Projects and Collaborations
The interest and work of our group divides into two broad science areas: the evolution of galaxies, and the observation of galaxy clusters through the Sunyaev-Zel'dovich (SZ) effect. Furthermore, we support the ALMA operations and its users through our ALMA Regional Center (ARC) node at Bonn/Cologne, we operate (with partners) the NANTEN2 submillimeter telescope in Chile, and we participate in the construction of the CCAT-prime submillimeter telescope.
Please click on the menu items to find more details.
CCAT-prime / FYST
The centerpiece of the Cerro Chajnantor Atacama Telescope (CCAT) Observatory is the Fred Young Submillimeter Telescope (FYST), a 6-meter telescope designed for observations at submillimeter to millimeter wavelengths. Located at an exceptional 5,600-meter site on Cerro Chajnantor in the Chilean Atacama Desert, it overlooks the ALMA array. FYST’s innovative optical design enables high-throughput, wide-field observations, allowing for rapid and efficient sky mapping. Its precision surface and superb location provide routine access to the 350-micron observing window.
Designed and built by CPI Vertex Antennentechnik GmbH, FYST is currently being transported from its construction site in Germany to Chile. First light is expected in late 2025.
The University of Bonn is a partner in the CCAT Collaboration which is responsible for construction of the telescope, instrument development, observatory operations, data analysis, and scientific publications. The Millimeter/Sub-Millimeter Astronomy Team at the Argelander-Institut für Astronomie supports both the scientific and technical aspects of the project.
For more details, visit the CCAT Observatory website.
SZ Effect and Cosmology
Our research is centered on the study of the Sunyaev-Zeldovich (SZ) effect from galaxy clusters, which is a tiny modification of the intensity of the cosmic microwave background (CMB) radiation, caused by inverse Compton scattering off the energetic electrons in the intracluster plasma. The SZ effect is a powerful tool in the study of galaxy cluster astrophysics and cosmology, providing information on topics as divers as the accelerated expansion of the universe and cosmic ray composition within AGN jets.
For over one decade we have been involved in the APEX-SZ cluster survey, using one of the world's first multi-pixel TES bolometer cameras, mounted on the APEX telescope in Chile. The data products from APEX-SZ are still being analyzed, while our research has moved onto multi-wavelength follow-up of galaxy clusters, particularly in X-rays and at radio wavelengths. Another focus of our SZ research had been the analysis of all-sky data from the Planck satellite, which we are using to gain expertise on SZ spectral measurements and prepare for future multi-wavelength CMB/SZ surveys.
At the moment, much of our scientific activities are centered on the CCAT-prime telescope, which will undertake one of the most sensitive and most wide-spectrum surveys of galaxy clusters. This survey will start collecting data as early as 2021, and our team in Bonn is heavily involved in all the relevant aspects of scientific and instrumental planning. The list of Bachelor's/Master's and PhD thesis topics on the right will give some idea on the breadth of our research.
To get a more general understanding of the many different aspects of the SZ effect and their impact on cosmological research, please have a look at the two recent documents listed below. One was prepared for the Astro 2020 Decadal Survey in the US, the other was prepared for the ESA Voyage 2050 call for their long-term scientific planning.
"SZ spectroscopy" in the coming decade: Galaxy cluster cosmology and astrophysics in the submillimeter (arXiv:1903.04944)
A Space Mission to Map the Entire Observable Universe using the CMB as a Backlight (arXiv:1909.01592)
For any question regarding SZ science, its future prospects, or the research opportunities in this group, please contact Dr. Kaustuv Basu or write him an Email (contact).
Galaxy Evolution
Understanding the formation and evolution of galaxies, and in particular the establishment of the Hubble sequence, is one of the most pressing question in modern astronomy. Interestingly, it is also one of the most challenging because it requires to constrain a variety of complex physical mechanisms acting over a vast range of spatiall scales: from mega-parsec scales tracing the gravitational collapse of the large-scale structures of the Universe, through kilo-parsec scales at which the assembly of galaxies and AGN-driven feedback happens, to parsec scales where the formation of stars and SNe-driven feedback take place. To add to this complexity, these mechanisms dramatically change over cosmic time, from the earliest epochs when the first galaxies hierarchically formed from pristine gas and re-ionize the Universe, through the cosmic peak of star formation activity when stars and bulges formed in gas-rich galaxies, to the present when most of the gas in galaxies is exhausted.
