Seminar: Galaxies in the epoch of reionization Investigating the high-redshift galaxy population through simulations and observations

  • Date: –15:00
  • Location: Zoom:
  • Lecturer: Christian Binggeli
  • Contact person: Sofia Ramstedt
  • Seminarium

In this pre-dissertation seminar, I will present my work on reionization-epoch galaxies to be included in my thesis. While current constraints indicate that these galaxies drove the cosmic reionization, our understanding of these objects still contains large gaps. With the upcoming James Webb Space Telescope (JWST), and the recent success of high-redshift studies with the Atacama Large Millimeter/submillimeter Array (ALMA), the prospects for filling these gaps in the coming years are good. In my thesis, I explore different ways to characterize galaxies at high redshifts and their role in the cosmic reionization. I do this using both models aimed specifically at the upcoming James Webb Space Telescope and observations with ALMA.

In the first two papers of the thesis, we use cosmological simulations and models in order to test a method for estimating the fraction of ionizing photons that are able to escape from reionization epoch galaxies. We investigate limitations of the method and possible complications arising from large variations in star formation activity. While it seems to be possible to identify galaxies with escape fractions >50% using only hydrogen-line equivalent widths and ultraviolet spectral slopes, significant complications may arise if dust properties are poorly constrained. Furthermore, we find that large and rapid variations in the star formation activity may pose a significant problem for methods such as the one discussed in the papers.

In the third paper we investigate to what extent contemporary simulations of high-redshift galaxies produce star formation rate variations sufficiently large to reproduce the observed Balmer break in the z~9 galaxy MACS1149-JD1. We predict Balmer break distributions that may be used to test simulations using future JWST observations. We find that several simulations are unable to account for the inferred Balmer break size.

In the fourth paper, we measure far-infrared emission lines and dust continuum in the z~7.7 galaxy z7_GSD_3811. We do not detect any line or continuum emission. We discuss implications of the non-detections and suggest that they may indicate that the galaxy has a low dust content and has a low metallicity (Z<10% solar).


We will run with the following setup:
- The zoom meeting will open at 13.45 so that you can log on and try it out.
- Participants should mute their microphones unless they have a question.
- Questions are allowed during the talk. Just raise your hand in the zoom app.
- After the talk has finished, unmute for applause.
- If possible, keep your video on during the full seminar so that the speaker gets visual feedback while talking.
- Questions after the talk will be administered as follows; raise your hand in the app and Sofia will chair and give the word.

-Finally, after the talk and question sessions are finished, the meeting will remain open for an informal ”bring-your-own-fika” if you want to hang around and chat with your colleagues and the speaker. The faculty will again meet in a breakout room.