiS and JWST/MIRI

Submillimeter continuum observations with high sensitivity of the Herschel satellite space mission have revolutionized our understanding of the link between the structure of the cold interstellar medium (ISM) and the star formation process. In particular, the Gould Belt Survey of nearby (d < 0.5 kpc) molecular star-forming clouds was able to resolve physical scales that are critical to reveal the fragmentation of the clouds towards the formation of dense prestellar cores. However, due to limited resolution, Herschel observations cannot resolve these scales in more distant and significantly more massive star-forming regions, which limits our understanding of the general star formation process.
To solve this problem, we combine observations from different telescopes and at different wavelength to compile high resolution and high dynamic range column density maps of star-forming regions across the Milky Way. In a first step we combine 350 micron and 450 micron dust continuum data observed with the ArTéMiS camera at the APEX telescope with Herschel/SPIRE maps to create column density maps of 8” resolution. Those maps have not only a factor 4 higher resolution than standard Herschel column density maps, but are also corrected for saturation in the Herschel observations. Most of those data are published as part of the CAFFEINE (Core And Filament Formation/ Evolution In Natal Environments) survey. In a second step we use those ArTéMiS-Herschel column density maps to calibrate the column densities derived from JWST/MIRI 8 μm dust absorption observations. This allows us to resolve the dense cold ISM at a resolution of 0.26” and cover 4 orders of spatial scales.
In the talk I will present not only these novel data products, but also show how they are essential to further understand the star formation process. In particular, we test the filament paradigm of star formation on a diverse sample of clouds. Our results indicate that the star formation efficiency stays constant for column densities above $10^{22}$ cm$^{-2}$ and drops drastically for lower values. We also can confirm the finding of a typical width of filaments of 0.1 pc outside the Gould Belt region.

Speaker: Michael Mattern (CEA Paris-Saclay)

31 Peering into the dark: high angular resolution view of high-mass star and cluster formation

Most stars form in multiple systems and clusters, especially OB type stars are frequently found in a clustered environment. Yet, the early phase of star and cluster formation is still poorly understood, and little attention has been paid to the complex interplay between the physical processes and the chemical evolution of the gas. Large area surveys of the Galaxy, such as ATLASGAL, provide ideal finding charts for high angular resolution studies that allow us to peer into the formation conditions of high-mass stars and their clusters.

I propose to present results from the ALMA-IMF large program that targeted 15 prominent massive cluster progenitors selected from the ATLASGAL survey and investigated at high angular resolution with ALMA. Based on its excellent statistics, a large number of chemically rich sites have been identified. Investigating the emerging chemical complexity, I will also present the recently started NASCENT-stars large observing program at NOEMA that performs a sensitive interferometric unbiased spectral line survey of the most active star forming massive dense cores in the Cygnus-X complex. It aims to obtain reliable measurements of molecular abundances towards statistically significant samples of individual protostellar envelopes. First results of NASCENT-stars reveal Class I methanol masers in the vicinity of a massive very early stage pre/protostellar core, highlighting the role of shock heating at the emergence of high-mass protostars.

Speaker: Timea Csengeri (Laboratoire d'astrophysique de Bordeaux)

32 IRc2/Source-I* and the Orion OMC1 explosion

The observational consequences of the merger scenario for massive star formation are explored and contrasted with the gradual accumulation of mass by disk accretion. In high-density protostar clusters, envelopes and disks provide a viscous medium that can dissipate the kinetic energy of passing stars, greatly enhancing the probability of capture. Protostellar mergers may produce high-luminosity infrared flares lasting years to centuries followed by a luminosity decline on the Kelvin-Helmholtz timescale of the merger product. Mergers may be surrounded by thick tori of expanding debris, impulsive wide-angle outflows, and shock-induced maser and radio continuum emission. While accretional growth can lead to the formation of massive stars in isolation or in loose clusters, mergers can only occur in high-density cluster environments. In 2005, we suggested that the outflow emerging from the OMC-1 core (“the fingers of Orion”) was produced by a protostellar merger that released between 1048 and 1049 ergs less than a thousand years ago. (We know Karl liked the idea).

