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How many galaxies are in the universe?

Christopher J. Conselice
University of Nottingham

Using deep Hubble Space Telescope imaging we are now able to measure the mass functions of galaxies up to z = 10, when the universe was less than 1 Gyr old. One major finding from this is that the ratio of low mass galaxies to giant massive galaxies increases significantly as you go further back in time. This implies that most of the galaxies in the observable universe are at high redshift. I will present these results and discuss how the total number densities of galaxies increases as we look further back in time and the implications for this. This includes the fact that there must be at least a few trillion galaxies in the observable universe, over a factor of 10 more than we can possibly see today with current technology. I will also discuss how these results have implications for galaxy evolution, background light and the classic conundrum of Olbers' paradox.

2016 May 30, 16:00

Observatório Astronómico de Lisboa (Seminar room)
Tapada da Ajuda, 1349-018 Lisboa

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia