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.
To help fill this gap, our team conducted high-resolution observations to explore the properties of stars that have just formed or are still in the process of forming, within four massive, near-primordial clusters. We identify potential binary or multiple star systems, study how their properties—such as separation and mass ratios—vary within and between clusters. In this framework, multiplicity serves as a tool to trace the initial conditions that drive the formation of massive stars in multiple systems.
To study the primordial multiplicity properties, the clusters must have similar chronological ages with slight variations and be young enough to ensure that significant dynamical interactions have not yet occurred. This increases the likelihood of observing systems in a near-primordial multiplicity state. The selected clusters—Hourglass Nebula, RCW 108, DBS 113, and DBS 121—are observable in the near-infrared and submillimeter wavelengths due to their significant dust emission. These clusters are located at a distance of 1.5 ± 0.3 kpc on average and can be classified by age. Based on this cluster classification, we trace the evolution of multiplicity and companion fraction between 1.0 Myr and 2.8 Myr.
Our preliminary results are derived from NACO K-band data, with Chinmaya, a PhD student in our team, leading this aspect of the project. The figure shows one of the fields of DBS121 for which we show the identified sources, hence potential companions per bin of separation. We find that multiplicity properties evolve with cluster age, as the other clusters show a gradually increasing trend in the number of stars, thereby indicating a possible increase in companion fraction with cluster age. To extend this study, we recently included VVV CL100 (7.5 Myr) to determine whether this trend persists in older clusters.
Emma, a postdoc in our team, successfully led an ALMA proposal to enhance this analysis. Data acquisition is now underway, promising exciting new discoveries in the evolution of multiplicity properties in massive star-forming clusters. Stay tuned!
The next SFB-colloquium will be on December 3 at 2 pm in lecture hall III of the physics institutes in Cologne. Friedrich Wyrowski & Sudeep Neupane from the SFB 1601 / Max Planck Institute for Astronomy, Bonn will talk about “Physical conditions and gas kinematics from giant molecular clouds to clumps scales“.
See also: https://sfb1601.astro.uni-koeln.de/events/sfb1601-colloquium/
The CRC’s Sustainability Board is responsible for coordinating the evaluation of the environmental impact of the CRC’s activities and proposing measures to reduce it. In addition, the Sustainability Board organises talks and workshops for the CRC members to raise awareness of sustainability issues and establish solutions for daily work. During the sustainability barbecue on October 17, among other topics, the University of Cologne’s sustainability strategy and the problem of conference trips were discussed. In the afternoon, several workshops took place, one of which involved participants building their own insect hotels. This Thursday, a total of seven insect hotels were put up around the physics department of the University of Cologne. Insect hotels provide shelter and nesting facilities for a variety of insects during winter. Introducing insect hotels can help with pollination and ecosystem diversity.
The Public Observatory Cologne is a private institution which is run by the members of the “Vereinigung der Sternfreunde Köln e.V.” on a voluntary basis. This association of interested amateurs and amateur astronomers was founded in 1922 with the aim of disseminating basic astronomical knowledge to the public and promoting the training and further education of active amateur astronomers within the scope of the available possibilities.With the 60cm refractor “Cologne Large Telescope” (CLT) installed in 2012, the Volkssternwarte Köln operates the largest freely accessible telescope in North Rhine-Westphalia
“Betrug in der Wissenschaft” – Dr. Oskar Asvany (Universität zu Köln)
Eine kurze Geschichte der Datenmanipulation in der Wissenschaft, insbesondere in der Physik (und Astronomie)
“Neighbourhood Watch: What’s going down in our Galaxy’s Center?” – Myank Singhal (Charles University Prague)
We still have so much to learn about our own Galactic Center, the supermassive black hole, the mysterious collection of dust, and the paradox of youth! The talk will not answer all these questions but will provide an overview of the core of our own galaxy.
Join us for the last event of Astronomy on Tap Köln in 2024! Program below.
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Prachi Prajapati, an observational cosmologist working at the Max Planck Institute for Radio Astronomy and affiliated to the University of Cologne, participated in the 73rd Lindau Nobel Laureate Meeting. She reflects on her career so far and the time she spent in Lindau.
As a school kid growing up in India, I was interested in science in general. When Sunita Williams, a NASA-astronaut of Indian origin, flew to space for the first time in 2006, I closely followed the news covering that event. That interest in space science stayed with me; and having finished school, it was an apt choice to apply for a bachelor’s in Engineering Physics at the Indian Institute of Space Science and Technology (IIST), followed by a master’s degree in Astronomy and Astrophysics.
After graduation, I was immediately placed to work at the astrophysics department of the Indian Space Research Organization, where I also experienced many night shifts for observations at optical infrared telescopes on the hilltops in Western and Northern India. One of the best things was to see the Milky Way with naked eyes. The job included mainly R&D tasks, including the back-end instrumentation for ground-based telescopes. After three years, I decided to go back into academia. Since autumn 2023, I am pursuing my PhD in Bonn-Cologne, Germany, at the Max Planck Institute for Radio Astronomy.
Birth of Stars, Galaxies, Clusters and Super Clusters
Galaxies are constituted of stars, gas, dust, and dark matter. Basically, my PhD is focused on understanding the process how galaxies are formed and evolved in the history of cosmic time. Big bang is one of the most popular theories for the beginning of universe. Tracing the star formation history using the cold molecular gas lines, we are trying to find out how and when different galaxies were born after big bang, how they developed over time to become what they are at present. For analogy, it is similar to human evolution; the Darwin theory says that maybe we were monkeys and eventually we developed into the human shape as we are today – so there is a link between the two stages which is called evolution.
We observe the high-redshift galaxies using radio and submillimeter telescopes, doing multiwavelength observations of the galaxies starting from the epoch when the universe was about a few hundred million years old, until now. Eventually, the aim is to observationally understand the overall picture of the universe from the earlier epochs (high-redshift) to the stars and galaxies that we see today all around us to find out how these large structures were formed. At the same time, we all are part of the Milky Way, which itself is a part of the local cluster which is a cluster of galaxies. Now we also know of the existence of super clusters that are clusters of clusters of galaxies.
Prachi meeting Brian Josephson
The Majority of the researchers in this research field try to understand physics at all these different astrophysical scales to answer numerous open questions. This is fundamental physics, which is not immediately affecting the humanity, but it is more of a curiosity-driven research to fulfill the inner quest for understanding how the nature works. Maybe in the future it might have some societal implications – who knows?! For example, Einstein’s general theory of relativity was a pure theoretical beauty, which led to GPS applications after almost a century and now it is an integrated part of our lives.
Real Life of an Astrophysicist
Many people imagine an astronomer looking at the sky with a telescope at night – of course, that is one part of it, i.e., we have ground-based optical-infrared telescopes which are operated only at nighttime – but we also have space telescopes like James Webb Space Telescope (JWST), Hubble Space Telescope (HST) and Chandra X-ray Observatory, which are always in the sky taking observations. In addition, we also have ground-based radio-submillimeter telescopes, operating at longer wavelengths. These waves are observable also during daytime from Earth as the atmosphere is transparent for them and the sunlight in radio is not super bright, so they do not need to be observed only at nighttime. Such multiwavelength observations using different observatories provide a holistic understanding of the astrophysical targets we look at. Now with advancements in technology, most of the observatories are working automatically, and one does not have to be on-site for observations; but it is good to learn how the observations are realized. This was the reason why I visited the Karl Jansky Very Large Array (VLA) in the United States once to experience the techniques using with which the radio data for my PhD was observed. But in fact, most of the time, I am not looking through a telescope – I am sitting in front of a computer screen either coding or using software for data reduction. Not all the data we observe are perfect, so one has to remove the noises caused by unwanted radio frequency interference (RFI). For our observations, signals from mobile phones, WiFi, Bluetooth, orbiting satellites, etc. are negatively impacting the data as they also transmit similar frequencies like those we are using in radio observations. Handling large data volume is also an important aspect for all observatories, in particular for radio telescopes, as the amount of data is increasing. Upcoming radio observatories like SKA, the Square Kilometer Array in Australia and South Africa, will achieve around 700 petabytes per year.
Proposals and Future Perspectives
We receive most of the data remotely via our accounts on the observatories’ websites, for which we had submitted proposals. Proposing for observations is also a crucial part of the PhD – scientists are motivated to submit observational proposals for making new observations. This process is quite competitive because the telescopes have limited timeslots for observations and there are lots of researchers from across the world competing for them. Some of the most demanded telescopes are JWST for infrared bands, VLA for radio data, and ALMA for submillimeter. After a successful proposal and getting promising results from it, we have proposed for more observations in the coming cycle of VLA; however, due to the competitive run on the telescopes, I need to have a plan-B for my PhD. It is important to be prepared to use some other archival data to accomplish the aims of my doctoral research project, if the latter proposal does not succeed. I am particularly interested in looking at galaxies farther in distance, in the high-redshift universe, which also means that I am really probing the faintest signal that one can get from the early universe. The future in the field is promising with the latest/upcoming observatories like JWST, ngVLA, and SKA.
My plan is to go back to India as an academician and make use of my knowledge and of western collaborations to promote the field in my home country, and facilitate younger generations to conduct good science.
My Lindau Experience
One of the opportunities to connect with other scientists and the Nobel Laureates was the Lindau Meeting. I met so many people from across the globe – and I am still in touch with many of them. The interdisciplinary aspect of the Meeting amazed me. It was quite fruitful to attend the Lectures by Nobel Laureates, not only on science but also on outreach, learn how they are trying to change the academic systems in different countries and doing promotion of science. Participants were always encouraged to keep an open mind and to explore unknown fields of research. It was a perfect mix of life, philosophy, and science!
Prachi stayed with a host family: “They were super lovely and I had an amazing time discussing and exchanging science, culture, and many other topics with them.”
Additionally, I was a part of one of the Sciathon groups this year and our project got shortlisted, which meant we had the chance to discuss our project during the Sciathon Forum. This is a good platform for people who are interested in startups: talking to experts from industries and academia, getting their input or suggestions to modify things in the project – and even to be appreciated that you are doing a good work, that provides motivation to continue.
My advice to future Young Scientists: Talk with as many people as possible. Connect with them. And enjoy your time there at Lindau for a life-long experience!
Prachi Prajapati, 2024 Lindau Alumna, is conducting observational cosmology at the Max Planck Institute in Bonn, Germany. After having completed her bachelor’s and master’s degree with a major in astrophysics, she was working at the Indian Space Research Organization for about three years, before she decided to pursue her PhD. She aims to understand the early history of the universe based on the data collected by telescopes around the world.
Text and photos: Prachi Prajapati Original Article:
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.
In order to distribute the LO power to the individual mixers, we developed a waveguide power splitter with an extremely even splitting ratio over the required bandwidth. Since the LO source is distributed to up to 32 mixers, we are employing a 5-level cascade of this divide-by-two splitter. Excessive asymmetry in the splitting ratio of a single unit would result in unacceptable power differences between the outputs of the cascade. Each of our splitting stages uses a simple Y-junction, upgraded by a drop-in chip, which suppresses crosstalk between the two outputs.
In order to illustrate the suitability of the concept for a multi-level cascade of binary splitters, we built the first section of CHAI’s LO distribution network: a 3-level cascade, which results in 8 equal output ports to serve one row of 8 mixer blocks in CHAI’s focal plane. The photograph shows a device manufactured as E-plane split block at our precision workshop. Waveguide dimensions are 0.460 mm x 0.230 mm for the low-frequency band of CHAI (420 – 510 GHz). Visible at each junction are the chips (600 µm x 60 µm) for the isolation between the output ports, which were manufactured in our microfabrication lab.
The graph shows the output power distribution measured at the 8 output ports of the 3-level cascade over the nominal bandwidth. No systematic asymmetry can be seen in the signal. The maximum power scatter – including significant measurement noise – is below 40% of the nominal output power – well within our tolerance range.
Title figure: Photograph of the two split-block halves of the 8-way power divider, showing the waveguides with the isolator chips. Output ports are numbered.
Artikel des Uni_Köln-Magazins: Bisher sind im ganzen Universum nur rund zehn mittelschwere Schwarze Löcher entdeckt worden / Das nun identifizierte Schwarze Loch führt dazu, dass sich umliegende Sterne unerwartet geordnet innerhalb eines Sternhaufens bewegen
Ein internationales Team von Forscher*innen unter Leitung von PD Dr. Florian Peißker hat einen Sternenhaufen in direkter Umgebung des supermassiven Schwarzen Lochs SgrA* (Sagittarius A Stern) im Zentrum unserer Galaxie untersucht und Anzeichen für ein weiteres, mittelschweres Schwarzes Loch gefunden. In unserem ganzen Universum sind trotz enormer Anstrengungen der Forschung bisher nur ungefähr zehn dieser mittelschweren Schwarzen Löcher gefunden worden. Wissenschaftler*innen nehmen an, dass sie sich schon kurz nach dem Urknall gebildet haben und durch Verschmelzung als „Samen“ für supermassive Schwarze Löcher fungieren. Die Studie wurde unter dem Titel „The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure“ im Fachjournal The Astrophysical Journal veröffentlicht.
Der untersuchte Sternenhaufen namens IRS 13 liegt in einer Entfernung von 0,1 Lichtjahren vom Zentrum unserer Galaxie. Für astronomische Verhältnisse ist dies sehr nah, allerdings müsste man unser Sonnensystem dennoch zwanzig Mal von einem Ende zum anderen bereisen, um diese Strecke zurückzulegen. Den Forscher*innen ist aufgefallen, dass die Sterne, die in IRS 13 enthalten sind, sich unerwartet geordnet bewegen. Eigentlich hätten die Forscher*innen eine zufällige Anordnung der Sterne erwartet. Die geordnete Bewegung lässt zwei Schlüsse zu: Zum einen scheint IRS 13 mit SgrA* zu interagieren, was zu der geordneten Bewegung der Sterne führt. Zum anderen muss es etwas innerhalb des Sternenhaufens geben, damit dieser seine beobachtete kompakte Form behalten kann.
Multiwellenlängenbeobachtungen mit dem Very Large Telescope sowie den Teleskopen ALMA und Chandra deuten nun darauf hin, dass der Grund für die kompakte Form von IRS 13 ein mittelschweres Schwarzes Loch sein könnte, welches sich im Zentrum des Sternenhaufens befindet. Dafür würde sprechen, dass die Forscher*innen charakteristische Röntgenstrahlung sowie ionisiertes Gas beobachten konnten, das mit einer Geschwindigkeit von mehreren 100 km/s in Form eines Rings um die vermutete Position des mittelschweren Schwarzen Lochs rotiert.
Ein weiteres Indiz für die Anwesenheit eines mittelschweren Schwarzen Lochs ist die ungewöhnlich hohe Dichte des Sternenhaufens, die höher ist als jede andere bekannte Dichte eines Sternenhaufens in unserer Milchstraße. „Es scheint sich bei IRS 13 möglicherweise um einen essentiellen Baustein für das Wachstum unseres zentralen Schwarzen Lochs SgrA* zu handeln“, so Florian Peißker, Erstautor der Studie. „Dieser faszinierende Sternenhaufen überrascht die wissenschaftliche Community immer wieder, seitdem er vor rund zwanzig Jahren entdeckt wurde. Zunächst dachte man, dass es sich um einen ungewöhnlich schweren Stern handelt. Mit den hochaufgelösten Daten können wir nun aber die bausteinartige Zusammensetzung mit einen mittelschweren Schwarzen Loch im Zentrum belegen.“ Geplante Beobachtungen mit dem James-Webb-Weltraumteleskop sowie dem sich im Bau befindenden Extremely Large Telescope werden weitere Einblicke in die Vorgänge innerhalb des Sternenhaufens liefern.
Inhaltlicher Kontakt: Dr. Florian Peißker Institut für Astrophysik +49 221 470 7791
Presse und Kommunikation: Jan Voelkel +49 221 470 2356
Did you know that the University of Cologne has its own Sustainability Office? We have invited them to present their daily work and challenges to make our university more sustainable. Do you have an idea on how to improve our university? Then join us and take this opportunity to talk to them directly!
We are happy to organize fruitful discussions where you can bring your ideas how to change our work and research to make the CRC more sustainable.
We will also have a number of workshops, and we will finish with a barbecue and a quiz. We will offer drinks and a vegetarian barbecue to all participants. You are welcome to bring your own meat/other food if you wish.
As we need to plan which room to use for which workshop and we need to buy the material for the insect hotel building we ask everyone to register for their preferred workshop. Please indicate there as well whether you join for the barbecue and for the drinking so that we can buy the appropriate amounts. https://sfb1601.astro.uni-koeln.de/sustainability/sustainability-bbq/
Neben Vorträgen zu aktuellen Forschungsthemen und Vorführungen von Experimenten kann mit Hilfe von VR-Brillen das Universum hautnah erlebt und das CCAT-Teleskop besucht werden.
Drucken Sie sich Ihre eigenen kleinen Versionen von Teleskopen (JWST, Hubble Space Telescope, CCAT) mit Hilfe von einem 3D Drucker.
Für Kinder wird der Bau von Luftraketen angeboten. Sie können ihre Raketen nach Ihren eigenen Vorstellungen und Wünschen gestalten und überlegen, wie sie ergonomisch am besten fliegen können. Als Highlight werden die Raketen zusammen fliegen gelassen.
Demonstrationsexperimente zur Laborastrophysik werden den ganzen Abend über aufgebaut sein. Mithilfe von diversen Teleskopen lassen sich Sonne, Mond und Sterne beobachten.
Wie funktioniert das ALMA Teleskop? Das ALMA Teleskop in der Atacama Wüste wird mit Hilfe von Legosteinen nachgebaut werden.
Was braucht es, um Planeten, Sterne, Galaxien und das ganze Universum in einem Supercomputer zu erschaffen? Was ist das tägliche Brot eines theoretischen Astrophysikers, und warum brauchen wir so astronomisch große Computer? Diesen und weiteren Fragen geht Dr. Tim-Eric Rathjen von der Universität zu Köln auf den Grund!
Rundwanderung zum Observatorium Hoher List, Schalkenmeeren zur langen Nacht der Astronomie am 19.10.2024 – Volker Ossenkopf-Okada
Wo kann man im Universum wandern? Auf der Erde haben wir das getan und uns auf dem Weg zum Observatorium “Hoher List” gefragt, wo wir denn noch frische Luft genießen könnten. Es gibt tausende Exoplaneten, aber könnten wir dort atmen? Die geologische Entwicklung unserer Erde hilft, diese Frage zu beantworten. Die Kombination aus Wanderung und astronomischem Beobachtungsabend erlaubt die Entstehung der Erde und die Entwicklung ihrer vulkanischen Aktivität im Kontext der Planetenentstehung und damit die besondere Stellung der Erde im Universum zu verstehen.