Speaker: Hans Zinnecker (Universidad Autonoma de Chile)

33 PHANGS and the cycle of baryonic matter

TBD

Speaker: Dario Colombo (Argelander-Institute for Astronomy, University of Bonn)

34 The HASHTAG project II. Giant molecular cloud properties across the M31 disc

The Andromeda galaxy (M31) is the closest massive spiral galaxy and thus serves as a unique testbed of the physical properties of the interstellar medium in an external galaxy. We present a study of molecular cloud properties in M31 using IRAM 30m CO(1-0) and James Clerk Maxwell Telescope (JCMT) CO(3-2) observations in selected regions. The CO(3-2) observations in the disk regions are obtained as part of the JCMT large program, HARP and SCUBA-2 High-Resolution Terahertz Andromeda Galaxy Survey (HASHTAG). We find that GMCs in the centre of M31 generally exhibit larger velocity dispersions and sizes compared to those in the disc, while their average surface density and turbulent pressure are lower. This low turbulent pressure in the central region is primarily due to the low density of molecular gas. The estimated GMC properties depend on the choice of CO transitions. Compared to CO(1-0), CO(3-2) exhibits smaller velocity dispersion and equivalent radius but higher surface density. These differences highlight the distinct physical conditions probed by different molecular gas tracers. We estimate the virial parameter and find that most molecular clouds exhibit high values (∼4–6) for both CO transitions, indicating that they are unbound. Furthermore, clouds in the nuclear ring display even larger α_vir values of ~100, suggesting that they may be highly dynamic, short-lived structures, although they could potentially achieve equilibrium under the external pressure exerted by the surrounding interstellar medium.

Speaker: Zongnan Li (National Astronomical Observatory of Japan)

3:20 PM Excursion

The excursion includes a scenic boat (lasting ~4 hours) cruise along the Rhine, complemented by a delightful dinner served on board. The program will include commemorative talks honoring Prof. Dr. Karl M. Menten, as well as scientific discussions on his contributions and their lasting impact. We encourage all participants to use this as an opportunity to network in an informal setting.

Thu, August 21

Instrumentation Landscape: Session IV: Instrumentation Landscape

35 A phanstatic journey: from Effelsberg to the Skies

Over the last few decades we (the more mature generation, still born as classical radio astronomers) have experienced a technological revolution. While this is true for many aspects of modern astrophysics, I will highlight the developments that have enabled a truly golden era of submm/far-infrared astronomy. The rapid advances in telescope construction and THz technologies in general have opened the way

to previously unexplored territories and led to an incredible increase in knowledge.

Given the occasion, I will discuss the technological developments at the MPIfR over the last decades, highlighting in particular the projects realized under Karl's leadership of mm/submm activities at the institute.

This is done from a standpoint emphasizing Karl's many contributions, while still not adequately reflecting the breadth of his scientific oeuvre.

Speaker: Rolf Guesten

36 Opening the Submm- and FIR-Skies: an exciting journey from KOSMA via ASTRO, SMT, NANTEN2, APEX, HIFI/Herschel, GREAT/SOFIA to CCAT/FYST

I will review the submm/FIR-instrumentation development int he group at the Universität zu Köln, in close collaboration with MPIfR, over the last 4 decades. The drivers were, first of all and obviously, the science goals and the rapidly progressing receiver technology development, but also the advancing technology and the stepwise better understanding of the atmospheric constraints, and the logistics at the various observatory sites. The journey was possible because of the trustful partnership with and support by Karl Menten and his group at the MPIfR, leading to a very successful complement of fundamental physics/technology development and engineering capabilities as a basis for a great joined science program.

Speaker: Juergen Stutzki (University of Cologne)

10:10 AM Coffee Break

37 Development of Radio Astronomy Infrastructure in Thailand: The Thai National Radio Telescope and Beyond

The Thai National Radio Astronomy Observatory (TNRO), established in Chiang Mai in 2017 by the National Astronomical Research Institute of Thailand, advances radio astronomy and geodesy infrastructure in Thailand. Its centerpiece, the 40-meter Thai National Radio Telescope (TNRT), operates from 0.3-115 GHz, supporting diverse scientific studies like molecular/maser lines and time-domain astrophysics. Developed with the Yebes Observatory (IGN), the TNRT features advanced L-band and K-band frontends with a universal backend both developed by the Max Planck Institute for Radio Astronomy, enabling spectral line, continuum, pulsar, and very-long-baseline interferometry (VLBI) observations. Scientific operations commenced in October 2023, initially focusing on L-band observations.

