JSPS Postdoctoral Research Fellow at the University of Tokyo
Me in front of the night sky.
I am a Postdoctoral Researcher at the University of Tokyo. I work on the formation of the first stars, the first galaxies, and the first black holes. My collaborators and I try to better understand early structure formation and the chemical evolution of the Milky Way. A main goal is to connect the so called "dark ages" with observables, such as high-redshift AGNs, the first galaxies, stellar archaeology surveys, or gravitational waves. Currently, we run high-resolution cosmological simulations to model the formation of the second generation of stars and predict their specific chemical fingerprint. You can find more about my research under Publications.
We also offer a variety of exciting research projects for students at all levels (Bachelor, Master, PhD): detecting the first supernovae in the Universe with next generation telescopes, the anthropic principle of star formation, stellar archaeology, the dynamics of dark matter in the Milky Way, the cosmic rate of superluminous supernovae,...
Students from less privileged countries are explicitly encouraged to contact us for research opportunities. We may also be able to financially support your research project in Tokyo or help to apply for additional funding.
Active Galactic Nuclei outflows in galaxy discshttp://arxiv.org/abs/1707.03826
Galactic outflows, driven by active galactic nuclei (AGN), play a crucial role in galaxy formation and in the self-regulated growth of supermassive black holes. With a novel 2D analytical model for AGN-driven outflows in a gaseous disc we demonstrate the main improvements, compared to existing 1D solutions. We find significant differences for the outflow dynamics and wind efficiency (see Figure). The recovery time of gas in the disc plane is remarkably short, of the order 1Myr. This indicates that AGN-driven winds cannot suppress BH growth for long. Submitted to MNRAS.
Time evolution of the position of the wind shock front in polar coordinates for our fiducial model. Top: 2D solution with the galactic disc in the horizontal plane. Bottom: 1D spherical solution. The concentric grey rings indicate the radius in log(r/pc) from 10pc to 100kpc. Whereas in the 1D model all the gas is ejected out of the halo, only 10% of the galactic gas is ejected perpendicular to the disc plane in our improved 2D model.
Gravitational Waves from the Remnants of the First Stars
Initiated by the groundbreaking observation of the first gravitational wave signal in 2015, we studied the detectability of the first stars by the merger of their remnant black holes. We developed a cosmologically representative dark matter merger tree and coupled it to a model for stellar binary evolution. The overall contribution from the first stars is small, but individual events can still be detected with aLIGO and depending on the initial mass function of the first stars, we will see several black hole mergers in the next years that originate from the first stars. Turning this result around, we can use the upcoming detections of gravitational waves to learn more about the masses and binarity of the first stars. Our catalogues of Pop III binaries are publicly available here. Published in MNRAS, 2016, 460, L74
Expected number of BH-BH merger detections per year as a function of the total binary mass for the current aLIGO sensitivity (top) and final design sensitivity (bottom). The mass range of GW150914 is indicated by the grey area. With sufficient detections around Mtot ~300Msun, we could discriminate different Pop III IMFs based on their GW fingerprint.
© 2018 Tilman Hartwig