Master Colloquium
Tanish Nandre	SCHEDULED

MPIfR

Carbon is one of the main coolants of the interstellar medium, and its distribution between C+, C0 and CO carries information about the physical conditions in the gas. H2 can survive at lower visual extinction than CO, so the outer layers of molecular clouds contain H2 while carbon is still mostly C+ or C0. This “CO-dark” gas is invisible in CO, but can be traced through [C II] and [C I] emission.Understanding how carbon is distributed between these phases, and how this varies across the Galaxy, is key to a complete picture of the interstellar carbon budget.However, atomic carbon has received comparatively little attention on Galactic scales, partly because its emission is faint and strongly affected by atmospheric absorption. In my talk, I will present a study that combines the Herschel GOT C+ [C II] survey with new [C I] and 12CO (2-1), 13CO (2-1) and C18O (2–1) observations of the same lines of sight across the Galactic plane. I will describe how the spectra were reduced and how Gaussian decomposition allows [C I] and 13CO components to be compared at kinematically matched velocities. Following Pineda et al. (2013), I will show how a detection based classification of the emission and the emissivity as a function of Galactocentric radius can be used to explore where the different tracers originate, and which emission could be a possible tracer of CO-dark gas. Using longitude–velocity diagrams and spiral arm models, I will explore how carbon is distributed through the Milky Way, including how it relates to the spiral arms and inter-arm regions.

	Main Colloquium
Prof. Dr. Tim Dietrich	SCHEDULED

Max-Planck-Institut für Gravitationsphysik, Potsdam/Golm

Neutron stars are among the densest known objects, and the merger of two neutron stars is one of the most energetic phenomena known. Interpreting these mergers through their multi-messenger emission requires accurate theoretical models that can be correlated with the observational data. Gravitational-wave models combine ab initio numerical-relativity simulations with analytical waveform approximations, enabling predictions that are both accurate and computationally efficient. Similar modelling strategies can be applied to electromagnetic counterparts, including the kilonova and the gamma-ray burst afterglow. Integrating these components into a unified multi-messenger framework enables the extraction of fundamental physics from observations, leading to tighter constraints on the equation of state of neutron stars, more precise measurements of the Hubble constant, and a better understanding of heavy-element production in the Universe. This colloquium is initiated by the IMPRS students of the MPIfR.