TNRT is envisioned as a key single-dish instrument and a future node in Asia-Pacific and global VLBI networks, enhancing regional and global capabilities for higher-angular resolution and higher-imaging-quality radio astronomy. Complementing this is a 13-meter VGOS-type geodetic radio telescope, scheduled for commissioning in May 2025, developed with the Shanghai Astronomical Observatory. TNRO has evolved into the Center for Radio Astronomy and Engineering (CRAE), including an Advanced Radio Frequency Laboratory and plans for two more VGOS stations in southern Thailand within two years.

These initiatives aim to realize Thai National VLBI Array (TVA), which will serve as a robust foundation for the establishment of a future regional VLBI network in Southeast Asia, known as South-East Asia VLBI Network (SEAVN), and supporting global research on the physics of star formation, stellar feedback, and the interstellar medium through enhanced observational capabilities.

Speaker: Koichiro Sugiyama (National Astronomical Research Institute of Thailand (Public Organization))

38 Science with AtLAST

TBD

Speaker: Amelie Saintonge (MPIfR)

39 Moving towards a panchromatic SMA

The Submillimeter Array (SMA) plays a leading role in numerous science areas, capitalizing on its strengths as an agile, wideband instrument, situated on Maunakea, Hawaii — the best site for year-round millimeter and submillimeter observing in the Northern hemisphere. The modest scale of the SMA allows for rapid adoption of technical innovations and nimble scheduling of science observations, two critical properties that keep the SMA a competitive and exciting facility going forward. In this talk, I will discuss a major ongoing upgrade known as the “wideband SMA” (wSMA) project, which leverage the SAO's expertise in wideband instrumentation for radio astronomy to build a full-polarization capable millimeter/submillimeter interferometer with a spectral grasp of 64 GHz. I will also discuss the future upgrade path of the SMA, which sees to build a panchromatic telescope to blanket the millimeter and submillimeter atmospheric windows with simultaneous spectral coverage. The broadband spectral coverage of this "panchromatic SMA", covering nearly a decade in frequency, would offer truly unique and ground-breaking capabilities in the submillimeter regime. Such an instrument will be transformative in key areas of astronomy, including time-domain studies, nearby galaxies, the Sun, supermassive black holes and active galactic nuclei, gamma-ray bursts, star-forming regions, evolved stars, high-redshift galaxies, clusters, comets, Solar System bodies, as well as other active areas of astrophysics.

Speaker: Raymond Blundell (CfA)

Interstellar Medium and Spectroscopy

12:00 PM Lunch

40 The interplay between laboratory spectroscopy and radio astronomy: recent examples

As of April 2025, about 330 molecules have been detected in the interstellar medium and circumstellar environments of late-type stars (e.g., https://cdms.astro.uni-koeln.de/classic/molecules), many of these detected in recent years. They include complex organic molecules, ions, radicals, (cyano derivatives of) polycyclic aromatic hydrocarbons, and others. In addition, minor isotopic species or transitions in excited vibrational states were identified for several of these. Laboratory spectroscopy is in most cases instrumental for unambiguous assignments. I will present some recent examples in detail, mention a few more briefly, and will try to provide an outlook.

Speaker: Holger Müller (Astrophysik/I. Physikalisches Institut; Universität zu Köln)

41 New one-dimensional and time-dependent model for COMs in molecular cores

Complex organic molecules (COMs) are synthesized on dust grain surfaces and later released into the gas phase, where they have been widely observed across diverse physical environments—from tranquil clouds to regions of star formation. They thus serve as valuable indicators of the local physical and chemical characteristics of these environments. Accurate models that can account for the synthesis and destruction of COMs are vital to interpreting observations. In this presentation, I will introduce our new time-dependent and 1D UCLCHEM model, a specialized gas-grain chemical code for protostars. I will then discuss our interpretation of observations from both single-dish and interferometry across various conditions, including both low- and high-mass star formation. Our study highlights the significance of employing astrochemical models in greater spatial dimensions to enhance our understanding of COM-related observations.