Die Veranstaltung bestand aus zwei separaten Teilen, die sich gegenseitig ergänzten. 34 Wanderfreunde starteten 16:30Uhr und folgten der Frage, was wir aus den Eifelmaaren über die Entwicklung anderer Planeten im Universum lernen können. Mit der Ankunft 19:00Uhr am Observatorium “Hoher List” vergrößerte sich die Besucherschar auf ca. 100 Astronomie-Interessierte, die einen Abend bei prächtigem Beobachtungswetter genießen konnten. Es gab Beobachtungsmöglichkeiten an verschiedenen Teleskopen, einen Vortrag zu den Besonderheiten des Abends, d.h. dem Kometen C/2023 A3 Tsuchinshan-ATLAS, dem Saturn und dem Mond bei den Plejaden. Daneben konnte die historische Instrumentensammmlung und der Lernraumes “Erläuterung der Himmelsmechanik” besichtigt werden.
Höhepunkt des Abends waren natürlich die Beobachtungen des Kometen Tsuchinshan-ATLAS, den man sowohl mit bloßem Auge, als auch mit den verschiedenen Teleskopen, wie dem neuen computergesteuerten Celestron bewundern konnte. Tatkräftige Unterstützung gab es dabei von der Astronomie AG des Johannes-Gymnasiums Lahnstein, die verschiedene Teleskope vor dem Turm 1 installiert hatte. Besonderes Interesse gab es für den Bonner Doppelrefraktor aus dem Jahr 1899 im Turm 5. Ein Blick auf das Mond-Spekrum mit dem DADOS-Spektrometer schloss den Kreis zum Start der Wanderung und der Frage nach der Zusammensetzung extraterrestrischer Atmosphären.
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. In Peißker et al. (2023c) and Peißker et al. (2024b), we have analyzed the densest stellar cluster, IRS 13, in our Milky Way, only about 0.3 lightyears away from Sgr A*. This massive embedded cluster shows two distinct generations of stars, implying independent and plausible triggered, star formation events. Until recently, it was unclear how and why this cluster so close to an SMBH seems to preserve its shape. As we show in both related publications, the cluster comprises three distinctive components. One of the components is associated with the dense core of the cluster, whereas the other one shows signs of evaporation. We argue that IRS 13 is the remanent of a more massive cluster that plunges into the gravitational well of our central SMBH. One key aspect of this analysis is the young age of the two stellar populations. From the young age and plausible star formation channels, we derive an unusually short cluster migration timescale. One explanation for the rapid infall of the cluster could be the presence of an IMBH inside the cluster. In Peißker et al. (2024b), we confirm that the presence of an IMBH is highly likely. Due to the evaporation nature of the cluster, it is expected that we identified one of the first pre-merger setups between an SMBH and IMBH to date.
Das Universum besteht zu 95 Prozent aus zwei mysteriösen, unsichtbaren Komponenten, der Dunklen Materie und der Dunklen Energie. Eines der Hauptziele der Kosmologie ist es, diesen Bestandteilen auf die Spur zu kommen und ihre Eigenschaften einzugrenzen. In diesem Vortrag werde ich die zugrundeliegenden Methoden erläutern und einen Überblick über die Durchmusterungen geben, die uns einen neuen Blick und neue Erkenntnisse über unser Universum geben werden.
A public talk during the Meeting of the Astronomical Society 2024
Andrina Nicola Universität Bonn, Argelander Institut für Astronomie
Thursday, 12 September 2024, 20:00, Aula, University of Cologne
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.
The Physics at High Angular resolution in Nearby GalaxieS (PHANGS) collaboration aims to create a comprehensive view of star formation and the lifecycle of gas and dust in nearby galaxies, using state-of-the-art facilities. In particular, by leveraging the James Webb Space Telescope (JWST)’s infrared capabilities, the PHANGS-JWST program has provided astonishing views of 19 galaxies in wavelengths that are typically obscured by dust in the optical range, reaching unprecedented resolutions and sensitivities.
We used observations of the emission from Polycyclic Aromatic Hydrocarbons (PAHs, e.g. complex organic molecules that emit strongly in the mid-infrared and are associated with photodissociation regions) from PHANGS-JWST to generate molecular gas maps of the 19 galaxies.
The application of the Spectral Clustering for Molecular Emission Segmentation (SCIMES) on the JWST data allowed the identification of more than 50,000 highly-resolved molecular clouds. SCIMES is a machine learning-based code that utilises graph theory concepts to segment out molecular clouds from the more diffuse medium by preserving their intrinsic morphology and internal structure.
Our preliminary results suggest that the molecular cloud mass spectra—specifically their steepness and truncation mass—are strongly influenced by the surrounding dynamical environment. This indicates that certain physical conditions may be more favourable to the formation of high-mass clouds than others.
Figure caption: Upper row: Left image shows the galaxy’s intensity map; right image displays dust structures identified by SCIMES with a greyscale intensity background and a colour bar indicating 7.7 μm intensity. Bottom row: Cumulative mass distributions of molecular clouds in different environments. Dotted black lines represent simple power-law fits; solid black curves are truncated power-law fits. Fit parameters—γ (spectral index), M0 (maximum mass), N0 (count in the distribution). The grey region represents the Poisson errors on the counts.
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).
Most particle-physics candidates for DM fall into the class of thermal relics (i.e. particles that were once in thermal equilibrium with the rest of the Universe). In this case, the velocity dispersion of the particles at early times turns out to be inversely proportional to their mass. This implies that less massive particles can freely stream out of shallow potential wells and, de facto, inhibit the formation of low-mass structures. Therefore, cold DM (CDM, with negligible velocity dispersion) and warm DM (WDM, with a free-streaming length of the order of 0.1 Mpc) give rise to a different mass spectrum of DM halos within which galaxy formation takes place.
Using the halo-model approach, we make forecasts for the constraints that LIM of the 150 μm fine-structure transition of [Cii] can set on the mass of the DM particles. Ionised carbon is a promising tracer that should be present also in low-mass halos, contrary to neutral hydrogen that cannot be shielded from the UV background after cosmic reionisation. We compress the data into the isotropic power spectrum and use Bayesian inference marginalising over the uncertain faint-end slope of the [Cii] luminosity function (LF).
Our results are shown in the figure as a function of the survey area and for two different measurements of the bright-end of the [Cii] LF (optimistic/pessimistic). Assuming a CDM scenario, we find that LIM can rule out WDM particle masses up to 2–3 keV, which makes this technique competitive with other probes, such as the Ly-α forest. Our study demonstrates that, taking into account the current limits on the LF, the [Cii] power spectrum is dominated by sources hosted in relatively massive halos and this diminishes its constraining power on the WDM mass.
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.
