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Summary:
This is the homepage of the of the weekly Astrophysics journal club at the Division of Particle physics and astrophysics at the University of Helsinki.
The meetings are of an unofficial nature and the main driver is to get together and discuss recent interesting papers. This meeting differs from the
Seminar series in that people are not expected to talk about their own research and in that no credits will be awarded to students. The meetings are
open to everyone and the aim is to stimulate discussion about recent results and provide the possibility to
 learn about research that is not necessarily
connected to one's own field of expertise.

All topics are welcome ranging from planetary science to larger scales involving stellar
 astrophysics, Milky Way studies, galaxies and cosmology.
The only requirement is that the
 presented papers should be interesting to a wider audience and that they should be presented 
in such a way that also
a non-expert can follow the presentation. In the meetings we discuss one paper each week for about 45 minutes.
 All meetings are in English.

Location: Conference room C310 on the third floor.

Time: Thursdays at 10.15-11.00am during term time.

Speakers: Please contact Peter Johansson, Mikael Granvik or Clif Kirkpatrick if you want to present a paper.

Present Program: The next talk will be on the 13th of September

Presenter: Till Sawala:
Paper title: The Imprint of Cosmic Reionization on the Luminosity Function of Galaxies
Authors: Bose, S., Deason, A.J., Frenk, C.S.
Reference: 2018, ApJ, 863, 123

Abstract: The (re)ionization of hydrogen in the early universe has a profound effect on the formation of the first galaxies: by raising the gas temperature and pressure, it prevents gas from cooling into small halos, thus affecting the abundance of present-day small galaxies. Using the GALFORM semi-analytic model of galaxy formation, we show that two key aspects of the reionization process—when reionization takes place and the characteristic scale below which it suppresses galaxy formation—are imprinted in the luminosity function of dwarf galaxies. We focus on the luminosity function of satellites of galaxies like the Milky Way and the LMC, which is easier to measure than the luminosity function of the dwarf population as a whole. Our results show that the details of these two characteristic properties of reionization determine the shape of the luminosity distribution of satellites in a unique way, and are largely independent of the other details of the galaxy formation model. Our models generically predict a bimodality in the distribution of satellites as a function of luminosity: a population of faint satellites and population of bright satellites separated by a “valley” forged by reionization. We show that this bimodal distribution is present at high statistical significance in the combined satellite luminosity function of the Milky Way and M31. We make predictions for the expected number of satellites around LMC-mass dwarfs where the bimodality may also be measurable in future observational programs. Our preferred model predicts a total of 26 ± 10 (68% confidence) satellites brighter than M V = 0 in LMC-mass systems.

Present program

 

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Autumn 2018:


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