Oral Presentation
The Impact of Radiative Feedback on The 21-cm Signature around The First Stars
Presenter: Toshiyuki Tanaka (Nagoya university, Japan)
The 21-cm signal around the first stars provides us with fruitful information about properties of the first stars. Since the escape fraction of the ionizing photons strongly affects the distribution of neutral hydrogen, we trace the time evolution of the escape fraction by conducting radiation hydrodynamics (RHD) simulations following dynamics of dense gas in a halo. What we find is that the radial profile of 21-cm differential brightness temperature strongly depends on the stellar and halo masses, which are important factors for the time evolution of the escape fraction. A less massive star creates a deep 21-cm absorption region at just outside the halo and keeps for long time because the dense halo gas absorb ionizing photons and confine the ionized region well inside the halo. On the other hand, a massive star creates a spatially extended 21-cm emission signature because ionizing photons escaped from the host halo heat up the ambient intergalactic medium. Even though individual stars are unlikely to be detectable with the Square Kilometre Array, our simple estimation using the results from RHD simulations shows that the amplitude of 21-cm global signal depends not only on the cosmic star formation rate density, but also on the typical stellar mass of the first stars. Finally, we will discuss the importance of the initial mass function of the first stars in understanding of the 21-cm global signal.
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