Michael Küffmeier
Carlsberg reintegration fellow at Niels Bohr Institute Copenhagen, Denmark
Michael Küffmeier
Welcome to my website! On this website you get to know more about my research. I rejoined the Niels Bohr Institute in Copenhagen in September 2023 to work on my Carlsberg reintegration project "Embedded disks: exploring the nurseries of planets". Before, I was affiliated with the University of Virginia in Charlottesville (2020 to 2022) and the Center for Astrochemical Studies (CAS) at the Max-Planck-Institute of Extraterrestrial Physics (MPE) in Munich-Garching (2022 to 2023) as a Marie Skłodowska Curie global fellow. Browse around to learn more about my past and current activities, my latest research, as well as my travel plans. Happy stalking and please don't hesitate to contact me if you have any further questions.
UPCOMING EVENTS
Start of Carlsberg Reintegration Fellowship at Niels Bohr Institute Copenhagen
01/09/2023-31/08/2025
Visit and seminar at University of Milan
11/09/2023
Harvard-Heidelberg Star formation meeting (TBC)
Fall 2023
MY LATEST RESEARCH
In the traditional star formation paradigm, stars accrete their mass solely from the collapse of a pre-stellar core. However, the detection of accretion streamers in both models and observations shows that stars can in fact be fed by material that is initially not gravitationally bound to the collapsing pre-stellar core. In our paper, we demonstrate that star formation is a two-stage process. The two phases are:
1) the initial collapse phase, which is conceptually similar to the traditional picture of a collapsing prestellar core.
2) optional periods of post-collapse infall, where the star "captures" material that was initially not bound to the prestellar core. The probability and contribution of late infall correlates with increasing final stellar mass,.
Moreover, late accretors have large reservoirs of angular momentum, which suggests that large disks are possible signs of recent infall events.
Finally, stars can become (apparently) "rejuvenated". We show an example of a star that is classified as a Class 0 object according to its bolometric temperature when becoming more embedded again during a substantial infall event.
Stars often occur as systems of binaries or higher order. For young embedded protostellar multiples, high-resolution observations with modern telescopes such as ALMA reveal the presence of arc and bridge-like structures associated with protostellar multiples. Using the zoom-in technique, we demonstrated that these bridge structures are a natural consequence of the underlying turbulence present in the parental Giant Molecular Cloud. The corresponding paper got featured on the cover page of the Ausgust edition of Astronomy & Astrophysics. More recently, we published a follow-up study in which we found that linear polarization of dust reemission observed at mm-wavelength can be used as tracer of the magnetic field around young protostars.
Observations show the presence of shadows for multiple disks. Such shadows can be nicely explained by a configuration of an inner disk that is misaligned with respect to an outer disk. In a series of papers, we investigated the effect of late infall and recently showed that late infall onto an existing star-disk system can lead to the formation of misaligned inner and outer disk. By post-processing the simulation data with a radiative transfer code, we show how the inner disk casts a shadow on the second-generation outer disk. The corresponding paper is linked here.
In contrast to previous models that studied the truncation of disks at a late stage of their evolution, we investigate whether disks may already be born with systematically smaller disk sizes in more massive star-forming regions as a consequence of higher ionization rates. A higher ionization rate leads to stronger magnetic braking, and hence to the formation of smaller disks. Accounting for recent findings that protostars act as forges of cosmic rays and considering only mild attenuation during the collapse phase, we show that a high average cosmic-ray ionization rate in star-forming regions such as the ONC or CrA can explain the detection of smaller disks in these regions. The corresponding paper is linked here.