To overcome this challenge, we have developed a new sub-grid model, HYACINTH – HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations – that can be embedded into cosmological simulations of galaxy formation to calculate the non-equilibrium abundances of molecular hydrogen and its carbon-based tracers, namely, CO, C, and C+ on the fly. Our model captures the effects of the ‘microscopic’ (i.e., unresolved) density structure on the ‘macroscopic’ (i.e., resolved) chemical abundances in cosmological simulations using a variable probability distribution function of sub-grid densities within each resolution element.
The chemical abundances from HYACINTH are in good agreement with observations of nearby and high-redshift galaxies. We are now running a suite of cosmological galaxy formation simulations with HYACINTH that will allow us to address fundamental questions regarding the contribution of different galaxies to the global H2 budget and the reliability of different molecular gas tracers across ISM conditions and galaxy environments at high redshifts (z ≳ 3).
Figure caption: Column density maps of different species in a pre-simulated galaxy (from Tomassetti et al. 2015) post-processed with HYACINTH. The first two panels show the distribution of total and molecular hydrogen from the simulation, while the other panels show the species obtained in post-processing. CO is concentrated in regions with the highest N(H2), while C and C+ are more widespread; C+ even extends out to regions lacking a significant amount of H2and closely mirrors the total gas distribution.
Our science is often not visible to the public because we don’t know how to present in properly. With the help of the UoC press department we are aiming to change that.
A first seminar about science communication will be on Monday, June 24 at 3 pm (regular colloquium time). All PH1 or SFB1601-members are invited to join, there is no registration necessary.
Forschungsmeldung der Universität zu Köln: Die jungen Sterne umrunden das Schwarze Loch im Zentrum unserer Galaxie mit mehreren 1000 km/s / Veröffentlichung in Astronomy & Astrophysics
Astronomische Beobachtungen zeigen, dass sich neu entdeckte Babysterne in der Umgebung von Sagittarius A*, dem Schwarzen Loch im Zentrum unserer Galaxie, anders verhalten als erwartet: Sie beschreiben ähnliche Bahnen wie bereits bekannte Hochgeschwindigkeitssterne und ordnen sich in einem bestimmten Muster um das Schwarze Loch an. Die Studienergebnisse deuten darauf hin, dass Sgr A* die Sterne zu bestimmten Anordnungen veranlasst. Die Studie wurde unter dem Titel „Young Stellar Objects in the S-cluster: The Kinematic Analysis of a Sub-population of the Low-mass G-objects close to Sgr A*“ in der Fachzeitschrift Astronomy & Astrophysics veröffentlicht. Beteiligt waren Forscher*innen der Universität zu Köln, der Masaryk-Universität in Brünn (Tschechien), der Karls-Universität in Prag (Tschechien), der Akademie der Wissenschaften der Tschechischen Republik und des Max-Plack-Instituts für Radioastronomie in Bonn.
Vor rund dreißig Jahren wurden in der direkten Umgebung des supermassiven Schwarzen Lochs Sgr A* im Zentrum der Milchstraße Hochgeschwindigkeitssterne entdeckt. Diese Sterne, auch S-Sterne genannt, umrunden das Schwarze Loch mit Geschwindigkeiten von mehreren 1000 km/s in wenigen Jahren. Die Sterne sind überraschend jung und ihre Anwesenheit rätselhaft, denn nach gängigen Theorien würde man nur alte und leuchtschwache Sterne in der unmittelbaren Umgebung eines Schwarzen Lochs erwarten.
Die technologischen Fortschritte der letzten Jahrzehnte und die lange Beobachtungszeit des galaktischen Zentrums durch moderne Teleskope werfen aktuell noch weitere Fragen auf. So wurde zum Bespiel im Jahr 2012 ein Objekt entdeckt, bei dem Wissenschaftler*innen von einer Gaswolke ausgingen, die vom Schwarzen Loch „aufgesaugt“ wird. Zwar hat sich die These nicht bestätigt, es war aber lange Zeit nicht klar, um was es sich genau bei diesem Objekt handeln könnte. Erst in den letzten Jahren verdichten sich die Anzeichen, dass es ein sehr junger Babystern sein könnte, umgeben von einer staubigen Wolke.
Inklusive dieses Babysterns untersuchten die Wissenschaftler*innen für die aktuelle Studie ein Dutzend Objekte in der direkten Umgebung des supermassiven Schwarzen Lochs, die alle sehr ähnliche Eigenschaften aufweisen. Sie fanden heraus, dass die Objekte nochmals deutlich jünger sind als die bereits bekannten Hochgeschwindigkeitssterne. „Interessanterweise verhalten sich diese jungen ‚Babysterne‘ aber so wie die S-Sterne. Das bedeutet, auch die Babysterne umrunden das Schwarze Loch mit mehreren 1000 km/s in wenigen Jahren“, so Dr. Florian Peißker vom Institut für Astrophysik der Universität zu Köln und Erstautor der Studie. „Bereits die S-Sterne sind überraschend jung. Nach gängigen Theorien ist die Anwesenheit eines stellaren Kindergartens mit den noch jüngeren ‚Babysternen‘ völlig unerwartet,“ fügt Dr. Peißker hinzu.
Es zeigte sich weiterhin, dass dieser Sternenhaufen, bestehend aus den Babysternen und den S-Sternen, auf den ersten Blick wie ein chaotischer Bienenschwarm aussieht. Wie ein Schwarm weist aber auch der Sternenhaufen Muster und Regelmäßigkeiten auf. So konnten die Forscher*innen zeigen, dass sich die Babysterne wie die S-Sterne auf bestimmte und geordnete Weise im dreidimensionalen Raum anordnen. „Das bedeutet, es gibt gewisse präferierte Orientierungen der Sterne. Die Verteilung beider Sternvarianten gleicht dabei einer Scheibe, was den Eindruck nahelegt, dass das Schwarze Loch Sterne dazu zwingt, sich in geordneten Bahnen anzusiedeln“, so Peißker.
The Near- and Mid-infrared observation of dusty sources in the S cluster, which harbors the supermassive black hole in the center of our galaxy, Sgr A*, is accompanied by a discussion about their nature. The current study, published today in A&A, aims to explore the Keplerian parameters of these dusty S cluster members orbiting Sgr A* and analyze their orbital distribution. The results indicate a clear disk-like pattern following the arrangements of the main-sequence cluster members, suggesting a common formation process for the young dusty sources. Based on the multi-wavelength photometric analysis, the study found strong indications that suggest that the dusty sources have a stellar nature consistent with the spectral energy distribution of Young Stellar Objects. The nature of the dusty sources and their organized arrangement around Sgr A* are unexpected and shed light on unexplored star formation processes in the high energetic radiation environment of the supermassive black hole.
