Promotionskolloquium
Arunima Dutta	SCHEDULED

MPIfR

Globular clusters (GCs) are gravitationally bound, dense stellar systems that contain some of the oldest stars in our Galaxy. Owing to their extreme stellar densities and high rates of binary interactions, GCs have long been known as breeding grounds for millisecond pulsars (MSPs), a subset of rapidly rotating and highly magnetised neutron stars with exceptional rotational stability and millisecond spin periods. GC pulsars serve as precision probes of the structure, gas content, magnetic fields, gravitational potential, and dynamical history of their host clusters, while the exotic binaries formed within them provide unique laboratories for fundamental physics. In this thesis, I have studied fourteen known pulsars in the dense globular cluster NGC 1851, using data primarily obtained with the MeerKAT telescope, and derived their timing solutions and physical properties. The astrometric positions of the pulsars reveal a striking east–west bar-like alignment, which is also observed for X-ray sources and may be an outcome of mass segregation influenced by the rotation of the cluster. Two of the systems are particularly interesting: PSR J0514-4002A and J0514-4002E (hereafter, NGC 1851A and NGC 1851E). NGC 1851A is a 4.99-ms pulsar in a highly eccentric 18-day binary, containing a 1.39 solar mass pulsar and a 1.08 solar mass white dwarf companion, and its timing reveals evidence for an ongoing three-body interaction with another nearby star. The most exotic pulsar in this cluster is NGC 1851E, which consists of a 5.6-ms pulsar in a 7-day eccentric binary with a total mass of 3.89 solar masses, making it the most massive known pulsar–compact object binary to be known. Its companion has a mass between 2.09 and 2.71 solar masses, placing it in the compact-object mass gap and suggesting that it could be either a very massive neutron star or a low-mass black hole. In either case, this system provides an unprecedented laboratory for studying the formation and nature of compact objects and testing fundamental physics.

	Main Colloquium
Prof. Sirio Belli	SCHEDULED

University of Bologna

I will present recent studies based on JWST spectroscopy from the Blue Jay survey and other programs, revealing the widespread presence of multi-phase outflows in massive galaxies at 2 < z < 5. The unprecedented sensitivity of JWST allows us to study not only the ionized gas, but also the hard-to-detect neutral atomic phase, which is colder and carries substantially more mass than the ionized phase. Neutral outflows are particularly common in quiescent galaxies, which also host low-luminosity AGNs that can only be detected by JWST. These observations represent the first direct evidence that the rapid quenching of massive galaxies at z~2 and beyond is likely due to powerful AGN-driven outflows.

	Special Colloquium
Prof. Dr. Julie Hlavacek-Larrondo	SCHEDULED

Université de Montréal, Canada

The best place to study black hole feedback processes is in the hot atmospheres of galaxy clusters, which host the most massive black holes in the Universe and where we can directly image their impact on the surrounding medium. Yet major questions remain about how this black hole feedback operates, from gas cooling out of the hot atmosphere to ultimately fuelling the central black hole. I will first review our current understanding of this field and highlight recent observational advances that are revealing the complete self-regulated black hole feedback cycle. I will then focus on how machine learning and new data-analysis techniques can provide a complementary view of this feedback cycle. Using mock X-ray observations from the IllustrisTNG and TNG-Cluster simulations, we are exploring how information about the thermodynamic state of the intracluster medium can be extracted directly from these simulations. I will present recent work using deep learning and simulation-based inference, as well as new results showing that AstroCLIP, a foundation model trained on optical astronomical data, can be transferred to X-ray observations to predict cluster cooling times. Together, these studies illustrate the potential of combining observations, simulations and modern machine-learning techniques to extract the physics of black hole feedback from the rapidly growing datasets of current and next-generation observatories.