Speaker: Tram Le (Leiden University)

42 Hot cores in the outer Galaxy: impact of metallicity on the formation of complex organic molecules

Many complex organic molecules (COMs) in star forming regions are believed to form on the surfaces of dust grains or in their ice mantles. Therefore, we expect both the reduced metallicity and dust-to-gas ratio in the outer Galaxy to have an impact on the chemical composition of these regions. To test this, we use NOEMA to perform an imaging spectral line survey of the hot core candidate G135.27+2.79 at a galactocentric distance of 13.1 kpc. Our NOEMA observations in the 1.3 mm range have led to the identification of 43 species, including their isotopologues and deuterated variants. Among these are COMs with up to ten atoms, detected toward a hot (>100 K) and compact (< 5000 au) region. These detections confirm G135.27+2.79 as the second known hot core in the outer Galaxy. The rotational temperatures and column densities of the detected molecules are derived under the LTE approximation. Hot-core simulations with the three-phase astrochemical code MAGICKAL with reduced metallicity and dust-to-gas ratio and under normal conditions predict that certain molecules have a significantly reduced abundance (relative to methanol) at low metallicity and dust-to-gas ratio while others keep a similar abundance. The model predictions are approximately consistent with our observations when we compare the COM abundances of G135.27+2.79 with those in hot cores/corinos within the Solar circle, suggesting that metallicity and dust-to-gas ratio do have an impact on the formation of COMs.

Speaker: Youxin Wang (MPIFR)

43 From Clouds to Stars: What ¹²C/¹³C Ratios Reveal About Molecular Inheritance

The $^{12}$C/$^{13}$C isotopic ratio serves as a fundamental probe of chemical evolution in the interstellar medium (ISM), with a canonical local value of $\sim$68 that decreases towards the Galactic centre and increases towards larger Galactocentric distances. Yet, recent observations across a broad range of environments in the solar neighbourhood—from prestellar cores to Class II disks and exoplanet atmospheres—highlight significant and systematic deviations from the local standard of 68. Intriguingly, variations appear not only between sources at similar evolutionary stages but also between different molecular species within a single source, pointing to multiple contributing factors.
In this talk, I will present new results from our study of the $^{12}$C/$^{13}$C ratios in young Class 0/I protostellar systems, using methanol (CH$_3$OH) and methyl cyanide (CH$_3$CN). We find systematically lower ratios (< 30) compared to the local ISM value, independent of molecular species. Through astrochemical modeling, we explore how these low ratios may arise through inheritance from earlier chemical stages.
By connecting isotopic signatures to evolutionary processes, I aim to spark interdisciplinary discussion on the power of $^{12}$C/$^{13}$C ratios as a diagnostic tool. Where else—across star-forming regions, evolved stars, the Galactic centre, or external galaxies—might we expect isotopic anomalies, and what can they reveal about the assembly and transformation of cosmic structures? In the spirit of Karl Menten’s broad scientific vision, this work encourages a collaborative exploration of isotopic ratios as windows into the chemical and physical evolution of cosmic structures.

Speaker: Laura Ann Busch (Max Planck Institute for Extraterrestrial Physics)

44 HyGAL: Characterizing the Galactic ISM with observations of hydrides and other small molecules

Understanding the physical and chemical interstellar medium (ISM) is the first step to understanding star formation/evolution and, ultimately, planet formation. The formation of molecular gas occurs in diffuse/translucent clouds. These clouds are also closely associated with the progenitors of molecular clouds and clumps, which are the potential birthplaces of stars. It is in this initial transition to molecular gas that the initial chemical inventory of molecular clouds is set from the composition of diffuse clouds. These initial chemical conditions are crucial to explain the observed molecular species toward star-forming molecular clouds and their chemical history. I will present absorption line observations for two atomic and molecular species, including two hydrides (CH and OH), carried out under the SOFIA legacy program (HyGAL) to characterize the properties of Galactic ISM in diffuse and translucent molecular clouds. In addition, I will also present highly sensitive CO absorption line observations with NOEMA toward the HyGAL sightlines, which cover different spiral arms and inter-arms of the Milky Way.