Published in A&A (2024)
Context: The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. Until now, the question of the origin of these two populations is vague, although all explanations favor migration processes for the individual cluster members. Aims: This work revisits the S-cluster and its dusty members orbiting the supermassive black hole Sgr A* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a non-random distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods: Based on the photometric analysis, we estimated the individual H − K and K − L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a Young Stellar Object Class I model. We obtained the position angle from the Keplerian fit results, and additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results: The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and mid-infrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of Sgr A* are much shorter (≪ 2 years) than the epochs covered by the observations (≈15 years). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions: The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and the longitudes of the ascending node, strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share the common formation history or migrated with a similar formation channel in the vicinity of Sgr A*. Alternatively, the gravitational influence of Sgr A* in combination with a massive perturber, such as a putative IMBH in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement.
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. Here, we measured the pure rotational spectrum of phosphabutyne (C2H5CP) for the first time and analyzed its vibrational ground state as well as its three singly 13C-substituted isotopologues. This will allow astronomers to search for phosphabutyne in space and determine the prevailing conditions of the corresponding regions. The figure shows a section of the measured broadband spectrum on top, highlighting the pattern repeating with the total angular momentum quantum number J, while the zoom-in on the bottom highlights the very good agreement between the calculated and measured spectrum, especially when applying a small shift of 126 MHz. This work was performed in collaboration with Jean-Claude Guillemin (University Rennes) and Michael E. Harding (KIT).
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. In a recently accepted paper by Nicola Schneider and collaborators we reported results from SOFIA/upGREAT observations of a number of diffuse and high latitude clouds in the Milky Way, in particular the Draco, Spider, Polaris and Musca clouds. In only one of them, the Draco cloud, we detected emission of ionized carbon in spite of it being neither the densest cloud nor the one irradiated the strongest by known sources. When trying to model the emission of all observations in terms of an astrochemical model of a photon-dominated region it turns out, that the model is not able to simultaneously explain the strength of the continuum emission from dust and the ionized carbon line. The ionized carbon detection and also the non-detections suggest a very low impinging UV field well below what is actually observed taking all the known stars in the environment. For the Draco cloud we can explain the difference by the additional energy from a shock that is produced when the cloud is hitting the interstellar gas of the Milky Way and some shielding of the cloud by interstellar dust in atomic gas. However, for the other clouds, we do not have a consistent explanation yet. The paper combined the results from a fruitful collaboration between the CRC 1601 subprojects B2 and A6.
Figure caption: Schematic illustration of the illumination of a high-latitude cloud by UV radiation from stars in the plane of the Milky Way. The orange cylinder along the path between star and cloud indicates the dust column which attenuates the UV-field.
The Kleinmann-Low nebula in the Orion is a location of intense star formation with a complex spatial and chemical dynamic. Its radiation originates from finely distributed atoms and molecules, which in the light of the young stars emit a characteristic spectrum. The piece „Leuchtstoffraum“ is informed by the unusually precise measurements of the Herschel space telescope from 2010. It is based on the simple principle that the natural laws are the same on earth as in the nebula 1300 light years away. We hear the structure of electromagnetic radiation of a minute point in the sky whose frequencies may be partitioned into series of molecule spectra, known from the laboratory. Leuchtstoffraum 2 is an outcome of a collaboration between Julian Rohrhuber, professor at the Robert Schumann Hochschule Düsseldorf, with the astro-physicist PD Dr. Volker Ossenkopf-Okada, who teaches at I. Physikalische Institut of the University, Cologne.
Pressemitteilung der Universität zu Köln: Am 04. April 2024 wurde das neue Fred Young Submillimeter Teleskop (FYST) in Xanten am Niederrhein präsentiert. Begleitet von Vorträgen zu den wissenschaftlichen und technischen Hintergründen konnten sich die Teilnehmer*innen bei einer Bewegungsdemonstration und in Führungen einen Eindruck von dem neuartigen Teleskopdesign machen. Das FYST ist ein hochmodernes Teleskop, dessen Spiegeldurchmesser allein sechs Metern misst. Damit ist es für den Betrieb im Submillimeter- bis Millimeter-Wellenlängenbereich ausgelegt. Es wird Einblicke in die Geburt der ersten Sterne nach dem Urknall sowie in die Entstehung von Sternen und Galaxien gewähren.
„Das neuartige optische Design wird Aufnahmen mit hohem Durchsatz und großem Sichtfeld liefern und so eine schnelle und effiziente Kartierung des kompletten Himmels der südlichen Hemisphäre ermöglichen. Wir versuchen nicht weniger, als die Entstehung und Entwicklung unseres Universums seit dem Urknall besser zu verstehen“, so Professor Dr. Dominik Riechers vom Institut für Astrophysik der Universität zu Köln. „Es ist schon etwas ganz Besonderes, dass sich Universitäten, wie hier die Unis Bonn und Köln, an der Bereitstellung einer so großen wissenschaftlichen Infrastruktur beteiligen können. Das ist nur durch eine langjährige Schwerpunktsetzung möglich. Wir danken allen Förderern und Konsortiumspartnern“, sagte Karsten Gerlof, Kanzler der Universität zu Köln. Zudem richteten unter anderem Professorin Dr. Stephanie Walch-Gassner (Präsidentin der Astronomischen Gesellschaft, Institut für Astrophysik der Universität zu Köln), Thomas Görtz (Bürgermeister der Stadt Xanten), Edeltraud Klabuhn (Bürgermeisterin der Stadt Duisburg) und Chapman Godbey (US-Generalkonsulat Düsseldorf) Grußworte an die Teilnehmer*innen.
Nach dem Event wird das FYST zunächst weiterentwickelt. Zum Jahresende wird es demontiert und in Einzelteilen nach Chile verschifft. Final wird es in 5.600 Metern Höhe auf dem Berg Cerro Chajnantor in der chilenischen Atacama-Wüste stehen und das Atacama Large Millimeter/submillimeter Array (ALMA) überblicken. Die Beobachtungen des Weitwinkel-Teleskops im Submillimeter-Strahlungsbereich werden durch Wasserdampf in der Erdatmosphäre leicht verzerrt und das Signal stark abgeschwächt. Daher wird ein hoher und trockener Standort benötigt.
