Seminars and Colloquia at ESO Garching and on the campus

Mid-infrared polycyclic aromatic hydrocarbon (PAH) features are among the most widely used tracers of star formation in galaxies, as they originate from small dust grains excited by ultraviolet photons from young stars. In active galactic nuclei (AGN), however, the strong radiation field from the central engine can modify or destroy PAH molecules, potentially biasing star-formation rate (SFR) estimates based on these features. Understanding how PAHs behave in AGN environments is therefore crucial to disentangling the nuclear and host contributions to the mid-infrared emission.
In this talk, I will present results from an analysis of low-resolution Spitzer/IRS spectra of 148 nearby AGN (⟨z⟩ = 0.03). We measured the fluxes of the 6.2, 7.7, 8.6, and 11.3 μm PAH bands, derived PAH-based SFRs, and compared them with X-ray properties such as luminosity, obscuration, and Eddington ratio. We find that the 11.3 μm feature is detected in over 90% of our sample and, Its luminosity shows a clear positive correlation with the AGN hard X-ray luminosity, suggesting that star formation and black hole accretion are connected on galactic scales.
Interestingly, this correlation becomes stronger in unobscured systems, consistent with the idea that PAH emission (and therefore star formation) can be affected by the AGN radiation field when the line of sight is relatively clear. No significant trends are found with the Eddington ratio or black hole mass, implying that global star formation is not directly regulated by the instantaneous accretion rate. Altogether, our results show that PAH emission can still be used to trace star formation in galaxies hosting AGN, provided that the effects of AGN luminosity and obscuration are properly taken into account. This work helps us understand how black hole growth and star formation coexist and/or possibly interact.

Laser propagation through strong turbulence has unique challenges, quite different from astronomical adaptive optics (AO), and therefore unconventional approaches must be developed to meet these requirements. At Fraunhofer IOSB, several wavefront sensing concepts have been either invented or further developed for this purpose. Specifically, focus has always been placed on wavefront sensors (WFS) suitable for monochromatic light, i.e. for lasers, and on achieving the highest possible bandwidth because these sensors' primary application has been deployment on fast-moving aircraft for laser-based communications and energy delivery to/from such aircraft. This presentation will focus on three sensors: the holographic WFS, the heterodyne WFS, and the angular transmission WFS. Application of these WFS to sensing from LGS will be discussed.

For more than a century, Einstein’s General Relativity has transformed our understanding of the Universe, revealing that space and time together form a dynamic fabric that bends and stretches under the influence of gravity.
In this talk, I will take the audience on a journey through the history and key ideas of this remarkable theory, leading up to one of its most spectacular predictions: gravitational waves.

We will explore how Einstein’s equations foresee the existence of ripples in the fabric of spacetime—waves that travel across the cosmos—and how these elusive signals were first detected thanks to extraordinarily sensitive instruments.

After presenting some striking examples of astrophysical phenomena—such as the mergers of black holes and neutron stars—we will look ahead to the future of gravitational-wave astrophysics with LGWA (Lunar Gravitational Wave Antenna), a visionary project that aims to place a gravitational-wave detector on the surface of the Moon. LGWA promises to extend our ability to listen to the cosmos, unlocking realms of knowledge inaccessible from Earth—a bold scientific and technological challenge that marks the next great adventure in our quest to understand the Universe.