Speaker: Wonju Kim (University of Cologne)

3:00 PM Coffee Break

45 The Search for Water: A Shared Interest with Karl

Karl Menten and I spent our early careers at the Center for Astrophysics. It was (and still is) a large institution, and there was a high chance we might have gone through those years without ever meeting. But Karl, being Karl, made sure that wasn’t the case. He learned of my interest in studying water, despite the challenges of doing so from within the Earth’s atmosphere. Perhaps it was these challenges that prompted Karl to seek me out, and what followed was a friendship that lasted over three decades, leading to 17 papers together on circumstellar and interstellar water. My talk will be in two parts. Part one will briefly discuss the work Karl and I did together. Part two will focus on my latest efforts to continue this research through SPHEREx, a recently launched NASA mission designed to collect nearly 10 million absorption spectra of H2O, CO2, and CO ices from within the Milky Way and Magellanic Clouds.

Speaker: Gary Melnick (CfA)

46 Discovery of widespread non-metastable ammonia masers in the Milky Way

Molecular maser lines are signposts of star formation, probing the excitation and kinematics of very compact regions in the close environment of young stellar objects and providing useful targets for trigonometric parallax measurements. With the Effelsberg 100-m telescope, we discovered widespread non-metastable NH3 maser emission toward 17 high-mass star-forming regions (HMSFRs) in the Milky Way. This doubles the number of known non-metastable ammonia masers in our Galaxy. These maser lines arise from energy levels between 342 K up and 1449 K above the ground state and probe the hot dense immediate neighborhoods of newly formed stars. With our higher angular resolution interferometric measurements from the Karl G. Jansky Very Large Array (JVLA), we determined detailed locations for maser spots emitted in multiple non-stable transitions toward a variety of regions. We greatly increase the number of detections in the Galaxy in all the lines targeted. The detected maser spots are not resolved by our JVLA observations. Lower limits to the brightness temperature are >400 K and reach values up to several 10^5 K, manifesting the lines’ maser nature. In view of the masers’ velocity differences with respect to adjacent hot molecular cores and/or ultra-compact (UC) HII regions, it is argued that all the measured ammonia maser lines may be associated with shocks caused either by outflows or by the expansion of UCHII regions. Furthermore, we recently detected linear and circular polarization of NH3 masers in Sgr B2.

Speaker: Yaoting Yan (Max-Planck-Institut für Radioastronomie)

47 Astrochemistry in the early stages of star and planet formation

TBD

Speaker: Paola Caselli (MPE)

4:30 PM Postcards for Karl

4:40 PM Poster Session

5:30 PM Wine Tasting

6:30 PM Conference Dinner

Fri, August 22

Galactic Centre: Session VI: Galactic Centre

48 High Pressure, Low Output: Galactic Center Star Formation through the Eyes of Karl and Others

Speaker: Jens Kauffmann (MIT)

49 Gas Dynamics, Shocks, and Star Formation Along a Bar-Driven Inflow in the Galactic Centre

The expanding molecular ring (EMR) appears as a characteristic parallelogram in position-velocity diagrams of the Central Molecular Zone (CMZ) and traces high-velocity (|V_LSR| > 100 km s$^{-1}$) gas structures linked to bar-driven inflow into the Galactic Centre (GC). The physical and chemical properties of the EMR and its connection to other GC clouds and its impact on the CMZ remains poorly understood. In this talk, I will present results from our multiwavelength investigation of a 200 pc long, high-velocity gas stream, located 15–55 pc above the CMZ, kinematically associated with the EMR. Using archival CO data, along with IRAM 30m, Yebes 40m, and APEX 12m molecular line observations, we trace the gas kinematics, shock signatures, and star formation activity within the stream. We propose that the helix stream represents a near-side bar-driven inflow lane, overshooting and interacting with the CMZ near the G1.3 cloud, as supported by both simulations and observations. These findings provide new insights into the physics, chemistry, and star formation activity within nuclear inflows in barred spiral galaxies.