Partner im Projekt sind die Cornell University (USA), ein deutsches Konsortium bestehend aus der Universität zu Köln, der Universität Bonn und dem Max-Planck-Institut für Astrophysik in Garching sowie ein kanadisches Konsortium mehrerer Universitäten. Entworfen wurde das Teleskop von Vertex Antennentechnik in Duisburg. Montiert wurde das FYST in Xanten auf dem Gelände der Wessel GmbH. Benannt wurde es nach Fred Young, der das Projekt über viele Jahre begleitet und großzügig finanziell unterstützt hat.
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.
We present new magneto-hydrodynamic (MHD) simulations conducted within the SILCC framework, exploring the multiphase interstellar medium
(ISM) within a patch of a stratified galactic disk. Our study incorporates a self-consistent modeling of
non-ionizing far-ultraviolet (FUV) radiation emitted by stellar clusters, aiming to understand its impact on star
formation and the chemical composition of the nearby ISM. We observe locally intense interstellar radiation fields
(ISRF) with values up to G0 ≈ 104 (in Habing units), contrasting with the canonical solar
neighborhood value of G0 = 1.7.
Our findings suggest that while FUV radiation influences star formation, its role in regulating the star formation
rate (SFR) appears less significant compared to other stellar feedback mechanisms such as ionizing UV radiation,
stellar winds, and supernovae. Additionally, our chemical analysis reveals enhancements in both the warm-ionized
medium (WIM) and the cold-neutral medium (CNM) beyond the vicinity of stellar clusters, indicating a complex
interplay influenced by the self-consistent and highly variable FUV radiation field, fostering the presence of a
diffuse molecular hydrogen gas phase.
Further details will be available in Rathjen et al., currently in preparation.
Figure:
Overview of the simulated ISM. Shown are the edge-on views of the total gas (Σgas, 1st panel), molecular
hydrogen (ΣH2, 4th panel), and ionized hydrogen (ΣH+, 5th panel) column
densities, as well as mass-weighted gas (Tgas, 2nd panel) and dust (Tdust, 3rd panel)
temperatures and ionizing photon energy density (eγ, 6th panel), the effective G0 field
(Geff, 7th panel), and cosmic ray energy density (eCR, 8th panel) in projection. The
star-forming galactic ISM is concentrated around the midplane. White circles in the 1st panel indicate active star
clusters.
The colloquium program for summer semester 2024 is online. https://sfb1601.astro.uni-koeln.de/events/sfb1601-colloquium/
We welcome you every Monday at 3 pm at the University of Cologne, Physics Institutes (Zülpicher Str. 77) in Lecture Hall III. The colloquia will start off with a coffee/tea reception at 02:45 pm in front of the lecture hall.
Jülich Supercomputing Centre offers a training programme of about 25 HPC-relevant courses per year. The courses comprise lectures and hands-on training on programming languages, usage of HPC systems, parallel environments, MPI, hybrid programming, GPU programming, deep learning, and – in the near future – quantum computing.
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.
Doing so, we simulate a collapsing core scenario of a subvirial, 1000 M☉ core with an initial radius of 1 pc and a linear magnetic field of 100 μG, which is a birthplace of massive stars.
For the post-processing we use RADMC-3D, which is an open source radiative transfer code that is based on the Monte-Carlo method. Here, we present synthetic observations of the dust emission (top left panel). The advantage of our simulations is that we calculate the dust temperature self-consistently, hence taking into account radiative heating by all young stars as well as shock heating. Thus, RADMC-3D is directly working on the simulated dust temperature. These results are post-processed with CASA, where different, respectively a combination of, possible ALMA channels and predictable water vapour (pwv) in the atmosphere can be simulated. We show the results for synthetic observations in different ALMA channels (labeled with AMLA TM1, TM2 and ACA; bottom panels), as well as their combination for two predictable water vapour settings (top middle and top right panel). In synthetic observations most of the structures in the less dense environment are not visible anymore; however, the emission of the main star forming regions remain.
This work was performed in collaboration with Dr. Álvaro Sánchez-Monge
Physikalischer Verein Mi., 22. Nov. 2023 19:30 Uhr bis 20:30 Uhr Livestream
Unsere kosmische Umgebung ist geprägt von unzähligen Sternen, die in den Tiefen des Weltraums entstehen. Doch wie genau formen sich diese strahlenden Himmelskörper, und wie entstehen die Planetensysteme, die sie umgeben? In diesem Vortrag werden wir uns auf eine Reise durch die Geburt von Sternen begeben und die komplexen Prozesse erkunden, die zur Entstehung neuer Planetensysteme führen.
Wir werden erfahren, dass Sternentstehung in gigantischen Gas- und Staubwolken stattfindet, in denen Gravitationskräfte und elektromagnetische Strahlung eine Schlüsselrolle spielen. Wir werden uns mit der Kollapsphase bis zur Geburt eines leuchtenden Sterns auseinandersetzen sowie die Entstehung von Planeten und deren Anordnung in einer Vielzahl von Planetensystemen erforschen.
Durch modernste astronomische Beobachtungen und Simulationen haben Wissenschaftler bedeutende Erkenntnisse über diese Prozesse gewonnen. Ich werde einige der neuesten Entdeckungen und bahnbrechenden Forschungsergebnisse präsentieren, die unser Verständnis von Sternen und Planetensystemen vertiefen.
Vortrag von Slawa Kabanovich (PH1): Sternentstehung im Eiltempo – Fliegende Sternwarte SOFIA liefert überraschende Ergebnisse
Beobachtungen des ionisierten Kohlenstoffs mit dem upGREAT (German Receiver for Astronomy at Terahertz) an Bord des deutsch-amerikanischen Stratosphärenteleskops SOFIA (Stratosphären-Observatorium für Infrarot-Astronomie) haben gezeigt, dass HII-Regionen sich rasch ausdehnen können, angetrieben durch den Sternenwind. Die Kompression des umgebenden interstellaren Materials initiiert die Entstehung neuer Sterne. Dabei konnten wir feststellen, dass die Sternentstehung auf viel kürzeren Zeitskalen erfolgen kann, als bisher angenommen wurde. Die Beobachtung des ionisierten Kohlenstoffs war ausschließlich durch SOFIA möglich, da die [CII]-Linie vom Erdboden aus nicht beobachtbar ist. Die analysierten Daten ermöglichten es uns, die Bildung interstellarer Wolken zu untersuchen, und darüber hinaus den Einfluss massereicher Sterne auf das interstellare Medium zu erforschen.