Our research focuses on the evolution of the star formation activity of galaxies across cosmic time and to understand the physical conditions of the interstellar medium driving this evolution. We employ a multi-wavelength approach using state-of-the-art observations with ground-based (e.g., ALMA, NOEMA, VLA, APEX, IRAM-30m, VLT) and space (e.g., HST, Spitzer, Herschel, Chandra) observatories.
From the present to the peak epoch of cosmic star formation (i.e., redshift 0 to 3), we take advantage of deep and large multi-wavelength extragalactic surveys, like COSMOS, to isolate the main mechanisms controlling star formation in galaxies. In particular, we study in detail their thermal dust emission via new deep (sub)millimetre galaxy surveys (e.g., GISMO-2mm, right) and their molecular line emission via dedicated follow-up. With these observations, we obtain critical constraints on their star formation activity, dust and gas content, as well as gas surface density, revealing thereby their principal modes of star formation.
Beyond the peak of cosmic star formation activity (redshift z>3), where cosmological dimming makes it difficult to observe large samples of typical galaxies, we study the detailed structure, dynamics and conditions of the interstellar medium of the brightest star-forming galaxies, such as quasars, lensed (sub)millimetre-selected galaxies, and galaxies selected through C+ line searches in ALMA archive.
Epoch of reionization: To shed light on this widely unexplored early cosmic epoch, we participate in the construction of the FYST (CCAT-prime) telescope and the development of its Epoch of Recombination Spectrometer (EoR-Spec). through three dimensional intensity maps of the C+ 158 micron line, with EoR-Spec we will perform the first high signal-to-noise large-scale measurement of the clustering signal from star-forming galaxies in the epoch of reionization. These intensity maps will not only trace the cosmic star formation activity at this epoch, but also illuminate the underlying and evolving Cosmic Web, and thus constrains the growth of structures in the early Universe.
We closely collaborate with international colleagues and in the past, within the Cologne-Bonn collaborative research center CRC-956 (2011-2022, a new CRC is being applied for). Our research benefits from the technical expertise in the German ALMA ARC node hosted by our group and that of Prof. Schilke in Cologne.
We offer exciting PhD, Master, and Bachelor thesis opportunities. If you are interested in any of these topics, please talk to us!
ALMA
The Atacama Large Millimetre Array (ALMA) is an interferometer operating with up to 66 antennae simultaneously, providing the deepest and most detailed view of the sky at 0.3 to 3 millimeter wavelength. ALMA is located on the Chajnantor Plateau in the Chilean Andes and began scientific operation in 2011. It has been delivering data that provides unprescedented insights on objects ranging from proto-planetary disks to the highest redshift galaxies.
NANTEN2
From 2008 to 2018, our group participated in the NANTEN2 observatory, which is located at 4865 m altitude on Pampa la Bola in the Atacama desert, Chile. NANTEN2 has been an important infrastructure within our CRC 956 (2011-2022), providing a platform for pilot studies at summ wavelengths, hands-on student training, and the development and testing of receiver technology.
Equipped with a 4-m submillimeter telescope, NANTEN2 was used to survey the southern sky in molecular and atomic spectral lines between 110 and 880 GHz (2.6 mm to 350 micron wavelength). The highest observing frequencies are covered by the KOSMA SMART receiver, a dual-frequency, 2x8 pixel array receiver operating between 460 and 880 GHz.
The NANTEN2 observatory (NANTEN is japanese for southern sky, 南天 nan = south, ten = heaven, sky) was a collaboration between research institutes in Japan (Nagoya and Osaka University), South Korea (Seoul National University), Germany (Universität zu Köln, Universität Bonn), Switzerland (ETH Zürich), University of New South Wales (UNSW), and Chile (Universidad de Chile).