Speaker: Veena Vadamattom (Max Planck Institute for Radio Astronomy)

50 The 3 kpc Arms: Not Expanding, Not Spiral, Not What You Thought

Near the center of our Milky Way is a bar-like structure and the so-called Expanding 3 kpc arms. We currently have limited knowledge of this important region, since we are about 8.2 kpc from the center and cannot directly observe it at optical wavelengths, owing to strong extinction from interstellar dust. Here we present extremely precise very long baseline interferometry measurements of H2O maser sources from the BeSSeL Survey, where extinction is not a problem, which accurately determine the three-dimensional locations and motions of three massive young stars. Combined with previous measurements, these stars delineate a trail of orbits outlining the Milky Way's Galactic bar. We present the first measurements capturing the dynamics of quasi-elliptical (X1) orbits around the Galactic bar. Our findings provide evidence substantiating the existence of such orbits populated by massive young stars. Our measurements of the position and velocity of a number of massive young stars, previously identified with the Expanding 3 kpc arms, show that they are more likely located in the X1 orbits about the Galactic bar. Also, some stars previously assigned to the Norma spiral arm appear to be in these orbits, which suggests that this spiral arm does not extend past the end of the bar.

Speaker: Jayender Kumar (CSIRO Space and Astronomy)

10:10 AM Coffee Break

51 The Central Molecular Zone of the Galaxy in [C II] from upGREAT/SOFIA

The Galactic center, deep at the bottom of the Galaxy's gravitational
potential well, is a region of complex dynamics and regions of massive
star formation. Observing it through the disk of the Galaxy, the
pileup of emission from line-of-sight structures makes discrimination
by excitation and velocity resolution essential.

This talk summarizes the GREAT Galactic center team's fully-sampled
spatial and velocity-resolved 158um [C II] SOFIA-upGREAT spectral
imaging of the center's 200 pc wide Central Molecular Zone. These data
cover 213 by 47 pc region (1.49 by 0.33 degrees) with 28,000 spatial
resolution elements at 1 km/s velocity resolution. The data provide a
high-resolution view that helps us understand center's structure, star
formation, and gas flows into the Galactic center and onto the central
black hole Sgr A*. They also serve as guides to interpreting
far-infrared fine structure line emission from other galactic nuclei.

We provide an overview of this unique data set and highlights of the
results toward Sgr A, B, and C.

Speaker: Andrew Harris (Department of Astronomy, University of Maryland)

52 Triggered Star Formation at the Galactic Crossroads: Insights from G358.69+0.03 in the Galactic Center

We investigate the high mass star formation (HMSF) activity in a sub-region of the SgrE star forming complex, centered at ($\textit{l}$, $\textit{b}$) = (358.69$^\circ$, 0.03$^\circ$) which is marked by an enhancement of infrared and radio sources along a semi shell-like structure. In order to identify and characterize the tracers of HMSF, HII regions, we used continuum data from the Global View on Star Formation (GLOSTAR) survey, which is a wideband radio (4-8 GHz) survey of the Milky Way combining data from the Karl G. Jansky Very Large Array (VLA) and the Effelsberg 100 m telescope. Using BLOBCAT source extraction software, we identified 49 radio sources in the target region. Based on the multiwavelength associations and spectral index estimates, we identified 27 HII regions that had been previously confirmed by earlier studies. We also detect radio counterparts for three sources that were previously considered radio-quiet HII region candidates. Additionally, we identified 5 new HII region candidates. We also found several cold dust clumps in the region of which 15 clumps have associated SiO emission with broad velocity ranges, indicating presence of shocks. The target region exhibits enhanced star formation activity, likely triggered by cloud-cloud collisions resulting from the interaction between the far dust lane and the Central Molecular Zone of the Milky Way. However, the presence of a large scale ionized shell spanning $\thicksim$71.5 pc, with the HII regions distributed along the rim of this shell, suggests additional possibility. This shell is likely a fossil remnant of a previous feedback event, such as an expanding HII region or a supernova remnant. The expansion could have further compressed the surrounding gas leading to a second generation of star formation.

Speaker: Anahat Cheema (Max-Planck-Institute for Radioastronomy)

11:10 AM Discussion I: Thushara Pillai

11:40 AM Postcards for Karl

11:50 AM Closing Remarks

12:00 PM Lunch