Monatsvortrag am 24.11.2023 um 20:00 Uhr in der Volkssternwarte Köln:
An unexpectedly high number of young stars has been identified in the direct vicinity of a supermassive black hole and water ice has been detected at the centre of our galaxy / publication in “The Astrophysical Journal”
An international team led by Dr Florian Peißker at the University of Cologne’s Institute of Astrophysics has analysed in detail a young star cluster in the immediate vicinity of the supermassive black hole Sagittarius A* (Sgr A*) in the centre of our galaxy and showed that it is significantly younger than expected. This cluster, known as IRS13, was discovered more than twenty years ago, but only now has it been possible to determine the cluster members in detail by combining a wide variety of data – taken with various telescopes over a period of several decades. The stars are a few 100,000 years old and therefore extraordinarily young for stellar conditions. By comparison, our sun is about 5 billion years old. Due to the high-energy radiation as well as the tidal forces of the galaxy, it should in fact not be possible for such a large number of young stars to be in the direct vicinity of the supermassive black hole. The study was conducted under the title ‘The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. I. Detection of a Rich Population of Dusty Objects in the IRS13 Cluster’ and has now appeared in The Astrophysical Journal.
In connection with the current study, a further outstanding result has also been published. For the first time, the James Webb Space Telescope (JWST) was used to record a spectrum free of atmospheric interference from the Galactic Center. A prism on board the telescope was developed at the Institute of Astrophysics in the working group led by Professor Dr Andreas Eckart, a co-author of the publication. The present spectrum shows that there is water ice in the Galactic Center. This water ice, which is often found in the dusty discs around very young stellar objects, is another independent indicator of the young age of some stars near the black hole.
In addition to the unexpected detection of young stars and water ice by the JWST, the researchers led by Dr Peißker have also found that IRS13 has a turbulent history of formation behind it. The study results suggest that IRS13 migrated toward the supermassive black hole through friction with the interstellar medium, collisions with other star clusters, or internal processes. From a certain distance, the cluster was then ‘captured’ by the gravitation of the black hole. In this process, a bow shock may have formed at the top of the cluster from the dust surrounding the cluster, similar to the tip of a ship in the water. The associated increase in dust density then stimulated further star formation. This is an explanation why these young stars are above all in the top or front of the cluster.
“The analysis of IRS13 and the accompanying interpretation of the cluster is the first attempt to unravel a decade-old mystery about the unexpectedly young stars in the Galactic Center,” according to Dr Peißker. “In addition to IRS13, there is a star cluster, the so-called S-cluster, which is even closer to the black hole and also consists of young stars. They are also significantly younger than would be possible according to accepted theories.” The findings on IRS13 provide the opportunity in further research to establish a connection between the direct vicinity of the black hole and regions several light years away. Dr Michal Zajaček, second author of the study and scientist at Masaryk University in Brno (Czech Republic), added: “The star cluster IRS13 seems to be the key to unravelling the origin of the dense star population at the centre of our galaxy. We have gathered extensive evidence that very young stars within the range of the supermassive black hole may have formed in star clusters such as IRS13. This is also the first time we have been able to identify star populations of different ages – hot main sequence stars and young emerging stars – in the cluster so close to the centre of the Milky Way.”
Media Contact: Dr Florian Peißker Institute of Astrophysics +49 221 470 3491 peisskerph1.uni-koeln.de
Wanderung durch die Vulkaneifel, 17. September 2023 in Schalkenmehren
Volker Ossenkopf-Okada
Die Wanderung führte durch die malerische Vulkaneifel in Rheinland-Pfalz um den Blick auf unsere Erde mit dem Blick ins Universum zu kombinieren. 40 Wanderfreunde waren begeistert, auf einem entspannten Weg zum Observatorium “Hoher List” etwas über die Entstehung der Erde und anderer Planeten zu erfahren. Die Tour führte entlang der HeimatSpur-Route MaareGlück bis zum Observatorium Hoher List. Anhand verschiedener Stationen gab es für die Teilnehmenden Einblicke in die Entstehung der Erde und die Entwicklung ihrer vulkanischen Aktivität. Dabei ging es auch um die Frage, was unseren Heimatplaneten so besonders macht. Im Observatorium erfuhren die Teilnehmenden zudem, wie wir fremde Planeten erforschen können.
Die Veranstaltung fand in Kooperation mit der Astronomischen Vereinigung Vulkaneifel am Hohen List e.V., Astronomers For Planet Earth und dem Natur- und Geopark Vulkaneifel GmbH statt.
Der Hiker’s Guide through the Galaxy fand im Rahmen des Wissenschaftsjahres 2023 – Unser Universum statt und wurde vom Bundesministerium für Bildung und Forschung gefördert.
To create a family friendly environment the Physics Department at the University of Cologne has set up a parent-child room supported by the German Research Foundation (DFG). The room offers a back-up option for combining work and child care in case of urgency, e. g. gaps in child care or in exceptional circumstances.
The University of Cologne has obtained a new Collaborative Research Center (CRC) from the German Research Foundation (DFG). In addition, two existing CRCs have been extended. The new CRC 1601 is entitled “The Cosmic Evolution of the Habitats of Massive Stars”. The CRC will be funded for four years. The spokesperson of the new Collaborative Research Center is astronomy professor Dr. Stefanie Walch-Gassner from the Institute of Astrophysics at the University of Cologne. The researchers are investigating the cosmic evolution of the habitats of massive stars – the gaseous environments in which these stars are born and with which they interact. Due to their short lifetimes and high energy output, massive stars have significantly influenced the evolution of galaxies since the beginning of the universe.
Within the CRC 1601, researchers are investigating the physical processes that determine the habitats of massive stars in different galactic environments. The new CRC combines four pillars: laboratory astrophysics, instrument development, observations, and theoretical modeling and simulations. The CRC partners have a strong profile as leading players in large international projects and have extensive experience in building and operating their own telescopes and developing state-of-the-art instruments in the infrared, submillimeter, and radio wave ranges. New developments, in particular the launch of the FYST/CCAT telescope in 2024, in which the Universities of Cologne and Bonn have a 25 percent stake, will be optimally supported by CRC 1601.
“We are extremely pleased about the new establishment of CRC 1601. The funding enables us to pursue an integrative approach. By combining the four pillars, we will be able to close major gaps in our understanding,” said Professor Dr. Walch-Gassner. “High-resolution studies of the habitats of massive stars will be combined with studies that look at the entire system ‘galaxy.’ This, and the inclusion of novel studies of the early universe and the associated extreme and highly variable conditions that prevail in young galaxies, will enable us to understand and quantify the cosmic evolution of the habitats of massive stars.”
